Jumper

A jumper is a low-cost substitute for a switch, where a connection has to be made (or unmade) only a few times during the lifetime of a product. Typically it allows a function or feature on a circuit board to be set on a semipermanent basis, often at the time of manufacture. A DIP switch performs the same function more conveniently.

There is no standardized schematic symbol to represent a jumper.

How It Works

A jumper is a very small rectangular plastic tab containing two (or sometimes more) metal sockets usually spaced either 0.1" or 2mm apart. The sockets are connected electrically inside the tab, so that when they are pushed over two (or more) pins that have been installed on a circuit board for this purpose, the jumper shorts the pins together.

The pins are usually 0.025" square and are often part of a header that is soldered into the board. In a parts catalogue, jumpers may be found in a section titled "Headers and Wire Housings" or similar. Three jumpers are shown in Figure 1.
The blue one contains two sockets spaced 0.1" and is deep enough to enclose the pins completely. The red one contains two sockets spaced 2mm and may allow the tips of the pins to emerge from its opposite end. The black one contains four sockets, each pair spaced 0.1" apart.

The set of pins with which a jumper is used is often referred to as a header. Headers are available with pins in single or dual rows. Some headers are designed to be snapped off to provide the desired number of pins. A dual 28-pin header is shown in Figure2 with a black jumper pushed onto a pair of pins near the midpoint.

Variants

A jumper assembly may be a kit containing not only the jumper but also the array of pins with which it is intended to be used. Check the manufacturer’s datasheet to find out exactly what is included.

The most common types of jumpers have two sockets only, but variants are available with as many as 12 sockets, which may be arranged in one or two rows.

Header sockets may be used as a substitute for purpose-made jumpers, with the advantage that they are often sold in long strips that can be snapped off to provide as many sockets as needed. However, the pins attached to header sockets must be manually connected by soldering small lengths of wire between them.

In some jumpers, the plastic tab extends upward for about half an inch and functions as a finger grip, making the jumper much easier to hold during insertion and removal. This is a desirable feature if there is room to accommodate it.

The sockets inside a jumper are often made from phosphor-bronze, copper-nickel alloy, tin alloy, or brass alloy. They are usually gold-plated, but in some instances are tin-plated.

Rarely, a jumper may consist of a metal strip with U-shaped connections suitable for being used in conjunction with screw terminals. Two jumpers of this type are shown in Figure 3. They should not be confused with high-amperage fuses that look superficially similar.

Values

The spacing between the sockets in a jumper is referred to as its pitch. As previously noted, 0.1" and 2mm are the most popular values.
A typical maximum rating for a jumper of 0.1" pitch is 2A or 2.5A at 250V.

How to Use it

A jumper may activate a "set it and forget it" circuit function. An example would be the factory configuration of a product to work with 115VAC or 230VAC power input. End users were expected to set jumpers in some computer equipment sold during the 1980s, but this is no longer the case.

What Can Go Wrong

Jumpers are easily dropped, easily lost, and easily placed incorrectly. When purchasing jumpers, buy extras to compensate for their fragility and the ease of losing them.
Any location where a jumper may be used should be clearly labelled to define the function of each setting.

Cheap, poorly made jumpers may self-destruct from mechanical stresses when removed from their pins. The plastic casing can come away, leaving the sockets clinging naked to the pins protruding from the circuit board. This is another reason why it is a good idea to have a small stock of spare jumpers for emergencies.

Oxidation in jumpers where the contacts are not gold- or silver-plated can create electrical resistance or unreliable connections.

Battery

A battery contains one or more electrochemical cells in which chemical reactions create an electrical potential between two immersed terminals. This potential can be discharged as current passing through a load.

An electrochemical cell should not be confused with an electrolytic cell, which is powered by an external source of electricity to promote electrolysis, whereby chemical compounds are broken down to their constituent elements. An electrolytic cell thus consumes electricity, while an electrochemical cell produces electricity.

Batteries range in size from button cells to large lead-acid units that store power generated by solar panels or windmills in locations that can be off the grid. Arrays of large batteries can provide bridging power for businesses or even small communities where conventional power is unreliable.

Schematic symbols for a battery are shown in Figure 2-2. The longer of the two lines represents the positive side of the battery, in each case. One way to remember this is by imagining that the longer line can be snipped in half so that the two segments can combine to form a + sign.

Traditionally, multiple connected battery symbols indicate multiple cells inside a battery; thus the center symbols in the figure could indicate a 3V battery, while those on the right would indicate a voltage greater than 3V. In practice, this convention is not followed conscientiously.

How It Works

In a basic battery design often used for demonstration purposes, a piece of copper serves as an electrode, partially immersed in a solution of copper sulfate, while a piece of zinc forms a second electrode, partially immersed in a solution of zinc sulfate. Each sulfate solution is known as an electrolyte, the complete battery may be referred to as a cell, and each half of it may be termed a half-cell.

A simplified cross-section view is shown in Figure 2-3. Blue arrows show the movement of electrons from the zinc terminal (the anode), through an external load, and into a copper terminal (the cathode). A membrane separator allows the electrons to circulate back through the battery, while preventing electrolyte mixing.

Orange arrows represent positive copper ions. White arrows represent positive zinc ions. (An ion is an atom with an excess or deficit of electrons.) The zinc ions are attracted into the zinc sulfate electrolyte, resulting in a net loss of mass from the zinc electrode.

Meanwhile, electrons passing into the copper electrode tend to attract positive copper ions, shown as orange arrows in the diagram. The copper ions are drawn out of the copper sulfate electrolyte, and result in a net accumulation of copper atoms on the copper electrode.

This process is energized partially by the fact that zinc tends to lose electrons more easily than copper.
Batteries for use in consumer electronics typically use a paste instead of a liquid as an electrolyte, and have been referred to as dry cells, although this term is becoming obsolete. The two half-cells may be combined concentrically, as in a typical 1.5-volt C, D, AA, or AAA alkaline battery.
A 1.5V battery contains one cell, while a 6V or 9V battery will contain multiple cells connected in series. The total voltage of the battery is the sum of the voltages of its cells.

Electrode Terminology

The electrodes of a cell are often referred to as the anode and the cathode. These terms are confusing because the electrons enter the anode inside the cell and leave it outside the cell, while electrons enter the cathode from outside the cell and leave it inside the cell. Thus, the anode is an electron emitter if you look at it externally, but the cathode is an electron emitter if you look at it internally.

Conventional current is imagined to flow in the opposite direction to electrons, and therefore, outside the cell, this current flows from the cathode to the anode, and from this perspective, the cathode can be thought of as being “more positive” than the anode. To remember this, think of the letter t in "cathode" as being a + sign, thus: ca+hode. In larger batteries, the cathode is often painted or tagged red, while the anode may be painted or tagged black or blue.

When a reusable battery is recharged, the flow of electrons reverses and the anode and the cathode effectively trade places. Recognizing this, the manufacturers of rechargeable batteries may refer to the more-positive terminal as the anode. This creates additional confusion, exacerbated further still by electronics manufacturers using the term "cathode" to identify the end of a diode which must be “more negative”(i.e., at a lower potential) than the opposite end.

To minimize the risk of errors, it is easiest to avoid the terms "anode" and "cathode" when referring to batteries, and speak instead of the negative and positive terminals. This encyclopedia uses the common convention of reserving the term "cathode" to identify the "more negative" end of any type of diode.

Variants

Three types of batteries exist.


  1. Disposable batteries, properly (but infrequently) referred to as primary cells. They are not reliably rechargeable because their chemical reactions are not easily reversible.
  2. Rechargeable batteries, properly (but infrequently) known as secondary cells. They can be recharged by applying a voltage between the terminals from an external source such as a battery charger. The materials used in the battery, and the care with which the battery is maintained, will affect the rate at which chemical degradation of the electrodes gradually occurs as it is recharged repeatedly. Either way, the number of charge/discharge cycles is limited.
  3. Fuel Cells require an inflow of a reactive gas such as hydrogen to maintain an electrochemical reaction over a long period. They are beyond the scope of this encyclopedia.

A large capacitor may be substituted for a battery for some applications, although it has a lower energy density and will be more expensive to manufacture than a battery of equivalent power storage. A capacitor charges and discharges much more rapidly than a battery because no chemical reactions are involved, but a battery sustains its voltage much more successfully during the discharge cycle. Capacitors that can store a very large amount of energy are often referred to as supercapacitors.

Disposable Batteries

The energy density of any disposable battery is higher than that of any type of rechargeable battery, and it will have a much longer shelf life because it loses its charge more slowly during storage (this is known as the self-discharge rate).

Disposable batteries may have a useful life of five years or more, making them ideal for applications such as smoke detectors, handheld remotes for consumer electronics, or emergency flashlights.

Disposable batteries are not well suited to delivering high currents through loads below 75Ω. Rechargeable batteries are preferable for higher-current applications.

The bar chart in Figure 2-6 shows the rated and actual capabilities of an alkaline battery relative to the three most commonly used rechargeable types, when the battery is connected with a resistance that is low enough to assure complete discharge in 1 hour.

The manufacturer’s rating of watt hours per kilo is typically established by testing a battery with a relatively high-resistance load and slow rate of discharge. This rating will not apply in practice if a battery is discharged with a C-rate of 1, meaning complete discharge during 1 hour.

Common types of disposable batteries are zinc-carbon cells and alkaline cells. In a zinc-carbon cell, the negative electrode is made of zinc while the positive electrode is made of carbon.

The limited power capacity of this type of battery has reduced its popularity, but because it is the cheapest to manufacture, it may still be found where a company sells a product with "batteries included." The electrolyte is usually ammonium chloride or zinc chloride.

The 9V battery in Figure 2-7 is actually a zinc-carbon battery according to its supplier, while the smaller one beside it is a 12V alkaline battery designed for use in burglar alarms. These examples show that batteries cannot always be identified correctly by a casual assessment of their appearance.

