Axiom Home Page Forums General Discussion Home Theater M80's and 4 ohm amp ratings

If an amp has power ratings listed as 125 watts per channel into 8 ohms, and 225 watts per channel into 4 ohms, and you are using the 4 ohm M80's, does the difference in watts result in a noticeable performance difference, or is this really only a statistical difference that does not result in increased performance? Would this setup perform like a 225 watt amp into 8 ohm speakers? What I really want to know is, if I am bragging to my friends about my new system, can I legitimately state that my amp puts out 225 watts , or would I have to be realistic and state that the amp puts out 125 watts, because that is how the speakers are actually performing, and really ignore the difference in power rating related the the 8 ohm / 4 ohm differential?

Hi BobG,

In terms of "performance difference", it kinda depends how you define that. If your amplifier produces 225 watts per channel into a 4-ohm load like the M80s, then the amplifier will indeed be delivering more current in amperes (because the 4-ohm load offers less resistance, so more current flows) and hence, referencing Ohm's Law, more power.

So you could quite legitimately boast to your friends that your amp puts out 225 watts of power (at peaks) into the M80s.

Now, if you had a pair of M60s (8 ohms) hooked up to your amplifier and it is delivering its maximum of 125 watts per channel, and you had a second identical power amplifier driving the 4-ohm M80s at 225 watts per channel, all other things being equal (which they never are), you'd still get roughly the same "sound" or acoustical output (loudness), give or take a few dB. Actually, the M80s would be a little bit louder, about 2 dB, than the M60s because the M80s have slightly greater sensitivity. That means that given 1 watt of input, they produce slightly louder acoustic output than the M60s, by 2 dB.

And of course if you have the M80s, or plan to get them, you could also boast to your budds that they'll handle up to 700 watts per channel of power.

Regards,

If you have friends that know something about audio amps, you'll find it difficult to brag just about power levels. You also have to tell them what the THD is at that power level.

If you really want to impress them, tell them that amount of power into the M80s produces the equivalent sound pressure level as standing in a ship's engine room. Which coincidentally is also the threshold of pain and can result in permanent hearing damage if listened to for 15 minutes.