Speakers peaking

[carsonld]

So I have a probably dumb question but here goes...

I have two line arrays on left and right all are powered by five Crown CTS 2000 amps and the sound board is a Behringer X32. I get a cable to the sound board for left and right. Each line array features five JBL VRX932LA and one JBL VRX918S. I am having an issue with the volume of the speakers. I can not get music, mics, really anything loud enough in the space. It's been a big issue this past year. When the Jazz choir had their concert, the speakers couldn't even handle the six wired mics they were using. The speakers would become muffled or peak when they all sang together. Unless they were singing at a lower volume. Now for our musical we are handling 21 wireless mics and I am experiencing the same issue. I have done everything I know how to from gain, compressors, etc. No matter what I do, I can not get the sound needed to fill the space. I talked with our local production company and he thinks that there shouldn't be an issue pushing sound to fill the space. I have them coming to look at the system next week but figured I would see if anyone had some answers on here. After doing some researching and inspecting, my thought is that the amp is not giving enough power to the speakers. I have attached the manual and spec sheets for the amps and speakers. Would someone be able to tell me if these amps are able to be powering the speakers to their full capacity?

Sorry if I sound illiterate, sound is not my speciality. However, I do know enough to realize this issue isn't a simple gain or volume knob issue.

Thanks all!

 

[DrewE]

Assuming nothing is physically broken, I rather suspect the system should be plenty for a jazz choir concert, assuming the venue is not enormous and you're going for appropriate sound levels. It sounds to me rather like a gain staging issue, possibly at the amplifiers or whatever speaker processing you might be using (an external crossover? Some limiter or other processing on the output bus of the mixer?) Or something needing maintenance/repair: defective cabling? Thermal problems causing the amps to go into protection mode due to excessive dust or dead fans?

There are a great many gain and volume controls between the microphone and the speakers; it's awfully easy to miss one or two.

 

[Aaron Becker]

Is this a fully installed system or is part of it portable? During a time when you can be in the space alone (ie, not during rehearsal) try to do some testing.

Hook up a microphone to an input on the mixer, route it through to the mains and test the volume with things on the board set at a nominal level. Just to get a baseline. Make sure the channel is normalized with no extra patches/EQ/compression/etc.

Then, bypass as much equipment as you can (you mention compressors, are these on the console or external?) and repeat the test. Is there a difference? If so, start looking at the settings of the external devices you bypassed. You might run a cable from the output of the mixer to the input of the amps/DSP (if applicable) for this test. It eliminates a lot of variables.

If this doesn't change anything, I'd start looking at the gain structure on the amps. Can you take pictures of the amp settings and post them here?

When you're pumping "full" sound through the system, where are the output meters on the mixer? How about signal/level indicators on the amps?

Also, do you have 5 or 6 total amps? I suspect 6 (just based off your diagram you attached).

 

[MNicolai]

Something probably isn't gained correctly. Those amps aren't too far off from what JBL shoves in their VRX932LAP powered version, which should be loud enough to peel paint off of the walls. Could be something on the output stage of the mixer, could be a DSP that the mixer hits before the amps, could be the gain settings on the back of the amps, or the crossover/gain settings physically on the backs of the speakers. Clear photos of the fronts and backs of the equipment racks and the amplifiers would be helpful.

First things first, confirm you are not clipping the inputs of your mixer. Generally want to stay below -12dBU on the meters.

Secondly, check that your signal routing inside of the mixer is not passing through mix busses, groups, effects, or other processing that could be engaged that you aren't aware of. Each one of the these "stages" could have gain/EQ/processing applied that's causing your symptoms.

Things like reverb, effects racks, compressors, limiters, etc. often have input and output gain. You want to understand if at any point in your mixer the gain is being messed with. If in doubt, bypass your mixer and hook a music source up directly to the amps.

Once you've reasonably ruled at the mixer as a source of issue, play some music at a nominal level. Go to your amplifiers and see what their input gains are set to and how high the signal lights are boosting on them. If you're not clipping the amp out, you shouldn't be hitting the internal compressors of the amplifiers.

