Film-Tech Forum ARCHIVE: Surround sound wiring

This is topic Surround sound wiring in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Paul Looker (Member # 5420) on 04-09-2014, 08:09 PM:

Forgive me, I'm new to all of this. I have three surround speakers on each wall. Each one has it's own separate run of wire. How do I wire them all together into one amplifier channel. Is it all positives and all negatives together or is it something else. The most recent setup had left and right surround both wired into one amplifier channel. There are a couple of positives to negatives in what was there. Can anybody walk me through this one. I am not keeping left and right on one channel I am separating them to each their own channel. How should the three speaker wires be spliced together?

Posted by Monte L Fullmer (Member # 2797) on 04-09-2014, 08:18 PM:

With just three surrounds on each side, it's fine to attach them per each side to run parallel.

You would tie all the positives together and with the negatives together, each polarity under a wire nut with a single wire in the loom for an easy connect to amplifier.

Posted by Paul Looker (Member # 5420) on 04-09-2014, 08:24 PM:

I love you film tech forum. It's like old school dominos pizza. 30 minutes or less. Thank you.

Posted by Kenneth Wuepper (Member # 1174) on 04-09-2014, 09:06 PM:

You might find this information useful.

http://www.bcae1.com/spkrmlti.htm

Posted by Scott Norwood (Member # 30) on 04-09-2014, 09:52 PM:

Depending on the speakers and amp in question, wiring them all in parallel may be fine or may fry the amplifier. Give us the model numbers of everything and someone will tell you if it will work.

Basically, you need to figure out the minimum output impedance of your amplifier and ensure that the load that you give it is at least that number. As an example, three 8-ohm speakers in parallel will look like a 2.6-ohm load to the amplifier. Not every amplifier will drive a 2.6-ohm load without heating up or failing completely.

Posted by Brad Miller (Member # 2) on 04-09-2014, 09:59 PM:

Heed Scott's advice there. You should post the make/model of your amplifier you intend on using.

Posted by Phil Ranucci (Member # 3820) on 04-09-2014, 10:11 PM:

You might want to pull wire from each speaker back to the booth and do your series/parallel wiring there and not at each speaker. It'll make troubleshooting easier.

Posted by Steve Kraus (Member # 476) on 04-09-2014, 11:42 PM:

He already has this.

Posted by Monte L Fullmer (Member # 2797) on 04-10-2014, 12:58 AM:

If he did series parallel wiring with three, 8ohm speakers - taking two speakers in parallel would give him 4 ohms, but adding the third in series gets him up to 12 ohms and his amplifier has an unswitchable 8 ohm output.

What would be best for him and be safe at it?

Posted by Jarod Reddig (Member # 6363) on 04-10-2014, 03:37 AM:

Try out the 12 ohm series parallel route at your own risk if any as Id assume an amp that can operate safely at 8 ohms would be safe at 12 ohms. Or look for a cheap used 2 channel 2 ohm stable amp and go parllel with each set of 3. Left 3 surrounds in one channel and right surrounds in the other.

Posted by Ken Lackner (Member # 1002) on 04-10-2014, 10:41 AM:

I agree with Jarod's suggestion of finding (if you don't already have) a 2-ohm per channel amplifier and wiring each group of 3 in parallel so that the power is evenly distributed among the 3 speakers.

I also agree with Scott's suggestion to give us the model numbers of your equipment, and I agree with Brad's agreeing with Scott.

Posted by Gordon McLeod (Member # 33) on 04-10-2014, 10:54 AM:

Most amps have no problem with a higher output impedence unless it is a transformer coupled output
to low of impedance and the amp will be delivering more current than possibly the transformer and or output stage can deliver

Posted by Paul Looker (Member # 5420) on 04-10-2014, 11:55 AM:

I'm working with a QSC model 1700. It has two channels. I want three speakers on each channel.

