Hi everyone -
I need an idiots guide to Compressor/Limiters - specifically
I've got a Behringer MDX4600 and the manual is deeply
confusing. I want to use it to protect my speakers (the
limiter function) - not so worried about the other functionalty 8)

All the best, Chris.

PS

for example I can toggle the operating level
between 'home recording level (-10 dBV) and
studio level (+4 dBu)'

For the output from my mixer I assume it's studio
level?

To protect speakers, use as a limiter by setting the compression ratio to infinity (fully clockwise) and set the threshold to the point at which you want to start limiting.

If this is to aviod the amp clipping, start with the threshold low and increase until clipping starts, then reduce down a little until clipping stops.

If there is an attack control, set this to the min time (fully anticlockwise) and set release to taste - short time will allow the volume to come back almost instantly, but may result in a "pumping" effect to the sound, long release will make the sound fade back in more slowly.

Hi there - I've got the Behringer 2600, the 2 channel version of the 4400 which you've got.

I included details of setting up the 2600 in this DJU review of my Behringer compressor limiter. Most of the setting up details will be the same between the two units. The 4400 offers slightly less features, but handles 4 channels of mono audio, instead of the 2600's two channels for stereo use.

Let us know how you get on.

Thanks Garry and Robie - it's a little daunting but you've both
helped a lot. I got the 4 channel version to sit between a crossover
and the amplifiers. You can chain them into 2xstereo channels
but I'm on a steep learning curve 8)

You might find it better having a slightly slower attack and longer release time, otherwise if the attack is too fast it will be an audiable attack, that is you will notice it and so will your clients, having a slightly slower attack and release time will make it more smooth without losing the protection.

Will do - the only reason I set it up that way
was because it's what Behringer recommend
so you can use different parameters on the bass/
mid-top signals.

All the best, Chris.

But a compressor/limiter never actually ducks a signal unless you buy a proper unit designed to reduce level once once a threshold is reached (Behringer Ultradrive has a dynamic EQ function that does this). It simply stops any higher levels getting through by squashing the wave (making it more square). The bass will continue to seem louder as a result of the compression (much the same way as producers use compressors on tracks to bring out basslines and kick drums).

The function of a compressor limiting a high bass signal shouldn't effect the mid/hi at all unless that was also above the threshold level. Having 2 lots of limiters to setup is complicating the process (imo) but you could do it that way.

I use digital LMS and i also set my limiting functions on each separate output because that's the way they work and there isn't an option to set a limiter on the input stages. I'm not overly familiar with the Driverack so i'm not sure what options you have available.

For what it's worth, despite (or because of) the limiters, i blew a pair of bass drivers last weekend due to me taking my eyes of things at the end of the night and the DJ went a long way over his levels. The higher sustained energy that was going to the drivers (squared off waves) caused them to heat up and melt the voice coils. A limiter should be a warning sign as you say, that things need to be turned down. The odd flash is ok, but sustained limiting is as bad as clipping an amp.

Ooh no you dont want any square waves going to any of your amps let alone speakers. Any compressor limiter has to go into gain reduction to avoid clipping whether its a soft-knee compressor (recording studio mastering) or brick-wall limiting (disco use.) The difference is that the limiter reduces gain over a longer period (several musical beats, say,) and only subtley as the threshold (limit) is crossed. It therefore is a continuous process at the threshold which increases as the overdriven input gets worse. A limiter should not square-off any signal, as this is essentially what happens if you clip your amps!!!! It will simply reduce amplitude, preserving the essential waveshape.

Musical compressors reduce and restore gain much more quickly to make quiet passages louder and louder passages quieter, ie levelling the signal to make it more pleasant to the ear especially on home-hifi. (and to keep the levels within the dynamic range of the recording or broadcasting equipment). It can eke out performance on an underrated system by making the amp work harder.

You can of course use a compressor on your disco but the results may be a little bizarre as a previous post mentioned if it tries to compress individual peaks (pumping or maybe causing the music to sound muddy and lacking definition.)