Compressor/Limiter

[timtheenchanteruk]

Hi,

I am getting shortly a compressor limiter, and want to know where the besat place to put it in my system is, I use a 4buss mixer for live theater work, usually with stage mics on 2buss`s, Radio Mics on a buss with one spare for band etc, I also route straight to mix for fx on minidisc etc.

I want want to know if putting the comp/lim in the group inserts is best, in my mind this would be the best place, use a 4 chan, one for each buss, being able to set for the radio mic/vocal seperate to stage micing,

or to put it in line with the lineout, I.e between the mixer out and the amps, either pre or post eq (Behringer feedback destroyer), where only a two channel would be required.

 

Any help greatfully received.

[Ben Langfeld]

The way I've always done it, and indeed the way I've always seen it done, is to have compressors, gates and limiters on each individual channel. If your budget will stretch to purchasing enough units to do this, then that might be a better idea.

[charlyfarly]

I would love to answer the OP, but it's gobbledegook.

Please, at least use a spellchecker, or at least read back your post for basic grammer.

Thank you.

[dosxuk]

What are you wanting to compress / limit? Vocals? Instuments? or using it as loudspeaker protection?

 

Our effects rack has 10 mono comps which can be inserted into any input channel, and a stereo comp/limiter for system protection, which is placed in line with the mix out.

[Rob_Beech]

to second what people have said. its normally better to compress individual channels. Compressing a group isn't bad but you are a little restricted to what you can achieve.

As mentioned, if budget and rack space allows it you've be better off with enough compressor channels to cover anything you may need to compress/limit.

 

Its vital to note that you really need a good basic (if not more) knowledge of exactly how a compressor works and what it can do and what it can't do before you even think about using one. A compressor can ruin a sound ALOT easier than it can improve it.

This has been discussed MANY times before on here so use the search function to read through a few previous posts about compressors. this should give you a few tips.

 

Its also important to remember that the 4 channel compressors don't normally have the same features as single or dual channel compressors. These may be features that you NEED to improve. On the other hand there may be things that don't need these features in which case the 4 channel compressor is ok. In my FOH racks I have a mixture of 2 and 4 channel ones. Remember, don't compress a channel because you have a spare compressor channel, if it needs it use it if it doesn't. don't even have the insert in*

 

Rob

 

 

* That's if it WONT need compressing, not if it currently doesn't require it but could as the night goes on. In this case its important to have the compressors threshold set at its maximum level and this will leave the sound unaffected unless you adjust this.

[mackerr]

I am getting shortly a compressor limiter, and want to know where the besat place to put it in my system is, I use a 4buss mixer for live theater work, usually with stage mics on 2buss`s, Radio Mics on a buss with one spare for band etc,

What exactly is the problem you are trying to solve with a compressor? You don't just stick a compressor in the signal chain because someone else does. You use it to solve a problem. Since you haven't seemed to found the problem, it is best to leave the comp alone.

 

Mac

[timtheenchanteruk]

sorry about the bad spelling etc.

 

My main problem is with vocals on the radio mics, sudden loud parts/words that overload the FB destroyer, causing distortion, and occasionally when piping the band thru the PA a member of the band suddenly turning up their keyboard etc and causing the same problem.

 

I have tried reducing the overall output of the desk, and increasing at the amps, but this seems to seriously reduce the effectiveness of the FBX,

[Solstace]

Is there any chance of any more detail, eg:

 

1) What the PA is being used for

2) What PA equipment is in use

3) How the equipment is set up, both in terms of what's doing what and in what kind of envirenment

 

TBH - From my experience with FBX units/processors, I don't have a lot of time for them. Yes, they can be very useful, but they can also encourage laziness in the basic design by masking (or sometimes even adding to) the real problem.

 

Without wishing to sound negative, I'd suggest that compression on it's own might not solve your problems, because:

 

If a person is singing/projecting over a band, then they're probably doing so for a reason. You *can* use a compressor to smooth out (attenuate) the dynamic range, BUT in order to make the attenuated signal audible over whatever is going on in the background, you'll have to boost the compressed signal by a certain amount.

 

Here's the problem: If you boost the compressor's output by 6dB, then as with any other fader or gain control, you're boosting the background signal by that same amount. If you're already verging on the edge of feedback, then as soon as the compressor backs off the attenuation, the increased background noise will probably throw your system over the edge!

 

Some more points for thought:

 

Have you tried running the same system without the FBX?

If so, did/does the distortion still occur?

Have you done all you can to minimise the causes of feedback in the first place? Even something as simple as moving the FOH/Monitor speakers, a change in mic choice/position can improve matters considerably.

How much headroom do you have in your amps during a show?

 

Sorry if this poses more questions than you have answers for - but I'm just trying to suss out your situation so as to try and work out some sensible answers!

 

C

[Tomo]

IMO, feedback exterminators are useless in the professional audio environment.

 

Purely and simply because of the way they work:

If running in a pre-set mode, you're better off with a graphic EQ as you have control over what is happening.

 

If running in dynamic mode they make the sound very odd, and if someone on stage sings or plays a long, pure note, they will automatically stomp on it because it sounds exactly the same as feedback.

 

I have possibly the worst ears ever, so if I spot an oddity it must be HUGE!