Posted by Dennis Benjamin (Member # 1137) on 04-10-2014, 12:27 PM:

quote: Ken Lackner
I also agree with Scott's suggestion to give us the model numbers of your equipment, and I agree with Brad's agreeing with Scott.

I agree with Ken's agreeing with Brad's agreeing with Scott.

[Big Grin]

Posted by Monte L Fullmer (Member # 2797) on 04-10-2014, 12:36 PM:

quote: Paul Looker
I'm working with a QSC model 1700

That's when you look on at the back of the amplifier and look where the speaker connection terminals are located. In this area, it should display what resistance of speaker can be used in ohms.

Posted by Steve Moore (Member # 4753) on 04-10-2014, 12:41 PM:

Dennis, you are right to agree with Ken's agreeing with Brad's agreeing with Scott.

As for that QSC amp, in theory it would drive into 2ohms OK, according to it's manual, but I'd be a little on edge going that low; unless they are not being driven too hard.

I have series'd two up and then paralleled one across the two in series before in a screen with three per wall, however the single speaker gets more punishment and would be more prone to damage. Possible cheaper than a new amp is purchase another pair of speakers and put 4 a side, but that depends on what speakers you are running and if they are available.

Posted by John Eickhof (Member # 323) on 04-10-2014, 01:02 PM:

Save the trouble, parallel each set of three then series them at the amplifier nominal impedance will be abou 3.75 ohms and there will be no reaction with impedance from voice coil movement.

Posted by Mark Gulbrandsen (Member # 72) on 04-10-2014, 01:20 PM:

John...

Series parallel was thrown out 20 years ago. Speakers in series parallel cause too much resultant phase shift and other nasty distortion's. Will it work? Sure. But it is typically not done any more. And that's one reason for the 4 channel QSC power amps!

Mark

Posted by Paul Looker (Member # 5420) on 04-10-2014, 02:27 PM:

It says. 4 ohms per channel. 8 in mono bridge mode

Posted by Carsten Kurz (Member # 5396) on 04-10-2014, 03:16 PM:

Same here:

http://www.tristatetheatre.com/Series_One_Manual.pdf

So it is only spec'd to a minimum of 4 ohms. That means, per spec, parallel all three speakers is not possible. I have no experience with this type of amp to guess wether they will deal with 2.6Ohms at the required power level in real life. Some amps do, some not.

Check the speakers as well, they should say 4 or 8 ohms at the back. Though it is unlikely they would have 4ohms.

- Carsten

Posted by Ken Lackner (Member # 1002) on 04-10-2014, 03:19 PM:

quote: John Eickhof
Save the trouble, parallel each set of three then series them at the amplifier nominal impedance will be abou 3.75 ohms and there will be no reaction with impedance from voice coil movement.

Unless I'm misunderstanding what you're suggesting, that will not satisfy his requirements. He needs TWO channels, each with three speakers. Wiring the three speakers in parallel is best, but the two groups of three would then not be wired in series.

quote: Paul Looker
It says. 4 ohms per channel. 8 in mono bridge mode.

Then as Carsten points out, you do not want to wire all three parallel with this amp. Series-parallel isn't ideal, but it would be your best option.

Thank you all for agreeing with me agreeing with Brad agreeing with Scott. You're the best.

[beer]

Posted by Jarod Reddig (Member # 6363) on 04-10-2014, 05:54 PM:

You could for now just run two surrounds per side parallel per channel until you find/buy another amp. Think I'd pick the two closest to the screen but that kinda depends on the layout. If your first surround from the screen is rather close to it than maybe pick the back two.

Posted by Gordon McLeod (Member # 33) on 04-10-2014, 06:19 PM:

I still do series parallel speaker arrays some fairly large and don't really have a issue with that
The best solution would be to add 2 more speakers on the rear wall and then one would be able to balance the load

Posted by Jarod Reddig (Member # 6363) on 04-11-2014, 12:37 AM:

Curious what impendance the surrounds are. Could hook a Multimeter/ohm tester to one of the wire runs and find out.