In an alkaline cell, the negative electrode is made of zinc powder, the positive electrode is manganese dioxide, and the electrolyte is potassium hydroxide. An alkaline cell may provide between three to five times the power capacity of an equal size of zinc-carbon cell and is less susceptible to voltage drop during the discharge cycle.

Extremely long shelf life is necessary in some military applications. This may be achieved by using a reserve battery, in which the internal chemical compounds are separated from each other but can be recombined prior to use.

Rechargeable Batteries

Commonly used types are lead-acid, nickel cadmium (abbreviated NiCad or NiCd), nickel-metal hydride (abbreviated NiMH), lithium-ion (abbreviated Li-ion), and lithium-ion polymer.

Lead-acid batteries have existed for more than a century and are still widely used in vehicles, burglar alarms, emergency lighting, and large power backup systems.

The early design was described as flooded; it used a solution of sulfuric acid (generically referred to as battery acid) as its electrolyte, required the addition of distilled water periodically, and was vented to allow gas to escape. The venting also allowed acid to spill if the battery was tipped over.

The valve-regulated lead-acid battery (VRLA) has become widely used, requiring no addition of water to the cells. A pressure relief valve is included, but will not leak electrolyte, regardless of the position of the battery.

VRLA batteries are preferred for uninterruptible power supplies for data-processing equipment, and are found in automobiles and in electric wheelchairs, as their low gas output and security from spillage increases their safety factor.

VRLA batteries can be divided into two types: absorbed glass mat (AGM) and gel batteries. The electrolyte in an AGM is absorbed in a fiber-glass mat separator. In a gel cell, the electrolyte is mixed with silica dust to form an immobilized gel.

The term deep cycle battery may be applied to a lead-acid battery and indicates that it should be more tolerant of discharge to a low level—perhaps 20 percent of its full charge (although manufacturers may claim a lower number).

The plates in a standard lead-acid battery are composed of a lead sponge, which maximizes the surface area available to acid in the battery but can be physically abraded by deep discharge. In a deep cycle battery, the plates are solid.

This means they are more robust, but are less able to supply high amperage. If a deep-discharge battery is used to start an internal combustion engine, the battery should be larger than a regular lead-acid battery used for this purpose.

A sealed lead-acid battery intended to power an external light activated by a motion detector is shown in Figure 2-8. This unit weighs several pounds and is trickle-charged during the daytime by a 6" × 6" solar panel.

Nickel-cadmium (NiCad) batteries can withstand extremely high currents, but have been banned in Europe because of the toxicity of metallic cadmium. They are being replaced in the United States by nickel-metal hydride (NiMH) types, which are free from the memory effect that can prevent a NiCad cell from fully recharging if it has been left for weeks or months in a partially discharged state.

Lithium-ion and lithium-ion polymer batteries have a better energy-to-mass ratio than NiMH batteries, and are widely used with electronic devices such as laptop computers, media players, digital cameras, and cellular phones. Large arrays of lithium batteries have also been used in some electric vehicles.

Various small rechargeable batteries are shown in Figure 2-9. The NiCad pack at top-left was manufactured for a cordless phone and is rapidly becoming obsolete. The 3V lithium battery at top-right was intended for a digital camera.

The three batteries in the lower half of the photograph are all rechargeable NiMH substitutes for 9V, AA, and AAA batteries. The NiMH chemistry results in the AA and AAA single-cell batteries being rated for 1.2V rather than 1.5V, but the manufacturer claims they can be substituted for 1.5V alkaline cells because NiMH units sustain their rated voltage more consistently over time.

Thus, the output from a fresh NiMH battery may be comparable to that of an alkaline battery that is part-way through its discharge cycle.

NiMH battery packs are available to deliver substantial power while being smaller and lighter than lead-acid equivalents. The NiMH package in Figure 2-10 is rated for 10Ah, and consists of ten D-size NiMH batteries wired in series to deliver 12VDC. This type of battery pack is useful in robotics and other applications where a small motor-driven device must have free mobility.

Values

Amperage

The current delivered by a battery will be largely determined by the resistance of the external load placed between its terminals. However, because ion transfer must occur inside the battery to complete the circuit, the current will also be limited by the internal resistance of the battery. This should be thought of as an active part of the circuit.

Since a battery will deliver no current if there is no load, current must be measured while a load is attached, and cannot be measured by a meter alone. The meter will be immediately overloaded, with destructive results, if it is connected directly between the terminals of a battery, or in parallel with the load.

Current must always be measured with the meter in series with the load, and the polarity of the meter must correspond with the polarity of the battery.

Capacity

The electrical capacity of a battery is measured in amp-hours, abbreviated Ah, AH, or (rarely) A/H. Smaller values are measured in milliamp-hours, usually abbreviated mAh. If I is the current being drawn from a battery (in amps) and T is the time for which the battery can deliver that current (in hours), the amp-hour capacity is given by the formula:

Ah = I * T

By turning the formula around, if we know the amp-hour rating that a manufacturer has determined for a battery, we can calculate the time in hours for which a battery can deliver a particular current:

T = Ah / I

Theoretically, Ah is a constant value for any given battery. Thus a battery rated for 4Ah should provide 1 amp for 4 hours, 4 amps for 1 hour, 5 amps for 0.8 hours (48 minutes), and so on.

In reality, this conveniently linear relationship does not exist. It quickly breaks down as the current rises, especially when using lead-acid batteries, which do not perform well when required to deliver high current. Some of the current is lost as heat, and the battery may be electrochemically incapable of keeping up with demand.

The Peukert number (named after its German originator in 1897) is a fudge factor to obtain a more realistic value for T at higher currents. If n is the Peukert number for a particular battery, then the previous formula can be modified thus:

T = Ah / In

Manufacturers usually (but not always) supply Peukert’s number in their specification for a battery. So, if a battery has been rated at 4Ah, and its Peukert number is 1.2 (which is typical for lead-acid batteries), and I=5 (in other words, we want to know for how long a time, T, the battery can deliver 5 amps):

T = 4 / 51.2 = approximately 4 / 6.9

This is about 0.58 hours, or 35 minutes—much less than the 48 minutes that the original formula suggested.

Unfortunately, there is a major problem with this calculation. In Peukert’s era, the amp-hour rating for a battery was established by a manufacturer by drawing 1A and measuring the time during which the battery was capable of delivering that current. If it took 4 hours, the battery was rated at 4Ah.

Today, this measurement process is reversed. Instead of specifying the current to be drawn from the battery, a manufacturer specifies the time for which the test will run, then finds the maximum current the battery can deliver for that time. Often, the time period is 20 hours. Therefore, if a battery has a modern 4Ah rating, testing has probably determined that it delivered 0.2A for 20 hours, not 1A for 4 hours, which would have been the case in Peukert’s era.

This is a significant distinction, because the same battery that can deliver 0.2A for 20 hours will not be able to satisfy the greater demand of 1A for 4 hours. Therefore the old amp-hour rating and the modern amp-hour rating mean different things and are incompatible.

If the modern Ah rating is inserted into the old Peukert formula (as it was above), the answer will be misleadingly optimistic. Unfortunately, this fact is widely disregarded. Peukert’s formula is still being used, and the performance of many batteries is being evaluated incorrectly.

The formula has been revised (initially by Chris Gibson of SmartGauge Electronics) to take into account the way in which Ah ratings are established today. Suppose that AhM is the modern rating for the battery’s capacity in amp-hours, H is the duration in hours for which the battery was tested when the manufacturer calibrated it, n is Peukert’s number (supplied by the manufacturer) as before, and I is the current you hope to draw from the battery. This is the revised formula to determine T:

T = H * (AhM / (I * H)n )

How do we know the value for H? Most (not all) manufacturers will supply this number in their battery specification. Alternatively, and confusingly, they may use the term C-rate, which can be defined as 1/H. This means you can easily get the value for H if you know the C-rate:

H = 1 / C-rate

We can now use the revised formula to rework the original calculation. Going back to the example, if the battery was rated for 4Ah using the modern system, in a discharge test that lasted 20 hours (which is the same as a C-rate of 0.05), and the manufacturer still states that it has a Peukert number of 1.2, and we want to know for how long we can draw 5A from it:

T = 20 * (4/(5 * 20)1.2) = approximately 20 * 0.021

This is about 0.42 hours, or 25 minutes—quite different from the 35 minutes obtained with the old version of the formula, which should never be used when calculating the probable discharge time based on a modern Ah rating. These issues may seem arcane, but they are of great importance when assessing the likely performance of battery-powered equipment such as electric vehicles.

Figure 3 shows the probable actual performance of batteries with Peukert numbers of 1.1, 1.2, and 1.3.
The curves were derived from the revised version of Peukert’s formula and show how the number of amp-hours that you can expect diminishes for each battery as the current increases.

For example, if a battery that the manufacturer has assigned a Peukert number of 1.2 is rated at 100Ah using the modern 20-hour test, but we draw 30A from it, the battery can actually deliver only 70Ah.

One additional factor: For any rechargeable battery, the Peukert number gradually increases with age, as the battery deteriorates chemically.

Voltage

The rated voltage of a fully charged battery is known as the open circuit voltage (abbreviated OCV or Voc), defined as the potential that exists when no load is imposed between the terminals.

Because the internal resistance of a volt meter (or a multimeter, when it is used to measure DC volts) is very high, it can be connected directly between the battery terminals with no other load present, and will show the OCV quite accurately, without risk of damage to the meter.

A fully charged 12-volt car battery may have an OCV of about 12.6 volts, while a fresh 9-volt alkaline battery typically has an OCV of about 9.5 volts. Be extremely careful to set a multimeter to measure DC volts before connecting it across the battery. Usually this entails plugging the wire from the red probe into a socket separately reserved for measuring voltage, not amperage.