 

Going back to your original question, compressors are generally used in two places:

 

1) For each vocal/instrumental channel usually via the insert, to reduce the dynamic range on those performers who have a tendency to YELL and then get very quiet...

 

2) On the main outputs of the desk before being sent to the amplifiers, to protect the amplifiers from excessive levels being sent by the desk.

 

I generally only use the latter of these for people like DJs who like to redline their mixer all the time - in other words, the idiots.

My last ship does this as well, presumably to protect the equipment from incompetent sound engineers.

 

When deciding where to put compression, it's usually the place where you feel you have to 'ride' the fader to keep a decent level, because that is essentially what a compressor does.

[Bobbsy]

What exactly is the problem you are trying to solve with a compressor? You don't just stick a compressor in the signal chain because someone else does. You use it to solve a problem. Since you haven't seemed to found the problem, it is best to leave the comp alone.

 

Mac

 

Mac's question was spot on. You don't just inlude a compressor because you have one...it's a tool to solve specific problems. Since moving mainly to digital boards, I now have the ability to use a compressor on every single channel if I choose to...but rarely use more than a handful to fix specific problems.

 

As for the answer about distortion in the feedback eliminator, I'd be looking at a couple of different avenues before using a compressor. First off, if the FBX is distorting before any other elements in the system, then it suggests to me that your gain staging could do with some tweaking. Second, I'd agree with those who are querying he need for the FBX anyway, particularly if the unit you have is prone to clipping. With a properly tuned system and a decent op, you shouldn't need one.

 

Finally, just to say that if, after all this, you still need the compressor...for this application you don't actually want a compressor...you want to run it in hard limiter mode.

 

Bob

[timtheenchanteruk]

"1) What the PA is being used for"

 

Mainly used for Amateur theatre productions, musicals, plays etc, but also for dance school shows for dance teachers who want volume from nothing

 

"2) What PA equipment is in use"

 

I have a Yamaha MG3214FX, with 5 Audio Technica Pro45`s hanging on stage, 4 VHF Beyerdynamic Radio Mics And 2 AKG WMS60 UHF Radios, All using lavalier, this is coupled with A behringer Feedback destroyer Pro DSP1100P, using A carlsbro CPX 600 powering 2 pairs of bose, A CPX300 powering 2 pairs of Toa`s A citronic PPX150 powering a pair of Torques, and an old Carlsbro Mono Amp for Foldback/Monitors Where required.

In some productions then the band/keyboards are thru the desk as well.

 

"3) How the equipment is set up, both in terms of what's doing what and in what kind of environment."

 

I usually set up the system with the FBX in bypass mode, in order to set the desk first, then use the FBX to get a bit more head room using the preset mode, I have stopped using in float mode, as mentioned it can cause more problems by cutting wanted sound, I sometimes keep a couple of filters free to uses in EQ mode, although this can be guess work as I have no spectrum. the monitors I use for shows dont usually have vocals throught them, so a bigger problem with that is picking up the band etc

 

 

I have taken the FBX out altogether, bypassing it still causes the problem of clipping, but I lose quite a bit of headroom.

Most of the speakers in the venue I work in are installed, so moving most of them isnt possible, but they were put there by somone who works sound in the venue quite a bit, and moved quite a bit before a position decided on.

 

The Carlsbro amps are usually running around 1/2 but running a 4ohm load, the citronic around 2/3 running an 8 ohm load, monitors depend upon whats required, but usually as little as possible.

 

hope this answers your questions, my main problem as I said before is when running at high gain then someone suddenly shouting/ loud bit of a song and pushing the FBX into clipping

[Solstace]

...but also for dance school shows for dance teachers who want volume from nothing...

 

Ain't that always the way? :)

 

Right - first off, good to see the FBX being used as designed, in that you're setting up first and then patching it in to get those last few dB. Sorted. I'm still a little confused as to what headroom you refer to. When saying that the FBX gives more headroom, are you implying that this is before distortion or before feedback, or both?

 

From the system/situation you describe, I think there are some other things that need solving before spending money on a compressor/limiter, unless you simply want to purchase one to place before the amps to protect your speakers.

 

If you're looking to get some tips on what might be up with your system and how you might make better use of it, you might want to start a separate topic, otherwise this thread will depart from the original title quite dramatically!!

[Rob_Beech]

You could also use the search function on here to find previous topics similar to this, if theres anything related read through it and then ADD your question to this. it keeps things a bit neater.

if there is nothing related........................................then start a new topic.

 

I agree that there may be other ways of solving this without the compressor.

 

Rob

[timtheenchanteruk]

the headroom I mentioned was before feedback, as you would expect removing the FBX, after the good advice, I think I will put the compressor idea on hold and do a bit more searching, thanx 4 all the help

[ghance]

hi,

 

sympathise with FBX problem.. had same problem when asked to op somebody else's show / rig. unplugging the FBX was the easiest option at the time.. the DSP1100 is pants anyway..too noisy, clips quickly and not very effective at finding feedback.. the new sharc's & ultracurves are better at automatic FBX then the old stuff.

 

however, you can get some okay-ish results from the DSP1100 if used carefully for certain jobs... suggest you beg / borrow / hire a basic 2-ch compressor, like a behringer composer and experiment. would be inclined to daisy chain the compressor & FBX and insert over your radio mic group. i.e. compressing the signal fed into the FBX.

 

good luck