Re-Connecting Speakers to Sound Processor

[Jake Sinn]

Hi all

We need to re-connect the sound processor back into one of our theaters. It is a small theater with only about 85 seats.

The processor got taken out of the theaters' projector booth. I need to reconnect the speakers to the processor. I have photos of the back of the processor from months ago when it was connected. If someone could kind of explain how it should be connected and if each wire needs to be connected to a certain spot. It's also worth mentioning that there is an Odyssey Adapter (the processor we have is USL-JSD60)

Jake

[Ian Freer]

Hi Jake
If the processor was removed, what are the chances it was used elsewhere and now has the incorrect config/EQ-ing for your location?
Best thing to do is get a cinema technician with appropriate tools in there and get it installed and commissioned correctly.

Having said that, if you are going to give it a go yourself, the Odyssey board will have Channel ID's printed on it. Connect the outputs from the Odyssey board to the appropriate inputs on the booth monitor and/or direct to the amplifiers. (This of course assumes you know (or can identify) which amplifiers are powering which speakers). Your question and situation is really a bit to broad to get a simple answer.

Cheers,
Ian

[Jake Sinn]

The processor was not used somewhere else.

I believe each amplifier is labeled with what speaker it is in the theater. If that is the case, can I just connect each wire (red and black) the same as in the picture? As far as I can tell from the picture when it was connected, wires were connected to each of the following:

- Rs+, Rs-
- Ls+, Ls-
- L+, L-
- C+, C-
- R+, R-

I can clearly see where the wires are plugged into the Odyssey board. I feel like it's more a matter of deciphering which wire goes to each speaker. I'm positive that matters which wires go into each slot in the board (correct me if I'm wrong).

In the event that each speaker is not labeled, what would be the best way to figure out which each one is (Ex: making a buzzing noise to each speaker?)

And, if it is done incorrectly, (Ex: doesn't end up working in the end), can that damage anything, or is it just a situation where it doesn't matter and it was worth a try)?

Jake

[John Thomas]

Grab a roll of masking tape and a pen. Purchase a set of flat-head precision screwdrivers.

Looks like you have 5 cables. They correspond to Left, Center, Right, Right Surround, and Left Surround -- but you will need to identify which is which. Follow each cable down to its other end, where it is hopefully labeled. You might have to cut some zip-ties to make this easier. Go back to the top of each cable and label it with the masking tape so that now, at the processor, you know which cable goes to which channel. This is the concept known as channel ID.

The red leads go to the + terminals, and the black leads go to the - terminals. If you have a third, bare lead, that goes into the the terminal labeled SH. That's called shield.

When you're connecting those tiny leads into the terminals, it's a good idea to twist the bare copper/tin a little to make sure no strays get loose and touch things they shouldn't.


Once they're all connected, it's a good idea to use the Dolby Channel ID DCP to check your work and identify any mismatches.

[John Thomas]

If the processor has wildly different levels set for the various channels, then yes there is a chance of damaging speakers if you make a mistake here. When you run it for the first time, start with your fader set pretty low, like 4.0.

[Jake Sinn]

Grab a roll of masking tape and a pen. Purchase a set of flat-head precision screwdrivers.

Looks like you have 5 cables. They correspond to Left, Center, Right, Right Surround, and Left Surround -- but you will need to identify which is which. Follow each cable down to its other end, where it is hopefully labeled. You might have to cut some zip-ties to make this easier. Go back to the top of each cable and label it with the masking tape so that now, at the processor, you know which cable goes to which channel. This is the concept known as channel ID.

The cables are wired in the wall. Can't I just touch each end of wire to a AA battery and listen for a buzz?

[Jake Sinn]

If the processor has wildly different levels set for the various channels, then yes there is a chance of damaging speakers if you make a mistake here. When you run it for the first time, start with your fader set pretty low, like 4.0.

The processor is going back in the same and only theater it has always been in, so I think that is unlikely.

