GearCast - How to Compress Electric Bass

Most of the time, the desired result for bass is to provide a uniform, even bottom end that becomes a consistent background for the other instruments. CompressionDefinition:
1. Reducing the dynamic range of an audio or video signal for consistency, to keep it from exceeding the available headroom, or providing a special effect. 2. With data, using a process to reduce the amount of data. Compression can be lossless, where decompressing replicates the original signal, or lossy, where compression occurs by judging some data as unnecessary, and can therefore be discarded from the file., which reduces dynamic rangeDefinition:
1. Range in dB between a device's noise floor and its maximum available headroom. 2. The difference between the maximum and minimum volume levels that occur in a musical performance. variations, can help achieve that goal by boosting soft sections and taming peaks.

The following offers suggested starting points for common compressorDefinition:
A device that reduces dynamic range by a certain ratio, and used primarily for audio signals. parameters (Fig. 1), but note that the input level is crucial. For example, if the input is always below the threshold, there won’t be any compression. These settings assume that the bass’s level to the compressor uses up most of the headroomDefinition:
1. The safety margin for an electronic signal that accommodates peak signals without overload. It is the difference (in dB) between normal operating levels (0-VU) and the clipping (overload) point. 2. The space between a subjects head or top and the top edge of a screen frame., and comes close to 0 dBDefinition:
1. A deciBel is a logarithmic ratio between two quantities, and is a nonlinear measurement that mimics human perception. 2. A unit expressing sound levels relative to a nominal level just audible by the average human ear, and equal to 1/10th of a Bel..

As you tweakDefinition:
1. To make minor adjustments. 2. A person who is a perfectionist. parameters, pay attention to the compressor’s gain reduction meter, which shows how much the compressor is restricting the dynamic range. For example, if the gain reduction meter shows ‑3 dB, that means the gain has been reduced by 3 dB to bring down a peak. Unless you’re going for a heavily compressed sound, you’ll probably want to compress by ‑6 dB or less. Also recognize that because the various parameters interact, it’s often necessary to go back and forth among several parameters until you dial in the exact sound you want.

1. Begin by setting the Ratio control to around 3:1. This means that for every 3 dB increase in input level above a specified threshold, the output increases by only 1 dB. Try a higher ratio if the bass signal is extremely uneven, but the higher the ratio, the more it will “squash” signals above the threshold. This can make the sound thinner. Because our ears are not particularly sensitive to level variations, it’s easy to over-compress—be careful.
2. Now set the Attack and Release (also called DecayDefinition:
   1. The natural volume falloff in an audio or resonating system, such as reverb, or an instrument's note. 2. A parameter in an ADSR envelope. See .) controls. Attack determines how fast it takes for compression to kick in once the signal exceeds the threshold, while release sets the time required to return to a non-compressed state after the signal returns below the threshold. Many compressors include an “auto” setting for these parameters, which is usually the easiest way to go and often nails the right values. Otherwise, start with a fast attack (0-20 ms) and medium decay (100-150 ms).
3. Next comes the Threshold control, which determines the level at which compression begins. Initially set it to the highest available value (usually 0 dB), which means only notes exceeding 0 dB will be subject to compression. Then, while the bass plays, look at the gain reduction indicator. Lower the threshold so that there’s an average of 2 or 3 dB of compression. The peaks from loud notes should indicate around 4-6 dB of compression. This is a common, “industry-standard” type of setting that avoids extremes.

If you need more compression to keep notes sounding even, lower the threshold so that compression begins with lower-level signals, or increase the ratio. But ideally, you don’t want to use too much compression. Hopefully, the bass player will have a sufficiently good “touch” that excessive compression won’t be necessary.

4. Compressing the dynamic range lowers the overall level; use the Output or Gain control to compensate. While observing the input levels feeding your mixerDefinition:
   Combiner, controller, and router for multiple audio or video signals. or recording software, adjust the output so that the maximum peak (not average) levels of the compressed and uncompressed signals are identical. You can tweak the output control a bit if you need more or less overall level.

Generally, the output gain will approximate the amount of gain reduction. For example, if the gain reduction meter shows 4 dB of gain reduction on peaks, set the output control to give +4 dB of gain.

5. Next, adjust the Hard Knee/Soft Knee switch, if present. Hard kneeDefinition:
   Abrupt onset of gain reduction in a compressor or limiter. adds more punch to the sound; for a ballad, soft kneeDefinition:
   Gradual onset of gain reduction in a compressor or limiter. See Knee. See Hard Knee. may be more appropriate, because the transition into compression is gentler, and more nuanced.

Once the general settings are squared away, you might want to re-visit the attack and decay settings. A fast attack compresses the beginning of the note’s transientDefinition:
A fast rising, non-repeating waveform, usually of short duration., which keeps the attack level even but reduces punch. The release timeDefinition:
With a dynamics processor, once the input signal drops below the threshold, the release time sets how long it takes for the dynamics processing action to stop. is a bit of a compromise. It needs to be fast enough so that it doesn’t affect the next bass note’s attack, but not too fast — because of the bass’s very low frequencies, a short decay setting may actually follow individual cycles of the string vibration, and cause a subtle distortionDefinition:
A change in an electronic or acoustic signal's waveform. This can undesirable if it impacts signal quality, or desirable when used for creative signal processing..

Select a very slow release (e.g., 250Definition:
Stereo Sound with 2 speakers and no subwoofer. See subwoofer. ms), play some notes, and listen to what happens. If the note attacks are low in volume because the release time has not yet recovered, shorten the release. Grammy Award-winning guitar player Jay Graydon says that the best way to find a good release time is to start with a fast release setting, and increase the time slowly. When you damp (hand muteDefinition:
1. To silence or squelch an audio signal. 2. A switch that silences a signal.) a bass string, the gain reduction meter should move back to 0 at a rate slow enough for you to detect, but not so slow as to take a significant amount of time.

Using EQ with Compression

If adding compression seems to make the sound smaller, try adding some low-end EQ around 100 Hz. Remember that placing EQ before the compressor increases the amount of compression in the frequencyDefinition:
A value, expressed in Hertz, that indicates how many cycles of a periodic signal occur in one second. range being boosted; because the EQ is increasing the level at those frequencies, they exceed the threshold more often. When adding low-end EQ, you may want to raise the threshold a bit to avoid over-compressing the lows compared to the rest of the signal.