Quick question, wiring power amp to speakers (PA)

ChrisB2 · #1 11-03-2011, 04:18 PM

We just got some new (to us) P.A. equipment at church and the guy wiring it up ran two pairs of speaker wires all the way from one of the power amps, through the attic, to two line arrays (8 ohms each). One pair of wires to each array. Left channel of amp wired to left array, right channel to right array. We're running a mono signal.

The speakers are wired with stranded wire on binding posts on the amp, not speakon or 1/4".

I already know we need to switch to bridged mono to get more power from the amp, and that daisy chaining the arrays with one pair of wires from the amp would achieve that. My question is: can we just use the 2 pairs of wires already running through the attic, putting the two + wires together on one post, and the 2 - wires on the other?

This would be much easier than going back up in the attic to daisy chain...

Thanks

bongomania · #2 11-03-2011, 04:27 PM

You DO NOT get more total power by bridging the amp. Additionally, if you bridge the amp incorrectly then it will burn up.

Before you touch the wires, find the instruction manual for the specific power amp and READ IT.

grendle · #3 11-03-2011, 06:15 PM

Quote:

Originally Posted by bongomania

You DO NOT get more total power by bridging the amp.

? Please explain.

My stereo power amp is 330 watts per side @ 8 ohms , 1200 watts bridged mono into 4 ohms.

grendle · #4 11-03-2011, 06:18 PM

+1 on bridging the amp correctly. Usually the amp has to be set to mono, cables hooked correctly there to bridge it and then hooked up correctly at the speakers for the proper load. If not you'll fry it.

RickenBoogie · #5 11-03-2011, 06:21 PM

Wattage ratings are tricky business. Bridging an amp increases the voltage swing, (+/-)- but it's all very much over my head. +1 to not doing anything until the manual's been read and understood. Easy to fry an amp if you're not sure of what you're doing.

bongomania · #6 11-03-2011, 06:29 PM

Quote:

Originally Posted by grendle

? Please explain.

My stereo power amp is 330 watts per side @ 8 ohms , 1200 watts bridged mono into 4 ohms.

330 + 330 = 660 watts at 8 ohms.

Say it puts out 600 W per side at 4 ohms,

600 + 600 = 1200.

So at 4 ohms you either get 600 + 600 in stereo, or you get 1200 bridged.

grendle · #7 11-03-2011, 06:55 PM

Quote:

Originally Posted by bongomania

330 + 330 = 660 watts at 8 ohms.

Say it puts out 600 W per side at 4 ohms,

600 + 600 = 1200.

So at 4 ohms you either get 600 + 600 in stereo, or you get 1200 bridged.

Yeah , so running the amp bridged at 4 ohms will give more power than stereo at 8 ohms. So how is that not more power?

greenboy · #8 11-03-2011, 07:01 PM

Because bridged at 4 ohms equates to dual mono at 2 ohms.

Von Felgenhauer · #9 11-03-2011, 07:03 PM

Lol. Check the ohms homie. More power can flow through less ohms, hence why you can get more of its power through 4ohm versus 8ohm.!

seanm · #10 11-03-2011, 07:03 PM

I would stay away from bridging. You will likely get the same, or slightly less, power than from running stereo. You can't get something from nothing.

What power amp is it?

seanm · #11 11-03-2011, 07:07 PM

Since we don't know the amp, here is a real example from my Peavey IPR 1600:

Rated Power (2 x 2 ohms) - 800 watts per channel @ 1 kHz at <0.1% T.H.D. both channels driven.
Rated Power (2 x 4 ohms) - 530 watts per channel @ 1 kHz at <0.1% T.H.D. both channels driven.
Rated Power (2 x 8 ohms) - 300 watts per channel @ 1 kHz at <0.1% T.H.D. both channels driven.
Rated Power (1 x 2 ohms) - 1000 watts @ 1 kHz at <0.1% T.H.D.
Rated Power (1 x 4 ohms) - 600 watts @ 1 kHz at <0.1% T.H.D.
Rated Power (1 x 8 ohms) - 320 watts @ 1 kHz at <0.1% T.H.D.

