Extensive compressor reviews and FAQ

What is the difference between a compressor and a limiter?
Limiting is a type of compression- a limiter is a compressor. However not all compressors are limiters. The primary deciding factor is that a very high ratio, typically 20:1 all the way to infinity:1, doesn't allow much of your signal past the threshold- which limits the signal to a certain peak level. A lower ratio allows a wider range of your signal past the threshold, compressing it but not capping it off so extremely.
The threshold setting is also very important. When using a "limiter", typically you want to set the threshold fairly high, so that only the biggest peaks of your signal cross the threshold and get squashed flat, leaving the rest of your dynamics untouched. But just because a certain pedal has the word "limiter" painted on it does not mean you can assume anything about its threshold setting- you still must take care to adjust either the threshold or input level in order to match the threshold with your specific signal peaks. Otherwise you may find that it does not work at all, or it squahes your signal too much.
So "compression" in general is associated with a lower ratio, reducing but not killing the dynamic range of the signal that crosses the threshold. Because of the lower ratio, you can get a much wider range of effects by adjusting the threshold, even to the point where your entire signal is above the threshold. Of course the results will depend on the specific signal and settings.
A lot of pedals have no ratio control, and a lot of them don't even state their ratio range (or fixed setting) in the specs advertised by the manufacturer. So you may have to do some research to find out whether a given pedal will work as a limiter. A lot of popular compressors for bass today are pre-set with a very low ratio, and are not suited for limiting big peaks. And you can't make any assumptions just based on whether the pedal has the word "compressor" or "limiter" painted on it. For example the Boss LMB-3 is marketed as a limiter, but it has a wide range of control over the threshold and ratio, so it can be used for any sort of compression; whereas the Boss CS-3 is marketed as a compressor, but it just has an extremely high ratio, so in that way it's closer to a limiter.
It's also the case that many compressors use a "feed back" circuit which increases sustain, while many limiters use a "feed forward" circuit which does not sustain so much. But again, you can't assume one way or the other just based on the word compressor or limiter printed on the box. So the difference boils down to the pre-set or adjustable amount of the ratio, and whether you are able to adjust the other parameters to achieve a specific compression goal.

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