There have been some valid points made here.

Certainly, one wouldn't want to use an amplifier to drive a speaker whose impedance was significantly below the amp manufacturer's spec; not only might the amp be damaged from over-current, but the amp's damping is reduced as well, possibly leading to "loose" bass and perhaps excessive voice coil excursion causing speaker damage.

Nor should an amp be driven into clipping, as the harmonic content of the "squared off" waveforms will often overheat voice coils, especially in high-frequency drivers (tweeters).

However, one of the most important aspects of choosing an amp/speaker combination hasn't been mentioned yet, and that's speaker efficiency, or sensitivity. Two speakers having identical impedance characteristics, and even cone size, can vary considerably in what their SPL (Sound Pressure Level) output is. I won't go into how SPL is determined ("Google" it if you'd like). What's important to understand is how it affects your choice. Let's assume two speakers of the same impedance and using the same method of determining SPL have ratings of 88dB and 91dB. That may seem like a small difference; the less-sensitive (some would say less "efficient") one (88dB) is "only" 3dB lower. But the 3dB needed to get the same sound level from the 88dB SPL speaker requires twice as much power as the 91dB model. A 6dB difference in SPL translates to a 4-times drive-power requirement difference.

There's more to matching amp/speaker/venue than impedance and watts.

Jim, QuietDIN,
Thanks for adding your information.
I have multiple situations, now and in the very near future, where the more knowledge on this subject that I have will help me to make some better decisions.


[This message has been edited by MrEd (edited 04-03-2006).]