So two x 8 ohms (his current setup) would give 2 x 300W = 600W. Bridging it at 4 ohms would give.... 600W. So no increase. But the amp will see a higher load and will run generally run hotter.

ChrisB2 · #12 11-03-2011, 07:08 PM

Quote:

Originally Posted by bongomania

You DO NOT get more total power by bridging the amp. Additionally, if you bridge the amp incorrectly then it will burn up.

Before you touch the wires, find the instruction manual for the specific power amp and READ IT.

Thanks for the help, Dad.

I did read the manual, several times.

The question had nothing whatsoever to do with wattage ratings or bridging correctly. It had to do with wiring the speakers, since the wiring options are not clearly discussed in the manual.

Quote:

Originally Posted by bongomania

330 + 330 = 660 watts at 8 ohms.

Say it puts out 600 W per side at 4 ohms,

600 + 600 = 1200.

So at 4 ohms you either get 600 + 600 in stereo, or you get 1200 bridged.

Precisely. Right now (under your scenario above), I'm getting 330 per side into two 8 ohm arrays. I want to get 1200 bridged on a 4 ohm load (daisy chaining the arrays), which will net 600 per side.

Sorry you were unable to comprehend the situation, but thanks for trying.

Von Felgenhauer · #13 11-03-2011, 07:10 PM

Quote:

Originally Posted by ChrisB2

Thanks for the help, Dad.

I did read the manual, several times.

The question had nothing whatsoever to do with wattage ratings or bridging correctly. It had to do with wiring the speakers, since the wiring options are not clearly discussed in the manual.

Precisely. Right now (under your scenario above), I'm getting 330 per side into two 8 ohm arrays. I want to get 1200 bridged on a 4 ohm load (daisy chaining the arrays), which will net 600 per side.

Sorry you were unable to comprehend the situation, but thanks for trying.

Lol. First are your speakers 4 ohms or 8 ohms? Since he wired it up in the 8 ohm way I would guess that's why it's not bridged. Second, I wouldn't be so quick to poke at Bongomania, he does know more then most. ...

steveksux · #14 11-03-2011, 07:18 PM

Quote:

Originally Posted by seanm

Since we don't know the amp, here is a real example from my Peavey IPR 1600:

Rated Power (2 x 2 ohms) - 800 watts per channel @ 1 kHz at <0.1% T.H.D. both channels driven.
Rated Power (2 x 4 ohms) - 530 watts per channel @ 1 kHz at <0.1% T.H.D. both channels driven.
Rated Power (2 x 8 ohms) - 300 watts per channel @ 1 kHz at <0.1% T.H.D. both channels driven.
Rated Power (1 x 2 ohms) - 1000 watts @ 1 kHz at <0.1% T.H.D.
Rated Power (1 x 4 ohms) - 600 watts @ 1 kHz at <0.1% T.H.D.
Rated Power (1 x 8 ohms) - 320 watts @ 1 kHz at <0.1% T.H.D.

So two x 8 ohms (his current setup) would give 2 x 300W = 600W. Bridging it at 4 ohms would give.... 600W. So no increase. But the amp will see a higher load and will run generally run hotter.

I think you are misinterpreting this....

The 1x numbers are probably for a single channel driven, not bridged. There's less load on the power supply with only one channel pumping out full power, so the power supply voltage doesn't sag as much, and you can squeeze a few more watts out. Hence 2x8=300 W, 1x8=320 watts. But that's per channel.

You're running each channel at 8 ohms in stereo, if you run both speakers paralleled, they are a 4 ohm load total, and the amp sees a 2 ohm load per channel=4 ohms.

Your 2 x 2 ohm wattage is 800 watts per channel driven, so you'd see 1600 watts bridged into 4 ohm loads.

No way an amp that puts out 300W per channel @8 ohms and 530 @4 ohms only puts out 320W bridged @ 8 ohms. That puts a 4 ohm load on both channels, so from the 2x4 ohm power of 530W per channel, you'd actually get 1060 W at 8 ohms bridged. The amp can't tell the difference between a stereo 4 ohm load per channel and an 8 ohm load bridged. Amp sees a 4 ohm load on each channel either way.

