Installs Help with Power Amp placement

dude2144

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Hello, I am the "Sound Tech" at my high school. I the quotes are because I had to teach almost everything to myself but what I am wondering about today is the placement for the amps powering all of the speakers. Our current set up was horribly done, wires are lose everywhere and its all a mess but the amps are on stage taking up a lot of room. The board is in our booth connected to the stage via a snake. The signal goes form the stage end of the snake into the amps. Should these amps be here or should they be moved up to the booth? We also have a graphic eq laying in the booth but it isn't hooked up.
 
Hello, I am the "Sound Tech" at my high school. I the quotes are because I had to teach almost everything to myself but what I am wondering about today is the placement for the amps powering all of the speakers. Our current set up was horribly done, wires are lose everywhere and its all a mess but the amps are on stage taking up a lot of room. The board is in our booth connected to the stage via a snake. The signal goes form the stage end of the snake into the amps. Should these amps be here or should they be moved up to the booth? We also have a graphic eq laying in the booth but it isn't hooked up.


Since you are a high school student you will want an instructor there with you when you move them. With that said the shorter the distance between mixer and amplifiers is always the best scenario. You are more likely to pick up interference and noise in a line pre-amp than post-amp.

It also really depends on how far you need to run the cables from amp to speaker. More info about your setup would give us a better understanding of what you are trying to do.

Just saying amps EQ and speakers is very, very Generic. It would help to know what speakers you have what amplifiers as well as what EQ among other things.
 
Putting the amps in in the control room seems like a great idea until you remember that they give off heat and noise. (fans)
 
@avkid thanks for the tips. Unfortunately we have close to no money to hire someone but I will see if i can find someone.

About the setup, we have four speakers in the house, two mains in the front of the house and two smaller ones in the middle, all of them are positioned on the walls. The wiring runs through the catwalk and under the stage where it comes out on stage left. Thats where the amps and mic inputs are. The mics are connected to a snake that connects to the board.


Sorry I do not know the models for any of the equipment off the top of my head all I kno is that its a graphic eq but ill post model numbers and amp voltages tomorrow or Wednesday. besides that is there any other info that would help?
 
I have a couple suggestions:

First, the amps are probably best on the stage. Two reasons here: One, since the current and voltage of line level audio (what comes out of your mixer) is low, there's really not much signal loss in line level cables due to the resistance of the cable. After that signal is amplified by the power amplifier, the current and voltage are high enough for the resistance of the cable to have a effect in longer cables.

For instance, if it's 200 feet from your booth to the speaker and you ran 14 gauge wire, you would lose 1.02dB just from the wire. Your 500W amp suddenly becomes a 395W amp!

Granted, 1dB isn't a lot (you probably couldn't hear the difference), but it's a loss you could avoid.

Two, microphone cable is much cheaper than speaker cable. 200 feet of mic cable (Belden 8451) would be $46, but 200 feet of 14 gauge speaker cable (West Penn 266) would be $80, basically twice the cost.

My other suggestion is to draw a line diagram of your sound system. You could download a student version of AutoCAD and draw it in that, however, a neat hand drafted copy would work as well. Generally, you want to start with the inputs on the left side of the drawing and work your way through the system, using lines a single line for each wire and boxes for each device. I've attached a very basic example I threw together in MS Paint.

Then post that, and we can take a look - it'll help you understand what is going on in your sound system and it'll help us better than a simple list of equipment.
 

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With that said the shorter the distance between mixer and amplifiers is always the best scenario. You are more likely to pick up interference and noise in a line pre-amp than post-amp.
At the same time, the line losses are much greater with with speaker lines and in order to minimize line losses and maximize damping factor, it is pretty standard practice for installed systems to try to locate the amplifiers as close as possible to the speakers.

In addition, if the system was designed to have the amps at FOH then it likely would have a dedicated path for the associated speaker cabling, however since the system was apparently designed to have the amps at the stage you might also need to look at the cabling paths involved. Even ignoring the potential issues associated with simply having to physically run new speaker wire, having a situation such as ending up with mic, line and speaker lines run in the same conduit to FOH may not be the best idea.

dude, it's great to see students show an interest in being proactive and taking the initiative, but the broader implications of any actions also have to be considered. I understand your situation but consider that if you are not sure of what you're doing and you have no money to hire a professional now to help you then you also probably cannot afford if anything done to the system causes any problems. Because of that, you may need to proceed very cautiously with some changes or intended improvements.
 
rwhealey
Sorry I did not have time to check the names of any equipment in the system but i did throw a line drawing together without it.

About possible loss because of a long connection from amp to speaker, the cable would only have to be extended 75 to 100 ft, the house is not very large and is only 70ft from the the speakers directly back to the booth.

bishopthomas I'm in northern NJ in a town called Verona
 

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Quick question; why do you feel they need to move? Why not let them happily live on stage and just clean up the wiring in their rack?
 
Eboy87 they don't really have to, in my first post I asked if the better place for them is the booth or on stage and so far it seems to be a mixed opinion but no they do not really have to be moved. Because of the complexity of moving them I might just end up just fixing the rack.

The only problem I have with the setup is the space and if I do hook up the graphic eq and compressor I have laying around it would take up even more space but its not the end of the world

bishopthomas yea thats a pretty far ride for something small like this, thanks anyway
 
Well, that's what I get for scanning a thread after a long load out.