The voltage delivered by a battery will be pulled down significantly when a load is applied to it, and will decrease further as time passes during a discharge cycle. For these reasons, a voltage regulator is required when a battery powers components such as digital integrated circuit chips, which do not tolerate a wide variation in voltage.

To measure voltage while a load is applied to the battery, the meter must be connected in parallel with the load. This type of measurement will give a reasonably accurate reading for the potential applied to the load, so long as the resistance of the load is relatively low compared with the internal resistance of the meter.

Figure 4 shows the performance of five commonly used sizes of alkaline batteries. The ratings in this chart were derived for alkaline batteries under favorable conditions, passing a small current through a relatively high-ohm load for long periods (40 to 400 hours, depending on battery type).
The test continued until the final voltage for each 1.5V battery was 0.8V, and the final voltage for the 9V battery was a mere 4.8V. These voltages were considered acceptable when the Ah ratings for the batteries were calculated by the manufacturer, but in real-world situations, a final voltage of 4.8V from a 9V battery is likely to be unacceptable in many electronics applications.

As a general rule of thumb, if an application does not tolerate a significant voltage drop, the manufacturer’s amp-hour rating for a small battery may be divided by 2 to obtain a realistic number.

How to Use it

When choosing a battery to power a circuit, considerations will include the intended shelf life, maximum and typical current drain, and battery weight. The amp-hour rating of a battery can be used as a very approximate guide to determine its suitability.

For 5V circuits that impose a drain of 100mA or less, it is common to use a 9V battery, or six 1.5V batteries in series, passing current through a voltage regulator such as the LM7805. Note that the voltage regulator requires energy to function, and thus it imposes a voltage drop that will be dissipated as heat. The minimum drop will vary depending on the type of regulator used.

Batteries or cells may be used in series or in parallel. In series, the total voltage of the chain of cells is found by summing their individual voltages, while their amp-hour rating remains the same as for a single cell, assuming that all the cells are identical.

Wired in parallel, the total voltage of the cells remains the same as for a single cell, while the combined amp-hour value is found by summing their individual amp-hour ratings, assuming that all the batteries are identical.
In addition to their obvious advantage of portability, batteries have an additional advantage of being generally free from power spikes and noise that can cause sensitive components to misbehave. Consequently, the need for smoothing will depend only on possible noise created by other components in the circuit.

Motors or other inductive loads draw an initial surge that can be many times the current that they use after they start running. A battery must be chosen that will tolerate this surge without damage.
Because of the risk of fire,

United States airline regulations limit the amp-hour capacity of lithium-ion batteries in any electronic device in carry-on or checked passenger baggage. If a device may be carried frequently as passenger baggage (for example, emergency medical equipment), NiMH batteries are preferred.

What Can Go Wrong

Short Circuits: Overheating and Fire

A battery capable of delivering significant current can overheat, catch fire, or even explode if it is short-circuited. Dropping a wrench across the terminals of a car battery will result in a bright flash, a loud noise, and some molten metal.

Even a 1.5-volt alkaline AA battery can become too hot to touch if its terminals are shorted together. (Never try this with a rechargeable battery, which has a much lower internal resistance, allowing much higher flow of current.)

Lithium-ion batteries are particularly dangerous, and almost always are packaged with a current-limiting component that should not be disabled. A short-circuited lithium battery can explode.

If a battery pack is used as a cheap and simple workbench DC power supply, a fuse or circuit breaker should be included. Any device that uses significant battery power should be fused.

Diminished Performance Caused by Improper Recharging

Many types of batteries require a precisely measured charging voltage and a cycle that ends automatically when the battery is fully charged. Failure to observe this protocol can result in chemical damage that may not be reversible.

A charger should be used that is specifically intended for the type of battery. A detailed comparison of chargers and batteries is outside the scope of this encyclopedia.

Complete Discharge of Lead-Acid Battery

Complete or near-complete discharge of a lead-acid battery will significantly shorten its life (unless it is specifically designed for deep-cycle use—although even then, more than an 80% discharge is not generally recommended).

Inadequate Current

Chemical reactions inside a battery occur more slowly at low temperatures. Consequently, a cold battery cannot deliver as much current as a warm battery. For this reason, in winter weather, a car battery is less able to deliver high current.

At the same time, because engine oil becomes more viscous as the temperature falls, the starter motor will demand more current to turn the engine. This combination of factors explains the tendency of car batteries to fail on cold winter mornings.

Incorrect Polarity

If a battery charger or generator is connected with a battery with incorrect polarity, the battery may experience permanent damage. The fuse or circuit breaker in a charger may prevent this from occurring and may also prevent damage to the charger, but this cannot be guaranteed.

If two high-capacity batteries are connected with opposite polarity (as may happen when a clumsy attempt is made to start a stalled car with jumper cables), the results may be explosive. Never lean over a car battery when attaching cables to it, and ideally, wear eye protection.

Reverse Charging

Reverse charging can occur when a battery becomes completely discharged while it is wired (correctly) in series with other batteries that are still delivering current. In the upper section of the schematic at Figure 2-16 two healthy 6V batteries, in series, are powering a resistive load.

The battery on the left applies a potential of 6 volts to the battery on the right, which adds its own 6 volts to create a full 12 volts across the load. The red and blue lines indicate volt meter leads, and the numbers show the reading that should be observed on the meter.

In the second schematic, the battery on the left has become exhausted and is now a "dead weight" in the circuit, indicated by its gray color. The battery on the right still sustains a 6-volt potential.

If the internal resistance of the dead battery is approximately 1 ohm and the resistance of the load is approximately 20 ohms, the potential across the dead battery will be about 0.3 volts, in the opposite direction to its normal charged voltage.

Reverse charging will result and can damage the battery. To avoid this problem, a battery pack containing multiple cells should never be fully discharged.

Sulfurization

When a lead-acid battery is partially or completely discharged and is allowed to remain in that state, sulfur tends to build up on its metal plates. The sulfur gradually tends to harden, forming a barrier against the electrochemical reactions that are necessary to recharge the battery.

For this reason, lead-acid batteries should not be allowed to sit for long periods in a discharged condition. Anecdotal evidence suggests that even a very small trickle-charging current can prevent sulfurization, which is why some people recommend attaching a small solar panel to a battery that is seldom used—for example, on a sail boat, where the sole function of the battery is to start an auxiliary engine when there is insufficient wind.

High Current Flow Between Parallel Batteries

If two batteries are connected in parallel, with correct polarity, but one of them is fully charged while the other is not, the charged battery will attempt to recharge its neighbor.

Because the batteries are wired directly together, the current will be limited only by their internal resistance and the resistance of the cables connecting them. This may lead to overheating and possible damage.

The risk becomes more significant when linking batteries that have high Ah ratings. Ideally they should be protected from one another by high-current fuses.

Microphone Guide and Uses

There are more microphone choices than ever before. There could be a whole book on just microphones and their uses. The following section will feature common mics and touch on a cross section of what is out there. I have incorporated mics that a home recordist could afford as well as a fewer high-end mics that you may encounter in a professional recording studio.

 This is only a taste of what is out there. The guide below provides a picture to help identify the mic, a price guide, the microphone's transducer type and pickup pattern, specifically what the mic was designed for, what instrument to try it on, and a frequency response graph.

Dynamic Mics

AKG D 12

The AKG D 12 is a dynamic microphone with a cardioid polar pattern. This means that it “hears” best what happens in front of it while rejecting sound from the sides or rear. The sound entry of the D 12 is bright nickel plated.

The dynamic transducer with its special “Bass Chamber” is handmade. The Bass Chamber boosts the lower frequencies in the 60 to 120 Hz range. The large diaphragm provides full, rich bass and ensures clean, undistorted reproduction at high sound levels. Its shock mount prevents pick-up of impact and structure-borne noise. A compensation winding rejects hum induction (from power lines, amplifiers, etc.) and a built-in windscreen eliminates pop noise.

Its unique sound established the D 12 as the world’s standard microphone for bass drum and bass instrument pick-up. the D 12’s frequency response extends down to 40 Hz, and the slight peak in the 60 to 120 Hz range enables the microphone to do full justice to the mellow, intimate quality of the trombone, tuba, or flügelhorn.

Features:
  • Full, punchy sound due to large diaphragm and special “Bass Chamber”
  • Excellent reproduction of low-pitched instruments
  • Handles high sound levels without introducing distortion
  • Cardioid polar pattern
  • Shock mount isolates transducer element from floor vibration

Technical Specifications
  • Transducer Principle: dynamic pressure gradient transducer
  • Polar Pattern: cardioid
  • Frequency Range: 30-15,000 Hz
  • Sensitivity at 1000 Hz: 2.2 mV/Pa ± –74 dBV re 1 µbar
  • Electrical Impedance at 1000 Hz: 260 ohms
  • Recommended Load Impedance: 600 ohms
  • Maximum SPL for 0.5% THD: 50 Pa ± 128 dB SPL
  • Hum Sensitivity at 50 Hz: 10 µV/5 ± T
  • Climactic Conditions: temperature range: –10°C to +70°C; relative humidity at +20°C: 90%
  • Connector Type: three-pin male standard XLR
  • Connector Wiring: pin 1: ground, pin 2: AF (in phase), pin 3: AF (return)
  • Housing Material: steel wire mesh 1.5 × 0.7mm
  • Finish: front grille glossy nickel plated, rear grille matte black paint
  • Dimensions: H 140mm (5½ in.), W 55mm (23⁄16 in.), D 76mm (3 in.)
  • Weight: 600g (21.2 oz.) net
AKG D 112

The AKG D 112 MkII professional dynamic bass drum microphone features a new integrated flexible mount, while retaining all the sonic strengths that have made it's predecessor the industry-standard. 

Over the years the D112 has earned a well-deserved reputation as one of the best bass drum microphones ever made, for its high SPL capability, punchy EQ and bulletproof construction. 

The D112 MkII can handle more than 160 dB SPL without distortion. Its large diaphragm has a very low resonance frequency that delivers a solid and powerful response below 100 Hz. 

