Volume problem has me stumped

[Eboy87]

I did a show back at my high school a few weeks ago, running sound, and ran into a problem I forgot about. We have a nice space, but I would like to slap whoever installed the sound (as is the case at most places). Our board is a RAMSA SR2444, no graphics (there's some hidden, hard-wired EQ modules, but they can only be programmed by computer), running through Renkus-Heinz crossovers (I believe the x12, x14, etc ones, if not them then the predacessors), on to Crown Com-Tech amps, then onto the speakers.

The amps are in a room in the back of the house we unaffectionatly call the crap room, while our main cluster hangs over the apron, about 5 feet too close together, and consist of what I believe is a dual 18" sub (which we just got working right before I left), and what I think is a 2" horn/15" trap; one cluster SL, one SR. Which brings me onto the problem.

When we do shows that require a band, we usually don't use the pit, instead, we leave the pit covered for more real estate on stage, and tuck the band far SR, to the point that half are playing in the wings while the other half is on stage. The problem with this is that when they get into it, all that volume is projected right into the house. I should probably mention the acoustics are really good, to the point we don't use mics for our normal productions (musical excluded, as well as renters), the actors projecting is enough to fill a 375 cap room.

Now, when we add in mics to get above the band, we run into problems. I can't coax enough oomph out of the system to cut it. And before you ask, yes, I'm sure there isn't bleed coming through the open mics from the band; that was the first thing I checked. When I was in there last, I ran some sine waves through the system, and for esses and gees, ran the board into the red considerably. The volume wasn't bad at all (though 1k sines are painful to me anyway), and when I went back to check the amps, all the LED's on them and the x-overs showed somewhere around -20dbu (keep in mind the board is running around +10dbu).

My first thought was that the board had the switch that switches the output from -10db to +4db, but this board doesn't have any. I hooked in my drive rack in-line from the board to where ever it ties in with the rest of the system, and saw it was getting around the output of the board (not exact, but I don't trust the meters on the board). My second thought was that there was some kind of limiting built-in to the system, or that the signal was attenuated some where. Went back to the amp rack and checked their gain controls. All were cranked to 11, and no limiters on the amps were engaged (if so equipped). My third thought was that the cable runs were hampering the signal, but dismissed that after checking meters.

So that led me back to thought number two. I know there's some built-in EQ in the system. I bet there's a signal attenuator somewhere there too, but I haven't found it. It does make sense though, since my high school was (is) the jock school, I could see someone not wanting drivers blown. But for the professional shows, we just don't have the volume to get over the band, and it's frustrating. SOP for me is to run the board into the last yellow bar constantly to even hear the singer.

Lately I've been taking my own drive rack to EQ the mains and mons (I can't believe there's no graphics for the mons). I've thought about using my DRPA (don't laugh) as the x-over and run from the board, to the DR, straight to the amps, but these shows use just about every mic cable we have (keep in mind, this place wasn't built with mics in mind), and all mine are tied up just patching in the EQs, so I don't have enough to make the run from FOH to amp land. I havn't been able to hear any compression, and it sure is hell ain't a brick-wall limiter (I'd be able to hear that), so it has to be a built-in attenuator somewhere (or really, really shoddy wiring). This is a pain in the arse to track down the cause, and I really need that volume. There's a show in there next month that'll have a full band, and I need all the volume I can get (industrious dummer).

Fully realizing that I'm the only one here who knows what exactly is going on in our venue, does my excessively long post hit the nail on the head? Am I sorry out of luck? Or does this seem like something gone horribly awry.

That's gotta be the longest post I've ever done Mark another first...

(I like parenthetical remarks)

[SHARYNF]

you have certainly done all the right things in debugging.

if you look at the schematic for the RH X
http://www.renkus-heinz.com/support/...ller_Schem.PDF

and Manual

http://www.renkus-heinz.com/support/..._pdf/x-man.pdf



You will see that there is a Limiter built in, which could be your problem, as you said some one could have set it to protect the drivers. Another possibility is that the HF diaphrams are blown, again, usually you can tell, certainly if you shut down the 15's but those RH units tend to be set and forget, but it is not out of the question worth a check, sometimes in a Three way, the Horn is crossed over reasonably high has a 12 db slope and you COULD be just hearing the mids, no horns and since they are a center hang it could be hard to tell.