How big are the wings, and how big is the amp rack? If it's a convenient work height, you can use it as a work station for wireless mics. Our cable trunk doubles as my RF workstation. I think you're fine leaving them on stage. The graphic and compressor are valuable tools, but only if you understand how to use them. Don't just hook them up because they have blinky lights or fun slidy thingies. There are plenty of threads about how best to use compression and EQ on CB, just do a search. Read what you can then ask questions; we're more than happy to fill in the gaps.
 
Something that worries me about that EQ system is the "feedback exterminator" if there is no option to turn that off there may be a very good reason why its disconnected. We have a DSP in our space that does our limiting and eq all via a computer interface but it had a feedback exterminator on it, it made our system sound horrible because instead of pulling back the frequency just enough to remove feed back it actually cut the freq all together. After 3 years of it being installed and no one knowing how to hold a microphone nor how to use a volume control it had developed a nasty blank section where there should have been a little mid range and high range. Lets just say as soon as we clicked the disable box next to it the system sounded much cleaner.
 
I've made a couple suggestions on the drawing but as of now I can't upload it. I'll try again in a minute. Specific equipment would still help!

I think your best bet is to put the graphic EQ inline with the mains outs. This should be in your Front of House position (where the mixer is) so the sound tech can hear the results. Play around with what it does and remember that you should always cut and almost never boost - boosting can increase the potential for feedback.

You can then use the channel insert for the compressor on a couple important channels and play around with it a bit (hopefully not during a show...). Once you have it figured out, use sparingly!

An insert is basically a loop - you send the sound out of the channel into an external processor and then back in to the channel after the processor. To do so, you'll need a special insert cable - like this one.

I'm not sure the feedback destroyer is needed - and if it is, it should also be used as an insert on the channel that needs it most, not not the main L an R outputs.
 
I've made a couple suggestions on the drawing but as of now I can't upload it. I'll try again in a minute. Specific equipment would still help!

I think your best bet is to put the graphic EQ inline with the mains outs. This should be in your Front of House position (where the mixer is) so the sound tech can hear the results. Play around with what it does and remember that you should always cut and almost never boost - boosting can increase the potential for feedback.

You can then use the channel insert for the compressor on a couple important channels and play around with it a bit (hopefully not during a show...). Once you have it figured out, use sparingly!

An insert is basically a loop - you send the sound out of the channel into an external processor and then back in to the channel after the processor. To do so, you'll need a special insert cable - like this one.

I'm not sure the feedback destroyer is needed - and if it is, it should also be used as an insert on the channel that needs it most, not not the main L an R outputs.

The problem with feedback eliminators is most of the time they come in as a pass through device and not an insert device. Not to mention this is an all in one unit (at least that's how it appears)
 
The problem with feedback eliminators is most of the time they come in as a pass through device and not an insert device. Not to mention this is an all in one unit (at least that's how it appears)

There's some good discussion on PSW about feedback destroyers and I'm sure Brad has more advice - I've never actually needed to use one myself, but I can imagine situations (unattended lav mics, for instance) where a properly set automatic feedback suppressor could be invaluable.

However, using one on the entire mix bus could lead to catastrophic results, as you discovered. I'm betting that since Dude2144 said "Feedback Destroyer", he means a stand-alone Behringer unit, since it seems they're the only ones who use that nomenclature. That could be inserted on a single channel and, if set up properly, could be of benefit (though you may need an insert cable with XLR instead of TS connectors on the end).
 
It could be that the amps used have integrated processing, one thing that did stand out in the system single line diagram provided was that you apparently have some delay fills but I don't see any associated delay or any other processing. If the amps do include processing then that may also affect how you might use the equalizer at FOH.

On a more specific note, it would help others better understand the system if the diagram was a bit more detailed such as showing the individual amps and how the speakers connect to them as well as any other outputs from the console used for monitors, ALS, etc. An example of how this might matter would be that if you the amps do indeed include processing and you have some tie line or monitor sends off the console that are not shown then that may affect where you would be most likely to use the equalizer.

I agree with rwhealey that the qraphic EQ, compressor and Feedback Destroyer may not be hooked up specifically because they were intended to be patched where and as needed. Then again, they might have been taken out of the loop because someone previously had no idea of how to use them so it was easier to eliminate them.
 
I think your best bet is to put the graphic EQ inline with the mains outs. This should be in your Front of House position (where the mixer is) so the sound tech can hear the results. Play around with what it does and remember that you should always cut and almost never boost - boosting can increase the potential for feedback.

You can then use the channel insert for the compressor on a couple important channels and play around with it a bit (hopefully not during a show...). Once you have it figured out, use sparingly!

An insert is basically a loop - you send the sound out of the channel into an external processor and then back in to the channel after the processor. To do so, you'll need a special insert cable - like this one.

heres an updated sketch. Once the signal goes from the main out from the mixer into the EQ where should it go next? right now its not going anywhere unless i tracked the wiring back wrong its going into the EQ but it doesn't come out
 

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heres an updated sketch. Once the signal goes from the main out from the mixer into the EQ where should it go next? right now its not going anywhere unless i tracked the wiring back wrong its going into the EQ but it doesn't come out

You need to identify and list what output jacks are being used on the mixer telling us the actual connections.

Sharyn
 
sorry that post was stupid yes the mains are being used right now the snake is connected to board, so if i took the main outs from the board went through the EQ and if i need it the compressor then into the snake. The last question I have is how to test specific frequency ranges to calibrate the eq to fit the space but i'm sure theres another thread about that on the forum somewhere. Thanks a lot for the help everyone
 

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