Hi, in my church we've just bought a new mixer (Yamaha MG32/14FX), a compressor/limiter (Behringer COMPOSER PRO-XL MDX2600) and a 31-band EQ. The technician from the shop did the connection whereby he made serial connection from main Stereo out of the MG32 to the 31-band EQ then to the Behringer MDX2600 unit before connecting to the power amp In summary: MG32 Stereo output >31-band EQ >Behringer MDX2600 >power amp >FOH speakers

However we feel not comfortable with this connection as most of the tutorials suggested to use the EQ and compr/limiter as an 'insert'. Therefore we are really hoping if someone experienced with live sound system to give some advice or opinion on how to correctly connect these devices.

thank you and God bless

I'd go with it as is, the only difference putting them in the main inserts is that they are then pre master fader. If you want the comp/limiter to protect your system it needs to be after the masters where it is now. Is that what you have the compressor for? Either way the graphic should be before the compressor.

--------------------
Turn it down lads (but only a little bit)

Quote Sam Spoons:

---

I'd go with it as is, the only difference putting them in the main inserts is that they are then pre master fader. If you want the comp/limiter to protect your system it needs to be after the masters where it is now. Is that what you have the compressor for? Either way the graphic should be before the compressor.

---

I would disagree only in the sense that Sam might inadvertently give you you the impression that this setup protects your system from all damage. You need to understand at least the basics of gain structure and the limitations (no pun intended but I'll take the laughs any way I can get them) of using the compressor in this way.

Personally I like output EQs on inserts because it makes them predictable. Placing them after the master faders means you have to allow for some idiot pushing the EQ into clipping.

--------------------
Ohm's Law states, "Your PA isn't as powerful as you think it is".

What was the thinking behind getting the compressor? I can't see it doing anything particularly useful.

PLEASE use the e.q. to help the sound be GOOD, not to let you make it LOUDER!

Good points both. Especially about making it sound good. Also I did wonder if the OP is reading about insert fx and send fx on inputs and confusing that with main buss processing?

Edited by Sam Spoons (07/08/12 09:07 AM)

Hi, the intention was to have some sort of protection to the speakers (as they are new as well) due to previous experience of 'burnt' speakers and this particular unit have a dedicated limiter function. The EQ is used to improve the sound coming out from the main speakers as well as to eliminate feedbacks. Thanks for your reply

For the compressor to do what you wish it would need to be after the main faders. Shuff makes a good point about the graphic, however if you use your ears to avoid clipping it will work in either location. IMHO the best speaker protection (for a well matched system at least) is your ears.

--------------------
Turn it down lads (but only a little bit)

OK, it's connected that way for speaker protection. That's fair enough - it should help prevent idiots from killing your speakers.

Next question: has anyone actually set it up? This requires knowing the output levels from the compressor, the input sensitivity of the power amps, and the power ratings of the speakers, and doing a bit of maths to work out exactly where your limiter threshold needs to be. Otherwise it's like a climber setting up a safety rope and neglecting to have someone on the other end holding it!

Quote jazzer256:

---

Hi, the intention was to have some sort of protection to the speakers (as they are new as well) due to previous experience of 'burnt' speakers and this particular unit have a dedicated limiter function.

---

I guess it might help a bit for that! But an operator who doesn't know what he's doing, and who can't resist trying "how loud will it go?" will find a way to break any system :-)

Quote grab:

---

OK, it's connected that way for speaker protection. That's fair enough - it should help prevent idiots from killing your speakers.

---

...except a clipped signal which has been compressed will do as much or more damage than an uncompressed one. Post master faders you're still at the mercy of the helpful idiot.

The theory is good and properly used this is a great idea. You cannot rely only on the compressor, however. Somebody will have to read a book at some point.

--------------------
Ohm's Law states, "Your PA isn't as powerful as you think it is".

Hi shufflebeat, your statement is a bit worrying.. can you please explain on how an 'operator' could possibly cause damage by wrongly adjusting the compressor settings? thanks

Quote grab:

---

OK, it's connected that way for speaker protection. That's fair enough - it should help prevent idiots from killing your speakers.

