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View Full Version : PA Wattage, Speakers, Ohms, Etc.



mainestratman
May 22nd, 2010, 06:46 PM
I *think* I've done the math correctly, and I *think* this will work.

PA Amp: 1000w/ch @ 4ohms (x2 channels)

Channel A (full range) = 1000w into (2) 400watt (program), 800watt (peak) FoH
Channel B (subs) = 1000w into (2) 400watt (program), 800watt (peak) FoH

Oh wisened electronic geeks... please assure me that at least in theory this setup won't blow up my speakers?


(Monitors run on a completely different amp, FYI)

Thanks!

:beer:

BigJD
May 22nd, 2010, 07:15 PM
I *think* I've done the math correctly, and I *think* this will work.

PA Amp: 1000w/ch @ 4ohms (x2 channels)

Channel A (full range) = 1000w into (2) 400watt (program), 800watt (peak) FoH
Channel B (subs) = 1000w into (2) 400watt (program), 800watt (peak) FoH

Oh wisened electronic geeks... please assure me that at least in theory this setup won't blow up my speakers?


(Monitors run on a completely different amp, FYI)

Thanks!

:beer:


What amp you using? and what are the speakers? Sometimes you really gotta be careful with manufactures amp and speaker wattage ratings.
Some combinations love alittle extra power others not so much.

mainestratman
May 22nd, 2010, 07:15 PM
All Peavey stuff.

PV115 for Full range, PV118 for subs. I'm looking at the IPR3000 for amplification, but not completely sold on it yet because it's still so new. And inexpensive. And light.

BigJD
May 22nd, 2010, 07:17 PM
All Peavey stuff.
Well I love Peavey stuff it's a work bands dream.
I usually power mine close to the lower end of their ratings and I try to match my amps to that rating so as to be safe.

BigJD
May 22nd, 2010, 07:21 PM
All Peavey stuff.

PV115 for Full range, PV118 for subs. I'm looking at the IPR3000 for amplification, but not completely sold on it yet because it's still so new. And inexpensive. And light.
By their specs you only need 600 watts per side to power them the most efficiently.

mainestratman
May 22nd, 2010, 07:22 PM
Yup. I figure an extra hundred watts per speaker isn't going to hurt too much. Plus, I can dial back the amp.

There aren't any venues around here big enough to handle that much power, unless we're outside... which is what I'm shooting to.. a good outside setup that can be "scaled back" for small club stuff.

BigJD
May 22nd, 2010, 07:22 PM
By their specs you only need 600 watts per side to power them the most efficiently.
Looks like the IPR is a good match if you use the limiters and crossover right.

mainestratman
May 22nd, 2010, 07:27 PM
So 600 watts into two 400 watt-rated speakers, for 300 watts per speaker?

And which IPR? The 1600 or the 3000? The specs in the manual listed online are for the 1600.

BigJD
May 23rd, 2010, 11:01 AM
So 600 watts into two 400 watt-rated speakers, for 300 watts per speaker?

And which IPR? The 1600 or the 3000? The specs in the manual listed online are for the 1600.


The IPR 3000 . That'll give you plenty of power for those cabs.
You'll need to use some limiting for protection.

mainestratman
May 23rd, 2010, 11:09 AM
Yup.

I've been discussing this amp with on the Peavey forum as well. Apparently there's another variable that comes into play.. "damping factor"..

Still working on it.

Your input has been extremely valuable.. thank you so much. :-)

BigJD
May 23rd, 2010, 02:11 PM
Yup.

I've been discussing this amp with on the Peavey forum as well. Apparently there's another variable that comes into play.. "damping factor"..

Still working on it.

Your input has been extremely valuable.. thank you so much. :-)
I realy believe in powering speaker at their program rating or close to it.
My experience with over powering or having a bunch of "headroom" is that one simple mistake can cost you alot in speakers.
The only thing is knowing which manufactures ratings are true and which are blown outta preportion by marketing hype.
Peavey has always been good at giving real world numbers.

deeaa
May 27th, 2010, 05:31 AM
Giving a speaker more than its rated power is seldom bad; you will (or should) hear they can't take it well before they blow, plus most any decent speaker has in-built fuses via means of lightbulbs or real fuses anyway.

It is quite hard to blow a speaker with too much amp power, only happens basically if you go into feedback, and then blow the tweeter. OR really disregard horrible sound and the sight of woofers trying to detach from their enclosures.

What blows fullrange speakers the easiest is too little power.
BECAUSE if you for instance have an amp of 600W and a speaker of 600W both rated that at RMS and 8 ohms for instance, then what happens when the speaker is pushed hard and the voice coil jumps almost out of the magnet with bass hits? Yep, the speaker impedance drops drastically, say down to 2 ohms.

Now there are plenty of amps that may give 600W to 8 ohms OK but maybe only 200W to 2 ohms, and that means that when the speaker impedance drops, the amp cannot provide a clean signal, and instead produces square wave, and THAT blows up the speaker faster than you can say oops.

With Peavey boxes & peavey amps I don't think that'd be much of a problem, but especially if you cannot verify what does the amp yield in low impedances, it's always better to err on the side of a bigger amp.

We used to have 1000W amps into 750W fullranges, and I recall one occasion where we blew a fuse on one of the cabs, or tweeter side actually when it fed back ugly...but it was a Peavey cab and had a lightbulb fuse so it was a 5-minute job to fix it back up.