Also look for a DSP in the mix. It is common that your signal from the mixer will dump into an external DSP probably in your amplifier rack before it passes the audio onto your amps. You could have issues with gain/EQ/compressors in the DSP file. If you don't have a DSP, your amplifiers may be "wyed" together and wired in parallel. This is not ideal and can create problems. I would want to know exactly how your mixer interfaces to your amplifiers and any components they pass through on the way to get there.

If you can get up to the speakers, check the backs of them. There are settings for crossovers "Passive, Biamp, etc.", and gain shading "short throw, long throw, etc." Take note of what those settings are at.

Warning!!! Resist the urge to start spinning knobs on the amplifiers just to see what happens. In the event your speakers are biamped, you don't want to crank the HF channels up and blow your horns.
Warning!!! When plugging directly into amplifiers, always make sure the amplifier is off when you connect the source, and turn the source all the way down and gradually bring its level up. Do not unplug while the amplifier is turned on.

Definitely double check how many amps you have and how they are configured for your speakers. If you only have 5 amps, something isn't set up the way you think it is.

Also check at a low level how clean the audio sounds. If it's muffled at a low level, you could have an EQ/crossover problem but that could also be an indication that your speakers may be damaged. If you don't have an external DSP acting as a system limiter/compressor, it would not surprise me if the speakers were overdriven in previous years and are in need of repair.

 

[microstar]

So a few basic questions...
Is this a permanently installed system and how long has it been in operation?
Has it ever worked properly?
Are you the first person to operate the system or are you taking over from the previous operator?
Do you have the system drawings?
Are there any indications on the rack or on system drawings who installed the system?

 

[Jay Ashworth]

also:
What city are you in?
Can you afford to pay someone to come out and realign the system and lock everything?

 

[Aaron Becker]

I talked with our local production company and he thinks that there shouldn't be an issue pushing sound to fill the space. I have them coming to look at the system next week but figured I would see if anyone had some answers on here.

Can you afford to pay someone to come out and realign the system

That is all.

 

[TimMc]

Well there a whole bunch of questions that come to mind and a couple have been asked already. How long has this been screwed up? Who operated it over the recent past?

Have you used another mixer like a little Mackie or Shure or Nady? Doesn't have to be great, it just needs to be NOT the X32. Just remove the XLR cables from the X32 outputs and plug them into the other mixer. SM58, tracks playback... any source. Does it work better/worse/not at all?

I have several ideas about what could be going on, and where, and none of them involve your amplifiers, and only the most egregious involves your VRX speakers.

 

[Jay Ashworth]

That is all.

Apologies; I read right past that.

 

[Aaron Becker]

we all await answers....

 

[BCAP]

P.S. you might also want to consider testing this with the pink noise signal generator inside the X32

 

[TimMc]

P.S. you might also want to consider testing this with the pink noise signal generator inside the X32

It the source of the problem is what I think it is, the pink noise test would give similar, but more difficult to distinguish, results. Pink noise has a crest factor of 6dB (typical) so the compression artifacts he's hearing wouldn't be obvious until things were really cranked. I'm a big PN fan but we've got an LD trying to figure it out so the less that depends on perception the better off we'll be, at least to get started.

Perhaps the OP can post the scene file or put it up on Google drive for us to look at.

 

[BCAP]

Correct. It might actually be very difficult or impossible to hear compression at all with pink noise. My thought was that it's helpful for an idea of establishing or diagnosing gain structure. I recently had a situation for a customer where the subwoofer amplifier was constantly cutting out, they had an X32 as well. I discovered that the amp was going into thermal protection (drastically underpowered subs too) but used the test signal to help diagnose.

 

[TimMc]

Correct. It might actually be very difficult or impossible to hear compression at all with pink noise. My thought was that it's helpful for an idea of establishing or diagnosing gain structure. I recently had a situation for a customer where the subwoofer amplifier was constantly cutting out, they had an X32 as well. I discovered that the amp was going into thermal protection (drastically underpowered subs too) but used the test signal to help diagnose.

Agreed. And points to why I think putting subs on an aux for amateur operators/designers is a Really Bad Idea, as much as I personally use it and set up music concert systems that way for 99% of the music events that my shop provides for.

 

[macsound]

Did this ever get figured out? I'm always interested in theoretical troubleshooting vs reality.