Speaker to Amp connection

[DCand]

I work at a school and our speaker configuration is confusing me.

Our set up is a square room with 1x speaker in each corner (4 in total) JBL 29AV-1. They are all connected to the ceiling on a bar as lights are also hung on the bar. This means I can't see where the speaker cable connects to exactly but I have tested them individually and they all work.

The problem is that in our control room we have 3 amps - labelled amp 1,2 and 3. Each have 3 connections L, C and R. we use a speaker with a speakon connector to connect the amp to the corresponding speaker. I found that only Amp 1 is able to produce sound. I've tried replacing cables in both amps 2 and 3 but no sound comes out. As a result, I only have 3 input sources (L,C and R) for 4 speakers. I've also tried adjusting the sound and it sounds horrible as it is obvious that one isn't plugged in.

I've checked the wiring at the back of amps 2 and 3 and they are connected properly - + to + and - to -.

I could be missing something very simple here, but it would be great to get some advice as I am still quite new to sound set-ups!

Thank you!

 

[slashbinslashbash]

I'm not really understanding what you're saying here. Let me try to clarify:

You have 4 speakers. You say they all work, but then it sounds like maybe one of them doesn't actually work? You have tested them all individually, or not? I.e., so that only 1 of them is playing at a time? You have 3 amps. Each amp has 3 output terminals (this seems strange, they should come in pairs). You plug the speakers into the amps using speakon connectors. What connectors go into the speakers?

The first thing that ran through my mind when I read your post quickly (before I read it again and got confused) was this: Speakers are able to be run in series. This means, connecting the + terminal of one speaker with the - terminal of the next speaker down the line. You can hook up as many speakers as you want in this way, and they kind of split up the power equally. However, this can do wacky things with the overall resistance (ohms) of the setup and cause your amp to overheat and/or fail. So you could actually run all 4 speakers from 1 amp terminal pair; or 2, if they are bridged. So maybe one pair of speakers is set up in series? Who knows. They could also be set up in parallel, basically splitting the cable as it comes out of the amp and having both be powered from the same terminal. Basically you will need to follow each wire and see how it is connected to each speaker.

It would be great if you could take photos of the backs and fronts of the amps too.

 

[DCand]

Thank you for your reply!

I can only take a picture from the front as all our sound systems have been installed into a metal cabinet which is attached to the wall....

When I tested each speaker, I used amp 1 (L) and used the speakon cable to connect through a range of speaker connections (labelled Sp1-16) so it was a trial and error to see which speaker corresponded to each number (in our case sp1, 3, 9 and 11).

An example of our current configuration is Amp 1 (L) *speakon cable* to Sp1.

However, when I test this with amps 2 and 3, Amp 2 or 3 (L) to Sp1, no sound comes out.

I will take a picture for you soon. I really appreciate your help!

 

[DCand]

That's why with my 3 connections, (L,C and R) I can only connect for example Sp, 1,3 and 9 and sp11 will not have a connection that works.

 

[slashbinslashbash]

Ok yeah, a photo of the front of the amps, and a photo of whatever speaker connectors you have coming out of the wall or whatever. If there's any way you can reach a camera back behind the amps and take a photo, that would be great... or simply pull one amp completely out.

You have 4 wires with speakon connectors coming out of the wall? Each corresponds to an individual speaker?

Do all of the amps have sources connected to them? The amp can't output any sound, if it doesn't have any input.... could be why you don't get anything when you hook up to amps 2 and 3.

 

[DCand]

Ah yes, the main issue I'm having is where to find the amp input.

The way our speakers were connected is impossible to trace as the wires actually go in the wall and about 20ft up high where the speakers are placed.

Here are the pictures:

Front view

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Amp 1 - with speak-on connectors in all 3 plugs front and back view


Amp 2 - back view



Amp 3 - back view



From all 3 amps, each have 2 wires, black and red.

 

[slashbinslashbash]

Those are not the amps, those are the backs of the patch panel. The black thing with all of the plugs and the labels is just a patch panel for connecting the amps to the speakers.

The amps themselves are the white Crown XTi boxes below the patch panel. The inputs would go into those, somewhere on the back sides.

 

[DCand]

Thanks for the clarification, I was definitely misled by the labels.

It makes sense now because we have 3x Crown XTi's which means two of them are not connected. It's just a matter having a look at the back inputs and hopefully that will solve the problem!


Thank you very much!

 

[slashbinslashbash]

No problem, I hope that solves it for you.

Taking a look at Crown's info on those amps.... they are 2-channel amps that can be used in bridged mode. I would definitely recommend using only the L and R, skipping the middle output, which probably corresponds to bridged mode. Or maybe, you can use the middle one only if the L and R are NOT being used on that amp. So maybe something like this:

Speaker 1: Amp_A_R
Speaker 2: Amp_A_L
Speaker 3: Amp_B_Bridged
Speaker 4: Amp_C_Bridged

This would probably be the way to make the most of the equipment that you have. But it also could over-power the speakers. To be completely safe, just use the L/R connections and skip the middle ones, and try to get someone in there who knows what they're doing, can take a look at the exact way that the amps are hooked up, and understand why the equipment would be set up in this particular manner (Are there no more speakers taking up the rest of the ports? Are larger speakers ever connected? This would make sense if there were extra speaker connections throughout the room, which are presently unused but which could be connected to other speakers for events, etc.... in which case, you might want to use the amps in bridged mode.).

 

[kanika]

This is a series/parallel connection (below)
First Connect the left and right channel speaker wires to the ‘Main’ or ‘Front’ speaker outputs from the the back panel of the amplifier, then take the wires to the terminals on the back of each speaker. connect the left channel output of the receiver to the left channel speaker and the same for the right channel reciever to the right channel speaker . Correct speaker phasing is very important for the best sound

 

[DCand]

Thank you again for your instructions. The reason why it's so difficult to get things done is because they were connected by a cheap company few years ago and they don't even have maintenance technicians! That's why I have taken to forums to ask for help...

 

[DCand]

Here is what the amp looks like from the back. Where do I plug the speaker cable to?

 

[slashbinslashbash]

Here is what the amp looks like from the back. Where do I plug the speaker cable to?

Looking at that diagram from left to right: 1x Power plug, 4x binding posts, 2x speaker connectors, 1x cooling fan, 4x XLR inputs, 1x USB input.

I assume that the wires from the back of your patch panel are raw wires, with the insulation stripped so that you can see the bare copper inside? If so, they should go on the round things on the far left, closest to the power plug. These are called "binding posts" and you twist them to unscrew them, they come back enough to let you slip the wire underneath and then screw them in to clamp them back down. You will have to attach red to red, black to black. Each speaker will require 2 wires connected in this manner.

If there is a plug on the end of the wire coming from the patch panel, then it should go into the circular sockets to the right of the binding posts.

The inputs (from microphones or other audio sources) will use the XLR jacks on the right side of the amp.

Really though you should examine the amp that is already working, and replicate the connections for the other amps.

 

[DCand]

We also use this DI box mainly for us to play sound from a laptop (via RCA cable) into the speakers. The XLR cables connect to our PA mixer with a specific channel for phantom power, where we can control volume using the faders.

 

[DCand]

Here are the connections at the back of the Crown XTi4000.

Top corresponds to 'amp 1' - the only amp that produces sound.
The one underneath is 'amp 2' - no sound