Its authoritative low end is complemented by a narrow-band presence boost at 4 kHz that punches through even dense mixes and loud stage volumes with forceful impact. One of the many reasons artists and sound engineers love the D112 MkII is that it requires no additional EQ to sound just right as soon as you bring up the fader. 

Further refining its performance, the D112 MkII features an integrated hum-compensation coil that keeps noise to an absolute minimum. In addition to being an exceptional bass drum mic on stage and in the studio, the D112 MkII is an excellent choice for miking electric bass cabinets and trombones.

Audix D6

The D6 dynamic instrument microphone is used for stage, studio and broadcast applications. Designed with a cardioid pickup pattern for isolation and feedback control, the D6 drum microphone is equipped with a VLM™ diaphragm for natural, accurate sound reproduction.

Lightweight, compact and easy to position, the D6 cardioid microphone is an excellent choice for miking instruments requiring extended low frequency reproduction such as kick drums, large toms and bass cabinets. 

The D6's transformer less design, low impedance and balanced output allow for interference-free performance.

Applications
  • - Live stage, recording
  • - Kick drum
  • - Floor tom
  • - Bass cabinets
  • - Leslie bottom
Beyer M 201

The classic dynamic, "workhorse stable" microphone for all instrumental applications

Another microphone from the "workhorse stable", the M 201 TG preserves its place in history through sheer performance and reliability and we are proud that it has come to feature here with the classics. 

A truly sensitive dynamic microphone with a range of applications spanning instruments to vocals, being particularly effective when the microphone has to be placed at a distance from the sound source. 

It incorporates a "hum-buck" coil that rejects mains borne interference introduced when using the microphone close to video monitors or other mains powered devices.

Features:
  • Universal microphone for instrument miking
  • Integrated hum-buck coil
  • Small dimensions for unobtrusive positioning
  • Rugged construction
  • Supplied with microphone clamp and storage bag
Electro Voice RE-20

The RE20 dynamic cardioid microphone is truly an industry standard, a firm favorite among broadcasters and sound engineers worldwide. 

Its popularity also extends into music production as a premium grade instrument microphone. Its Variable-D™ design and heavy-duty internal pop filter excel for close-in voice work, while an internal element shock-mount reduces vibration-induced noise.

Features
  • Variable-D™ for minimal proximity effect
  • True cardioid with no coloration at 180-degrees off-axis
  • Voice tailored frequency response
  • Studio condenser-like performance
  • Large diaphragm
  • Humbucking coil 
  • Bass roll-off switch
Sennheiser E 609

Sennheiser e609 Silver Dynamic Instrument Microphone; Based on the legendary Sennheiser MD 409. Able to withstand high SPLs without distorting, the e609 Silver's flat-profile capsule allows extremely close miking of guitar cabinets and precise drum miking, particularly toms. 

The e609 Silver's super-cardioid design improves isolation while its increased output and wider frequency response improves performance. Its sound inlet basket, made of refined steel, is distinguished by a unique silver address side. 

Sennheiser Evolution e609 Silver Features Metal construction - rugged and reliable Super-cardioid pick-up pattern provides isolation from other on-stage signals Hum compensating coil reduces electrical interference Neodynum ferrous magnet with boron keeps mic stable regardless of climate.

Features

  • Exceptional full-size sound quality
  • Very high sound pressure handling capability
  • Super-cardioid pick-up pattern provides isolation from other on-stage signals
  • Hum compensating coil

Sennheiser MD 421

The MD 421 II continues the tradition of the MD 421, which has been one of Sennheiser's most popular dynamic mics for over 35 years. 

The large diaphragm, dynamic element handles high sound pressure levels, making it a natural for recording guitars and drums. The MD 421's full-bodied cardioid pattern and five-position bass control make it an excellent choice for most instruments, as well as group vocals or radio broadcast announcers. One listen and you'll know why it's a classic.

Features
  • Rugged professional microphone
  • Five position bass roll-off switch
  • Effective feedback rejection
  • Clear sound reproduction
  • Easy handling due to pronounced directivity
Shure Beta 52A

The Shure BETA®52A is a high output dynamic microphone with a tailored frequency response designed specifically for kick drums and other bass instruments. It provides superb attack and "punch", and delivers studio quality sound even at extremely high sound pressure levels. 

The Beta 52A features a modified supercardioid pattern throughout its frequency range to insure high gain-before-feedback and excellent rejection of unwanted sound. A built in dynamic locking stand adapter with an integral XLR connector simplifies installation, particularly if the microphone is to be placed inside a kick drum. 

The stand adapter keeps the microphone position fixed and resists slipping, even when subjected to sharp blows and strong vibrations. A hardened steel mesh grille protects the Beta 52A from the abuse and wear associated with touring.

Features
  • Frequency response shaped specifically for kick drums and bass instruments
  • Built–in dynamic locking stand adapter with integral XLR connector simplifies setup, especially inside a kick drum
  • Studio quality performance, even at extremely high sound pressure levels
  • Supercardioid pattern for high gain before feedback and superior rejection of unwanted noise
  • Hardened steel mesh grille that resists wear and abuse
  • Advanced pneumatic shock mount system that minimizes transmission of mechanical noise and vibration
  • Neodymium magnet for high signal–to–noise ratio output
  • Low sensitivity to varying load impedance
  • Legendary Shure quality and reliability
Shure Beta 57A

The Shure BETA®57A is a high output supercardioid dynamic microphone designed for professional sound reinforcement and project studio recording. 
It maintains a true supercardioid pattern throughout its frequency range. This insures high gain-before-feedback, maximum isolation from other sound sources, and minimum off–axis tone coloration. 

Excellent for acoustic and electric instruments as well as for vocals, the extremely versatile Beta 57A dynamic microphone provides optimal warmth and presence. Typical applications include drums, guitar amplifiers, brass, woodwinds and vocals. 

Features
  • Tailored frequency response provides drums, guitars, vocals, and horns with studio quality sound
  • Uniform supercardioid pattern for high gain-before-feedback and superior rejection of off–axis sound
  • Hardened steel mesh grille that facilitates use of proximity effect and resists wear and abuse
  • Neodymium magnet for high signal–to–noise ratio output
  • Minimally affected by varying load impedance
  • Advanced pneumatic shock mount system that minimizes transmission of mechanical noise and vibration
  • Legendary Shure quality and reliability
Shure SM57

The legendary Shure SM57 is exceptional for musical instrument pickup and vocals. With its bright, clean sound and contoured frequency response, the SM57 is ideal for live sound reinforcement and recording.
The SM57 has an extremely effective cardioid pickup pattern that isolates the main sound source while minimizing background noise. In the studio, it is excellent for recording drums, guitar, and woodwinds.

Outstanding performance, reliability, and application diversity make this "workhorse" the choice of performers, producers, and sound engineers worldwide.

Features
  • Contoured frequency response for clean, instrumental reproduction and rich vocal pickup
  • Professional-quality reproduction for drum, percussion, and instrument amplifier miking
  • Uniform cardioid pickup pattern isolates the main sound source while reducing background noise
  • Pneumatic shock-mount system cuts down handling noise
  • Extremely durable under the heaviest use
  • Frequency response: 40 to 15,000 Hz
  • Replacement cartridge: R57
Shure SM58

The legendary Shure SM58 vocal microphone is designed for professional vocal use in live performance, sound reinforcement, and studio recording. 
Its tailored vocal response for sound is a world standard for singing or speech. A highly effective, built-in spherical filter minimizes wind and breath "pop" noise. A unidirectional (cardioid) pickup pattern isolates the main sound source while minimizing unwanted background noise.

Rugged construction, a proven shock-mount system, and a steel mesh grille ensure that even with rough handling, the SM58 will perform consistently, outdoors or indoors.

Check out the history, the technology, the artists who use the SM58, and more at sm58.shure.com.

Features
  • Frequency response tailored for vocals, with brightened midrange and bass rolloff
  • Uniform cardioid pickup pattern isolates the main sound source and minimizes background noise
  • Pneumatic shock-mount system cuts down handling noise
  • Effective, built-in spherical wind and pop filter
  • Supplied with break-resistant stand adapter which rotates 180 degrees
  • Legendary Shure quality, ruggedness and reliability
  • Cardioid (unidirectional) dynamic
  • Frequency response: 50 to 15,000 Hz
  • Replacement cartridge: R59
Shure SM7B

The SM7B dynamic microphone has a smooth, flat, wide-range frequency response appropriate for music and speech in all professional audio applications. 
It features excellent shielding against electromagnetic hum generated by computer monitors, neon lights, and other electrical devices.

The SM7B has been updated from earlier models with an improved bracket design that offers greater stability. In addition to its standard windscreen, it also includes the A7WS windscreen for close-talk applications. 

Features
  • Flat, wide-range frequency response for exceptionally clean and natural reproduction of both music and speech
  • Bass rolloff and mid-range emphasis (presence boost) controls with graphic display of response setting
  • Improved rejection of electromagnetic hum, optimized for shielding against broadband interference emitted by computer monitors
  • Internal "air suspension" shock isolation virtually eliminates mechanical noise transmission
  • Highly effective pop filter eliminates need for any add-on protection against explosive breath sounds, even for close-up vocals or narration
  • Now shipping with the A7WS detachable windscreen, designed to reduce plosive sounds and gives a warmer tone for close-talk vocals
  • Yoke mounting with captive stand nut for easy mounting and dismounting provides precise control of microphone position
  • Classic cardioid polar pattern, uniform with frequency and symmetrical about axis, to provide maximum rejection and minimum coloration of off-axis sound
  • Rugged construction and excellent cartridge protection for outstanding reliability
  • Replacement cartridge:  RPM106

      Microphone Guide

      Microphones, or mics, are used to capture a sound much like our ears. Microphones are one of an audio engineer's finest tools. If you were an artist, microphones would be analogous to your color palette. Every microphone choice is like a stroke of the brush adding texture, tone, and color.
      Which microphones you choose can influence whether a recording is bright or dark, edgy or mellow, or muddy or clear. Three steps are involved in recording: capturing the sound, storing the sound, and listening back to the sound. The microphone represents the first step, capturing the sound.

