Bass compressor - Bass Compressor Pedal - Bass Compression

A bass compressor is intended for the characteristics of bass guitars, so we could also say bass guitar compressor. Most common ones as "pedals". They might work well with other instruments too and electric guitars in particular because they rather have a wider frequency range, and lower.
I will both keep the level simple on this page, but I also include some things that I have thought about below.

*** Update ! ***
Read below in the "Bass compression"-part about getting a kind of bass compression using a gate ! It came to my mind two days ago when I was walking in a super market and I thought I would include it here!
Also I have included a "conclusion" in this page's topic, see below!

Bass compressors at amazon

Bass compressors are used to:
- Improve the bass sound either by flatten out, to "squeeze" the dynamics and/or the attack of the sound, or to make the attack stronger (longer attack time). The sound level/dynamics may sound more balanced.
- limit the dynamics more near clipping, so that it works both as a compressor and limiter. Limiting can protect amplifiers and speakers from damage due to signal overload, since bass signals are stronger.

Any compressor can, of course, work as a bass compressor, whether it be a studio, rack or stereo compressor but pedal compressors are probably the most used type.
The best bass compressor is defined by your own preferences and here is a valuable link that we made for you, to look up
bass compressor reviews as on harmony-central.

With recording experience, I have played bass and I have used a lot of various effects, not only for bass, so I think I know quite well about the various aspects that has to do with sound. Noone has used all gear but with some experience you could often understand what others are saying in their reviews.
So first a look at various bass compressor models and compressors that can be used for bass.

Keeley compressors

Keeley compressor.
Keeley compressor plus.

Newer models as of now have internal controls for attack time and input sensivity which sounds as another name for input gain. used to match to signal levels from other sources.
Keeley Compressor
Keeley compressor reviews -
Keeley compressor reviews -

Keeley compressor plus

The attack and input controls on the box.
Keeley Compressor Plus
Keeley compressor plus reviews -

Bass compressor pedal

T Rex Squeezer tube bass compressor.

T Rex Squeezer tube bass compressor pedal.

Because they are portable, can be quite cheap yet quite good and easy to control. Some popular bass compressors that are looken at on this page is the T-Rex tube bass compressor to the right and dual band bass compressor pedals below.

Bass compressor pedals can infact sound subjectively better than professional studio compressors because some pedal compressors use simplified electronics that shape the tone, timbre etc of the sound in a combined way, that professional compressors don't.

Compressor vs. tube compression

A tube compressor will also perform a tube gain compression which is a compression that is independent of time settings as with attack and release time.
Infact, any tube stage, as a tube preamp, will have tube compression. If you are impatient, you may already now go to the chapter below, Mild bass compression done better with a tube preamp/amp .

Best compressor for bass

The best compressors for bass are depending on the preferred style. Generally, studio compressors should for the most have a good audio. Because they are too large to carry around, compressor pedals are more used. Many bass compressor pedals have simpler electronics which infact may give a certain character that a studio compressor would not do.

Bass compression

Bass compression is the name of the bass compressor effect. Bass compression can be realized with other devices than a bass compressor. It merely came to my mind, a sound that sounds as a bass compression.

Use a gate to get a good studio bass line sound <--- Good tip !

Namely, there is a bass sound in Alan Parsons project - The raven. Listen in the beginning. It is a bass sound, sounds very compact and it has a fast yet a mild attack. A couple of years ago I somewhat recreated that sound quite well using a gate on a bass guitar. I used a Vesta Kaza DG-3 but any good gate unit should be ok. Quite short attack time but not too short, and short to medium release time and the threshold set to trig just above the normal playing level. A gate causes a delay of the initial sound but this delay is so short, like a few mS so it doesn't care. If it would, the bass sounds can be delay-corrected/moved back a little, in a studio recording program.

2-channel Gate Vesta Kaza DG-3

My gate looks a lot better than this one !

Bass limiter

Bass limiter Boss LM-2

The Boss LM-2 was sold from 1987 until 1992.

Simply a limiter intended for bass. The most popular bass limiter is probably Boss LM-2.

Compressor limiter

A compressor limiter can mean two things. Either a compressor with a fixed high compression ratio = limiter. Or it is a compressor with variable ratio that can be set to work also as a limiter.
Limiting limits just before clipping otherwise would occur, to protect the output from getting too high. This also protects the amplifiers and speaker(s).