Randy

ChrisB2 · #15 11-03-2011, 07:20 PM

Quote:

Originally Posted by Von Felgenhauer

Lol. First are your speakers 4 ohms or 8 ohms? Since he wired it up in the 8 ohm way I would guess that's why it's not bridged. Second, I wouldn't be so quick to poke at Bongomania, he does know more then most. ...

Bongomania may know it all, but the attitude of assuming I didn't read the manual or understand load ratings is unwelcome.

The line arrays are 8 ohm each, as stated in the OP.

Why are we even discussing this? I was just looking for an answer to my question; is doubling up two pairs of wires on the bridging posts the same as daisy chaining???

greenboy · #16 11-03-2011, 07:20 PM

Quote:

Originally Posted by seanm

I would stay away from bridging. You will likely get the same, or slightly less, power than from running stereo. You can't get something from nothing.

There is no getting something for nothing involved here. That is not the consideration when choosing to bridge or not to bridge.

And your IPR stuff has no bearing here since you don't even have the bridge output listings in there (though they require only easy addition to calculate).

**B-string** · #17 11-03-2011, 07:21 PM

You do not have to go back in the attic. Just use the wires already run to the amp, I hope the speaker wires are at least 12 awg for the long distance run or better 10 awg?

ChrisB2 · #18 11-03-2011, 07:23 PM

Quote:

Originally Posted by seanm

Since we don't know the amp, here is a real example from my Peavey IPR 1600:

Rated Power (2 x 2 ohms) - 800 watts per channel @ 1 kHz at <0.1% T.H.D. both channels driven.
Rated Power (2 x 4 ohms) - 530 watts per channel @ 1 kHz at <0.1% T.H.D. both channels driven.
Rated Power (2 x 8 ohms) - 300 watts per channel @ 1 kHz at <0.1% T.H.D. both channels driven.
Rated Power (1 x 2 ohms) - 1000 watts @ 1 kHz at <0.1% T.H.D.
Rated Power (1 x 4 ohms) - 600 watts @ 1 kHz at <0.1% T.H.D.
Rated Power (1 x 8 ohms) - 320 watts @ 1 kHz at <0.1% T.H.D.

So two x 8 ohms (his current setup) would give 2 x 300W = 600W. Bridging it at 4 ohms would give.... 600W. So no increase. But the amp will see a higher load and will run generally run hotter.

No increase for your amp, but the one in question gives more power bridged mono 4 ohms than it does running two channels at 8 ohms.

ChrisB2 · #19 11-03-2011, 07:27 PM

Quote:

Originally Posted by B-string

You do not have to go back in the attic. Just use the wires already run to the amp, I hope the speaker wires are at least 12 awg for the long distance run or better 10 awg?

Thank you for your helpful answer!

Yes, the wires are 12 guage.

steveksux · #20 11-03-2011, 07:33 PM

Quote:

Originally Posted by ChrisB2

I already know we need to switch to bridged mono to get more power from the amp, and that daisy chaining the arrays with one pair of wires from the amp would achieve that.

Not sure what you mean by daisy chaining in this context.

Quote:

My question is: can we just use the 2 pairs of wires already running through the attic, putting the two + wires together on one post, and the 2 - wires on the other?

This is fine. This lets each set of wires carry half the current, since each wire only drives one speaker.

Quote:

This would be much easier than going back up in the attic to daisy chain...

Thanks

I think what you may mean by daisy chaining, is running one set of wires from amp, through attic to one speaker, then run wires from one speaker to the other. This would be worse than your current setup, as the wires from the amp to the first speaker would be carrying all the current for both speakers. To try to be equivalent to what you have, you'd have to get 10 ga wire run in the attic since that wire would be driving both speakers.

Hard to find wire much thicker than 12 ga, so you're better off with your current setup on 12 ga wire going to each speaker.

Randy