      Getting to know how a microphone captures a particular instrument or sound takes time and experience. So what differentiates one microphone from another? Besides cost and esthetics, there are many other factors.

      Microphone Basics

      Microphones, or mics, are used to capture a sound much like our ears. Microphones are one of an audio engineer's finest tools. If you were an artist, microphones would be analogous to your color palette. Every microphone choice is like a stroke of the brush adding texture, tone, and color.

      Which microphones you choose can influence whether a recording is bright or dark, edgy or mellow, or muddy or clear. Three steps are involved in recording: capturing the sound, storing the sound, and listening back to the sound.

      The microphone represents the first step, capturing the sound. Getting to know how a microphone captures a particular instrument or sound takes time and experience. So what differentiates one microphone from another? Besides cost and esthetics, there are many other factors.

      When choosing a microphone, there are three major categories to consider:
      • Transducer/element type
      • Directional characteristic
      • Frequency response
      What is a transducer? A transducer converts one form of energy into another. Speakers, our ears, and microphones are all transducers. A speaker converts electrical energy into acoustic energy. Our ears convert acoustic energy into mechanical energy and then finally into electrical energy, which is sent to our brains. A mic converts acoustic energy into electrical energy.

      Transducers are often considered the weakest link in the recording chain. This is because they exist in almost every stage of the signal path. For instance, there are quite a few transducers involved in recording an electric guitar plugged into an amplifier.

      First, the pickup in the electric guitar is a transducer. This transducer takes the acoustic vibrations from the guitar strings and converts them into the electrical equivalent. This electrical signal is sent to the amplifier and converted back to acoustic energy through the amp's speaker.

      The mic placed in front of the amplifier converts the acoustic energy from the speaker back into electrical energy. The signal is then sent to headphones or monitor speakers and converted back to acoustic energy. Finally, acoustic energy travels to our ears where it is converted back to electrical energy, and then sent to our brains to be processed as sound.

      In this particular scenario, we have identified five transducers in the signal path of an electric guitar recording: the guitar pickup, the amp's speaker, the mic placed in front of the amp, headphones/ studio monitors, and our ears. If any one of these transducers is flawed or inadequate, the end result of capturing a quality guitar sound could be jeopardized.

      Basic Vocabulary

      • Transient – A short, quick burst of energy that is non-repeating. Commonly associated with the attack of percussive instruments. However, all music contains transients. In speech, transients are associated with consonants. Transients are typically weak in energy and associated with the higher frequency range.
      • Transient response – How quickly the microphone reacts to a sound wave and specifically to those transients just described. This differentiates one mic sound from another. Condenser mics typically have the best transient response.
      • Preamp – A control used to boost an audio signal's level. Microphones are plugged into preamps. The preamp knob is turned up to a useable and desired signal level. This level is generally sent to a recorder or a set of speakers
      • Leakage aka bleed-over – The amount of sound that bleeds into the source being recorded. Leakage could be anything from room ambience to another instrument sound. This is common when a full-band performs together with all the instruments in the same room or stage. Microphones with tighter pickup patterns provide less leakage from other sources and the environment. A mic with a hypercardioid pickup pattern provides the best isolation and prevents the most bleed-over from other sounds.
      • Pop filter – A nylon screen around a hoop or a perforated metal disk placed in front of the microphone in order to avoid plosive “b,” “p,” and “t” sounds that create destructive air movement. Pop filters are usually mounted on the mic stand with the mic or on a separate mic stand and are placed a few inches away from the mic. Pop filters are typically used when miking vocals. Some mics have built-in screens but an external filter is still needed. Filters also keep saliva off the actual microphone.
      Common switches found on microphones:
      • dB pad – Used to attenuate gain on a mic. Typically found on condenser mics. Usually specifies the amount of gain cut in dB: −10, −15, −20. Use this when miking louder sounds. Many mic preamps also have this function. This pad can identify a condenser mic, although not all condensers mics have dB pads.
      • Low-cut or high-pass – Used to roll-off low frequencies and pass highs. Typically found on mics with cardioid pickup patterns. The user can select where the cut takes place, such as 20, 75, and 100 Hz. Great for non-bass instruments. Can help clear up a sound, cut out mud, and reduce low frequencies. Pickup pattern selector – Allows the user to choose the directional characteristic of the microphone.
      • Shock mounts – Helps isolate the mic from traffic, thumps, and microphone stand transmission of sound. Included with many microphones, especially condenser mics.

      Transducer Types

      The first category to consider when choosing a microphone is the transducer type. Dynamic mics are built tough and can handle loud sound pressure levels. General characteristics and uses of a dynamic mic:
      • Very rugged, which makes it the main microphone type utilized in live sound.
      • Great for loud things such as amplifiers, kick and snare drums, toms, and horns.
      • Generally used in conjunction with close miking. This makes sense, considering that they are extremely rugged (they may be hit by a drumstick or two) and good with high sound pressure levels (a cranked amplifier).
      • General frequency response is between 40 Hz and 15 kHz.
      • Common dynamic microphones: Shure SM57 or SM58, AKG D 112, Sennheiser MD 421, Electrovoice RE 20, Audix D1 – D6.
      Condenser microphones are best at reproducing transients and generally provide greater clarity. General characteristics and uses of a condenser mic:
      • Excellent transient response; therefore, great for reproducing higher frequencies and quiet sounds. Adds “air” to a sound. Because the transducer is lighter, it reacts better to weaker sounds (highs).
      • Most require external power known as phantom power. Phantom power is usually located near the microphone preamp. It is often labeled +48 V. Engaging this button will supply a condenser microphone with its required charge. Some condenser mics can use 9 V or AA batteries to supply the charge.
      • Fragile. Condenser mics, unlike dynamic mics, are considered fairly fragile. Hitting a condenser mic with a drumstick or dropping it could be the end of this mic's life. ? Often have a dB pad. A db pad, used to attenuate input into the microphone, can help identify a mic as a condenser microphone.
      • Available as a Large-Diaphragm Condenser (LDC) or Small-Diaphragm Condenser (SDC).
      • Small-diaphragm condensers (SDC) are best at reproducing transients. Great for recording acoustic instruments, high hat, overheads on drums, room mics, flute, and shaker. Sometimes referred to as pencil condensers. Common SDC microphones: AKG C 451 B, Shure SM81, Rode NT5, Neumann KM184, and MXL 600.
      • Large-diaphragm condensers (LDC) are typically my choice for recording vocals. They add presence to vocals and usually help vocals sit in the right place. A LDC also exhibits better response to low frequencies and can help to fatten up an instrument or voice. It should be mentioned that ribbon mics and dynamic mics can also record vocals quite effectively.
      • General frequency response – 20 Hz–20 kHz.
      • Common LDC microphones: AKG C414; Neumann U 47 or U 67; AT4050; and Shure KSM27, 32, or 44.
      Ribbon microphones are often used to take the “edge” off an instrument's tone. General characteristics and uses of a ribbon mic:
      • Extremely fragile.
      • Great for digital recording!
      • Usually darkens and makes a sound appear smoother.
      • Great for room sounds, acoustic instruments, drum overheads.
      • Not meant for outdoor application (they don't like wind) although there are models that can be used in live sound or outdoor situations.
      • Can often provide a “retro” type sound.
      • Typically excel in the low-mid frequency range.
      • General frequency response is between 40 Hz and 15 kHz.
      • Common ribbon microphones: Royer R-121 or R-122, RCA 44, Beyerdynamic M 160, and Cascade Fat Head.
      Try setting up three mics, one dynamic, one condenser, and one ribbon. If you don't have all the three available to you, just use what you have. Mic a tambourine or shaker from about 1 ft away. These instruments produce a lot of transients and have very weak energy.

      Note the results. Which mic changed the source the most? Which one darkened the sound? Brightened the sound? Sounded most like the source? The lightest, most sensitive transducer will likely reproduce more highs. Note the results for future sessions.

      Directional Characteristics

      Pickup Patterns
      The next category to consider when choosing a microphone is the directional characteristic of the microphone, also referred to as a mic's pickup or polar pattern. The directional characteristic of the mic determines the direction from which the mic will be able to pick up the sound. When the mic is positioned as designed, this is called “on axis.”

      The pickup pattern also determines how well the recorded sound is isolated. Determining whether the microphone is a side or top address is also important.
      • Cardioid pickup patterns are the most common. Their pickup pattern is heart-shaped. Cardioid mics are sometimes referred to as unidirectional. With a top address microphone the sound is rejected from the rear of the microphone. Lots of cardioid pattern mics are used with live sound. This is because the mic rejects sound from the monitor and decreases the chance of a feedback loop.
      • Supercardioid has a pattern that is tighter than a cardioid pickup pattern. It rejects more from the sides, but picks up a small amount of sound from the rear. Most beta series mics have a supercardioid pickup pattern, such as a Shure beta57.
      • Hypercardioid is the tightest pickup pattern of all. It provides the most isolation for an instrument and virtually excludes the environment.
      • Subcardioid has a pickup pattern that is a cross between omnidirectional and cardioid. It rejects some sound from the rear of the mic.
      Microphones with cardioid pickup patterns exhibit proximity effect. Proximity effect is a lowend boost of 100 Hz + 6 dB when you get within a ¼″ of the diaphragm. Basically, you get a bassier tone as you place the mic closer to the source. There are three ways to avoid proximity effect.
      1. Back away from the mic.
      2. Use a low-cut filter or roll-off. Low-cut filters are located on the microphone itself or near the preamp section.
      3. Use a microphone with an omnidirectional pickup pattern. Mics with an omnidirectional pickup pattern do not exhibit proximity effect.
      Take advantage of proximity. A beefier, bassier tone can be achieved by placing a cardioid pickup pattern mic right next to the source. Beware, this can also make sounds muddy and overly bassy. Directional characteristics determine how isolated a sound will be from other sounds and how much environment will be heard in the recorded sound.
      • Bi-directional pattern picks up sound from the front and the back of the mic and rejects sound from the sides. Ribbon microphones tend to be bi-directional, although they come in all pickup patterns.
      • Omnidirectional pattern picks up sound pressure equally from all directions. It does not exhibit proximity effect and tends to have more “environment” in the sound and a flatter frequency response. It is often used when a reference mic is needed. Most lavalier mics are omnidirectional.
      It is worthwhile to mention that mics can be a combination of transducer types and directional characteristics. Any transducer can have any pickup pattern. Some microphones will have a pickup pattern selector switch where you can select different patterns.