Re the band on stage, I tend to work with a lot of acoustic treatment etc, and one thing to consider is getting absorption panels behind the band, and above sort of an absorbing band shell, to reduce the reflected horn type of effect, and in essence cut down the sound level. other thing is to have a low absorption temp barrier placed in front. There really is a reason for a pit as you obviously know, in that it dramatically reduces the transmitted sound level, I have on occasion when there was no pit created one from some panels/drapes etc.
Hope this helps

Sharyn

[maccor]

I've got a similiar situation where I need to construct some sort of front 'sound shield' around our pit orchestra. What fabric would you recommend be used? Would it be streched tight or left with folds? I'll only be able to build it 30" tall due to sight lines....Will something that short still be beneficial?

Thanks for the input.... Mike

[the_dude]

The crossover shows -20dbu on the input or output or both?

What model of com-tech's for which drivers?
Regardless, if these are somewhat pro level drivers that doesn't sound like a whole lot of power.

There is also an input sensitivity switch on each channel which changes between an 8/4 ohm mode and a 70 volt mode.

Have you tried looking for the program to access the eq's?

I can't emphasize how much I doubt it's the case but maybe the the L/R is out of polarity?



Mike, no. A 30" sound barrier is not going to do much of anything.

[Eboy87]

Thanks Sharyn for those links. Looks like if the X-over is the culprit, I'm out of luck, can't adjust the limiters on those. The sad thing is that part of me sees that as a good thing for installs, but they may well be my problem here. I'll run some more sine waves next time I'm in there. And we can't really put some pipe and drape in the wings for the band. We have one extra curtain that we hang around them, but the problem is that our wings are open to the house at the top because our catwalks run along the sides of the house, onto the grid (one of those airplane cable ones, 20ft above the stage). The walls, even with some drape, just form a horn straight up.

The dude, I honestly don't remember what the x-over was showing. They only have signal LEDs anyway. I'll check them compared to the amps next time. I'm sorry, I don't now the model number off the top of my head. I know there's a 3U amp for the sub, then two or three 2U amps. I don't recall the numbers off the top of my head, but I can check, just a phone call away.

As for looking for the program to program the modules, out of the question. As far as I know, they may not even be able to be programmed, it may all be hard-wired. Furthurmore, I don't even know where these modules are. The problem is, neither does the theater manager. We've had someone from the install company out a few times to fix gremlins, but after talking to him one time, he wasn't much of a help either.

As far as polarity, you may be closer to the truth than you know. The input on the back of the traps doesn't have Speakon or even 1/4". Instead, R-H put a terminal strip on the back. 3, maybe 4 years ago, a bunch of immature frosh ran wild in the theater and pulled those wires off the terminal stirps (even cracked the lenses in some of our fresnels and S4s). Our house right cluster wasn't working for the longest time after that, and even when I graduated, it was working intermittantly (sp?)

I'll try and take a day before the show to go in and see if I can't get everything working. Thanks for the suggestions guys.

[SHARYNF]

I don't think you have much flexibility to alter the settings in those, certainly not without the setup program, I would try to see if by some wierd chance the drivers are blown, but you might be correct that you are simply running into the design install limit.

Cannot completely visualize your setup, but a couple of things.

What you need to do is remove the horn effect, I have used home made panels made from Lanai on 1x6's cut to a curve so that the 4X8 panel has a slight bend in it, than hung these via cables from above so that the reflect the sound back or break up the surface. They can have a major effect (a lot of the post architectual design correction work uses to some degree a system like this.

Other thing is a large drape, that has a pipe in the front and then a pipe in the back, and is hung so that it forms a stage top and back.

There are a lot of tricks with panels for absorption/reflection that you can do

I panel across the front up high, angled down so that it reflects the sound from the horn effect back, and has some absorption on it can work. If you look at what is done on some prof sets, you can also use lexan panels that are placed infront of the band, and then you use this for isolation, but it can be somewhat trickey to get the sound to balance. (you probably have seen clear panels around drum sets for instance)

A lot is experimentation, for instance carpeting the floor under the group, the area behind them and even a low barrier in front can nam times help.

For drapes I usually use Commando cloth. People also build panels with compressed fiber glass on each side of, a piece of sound adsorbing board that you can get from home depot etc, and then cover them with cloth.

Low frequencies need a lot of mass to absorb, higher frequencies need less.

this will sound really crazy but I have seen situations where a wall of concrete blocks was constructed such that there was a complete set of opening in it, or slots in it to control bounce back. these were set up and taken down and had a frame to support them.
Sharyn