Limiters v Compressors - what's the difference?

[Bass Culture]

I'm doing a bit of homework on a potential new combo purchase.  I run my current, TC RH750, head with its compression all the time.  Of the combos I'm looking at some have on board compression and others have a limiter.  Are these different names for the same effect or do they do different things?  If so, what's the difference in terms of the impact on the sound of my bass?  Yours, confused of Chester. [Mods - if you think this is the wrong forum for this query, please move.]

[ped]

A compressor will reduce any signal above a certain threshold a certain amount. Usually that's a ratio say 4:1 and active on most notes you play, certainly when you play hard.

 

A limiter is a high ratio like infinity:1 but usually set at a higher threshold, so usual playing is unaffected but can provide a 'point' where the signal is reduced at a certain limit.

 

Both have their applications and most compressors can do both if they have a ratio control that goes high enough. For example the Boss LMB3 is just as much a compressor as a limiter.

[ped]

Some amplifiers with a single knob for compression tend to change the ratio and threshold as you turn, so it's worth looking at the details if you can find them. For example my Blackstar U500 says:

 

(compressor knob) Controls the overall amount of compression by adjusting the threshold, attack, release and make-up gain simultaneously. Lower settings of the control result inslower attack and release times and a higher threshold. Increasing the control will lower the compression threshold and increase the make-up gain, and make the attack and release times quicker accordingly.

[Yango]

Essentially, a compressor compresses the dynamic (volume) range of the track. A limiter on the other hand limits the amount of a signal passing through. Both use a user dialed in volume output cap (known as the threshold) but instead of taking the volume overage and compressing it, a limiter just completely removes it. 

[deepbass5]

I do own and have used the EBS dual comp pedal more recently, I got this as i was familiar with the old Trace elliot big dual compressor pedal no longer available. which allowed you can control the bass end and high signal end seperately. There are lots of good articles on compressors that explain all the jargon, soft knee, hard knee and thresholds and release etc. and you can buy pedals with all the features you may require to tweek. But live on stage a good quality pedal that is easy to control is best, even these can completely destroy your sound if you forget and turn your bass up after sound check. 

My EBS was only set up to really make a difference when I was required to do some slap and pop stuff, which is the only time i needed one to control those harsh transients. home recording would be the other.

having tried the Boss LMB3 Ped mentioned they sound great and do the job without the fuss, without getting into all the head scratching and messing up your big stage entry    

[Bass Culture]

Thanks for your replies, folks. I think i’m getting my head round it now!

[TimR]

I'll add to what Ped says.

 

A compressor compresses the peaks. Any sound that is above a certain level will be reduced. That level is the threshold. 

The ratio is how much that extra bit will be reduced by. So for a 1:4 ratio, you'll have the threshold level plus 1/4 of the bit above the threshold level.

In addition there will often be 'make up gain' so the lower levels will have more gain added to bring them closer to the threshold. 

This results in a less dynamic output, but louder and more consistent. 

Depends really on the environment and music how hard you compress, how low you set the threshold and how high you set the make up gain. 

 

A limiter just stops anything getting any louder than that certain level. If you're playing loudly all the time above that threshold this will just result in distortion. 

 

The limiter is like a compressor where the ratio is infinite so all of the sound above the threshold is reduced to the threshold level.

 

Difficult to explain in words. One of the most misunderstood topics. There's loads of YouTube explanations available, you just have to find one that you understand. 

Edited April 7, 2022 by TimR

[TimR]

Oh and there's soft knee and hard knee compression. With hard knee that ratio is applied immediately you cross the threshold, a hard angle. With soft knee it's more of a soft curve from 1:1 to to the set ratio.

[FDC484950]

It’s also worth mentioning that compression can be applied as a control/effect when recording but is also present naturally - so driving a tube amp will result in some compression by design, whether a compressor/limiter is used or not. It’s also why it’s generally better these days, with all the advances in speaker design and power output to ensure the amp is rated above a given cab so the amp has headroom to operate efficiently (yes, some amps may be capable of running continuously on 100% but it’s not normally good news). Bass amps often used to come with a limiter precisely for this reason - to prevent overloading the power amp stage and causing damage.

[Bass Culture]

Excellent information everyone - thank you.