      These switches are found on multi-pattern mics such as the AKG C 414, AT 4050, and Cascade Elroy. The transducer type influences the coverage area the mic picks up. If a condenser, dynamic, and ribbon mic with the same pickup patterns are placed in the same room, a condenser mic will pick up a much larger area.

      Frequency Response

      The last category to consider when choosing a microphone is the frequency response. Frequency response refers to how well a particular mic is able to respond to all the frequencies that strike it. Put simply, does the final result sound like the original source or does it darken or brighten the original source?

      Frequency response can be divided into two categories: linear and non-linear. Since a microphone is used to reproduce the source of a sound, the concern is how the microphone will represent and capture the original sound.

      A microphone with a non-linear frequency response will affect the source and alter the original sound. Will it make the original sound brighter or edgier? A microphone with a nonlinear frequency response will have peaks and valleys in its frequency response. Some engineers refer to this as “coloring” the sound.

      For example, you are miking a guitar amp that is very bright, with a lot of mid-highs/highs in the sound. Your intention is to darken the sound, or at least, not accentuate the higher frequencies. In these circumstances, you might choose a microphone that has a frequency response to boost the lows or reduces the higher frequencies, most likely using a dynamic or ribbon mic to help color the sound.

      If you had chosen a mic with a brighter frequency response, like a condenser, the result would have been an extremely bright recording. Coloring a sound can be good or bad, depending just on what you are trying to achieve. A microphone with a linear frequency response is said to have flat frequency response.

      That means that it reproduces the sound in a much more transparent way. A mic with a flatter frequency response will be the best choice if the source does not require any tone alterations. Most mics come with a frequency response chart or at least specifications.

      You can also find additional technical information on the manufacturer's website. A microphone with a non-linear frequency response will color or alter the way the source sounds and will not capture the source in a transparent way. A microphone with a linear response will capture the sound in a much more transparent way altering the tone little, if any.

      Microphone Placement

      Where to Place the Microphone?

      Now that you know a little more about how microphones work, it is time to discuss where to place them. Mic placement is an art and is one of the engineer's most important tools. Mic placement is as important as mic selection. A cheap mic placed in the right place can be as effective as an expensive mic placed in a wrong place.

      Before you determine a microphone's placement, consider where the performers will be placed according to sight, feel, and acoustics. Don't overlook the importance of sight and feel, because both can heavily influence a musician's performance. Musicians use nonverbal cues to communicate when they are performing.

      Make sure the musicians have a line of sight between them in the studio. It is also important for the musicians to feel comfortable where they are placed. For instance, placing a musician who is claustrophobic in a small isolation booth probably will not result in a good performance, no matter what mic is used.

      Finally, have the musicians play their instruments in different locations and hear where they sound best. Many instruments will jump out when placed in the optimum spot in a room.

      Next, before deciding mic placement, it needs to be determined where the majority of the sound is coming from and the direction it is being projected. Note: some instruments' bodies have a single area from which the sound is being projected (a trumpet), while others may have several areas from which the sound is being projected (a saxophone).

      The easiest thing to do is simply listen to the instrument to find out where it sounds best and start by placing a mic there. After all, a microphone is being used to represent our ears.

      Be aware that moving a mic even a small distance can dramatically change the sound. It is often hard to determine how good something sounds without comparing it with another sound. Don't be afraid to move the mic around and compare it with other mic positions.

      Recording these positions and comparing them can be helpful. Keep in mind that sound is divided into three successively occurring categories: direct path, early reflections, and reverberation.

      The direct path is the quickest path to the listener and it helps determine where the sound is coming from and provides a clear sound. Early reflections occur right after the direct path and clue us in to the surface(s) of the environment.

      Finally, the reverberant field is the last part of a sound heard and helps us identify the size of the space or environment. This is especially important when deciding where to place a mic.

      Four Fundamental Styles of Mic Placement According to Distance

      Here are some great starting points for miking instruments. Note that each position yields a different result and each position either accentuates the sounds direct path, its early reflections, its reverberant field, or any combination of the three.
      1. Close miking – placing the mic from 0 to 1 ft from the source. This provides the best isolation for the source and reduces the environment in the sound the most. Picks up the “direct path” primarily with little or no early reflections or reverberation present in the sound. Provides an “in your face sound” that can be described as tight and clear. Ultimately, it isn't very natural (how many times have you stuck your head in a kick drum?); that is why it is common to combine close miking with other techniques or to add artificial reverb to the sound. Watch for proximity effect when close miking.
      2. Accent miking – 1–3 ft. Common with live sound. As the name suggests, it helps accent a sound. Great for soloists and ensembles. This miking technique captures both the direct path and early reflections, with a small amount of reverberation in the sound.
      3. Room or distant miking – 3 ft – Critical Distance is the point where the sounds direct path and reverberant field are equal. I would consider this the most natural miking technique. This is the distance we would listen to someone playing drums or playing a guitar through an amplifier. This technique is often combined with close miking. Room miking doesn't provide much isolation and will have a good amount of the environment present in the sound. When miking this way, the sound will be made up of the direct path, early reflections, and reverberant field more evenly. Try miking drums with a single large diaphragm condenser from 3 to 6 ft away. Drums will sound big and likely won't interfere spatially with close mics used on other instruments. Because the drums cannot be individually balanced, a good or an interesting sounding environment is essential with this method as well as good sounding drums.
      4. Ambient miking – Miking beyond the critical distance. Like room miking, it is often combined with close miking to retain clarity. With ambient miking the reverberant field is dominant and the source is usually less intelligible and clear

       Two Great Stereo Miking Techniques to Know

      Stereo miking involves using two or more microphones to represent an image. It makes a sound wider, bigger, and thicker. Actual stereo miking provides greater localization than taking a mono mic and applying a stereo reverb/ effect to the sound.

      In the age of digital recording, stereo miking will make an mp3 sound a lot more interesting and the sound will have more depth and character to it. With stereo miking you will record each mic to a separate track. You can then pan each track to opposite directions or anywhere in between.

      Make sure you hit the MONO button on your console, audio interface, or software application to insure that the mics are in phase.
      • XY is a great technique to use when miking yourself playing an instrument. This technique is considered coincident miking, meaning that the transducers are placed in the same place. XY provides a pretty good stereo image with little or no phase issues. Because time is not an issue between the transducers, phase is not an issue. This technique translates well in mono. Typically, two like microphones are used for this technique. SDC are often utilized in this technique, such as a pair of SM81s.
      • Spaced pair is a common stereo miking technique involving two mics spaced apart to capture a sound. Unlike XY, spaced pair can have some phase issues. This is due to the fact that time does become an issue with the spaced pair setup. Again, any time there is a time difference between two or more microphones, you will likely have some phase issues. This technique typically provides a more extreme stereo image than XY but doesn't translate as well in mono. Make sure that the two mics are placed three times the distance from each other as they are placed from the source. This will help with phase issues. Keep in mind the 3:1 rule when using multiple microphones.

      Direct Box

      In some cases, you may use a direct box instead of miking up an instrument. A direct box is most often used with bass guitar and electric keyboards. Direct boxes are also used with stringed instruments such as violin, cello, and acoustic guitar.

      It eliminates the need for a mic by taking the instruments line out and converting it into a mic input. This direct signal is supplied by the instrument pickup or line out. Direct boxes can be either passive or active and some require phantom power.

      Quick Mic Setups

      How to Mic a Drumset

      Unless you have an unlimited amount of time, keep it simple when miking a drumset. Many classic drum sounds used only a few mics. Of course, that technique won't work for all styles of music but it works for most.

      Dynamic mics are typically used for close miking of drums and overheads and room sounds are represented with condenser or ribbon mics. In the following illustrations, I demonstrate four ways to mic up a drumset.

      Try using a single large diaphragm condenser or ribbon mic and placing it about waist high 3 ft from the kick drum. Raise the mic up if you want less kick and you desire more snare drum. Close miking a kit takes time but it can result in a tight, dry sound. Place a dynamic mic a few inches away from each drumhead at an angle of 45–60 degrees.

      Place a stereo pair of condenser or ribbon mics in the room. Remember that if you use a spaced pair, don't forget to apply the 3:1 rule discussed earlier in this chapter. A simple way to get a quick and decent drumset sound is by placing one mic over the center of the kit to capture the snare, toms, and cymbals.

      Try using a condenser or ribbon mic for this. For the kick drum, try placing a dynamic mic inside the drum and adjusting it until you get the desired tone. A great stereo drum sound can be achieved easily with the top/side miking technique.

      With this method place two mics equal distance from the snare (a mic cable is handy to measure the distance), one mic is placed over the drummer's shoulder and the other mic is placed lower on the floor tom side. Pan the mics opposite directions.

      Since the two mics are equal distance from the snare, the snare will be in phase and no mic will be needed to hear the snare drum. Place a mic inside the kick drum for the low-end.