A bass compressor pedal, or another compressor, is often used with a bass amp, especially if the amplifier doesn't have a compressor, as with older bass amps. Typically, a bass compressor or other compressors have more functions than a compressor section in an amplifier.

Compressor parameters

The compressor functions, or parameters, are commonly attack and release time, ratio and threshold. Most bass amps with a compressor do not have these controls so it is worth giving some info about the very good advantage of having a separate bass compressor, which is even designed for bass.

Bass compressor attack and release settings

The combinations vary for different sounds. Often a preferred sound has a smooth balanced decay between pauses, giving more "sustain" and being somewhat flat/compressed though with some dynamics left.

Basically, there are four extreme settings:

1. Short attack and short release time:

A short attack lowers the transient level (over the compression threshold), making the sound more flat. With a short release time, the compressor may react sooner, on transients coming after.

2. Short attack and long release time:

A long release time still holds down the gain even if the signal level has fallen. If the signal comes back before the release time has decayed, its gain is low until the release time is over. Though the level is then still low, a first transient in the sound will be heard.
This setting is generally not well for music but there are always exceptions for various situations.
This setting is common in agc-circuits (automatic gain control) in so called AM/SSB/shortwave receivers where the "AGC" can be switched between "Fast" (fast attack and release time) and "Slow" (fast attack and slow release time).

3. Long attack and short release time:

This keeps the original transient since it takes time for the transient to get compressed. If more "punch" is wanted, this may be a way to do it. With a short release time, the compressor may react shortly after in the same way.

4. Long attack and long release time:

This setting also emphasizes the first transient but the sound has to decay otherwise next transient becomes compressed.

Compressor distortion

Unsymmetrical waveform at fast attack compression.

Fast attack time can make the first waveform unsymmetrical.

Smoother transient at medium attack with delayed compression.

Medium attack time delays compression which gives a smoother transient.

Going into theory, about frequency and time. The lowest frequencies on a four-string bass guitar go down to ca 40Hz and the time for a 40Hz waveform to reach from zero to peak is [1/40]/4= ca 6ms. If the attack time is too fast, like 5ms, the first half waveform and transient will be unsymmetrical and the transient will have overtones that are above one octave, which might give a too edgy sound.
Seen to the right are oscilloscope images of a compressed sine wave.
Although this is quite a theoretical approach, the first example shows that the first transient is not symmetrical because the first waveform gets compressed before it is complete.
In the other example, the attack time is longer, making the first halv waveform smoothed out into compresssion better, making more of an one-octave up overtone transient and generally considered as more musical.
In reality, differences can be larger than in these examples but even small differences as shown here, can make audible changes in the sound. Different compressor manufacturers may have their own circuits so it is worth looking at various compressor reviews.

Bass compression distortion

Human hearing frequency range curve/graph

The non-linear bass frequency perception emphasizes the perceived loudness of one-band compressor distortion. For the low E, 40Hz, the random compression distortion also creates the non-musical 3rd overtone at 120Hz. If this 3rd overtone would be at a 5% level, the perceived level will be 15 - 25dB more depending on the sound level, which is about 30% to 85%.
There are similar non-linearities at about 1.5k to 4kHz but for a bass, those frequencies are above the string's funtamental frequencies.

Now let us look at this a little more. It is a well known fact, that a bass guitar may sound quite differently with various bass compressors. A circumstance, as shown below, is that compression alters the first waveform each time compression acts on the first part of the signal. Hence harmonic distortion is created. The bass frequency harmonics are heard relatively stronger than its fundamentals due to the non-linear human hearing characteristics as seen to the right. When the sound from the lowest E-string on a four string bass guitar is compressed, then the compression alters the waveform, resulting in 2nd and 3rd harmonic distortion which is perceived 10-15 and 15-25dB stronger than the fundamental E-tone, due to the hearing non-linearity, which is more significant at the lowest frequencies.

This distortion is randomly symmetrical and asymmetrical which affects the sound a lot. Symmetrical distortion only has odd order harmonics (3rd, 5th, 7th etc). Asymmetrical distortion creates also even harmonics (2nd, 4th, 6th etc) which is considered more musical. But this distortion pattern, or asymmetrical/symmetrical ratio, will be non-linear throught the frequency range so we may believe that keeping this distortion should be as low as possible.