[Dave Macaulay]

I use a 9v battery to identify speakers when wires are not labelled, 1.5v would not make much of a click.
Some confusion though, you keep talking about connecting speakers to the processor... the processor outputs (ftom the Odyssey card) connect to power amplifiers which then connect to the speaker wires. I expect you know this, but just want to make sure.

[John Thomas]

Where are your amplifiers? Are they in the rack with the processor?



Regarding the battery thing: that trick works between the amps and the speakers. Not a good idea to send 1.5VDC into an amp.

Regarding differing channel levels: Left Surround and Center (for example) may have wildly different levels from each other. Swapping them accidentally could send a very high level signal into a channel that can't handle it. Not a huge worry though if you are certain that you start at a low fader.

[Jake Sinn]

Yes, the amps are in the rack with the processor.

I am not too familiar with the whole setup, I am familiar with the speakers and the sound processor.

Please correct me if I'm wrong. Each speaker needs power, and each speaker has its own "power amps". Each power amp has power going to it (obviously). How is each speaker connected to each power amp, and then also being connected to the processor?

[John Thomas]

It might be simpler than you think.

The audio goes Processor -> Amplifier -> Speaker.

Why the amplifier?

The processor is putting out audio in the millivolt range. Very low power. Not enough to physically move a speaker driver back and forth to make sound.

So the amplifier just takes that very low power audio signal and makes it high enough power to drive the speaker. It amplifies the audio.

[Jake Sinn]

John,

Thank you for the explanation. My question is, I don’t have to mess around with the amplifiers at all, assuming that they weren’t touched from when the processor was taken out. I am 95% sure that the wires are labeled, so if that is the case, the only task would be to re-install the processor in the rack, then re-connect the five wires to the Odyssey board (each wire going to the odyssey board should be coming from each speaker amp, correct?)

My other question is, just wondering for myself, how/what kind of wire is connecting the processor to the amplifier?

[Randy Stankey]

This is how we identified speakers when we were setting up Tinseltown, when I first started working there.

Have a reasonably intelligent person go to the auditorium and listen while you tweak the bare ends of each pair of wires with a 9-volt battery. The person in the auditorium will point to the speaker where he heard the noise or shine a flashlight on it.

Using a Sharpie marker and white electrical tape, mark each pair for what it is. Right - Center - Left - Left Wall - Right Wall.
You might also have Back Wall - Subwoofer. It is also possible for the wall speakers to be wired separately or in groups RW[1...n] and LW0[1...n].

Double check to be sure you've got them right. Not only will it be confusing if you get them mixed up, it is possible to damage speakers if you get them wrong.

You can talk all day about how to hook the speaker wires back up but you can't do anything until you know which speaker wires are which.

BTW: While you are working with stranded wires, make sure all of the strands get into the connection terminal if you can. Try not to let any more than three strands poke out. If you don't get them all through the terminal break them off and cut them back to the insulation so that no metal pokes out. If you cut off more than three strands or if they get damaged or broken, you'll have to cut and restrip the wire again. You can't have more than three missing or damaged strands in a 12 AWG wire.

Also, don't twist the strands in order to get them into the terminal. Just gently twirl it to restore the lay of the strands to their original shape but don't twist them any more than that.

Twisting the strands makes the wire weak and more likely to break. Damaging more than three strands messes up the electrical characteristics of the wires and also makes for weak connections.

You don't want to have to go back, behind the screen or crawl around the bottom of a sound rack in the dark to chase down bad connections.

Those kinds of failures always seem to happen at the worst possible moment... Usually with a full house.

That's why we have the "Three-Strand Rule" and the "No Twist" rule, to prevent those things from happening.

[John Thomas]

Look at the pictures he posted. Those leads don't go to speakers, they go to amps. Don't touch a 9V to those.

[John Thomas]

Jake: Yes, the amps should not need any attention. If those five wires are labeled, then yep, just follow them up and connect them to where they go on the Odyssey board like I described above.

The connection you're re-establishing here is in fact from the processor to the amplifiers, so the answer to your second question is, exactly what you're looking at. If you mean like what kind of wire specifically, it's probably 22 awg stranded shielded. Something like West Penn 452.