      How to Mic a Bass

      The most common practice is to use the direct sound from the bass and avoid using a mic. Try a direct box or a direct output from the bass head. If you do mic the bass amp, try a dynamic mic up close and/or a condenser mic in the room. To get tricky, you could blend all the three sounds: the direct signal, the close mic, and the room sound.

      How to Mic a Guitar Amp

      The fastest way to mic up a guitar amp is to place a close mic on the speaker. If you want a brighter, tighter sound, position the mic close to the center of the speaker. A darker, looser tone is achieved by placing the mic more to the outer edge of the speaker.

      If you have more than one track for guitar at your disposal, try combining the close mic with a ribbon mic that is placed 1–3 ft away from the amp. Some engineers like to record a DI signal from the guitar at the same time as the microphones.

      Although you may not use it in the final mix, it will be invaluable later on if you need to reamp.

      How to Mic an Acoustic Guitar

      The easiest and fastest way to get a good acoustic guitar sound is to place a mic about 5″ away from the 12th fret (the double dots on a guitar).

      How to Mic a Vocal

      Every voice is unique. Once you figure out what mic sounds best on the singer, place the mic about 6″ away from the singer. To determine what mic sounds best, setup two mics at a time, side by side, and compare the results. Repeat this until you are satisfied.

      How to Mic Backing Vocals

      Try placing an omnidirectional mic in the room and have the musicians circle around the mic. Move the singers around until you have your desired blend. Try doubling the backup vocals and panning the two tracks for an even bigger, thicker sound.

      For more on microphone techniques check out Practical Recording Techniques, Bruce Bartlett, Focal Press, 2008.

      Equalization (EQ) and Frequency


      Equalization, or EQ, can be used to describe the action of equalizing a sound, a control to change the tone, or a reference to the tone of a sound. More than likely you have already equalized something in your life. If you have ever changed the bass or treble settings on your car or home stereo, then you have performed this basic engineering function. In audio production, there are a variety of equalizer controls at your disposal, to change the tone of a recording.
      Equalizers, also called EQs, are available as standalone rack units, as part of a channel strip, and as software plug-ins. What actually happens when a sound is equalized? The tone of an overall sound is altered by increasing or decreasing the amplitude of a particular frequency or a range of frequencies, such as bass. Remember the terms frequency and amplitude? They are two essential elements in understanding audio, especially when we are discussing equalization.

      Understanding the different frequency ranges and how to describe them is a necessary skill before you can begin to equalize. It is important to be familiar with specific frequencies and how they are often described and reproduced. This will make it much easier for you, as an engineer, to create or re-create a sound the client may be describing.

      Although there are exceptions, most musicians do not communicate using technical terms like “boost 100 Hz 3 dB on my bass.” They are more likely to describe something in layman's terms. “I wish my bass sounded ‘fatter’,” or “My bass sounds too ‘thin’.”

      While there is no universal language to describe sound, there are many helpful ways to communicate with musicians who may describe sound quality in their own ways.

      Boost or Cut

      As previously stated, equalization is boosting or cutting a frequency or a range of frequencies by using an equalizer. Boosting a frequency increases the amplitude (volume) of a particular tone or pitch. Cutting a frequency subtracts amplitude from a particular tone or pitch.

      If a frequency is neither boosted nor cut, it is said to be “flat.” In music production, a flat frequency response does not have a negative connotation, like a “flat note” or “flat performance” does. It simply means no particular frequency range is added or subtracted from the sound.

      Slope

      When a sound is equalized, the frequency that has been boosted or cut may be referred to as the “peak” frequency. Typically, this will be the frequency that is boosted or cut the most. Other frequencies are affected on either side of the peak. This area is known as the slope, or Q.

      Low-Cut or High-Pass Filters

      A button or switch often located on a console, preamp, or mic, when selected, cuts low frequencies and passes high frequencies at a predetermined setting. It does not allow you to control Q. These EQs also come in a high-cut or low-pass filter. A low cut is great to clear up any “mud” in a mix (see muddy, below).

      Try applying a low cut to instruments that don't have lows (electric guitar and snare drum) and a high cut to instruments that don't have highs (bass/kick drum). These filters can help eliminate any extraneous or unwanted frequencies in the instruments, leaving only the desired sound.

      Applying high and low cuts for clearing recordings of unwanted frequencies also helps in reducing the overall headroom of a track, allowing it to be louder overall without clipping (distorting).

      Subtractive Equalization

      Subtractive equalization is a technique used by most professional engineers to create clearer, more defined mixes. In order to have a clear mix where all instruments are heard, space will need to be made. Two sounds cannot occupy the same tone or frequency range and maintain clarity.

      If two sounds do occupy the same frequency range, the louder sound may mask, or hide, the quieter sound. Ultimately, mixing is about “crowd control.” Space must be created for a sound to be heard. Many inexperienced engineers tend to add what they want to hear first.

      For instance, if the goal is a bigger, bassier kick drum, a novice may add more bass to the mix. A better solution is to take away from one of the other frequency areas that are dominating the sound, for example, reducing the amplitude around 600 Hz.

      The result will be more bass on the kick without adding destructive low-end. When mids or highs in the kick drum are cut, more bass will be present. Also, the area that has just been cut opens up more space in the mix for other instruments to be heard. This is the subtraction in subtractive equalization. This doesn't mean that frequencies should never be boosted.

      Start by subtracting first, and then add frequencies only as needed.

      General EQ Areas

      Frequency recognition is crucial to being successful in audio production. One of the easiest ways to become familiar with the different frequency ranges and the number that goes with them is to initially divide them up in the following manner:
      • 100 Hz – makes things bigger, fatter (kick drum).
      • 1 kHz – adds attack, makes the sound more “In Your Face” (snare drum).
      • 10 kHz – makes a sound airy, breathy, or brighter (hi-hat or cymbals).
      These are great EQ starting points. After you have taken out any unwanted frequencies (applied subtractive EQ'ing techniques), ask yourself, “Do I want the sound to be fatter, more up front, or brighter?” If the answer is “fatter,” start at 100 Hz and adjust from there. If the answer is “more up front” or “more aggressive,” boost 1 kHz.

      It may turn out that the correct equalization is another frequency like 2 kHz or 900 Hz. Whatever the adjustment, the key is in getting to the general area. If the answer is brighter, breathier, or airy, try boosting 10 kHz. Ultimately, a different frequency may be boosted, but adding 10 kHz should get you started.

      With some generalization and through communication with the client, it will be much easier to recognize the frequency that needs to be adjusted. Locating and equalizing something quickly will hopefully keep a client happy and coming back for more!

      The following are seven common EQ points of interest: subs, big/fat, muddy, boxy/hollow, in your face!, presence/clarity, and airy. Becoming familiar with these seven areas can help you locate a specific EQ point quickly. Following this section are even more terms to help you describe and communicate audio frequencies and sounds.

      Subs (Below 80 Hz), Low Frequencies

      Frequencies below 80 Hz can make sounds huge and are referred to as “subs.” Subs are often accentuated in various dance, electronic, rap, R&B, and reggae styles of music. This is the frequency area that is represented by a subwoofer. Pay close attention to this frequency area. Too much sub information can dominate a mix and make the other instruments appear weak and hidden.

      Big/Fat (20–200 Hz), Low Frequencies

      The low-frequency area generally makes sounds appear bigger and fatter. The human ear doesn't hear bass as well at lower volumes. But when we do crank it up here, terms such as big, fat, beefy, huge, and thumping are used to describe these powerful wavelengths. Too much sound here can blanket a mix, and not enough could make a mix sound weak.

      Muddy (100–300 Hz), Low – Low-Mid Frequencies

      Too much of the low and low-mid frequencies can muddy an instrument or mix. If a sound isn't very clear, or muddy, try subtracting between 100 and 300 Hz. This is especially helpful with vocals, acoustic guitars, and piano. Because close miking can cause proximity effect, a low-end boost of around 100 Hz, it is often unnecessarily present, and will likely need to be rolled off.

      Boxy/Hollow (300–700 Hz), Low-Mid Frequencies

      The frequency range 300–700 Hz is often described as boxy or hollow. This is typically an area where subtractive EQ is applied, although there are always exceptions. Kick drum mics are often designed to cut frequencies from this area.

      Subtracting low-mids can clean up a sound and make it more distinct, but it can also leave a sound hollow and colorless. This is not the most flattering frequency area on many instruments. An electric guitar tone, if described as boxy, has too much of this frequency range. A boxy sound can also be the result of overly compressed audio with a very fast attack setting, especially with a snare drum or tom.

      In Your Face (1.5–4 kHz), Mid-Mid – Upper-Mid Frequencies

      Sounds in the midrange area, especially in the mid-mid and upper midrange are best heard by the human ear. This is the area between 1.5 and 4 kHz. This also happens to be the same frequency area as a baby crying.

      Because we hear best in this area, sounds often appear “In Your Face.” 1.5–4 kHz is often described with aggressive terms such as slap, bite, crunch, edge, and attack. Punk rock music accentuates this frequency range. Some country, folk, and acoustic music might also have more sounds in the midrange. Too much here can cause ear fatigue, whereas not enough here can make a mix or sound appear dark and distant.

      Presence And Clarity (4–10 kHz), Upper-Mid – High Frequencies

      The frequency area between 4 and 10 kHz is an area that can add presence and clarity to a mix. Often vocals are emphasized in this range to help them cut through or sit on top of a track without making the vocal sound too edgy. Note that sibilance is also in this area. Sibilance is associated with the “s” sound and this frequency area may need to be carefully managed with some singers. A de-esser is often used to help remove or soften sibilance. Inclusion of just enough information here makes a mix have presence and clarity.

      Airy (Above 10 kHz), High frequencies

      Frequencies above 10 kHz make sounds appear higher in the mix. Make sure to highlight this area to make a vocal, string, tambourine, or any other sound appear airy, breathy, thin, or bright. Transients and harmonics dominate this range.