Next question: has anyone actually set it up? This requires knowing the output levels from the compressor, the input sensitivity of the power amps, and the power ratings of the speakers, and doing a bit of maths to work out exactly where your limiter threshold needs to be. Otherwise it's like a climber setting up a safety rope and neglecting to have someone on the other end holding it!

---

thanks for bringing this up..the whole system has not been fully setup by a competent person, as I said earlier it was setup by local dealer guys..is it possible to explain briefly on how to do the math for correct setting of the limiter? thanks

Quote jazzer256:

---

Hi shufflebeat, your statement is a bit worrying.. can you please explain on how an 'operator' could possibly cause damage by wrongly adjusting the compressor settings? thanks

---

That's not quite what he said! If the operator has access to the compressor controls he can use them to do anything from simply turning off the limiting to using the device to INCREASE overall volume!

If the limiter is "locked down" he can still (and, if inexperienced, probably will) turn up everything before it in the signal chain until it's getting a distorted, clipped input. If the limiter is set to allow through a useful dynamic range, this "constant peak" could contain enough energy to do damage. (Some of the popular descriptions of how an underpowered amp can blow a speaker as readily as an overpowered one get rather confused though.)

The point is - "Locking down" a system, unless set at a ridiculously low level, just doesn't work very well.

Wot 'e said ^^^^

My main concern would be the assumption that the issue has been dealt with by a magic box and therefore none of the basic fundamentals of using a system properly need addressing. It's usually blindingly obvious after a speaker has blown what caused it and how it could have been prevented. That's an awfully expensive way to learn though.



--------------------
Ohm's Law states, "Your PA isn't as powerful as you think it is".

Frankly you need to supervise operators who do not understand the system, a compressor will not do that for you. That said I always run eq and comp after the desk not before the faders.
It seems to be an english idea to run them on inserts, I have rarely seen it done that way in
.au. A decent digital system controller would be a much better way to go.

Quote Falconhell:

---

Frankly you need to supervise operators who do not understand the system, a compressor will not do that for you. That said I always run eq and comp after the desk not before the faders.

---

Yeah. But this is a church, where the idea can be more "give a problem kid some toys to play with to keep him in the flock" than "give the job to the right guy".

What was the overall compressor for?

What was the overall compressor for?

---

The unit is needed as protection to the new front speakers (the limiter part of the unit)..with the compressor placed after the fader, can it still be used as 'compressor' to soften the overall sound? I thought the unit will be compressing the 'stereo mix' and usually people use multi-band compressor for this purpose right? thanks

Quote Falconhell:

---

Frankly you need to supervise operators who do not understand the system, a compressor will not do that for you. That said I always run eq and comp after the desk not before the faders.
It seems to be an english idea to run them on inserts, I have rarely seen it done that way in
.au. A decent digital system controller would be a much better way to go.

---

Hi, would you place the EQ before or after the compressor? by the way, this particular unit has a dedicated 'limiter' separate from the compressor, the limiter should cut any excessive signals going to the power amp and thus protecting the speakers, am I right? of course provided that the limiter is 'locked' to certain level...could you suggest any decent digital controller dedicated for speakers protection? thanks

Quote jazzer256:

---

What was the overall compressor for?

---

The unit is needed as protection to the new front speakers (the limiter part of the unit)..with the compressor placed after the fader, can it still be used as 'compressor' to soften the overall sound? I thought the unit will be compressing the 'stereo mix' and usually people use multi-band compressor for this purpose right? thanks

---

The question was actually directed at Falconhell. But no matter :-)

I think we've established that it won't be much protection,

People often use (far too much, sometimes) overall compression on a recording. But this is PA. Compression will, apart from anything else, increase the likelihood of feedback. Think about it.

If running at moderate levels, thinking sound reinforcement rather than !ROCK PA! some compression might be useful. But aren't the kids going to try to use it the way they would on a recording, to get punch and loudness?

I always put the compressor after the eq, as the compressor will not trigger then on the peak frequencies in the system before they are removed. There are many opinions on this however. I usually run sub group inserts compression on vocals too, so that the main system comp does not activate on vocal peaks and pull down the instrument volume.