Compressor v Limiter.....what's the darn difference?

StanleyAccrington

While sorting out a few boxes in the loft, I've come across a Boss LMB3 Bass limiter enhancer pedal that I didn't  know that I had or maybe bought and dont remember purchasing it. Isn't it just a compressor pedal that has been given a different name in an attempt to sell them to feckless peeps like me. It has 4 knobs on it.....3 of which that are usually seen on compressor pedals......Level/Enhance/Ratio/Threshold. 
Is it worth me putting my guitar through it or is the pedal solely for bass use?
If ok to run guitar through it.....what knobs do what?

Thank you.

peteri

Can't comment on the pedals - but to answer the topic, there's really no difference between a limiter and a compressor apart from the ratio.

Ratio is the amount of gain reduction - so a ratio of 2:1 means that for every 2db over the threshold only 1db will show at the output - so 6db would be reduced to 3db.

Limiting is classically described as any compression which exceeds a 10:1 ratio - meaning to see 1db over the threshold you'd actually need to be 10db over.

If you have a limiter pedal with a ratio that goes down to 2:1 or lower, I'd argue it's not a limiter but a compressor - on this pedal the pictures show it has a ratio range of 1:1 to infinity:1 so that's fine, you can compress with it but you can also limit.

So in that regards lots of flexibility and it looks good and usable (more versatile than a compressor for example).

Personally, I'd get a pedal for a guitar - reason being this pedal is likely optimised for bass frequencies, and how bass guitars tend to use compression/limiting is quite different than a guitar.

This is to do with the side chain, which is basically the sensor part of the circuit which drives the compression/limiting, similarly the enhancer is likely tuned for a different frequency range.

Doesn't mean it won't work - but might not work as intended.

That said, since you've already got it - why not plug in and give it a go it won't kill you and might sound cool.

Looking at a picture of the pedal - Level is the output level of the pedal (so makeup gain if you like)

Enhance - this is the enhancer circuit, an enhancer puts a high end 'sheen' on a signal, increasing the perceived upper treble (think of it as a polished presence control and you won't be far wrong) - this may not be that well tuned for a guitar

Ratio - see above explanation

Threshold - the level that limiting or compression starts, so if the threshold is -10db a signal at -11db will pass through uncompressed, anything about that will be compressed/limited.

Hope this helps

Musicwolf

According to my definition, a limiter shouldn't have a ratio control as the ratio would infinite.  Basically with a compressor as the level exceeds a certain amount (threshold) the device applies reduction to signal above that level.  How much reduction it applies depends upon the ratio.  2:1 ratio would mean that for every 2dB of input signal above the threshold the output would increase by 1dB.  4:1 would mean 0.5dB out for 2dB in.

In a limiter there is no increase in output once the input reaches the threshold (brick wall)

Sassafras

Aren't limiters generally used to stop speakers from blowing up, especially with the large volume spikes from a bass?

peteri

Sassafras said:

Aren't limiters generally used to stop speakers from blowing up, especially with the large volume spikes from a bass?

Sassafras said:

Aren't limiters generally used to stop speakers from blowing up, especially with the large volume spikes from a bass?

They're used for a lot of reasons, that's one - but also you get Brickwall limiters in recording (infinity to 1) to stop overs when you're mixing

prlgmnr

As expander is to gate, so compressor is to limiter.

Blueingreen

I have a Limiter knob on my Quilter amp, no idea what it does technically but sonically seems to work something like a compressor.

StanleyAccrington

Thanks for the replies folks. Some of your information/explanation of limiting has got through my thick head whilst some has gone straight over it. But enough to pique my interest in the subject so as to do some more research online.
3 of the knobs have just min-max parameters but the ratio knob has a 1:1 to infinity:1  parameter. Any changes to the sound of my guitar would be good......I'm hoping that, if nothing else, the pedal might be able to add some sustain to my guitar. Although I will prolly need a compressor/sustainer for that!

peteri

This will do that too, but it would help to understand why.

Compressors cannot actually make your guitar sustain longer - that's a physical thing, but they can make it sound like it sustains longer.

Compressors normally have a gain control (here it's your level).

Imagine the compressor had no other controls than gain - turning up the gain (level) control will make your guitar louder - obvious right?

Part of the impact of that will be maybe not what you want - I.e. the start of the note will be louder, maybe too loud.

But part may be nice - meaning that as the note dies, this will seem not to be so much because it will be made louder.

So think of it as a clean boost.

But then the compression part comes in, the compressor will undo the bad parts of the above - because it will make the bits made too loud quieter.

So, if you set it right, the initial part of the note will stay the same, but the 'tail' as the note dies will be amplified and therefore seemingly sustain longer.

Wow - cool eh? Well it's not for free, in doing this you'll also amplify the background noise (everything gets louder) and also reduce the dynamic range of the note (the loud part is kept at the same value but the quiet part is made louder).

Neither are an issue if not done to excess, but good to be aware of

Again, hope this helps

StanleyAccrington

I've tried my guitar through the pedal and the only positive that I can hear is that it gives a volume boost. It's a load of gash really and this is why I probs forgot that I had the pedal in the first place. 

thermionic

Compressors (and limiters) can cause an apparent loss of higher frequencies I think (can't remember why...) so the enhancer is there to compensate - it's not a presence or treble boost, it actually generates higher harmonics from the signal fed into it (a bit like an Octavia generating an octave-up signal).

I fancy trying one of these (on bass), so if you're thinking of getting rid of it...

exocet

thermionic said:

Compressors (and limiters) can cause an apparent loss of higher frequencies I think (can't remember why...) so the enhancer is there to compensate - it's not a presence or treble boost, it actually generates higher harmonics from the signal fed into it (a bit like an Octavia generating an octave-up signal).

I fancy trying one of these (on bass), so if you're thinking of getting rid of it...

Traditional Single Band compressors / limiters will do this. In any audio signal, the higher frequencies are at a lower level than bass frequencies. The most obvious example is a drum kit (kick drum v high hat). If you process the entire drum kit via a single band compressor, the kick bass will effectively modulate the high hat signal - more commonly known as pumping. Using separate compressors for different frequency bands gets around this but Multi-band compressors within a single unit (or software plugin) have been around for many years.