P.A. Amp and Speaker Power Match

Bruce Hamilton · Post by **Bruce Hamilton** » 17 Oct 2003 7:41 pm

Maybe you guys can help me. I've done a search and sort of answered my question but am still a little confused. I have a new box P.A. mixer which has a power rating of 250rms x 2. The speakers I have are rated at 200 watts program and 400 watts peak power. With all the different power rating scales I am getting totally confused. I have asked various supposedly knowlegdeable sales persons whether the speakers will be able to reliably handle the power from this mixer but they have been unable to give me an answer that sounds logical. The typical answer I get is that as long as I am only running voices through the system there should be no problem. What is the standard way to safely match up a power source and the the speakers?
Thanks

Wayne Brown · Post by **Wayne Brown** » 17 Oct 2003 8:04 pm

your fine bruce...you won't be driving them at there limit all the time ...your board won't see 250 until the upper end

Andy Greatrix · Post by **Andy Greatrix** » 18 Oct 2003 4:59 am

Bruce, just add a powered sub-woofer, like the kind from Yorkville, and then your speakers will only be handling the top end.
I've done it and they work like a damn,
You'll have all the headroom you need.
Long and McQuades rents them very reasonable, so you can try one and see if you like it.[This message was edited by Andy Greatrix on 18 October 2003 at 06:01 AM.]

Michael Holland · Post by **Michael Holland** » 18 Oct 2003 7:03 am

Hi Bruce,

The speaker load is the important factor in this question. Your mixer's amp(s) is rated for its output into specific loads (the 'ohm' rating of your cabinets). I also have a powered mixer that I use for small rooms, a Fender SRM6302. It has two power amps that can be switched either to use one for each main cabinet or one for mains and one for monitors. The maximum load recommended is 4 ohms for each amp. That means I can use two 8 ohm cabs for mains and two 8 ohm wedges for monitors and operate at maximum power. I can't daisy chain two more main cabs or two more monitors as that would be a load greater than 4 ohms (the higher load is actually a smaller number - it's inverted) and the power amps might be damaged.

What type of mixer and cabinets are you using?

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Bruce Hamilton · Post by **Bruce Hamilton** » 18 Oct 2003 8:14 am

Initially I bought a Yamaha sytem which consisted of a EMX62m box mixer and two S10e speakers. I found the box mixer to be underpowered for what I want to use it for and replaced it with a Behringer Europower PMX2000. The Behringer has 250rms X 2 as opposed to the Yamaha which has 200watts maximum power. When I did a search on the forum it seems from what I can gather that if you match the program power of the speakers to the power of the amp you have the ideal mix. What I am not sure of is whether the amp power referred to is maximum or rms. [This message was edited by Bruce Hamilton on 18 October 2003 at 09:32 AM.]

Michael Holland · Post by **Michael Holland** » 18 Oct 2003 10:36 am

match the program power of the speakers to the power of the amp you have the ideal mix

It's not as simple as that. The speaker load is a critical factor in this equation. Here are the specs for your gear.

Behringer PMX2000

In Stereo mode - 250 watts into 4 ohms
180 watts into 8 ohms
In Bridged mode - 500 watts into 8 ohms

The Yamaha S-10e are 8 ohm speakers rated at 200/400 program/peak. If you're using the mixer in bridged mode and connecting the two 8 ohm speakers you're overloading the amp. And I sure wouldn't feel good about running that overloaded amp through them little ten inch speakers no matter what it says on the label.

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Bill Ferguson · Post by **Bill Ferguson** » 18 Oct 2003 11:03 am

Being in sound, I agree completely that the most important factor is the impedance load. Overload an amp and it will shut down.

My power amps can carry a 8, 4 or 2 ohm load, but I do not like to run at 2 ohms. It does not leave enough headroom.

But I also see bands all the time overloading a Peavey XR600 (even my band sometimes) and we have had no problems because we NEVER use the full 250 watts of power.

So things are debatable.

Bill

Bruce Hamilton · Post by **Bruce Hamilton** » 18 Oct 2003 11:42 am

I'm not that familiar with the various configurations but the options that are given in the mixer manual are 1. 250watts to each side 2. 250watts to one side and 250watts to the monitors. 3. Bridge mode-500watts to one speaker. I would be using the first option. Would the speakers be adequate for that configuration?

Bobby Lee · Post by **Bobby Lee** » 18 Oct 2003 3:48 pm

What is the impedence of the speakers, in ohms?

Bruce Hamilton · Post by **Bruce Hamilton** » 18 Oct 2003 4:35 pm

As Michael states above they are 8ohms speakers. I guess if they are running in the even split configuration the amp would be producing a maximum of 180watts rms on each side which would be fit into the specs of the speakers. But I would just like to be sure. As I have purchased these speakers only recently I have the option of exchanging them without losing any money on the deal.

Michael Holland · Post by **Michael Holland** » 18 Oct 2003 5:51 pm

Yes, in the first mode one amp would be running 180 watts into one 8 ohm speaker and the other would be running 180 watts into the other. If you add two monitors you should run in mode 2. If you are going to be using the system in a space larger than your living room and can 'trade up', I'd recommend that you get a pair of 15" two or three way cabinets with built in crossovers. The ten inch speakers are not adequate to provide full range coverage.

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Bruce Hamilton · Post by **Bruce Hamilton** » 19 Oct 2003 1:13 am

Thanks for all the advise from everybody. I have been playing in bands for over 40 years and have been lucky or unlucky enough depending on your point of view, to not have to invest in a P.A. However my kids whom I am extremely proud of, have taken up the calling of music very seriously. This system will be mainly used as a practice P.A. in our music room for them. However the way the music business is going around here my wife and I are seriously considering doing gigs as a duo and I would like to be able to have a system that will handle lounges and small halls. I think I am going to take the upgrade mode just to be sure.
Bye the way this Behringer mixer sure seems to be a bargain for the money. It has incredible grunt and the effects are really first rate.
Thanks Again