With a dual band compressor (see below), the upper distortion of the first compression band is more or less filtered out. Each band's circuit can be optimized to match even though the compressor may have controls that affect overall settings.

Mild bass compression done better with a tube preamp/amp

There is another way to obtain more musical compression with less odd order distortion. However if a bass limiting sound is preferred, a compressor (also) with a high compression ratio (=limiting) has to be used. But what other devices can provide a more musical compression? Namely, class A tube compression. When used for bass, there will be a tube compression with asymmetrical distortion.

A tube compressor (with compressor circuits) will provide more perceived odd order compression distortion when used for bass.

Tube compressors do well for vocals and sometimes for a whole mix, if the circumstance for bass compression distortion is lowered with a tube compressor's side chain filtering. But if a mild bass compression is preferred, then it is very much a good idea to try out class A tube preamps or even solid state preamps that emulate the asymmetrical characteristics of class A.

If heavy compression/limiting is wanted, a tube compressor will create odd order distortion unless two or more bands are used to lower it. A dual band tube bass compressor could create symmetrical/even order distortion and minimize the odd order distortion. But I do not know of any "dual band tube bass compressor".


The conclusions are, when a bass "tube sound" is preferred, and a compressor with ability for more compression is wanted, except for the mild tube compression which always happens in class A stages, a dual or multi-band compressor (solid state or tube) should sound more musical with less odd compression overtones, than a standard class A tube compressor.
Therefore, a good combination would be a tube bass preamp for mild tube compression with even overtones, and a multiband compressor (which all of them are solid state). For mild compression, only the tube preamp would do quite well and for more compression, the other multiband compressor would be used.

Dual band bass compressor pedals

Dual band compressors have been mentioned so what is there available? Some are shown here, first the Ashdown Engineering which has a dual band bass compressor. When looking at the user reviews at Harmony Central, the views are somewhat apart. One user wrote that Ashdown suggested to modify some component values.

Digitech Bass Squeeze is another cheaper model. The Digitech Bass Squeeze reviews give about the same ratings although it is different compared to the Ashdown compressor.

EBS Multicomp seemes to be a better compressor according to the EBS Multicomp reviews. EBS mainly manufactures bass amplification products.

Ashdown Dual Band Bass Compressor.

Ashdown Dual Band Bass Compressor.

Digitech Bass Squeeze Dual Band Bass Compressor

Digitech Bass Squeeze Dual Band Bass Compressor

EBS Multicomp Dual Band Bass Compressor

EBS Multicomp Dual Band Bass Compressor

BBE Opto Stomp compressor BBE Opto Stomp compressor

Update April 22 - Compressors that are a lot cheaper than usual, yet valued among users. Look at user review liks.
Yes here are some that really are, you may compare for yourself. I put these compressors below because I recommend them. Available through Amazon and a lot cheaper. At each compressor's page, look if it says "See price in cart" in the middle and also below right. The price is lower than can be displayed and you'll see it when clicked at. Those prices usually not found elsewhere.
Otherwise look below to the right where it says "More Buying Choices" to see the lowest price. At Amazon, you can choose between several music/studio equipment retailers as here for Opto Stomp, and on the page the "best" price is up, even if is it not displayed.

Anyway I looked up some reviews,
BBE Opto Stomp Info at BBE homepage.
BBE Opto Stomp compressor review -
BBE Opto Stomp optical compressor pedal -
BBE Opto Stomp reviews at Amazon

BBE Opto Stomp compressor ToadWorks Mr. Squishy Compressor Effect Pedal

Here other high rated compressors at
usual prices or little lower.

The ToadWorks Mr. Squishy Compressor really has good reviews at harmony-central, almost seems too good.
ToadWorks Mr. Squishy compressor reviews
Mr. Squishy Compressor - Toadwork homepage.

The Carl Martin compressor limiter pedal also has very good reviews at Harmony-central.
Info at homepage.
Manual -

BBE Orange Squash Fet Compressor Pedal
BBE Orange Squash Compressor Pedal - Reviews Harmony central

Updated December 16th 2009

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