Bridge vs Stereo

Posted: Mon Oct 30, 2006 2:21 am

Ok, so the question is surrounds practicality of bridged mode vs. stereo in terms of power amps. Does a poeramp run more efficiently in bridged mode or stereo mode? Following this question is a situation:

I play in a band where we setup our PA gear most of the time. We need a poweramp for the FOH because we are currently under powering our speakers (500watt speakers) with an amp that only outputs 275 watts stereo.

We can easily buy an amp say like a Crown XLS-802, but it seems that you're mostly paying for bridged power vs stereo power. The other solution was to buy two (2) Crown XLS-202's and run them both in bridge mode considering that it will be about $100 cheaper.

Posted: Mon Oct 30, 2006 11:32 am

You're hopelessly misinformed. Let me see if I can clarify for you?

500 W speakers means that they can handle 500 W of continuous power. Chances are if you belch 500 W of power into your speakers continuously, they won't last long and neither will your audience. Yes, it is always good to have an amplifier rated at a higher power than your speakers are rated at. That's right! Higher than the speakers are rated at! Why would you want to do that? For freedom from amplifier clipping. If your amplifier is underpowered like your 275 W stereo amplifier and you try to push it beyond its 275 W to your speakers, you will be clipping the amplifier. When you clip your amplifier it produces a lot of third harmonic distortion which includes upper harmonics that are much more likely to blow up your speakers than a 1000 W amplifier that's hardly working.

So as you surmise, if your speakers are rated at 500 W each, you should have at least 1000 W of power available for each. But beware! If you're playing in a small club, this is total overkill. Since you did not specify the size of the venue, I can tell you that I have done a lot of PA work in reasonably sized clubs utilizing a single Peavey 800 in stereo mode. If you have the money and you want the greater headroom, buy 2 and run them bridged but understand the difference between 250 W and 500 W is only 3 DB! Just how much hearing damage do you want to inflict on everybody? That's the next question you must ask yourself. So is the sound of your PA system substandard the way it is now?? If so what are the symptoms?? It may not be a power issue?

Soft acoustic in a metallica world
Ms. Remy Ann David

Posted: Mon Oct 30, 2006 9:17 pm

We don't know anything about those speakers. What are the specs? Actually, what is the sensitivity? What is the continuous power rating. Or better, what models are they?

First of all, bridging causes more distortion, increases slew rate, but decreases damping (woofer control/dynamic braking). Running a bigger amp in stereo is prefered.

If you give specifics about your speakers, and how much headroom (power on reserve) you would like to have, I will show you the math to determine which amp to buy.

Posted: Mon Oct 30, 2006 11:16 pm

Sorry, should have put specs first.

Pair of Yamaha S1151V
Crown CE1000

For the last 2 gigs we ran the amp in bridge mode and only ran a mono-mix which is all we needed at the time.

The S1151Vs take 500 watts of continuous power @ 8 Ohms. I figured the amp also runs 1000 watts @ 4 Ohms, so I could setup the speakers in parallel and run them at 4 Ohms. Right thing to do to avoid clipping, right?

We usually play for 200-400 crowds. It's a humble system and the weakest links are definitely the power amps.

Other equipment in the chain
Allen & Heath WZ16:2 (1997 model)
DBX Dual 15-band eq

Thanks all. I appreciate your insight and love for making music.

Posted: Tue Oct 31, 2006 10:38 am

Ok, think about this now. Two 500W 8ohm speakers, or one 1000W four ohm speaker. That is what you are asking. That is the same thing.

Your amp is going to put out the same power, actually cleaner, more controlled power in stereo with those speakers, as it will bridged mono.

The Crown C1000 is an amp to avoid in my opinion. It had issues when they first released it. Unless you are the original owner and it is a late model, then you might consider checking to see if it has been serviced for the recall items. If you put that amp up against a Crown PB, PT or MT amp of the same power, you will hear why. It is a dumbed down version of the K2. Unless you have perfect power (and who does?), and stable loads, you are not likely to get your money's worth out of it. If you have to start with a Crown CE, make it the 4000.

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