July 24, 2008 by Bryant Moore
Q. I’m shopping for new speakers and I’m wondering how you know if the receiver won’t supply enough power? And how many amps you will need to power everything? - Dave, San Francisco
A. You can certainly check the speaker specifications in the owner’s manual to see the speakers “minimal power handling” specs. However, this is largely a theoretical number and is usually around 15-25 watts per channel. Any decent, modern, receiver/amplifier will have plenty more power than this. The more important things to look at here is the speakers power handling at a specific impedance, or ohms. The specification might say something like - 100 watts per channel at 4 ohms. This is what you want to match your amplifier to and here’s why..
Generally speaking, you can never have too much power. That’s right, I said it, and unless you plan on cranking your speakers up to levels that cause your ears to bleed and neighbors (2 miles away) to call the police, you typically won’t have any problems. What damages speakers a great deal more than too much power is too little power. When you really drive a pair of speakers by turning them up to a level higher than the amplifier is capable of, the amplifier will begin to “clip.” Clipped waveforms create great amounts of heat and can damage tweeters and midrange drivers far faster than you ever would by sending lots of high-quality power to them. The best way to ensure this never happens is to always provide good, clean power to the speakers, by using a large, high-quality power amplifier.
As a general rule of thumb, you can usually be safe by using an amplifier that is rated at 1.5 to 2 times more power than a speaker’s power rating. For example, if a speaker is rated at 100 watts per channel, you could safely use an amplifier rated at 200 watts per channel. Again, the idea is to have enough clean power to handle whatever you throw at the amp without clipping. If you being to hear even the slightest amount of distortion - turn it down.
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A classically-trained musician and former network administrator, Bryant Moore has turned a lifelong passion for music and A/V equipment into a thriving business with Charlotte, NC based Moore Audio Design. He has over a decade of experience in designing and implementing home electronics systems.
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