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Microphone Month

David Stewart’s Guide to Reading Specs – Power Rating

Welcome to David Stewart’s Guide to Reading Specs! inSync Guru David Stewart has graciously agreed to write an inSync Tech Tip from time to time based around the mysteries of reading and understanding manufacturer’s specifications.

Today’s Installment:
Power Rating – As it relates to power amps, what does this mean and why do I care?

The amount of power a given amplifier is capable of producing is rated in watts. Watts are a measure of the rate of energy transfer, in this case from your amp to your speakers. More energy transfer per unit of time (more watts) equates to louder volumes. So an amplifier suitable for getting your car stereo to a listenable volume may have significantly less power than an amp designed for a concert hall PA system. A higher wattage rating signifies more power.

Another specification that must be considered along with wattage is the load impedance. The lower the net (total) load impedance the more power your amp is likely to produce…up to a limited amount. In order to evaluate different amps you need to know the load impedance it will be driving. (There have been several past Tech Tips given on calculating load impedance so check out the TTOTD archives if you aren’t sure.) If you have two speakers that are 8-ohms each, and you will connect one to each side of an amp, then you will be most interested in its power output at 8-ohms when looking at the specs.

Is more power better? Yes, up to a point. When you go too far beyond the power handling capabilities of your speakers the extra power is wasted, and potentially dangerous to the speakers. On the other hand, not enough power is generally worse. More speakers are blown from inadequate power than from too much. This is because when an amp runs out of headroom (power) it may begin to distort (depends on the operator of course). This distortion is actually harder on speaker components than giving them too much clean power – of course that only applies up to a point, but you get the idea. In general we recommend an amplifier rated at roughly twice the power handling rating of the speaker.

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