      Terms associated with the sky are often used to describe this area: airy, sunny, bright, light, angelic, clouds, sparkle, and feathery. This frequency range often helps differentiate what is considered high fidelity (hifi) and low fidelity (lo-fi). A lo-fi recording will likely have very little, if any, frequency information above 10 kHz.

      Pay special attention to the range of frequencies below 80 Hz. This is the most destructive frequency range and too much here can negatively affect a mix. On the other hand, just enough of this frequency range can make a mix sound huge and powerful!

      Adjectives: Speaking About Audio Using Plain English

      Additional adjectives are needed by nonengineers to describe a tone, sound, or the physical space that surrounds a sound. Although professional engineers typically use more technical descriptions, particularly in discussing frequency ranges, most engineers are familiar with interpreting a musician's request.

      It is likely that not all engineers will agree on the definitions used here, because of the subjective nature of describing sound, but I have full confidence that these terms, in most cases, will help you communicate and interpret ideas related to music production.
      • Angelic – Usually a sound buried in a large reverb and with the high-frequency range accentuated. Try applying a “cathedral” or “church” reverb and boost the extreme highs.
      • Beefy – Probably a sound with a lot of low and low-mid frequencies. May also be described as “thick.” Guitarists often request a beefy guitar tone. When the term beefy comes up, think of a sound with a solid lowend that probably isn't too quiet in the mix.
      • Big – Contains a lot of low-end. Associated with the frequency range 20–200 Hz. A large room can make a big sound seem even bigger if miked from a distance. Applying certain reverbs may also make a sound appear bigger. Some musicians may also say that they want a bigger sound and all they really want you to do is turn it up!
      • Bite – A sound emphasized in the midrange area. If a snare is described as having bite, imagine the snare being tight and in your face. It would sit somewhere between 1 kHz and 3 kHz. Some guitar tones are often described as having bite.
      • Body – Depending on the frequency range of the instrument or voice, the lower frequency area would need to be dominant. Often people want to hear the body of an acoustic instrument, such as an acoustic guitar or snare drum. This request would require plenty of 100–250 Hz present in the sound.
      • Boomy – A sound that is boomy resides in the low and low-mid frequency range. Similar to body but is generally more of a negative term. Try cutting between 100 and 400 Hz to reduce boominess.
      • Brittle – As the word suggests, it means “about to break.” This is seldom a flattering term. A brittle sound lacks low frequencies and highlights the upper midrange and high-frequency area above 3 kHz. Cheap digital equipment can make the high frequencies sound brittle.
      • Breathy – A term often associated with a vocal tone. A breathy tone would be dominated by high frequencies. Try boosting 10 kHz and up for a breathy vocal. This can be achieved by EQ and/or compression.
      • Chimey – Contains mostly high frequencies in the sound and would accentuate an instrument's upper harmonics. Can be found in the 10 kHz and up range. Similar to glassy.
      • Chunky – A chunky vocal or guitar tone would have a lot of low-mids and would likely have emphasis in the 100–300 Hz area. Similar to a thick sound.
      • Crispy – Think of sizzling bacon. A crispy sound would emphasize the upper-mids and highs above about 4 kHz. A crispy sound may even have some distortion present. Not usually a flattering term.
      • Crunchy – A crunchy sound often involves some degree of distortion or overdrive. The emphasis is in the midrange area between 1 and 4 kHz. Crunchy may be used to describe a certain guitar tone.
      • Deep – A sound that has a lot of depth to it from front to back, or enhanced low frequencies under 250 Hz. An example would be a deep bass tone.
      • Dirty – The opposite of a clean, clear sound. A dirty tone would have some amount of distortion, noise, or overdrive in the signal. Similar to fuzzy.
      • Distant – If a sound lacks midrange and high frequencies, it will appear further back in the sound field. Add upper-mids or high frequencies to make a sound less distant. A distant sound could also mean that it is too low in the mix or has way too much reverb.
      • Dry – A sound with little or no FX can be described as dry. A dry sound would not have reverb or other obvious effects present. A dry sound is most common with folk, bluegrass, and acoustic styles of music.
      • Dull – A sound can appear dull if it is lacking energy, highs, or is overly compressed. Add upper-mids or highs to a dull sound, or slow the attack setting on a compressor to make a sound less dull.
      • Edgy – Describes a sound that accentuates where we hear best, in the 1–4 kHz range. An edgy sound can make the listener feel uncomfortable like nails scratching on a chalkboard. Definitely in your face!
      • Fat – A fat sound accentuates the lower frequency range. A fat guitar tone, a fat vocal, a fat kick, and a fat snare sound are common requests. The fat frequency range would be around 20–250 Hz.
      • Fuzzy – Describes a tone that is not clear and likely has a substantial amount of overdrive or distortion associated with it.
      • Glassy – A glassy sound is a very thin sound with lots of apparent highs. Definitely not bassy! A clean, electric guitar tone that is extremely bright could be described as glassy.
      • Hard – A hard sound has a lot of midrange and accentuates the attack part of a sound's envelope. Harder frequencies are found between approximately 1 and 4 kHz.
      • Hollow – A hollow sound lacks a portion of its frequency range. This can be caused by phase cancellations due to room acoustics or other variances.
      • Hot – A sound described as hot may mean that it is turned up too loud, or the high frequency range is more noticeable. Try turning the amplitude down or rolling off some higher frequencies.
      • Huge – Describes a sound with excessive lows or one that is recorded in a big space.
      • Loose – A loose sound would lack the harder mid-mid frequency area. Loose could also describe a space or environment that has very little treatment and results in a less focused sound.
      • Mellow – A sound lacking upper-mids and highs is often described as mellow. A mellow guitar tone would be a darker, tubey sound as opposed to a distorted, in your face tone with a lot of 2 kHz present. Also, reverb can mellow a harder sound.
      • Muffled – A muffled sound would be dominated by low and low-mid frequencies in the 100–250 Hz range, resulting in a tone with less presence and clarity. Imagine singing with a blanket over your head.
      • Nasally – Often used to describe a vocal tone. Try cutting between 500 Hz and 3 kHz. People may also describe this same area as telephone-like, honky, or tinny.
      • Ringy – A ringy tone will be dominated by the mid frequencies. Snare drums are often described as ringy. A ringy tone is produced when the mic is placed close to the drum rim and both heads are tuned extremely tight. Taking away frequencies between 900 Hz and 3 kHz will likely reduce a ringy tone.
      • Shimmering – A sound dominated by extreme highs. A shimmering sound is in the 10 kHz and up range. To create a shimmering sounds boost the upper highs.
      • Shiny – Similar to shimmering. A shiny sound has plenty of highs.
      • Sizzly – Rarely a flattering term, sizzly describes a tone with a great deal of treble. Something referred to as sizzly can also be called glassy or crispy.
      • Slap(py) – Usually associated with the neck of a guitar or bass, or the kick pedal striking the head of a drum. More slap would be in the 500 Hz–3 kHz range. It can also describe a sound reflecting back, as in a slap echo.
      • Small – A small sound would either be overly compressed or a sound with little low or low-mid frequencies. It is likely that a small sound wouldn't have frequencies below 200 Hz. Close miking produces a smaller sound versus room miking. A snare or guitar amp may appear smaller when mic is extremely close.
      • Smooth – A smooth tone generally has a flatter frequency response. No frequency range would be emphasized over another. It can also be described as easy on the ears.
      • Soft – A soft tone typically lacks the harder midrange frequencies. Therefore, it is safe to say that extreme lows, extreme highs, or a combination, creates a softer sound. It could also refer to volume. If it is too soft, turn it up. If it's not soft enough, turn it down.
      • Thick – See beefy. A sound that is thick has plenty of lows and low-mids. The thick area is between 20 and 300 Hz. Thin – A sound that is not very fat or deep. A thin sound is dominated by upper-mids and high frequencies above 4 kHz.
      • Tight – Tight sounds have very little reverb or environment in the sound. Close miking an instrument or voice will result in a tight sound. A tight sound is dominated by the direct signal instead of the early reflections or reverberant field. Any frequency range can be considered tight, but it is often used to describe a bass or kick drum sound that is too boomy or resonant.
      • Tinny – A tinny sound is a thin sound dominated by the mid-mid and upper midrange. If the vocals are described as tinny, it is not a compliment. Try cutting between 2 and 7 kHz or adding some low or low-mid frequencies.
      • Tiny – A sound with extreme highs and almost no lows will likely sound tiny. Not enough volume may also make a sound tiny.
      • Tubby – An unflattering term that describes too much low or low-mids in a sound. Try cutting between 100 and 400 Hz.
      • Warm – A warm tone accentuates the low and low-mid frequency range. Analog tape and tube amps are often described as warm. The opposite of a warm sound would be a cold or brittle sound.
      • Wet – A wet sound or wet mix would have an obvious amount of FX present. The opposite of a wet sound is a dry sound. If the vocals are drenched in reverb and the guitar sounds like it is floating in space, then you have achieved this adjective.
      Here are some more helpful terms when communicating with others about the quality of sound:
      • If a sound lacks highs, it may be described as dark, distant, or dull.
      • If a sound lacks midrange, it may be described as mellow, soft, or unclear.
      • If a sound lacks lows, it may be described as thin, small, or bright.
      • If a sound has too little reverb, it may be described as dry, dead, flat, or lifeless.
      • If a sound has too much reverb, it may be described as wet, muddy, washy, distant, or cavernous.
      • If something is too loud in a mix, it may be described as in your face, up front, on top, forward, masking, dominating, hot, or separate.
      • If something is too quiet in a mix, it may be described as buried, masked, hidden, lost, in the background or distant.
      People communicate differently when referring to the quality of sound. By learning to describe sounds in a descriptive manner, you will be able to identify and execute a sound change much more quickly than randomly searching for an unknown frequency or sound.

      These terms offer a starting point when equalizing, applying reverb, or executing other audio engineering functions. Without this starting point, much time will be wasted turning knobs without direction.