Underpowering Stage monitors

[Blah067]

Our facility has QSC CX 302 amplifiers.

I have monitors that I want to use, but they are rated for 400 watts. They would be hooked up in a daisy chain style, two per side. (or so is my hope).

Problem...the 302's only are rated for 300 (something like that) per 4 ohm side. Thats providing 150 to each monitor....and...yeah....400 watt speakers.

HELP???
Thanks....

PS-buying new gear is out of the question. How can I make this work with what I've got?

[Chris15]

Originally Posted by Blah067

How can I make this work with what I've got?

So long as you don't run the amps into clip you will be fine.

[Blah067]

So provided the amps don't show a clip, the speakers will be fine?
Where should I adjust the volume then if I try to get the most volume out of them...
on the board or at the amp?

[waynehoskins]

Your loudspeakers are rated to dissipate up to 400 watts of power. Your amplifier will deliver up to 150 watts of clean power. No problems.

When you clip an amplifier, that's when nasty things happen. Don't do that, and you'll be fine.

400 watts coming out a monitor speaker that's pointed right at my face? Ouch. 400 watts is loud.

[TimmyP1955]

Our wedges are 8 Ohm, rated 350W, sensitivity is 99dB. The amps are rated 350W/channel into 8 Ohms, and we run one wedge per channel. The amps are barely big enough, and that's because we run limiters, and we make the bands keep their stage volume under control (owing to a loud & lively room). I'd like to have another 3dB of power at least.

[rwhealey]

PDF Warning:
http://electrovoice.com/download_document.php?doc=2320

I found this guide to be helpful in figuring out how to power speakers.

You will be fine as long as you don't try to make up for the loss of volume (because of less power) by driving the smaller amp into clipping.

[Les]

Originally Posted by rwhealey

PDF Warning:
http://electrovoice.com/download_document.php?doc=2320

I found this guide to be helpful in figuring out how to power speakers.

You will be fine as long as you don't try to make up for the loss of volume (because of less power) by driving the smaller amp into clipping.

Sorry for the hijack but I love the PDF warning. We should make that a more common courtesy. At least until I get a better computer that doesn't freeze while it loads a PDF.

[museav]

First, what 'ratings' are being referenced? Is that 20-20kHz or 1kHz on the amps? Is the speaker power rating continuous, program or peak? This information, especially the differences in the speaker ratings, can be important.

Second, you cannot 'underpower' a speaker, only provide insufficient power for the application. As long as you can obtain the output levels and headroom desired, it doesn't matter if what that takes is less than the speaker rating. I like to say that the power ratings indicate what an amp can deliver and what a speaker can accept, they really have nothing to do with what is needed or appropriate, that is dependent upon the application (the 'rules of thumb' many use simply assume some typical application). As Wayne said, avoid clipping the amp input by trying to get it louder than it can go and you should be fine, it just may not be as loud as desired.

On the latter, keep in mind that doubling the power to the speaker results in a 3dB increase, barely noticeable to some people. Going from 162.5W per speaker, one half of the CX302's rated 325W/Channel at 4 Ohms, to 400W per speaker would be just under a 4dB increase. Definitely noticeable but does it matter in your application? That I can't tell you.

[SjonRokz4u]

When matching amps to speakers the general rule of thumb is 1.5-2 times the speakers rms. Give or take 20% either way. Is the 400 watt rating rms, peak, or program?

[David Ashton]

The gain structure of your system can improve the results of your sound, you need to understand this, it is crucial to an efficient system,
read and understand this pdf,
http://www.gain.pe.kr/spboard/board....ownload&gul=14

hard work but worth it's weight in Db