Amplifier Power Rating Confusion! Aarrgh!

[discreet]

[b]Amplifier Power Rating Confusion! Aarrgh![/b]

OK, I'm looking at power amps - and this is a typical bit of spec:


• Maximum output power (1 kHz; THD < 1%):[color=#000000]
- 2x 1000 W @ 4 ohm
- 2x 500 W @ 8 ohm[/color]

[color=#000000][color=#984806]• Rated output power (20 Hz-20 kHz; THD < 0.5%):[/color]
- 2x 300 W @ 4 ohm[/color]


Can someone please explain the difference between Maximum output power and Rated output power?

What will happen if I use the above amp with 2 X 8 ohms cabs?

Will I actually get 2 X 500W - or more like 2 X 150W??

The bottom line is, will it be LOUD enough for use in a band with a VERY LOUD DRUMMER AND GUITARIST?? EH??

[flyfisher]

Blimey - the worms are wriggling out of the newly opened can as I type.

One interpretation could be that 'maximum output power' is an instantaneous peak power output measured at 1kHz. You must judge if that's a useful measure, I'd suggest only vaguely in a sort of how-cool-is-your-car type way - i.e. nice to look at by not massively helpful regarding what's really under the bonnet.

'Rated output power' is probably a continuous power measurement meaasure over the entire operating range of the amp. This is what it can crank out hour-after-hour.

The "2x" suggests that this is a two channel amp. If I'm right about this then using two 8 ohm cabs is really just one cab per channel and you're suggestion of 2x 150W (-ish) is probably correct (on a continuous power basis).

The actual volume created by such a combination will depend a lot on the sensitivity of the speakers.

I'm not sure this is a particularly helpful or definitive answer, but then the specs are somewhat ambiguous, as is the question of 'loud enough'?

[BOD2]

One of the main reasons for checking amplifier power specs is so that you can compare different amplifiers to see how they match up.

This is only possible when manufacturers provide the same specifications.

It's been generally accepted over the years that the most practical power specs to use are "RMS Power" ("Root Mean Square") ratings, as these are reasonably close to "real world" power use. Is RMS power listed in any of the specs for these amplifiers you are trying to compare ? If, so, then that's the best one to use.

"Maximum Output Power" is not very useful in a real world scenario (would you ever run your car at it's absolute maximum speed ?)

"Rated Output Power" is a more useful spec, probably a more practical "everyday" power spec but meaningless for comparison purposes unless other manufacturers use the same spec.

None of these power ratings give any indication of "volume" (or "loudness"). Volume is provided by the loudspeaker which converts the electrical power of the amplifier into sound. So the speaker cabinet used is very important as in indication of how loud a setup will be.

The best way to find out how loud an amp/cab setup will be is to ask on this forum about other user's experiences of that particular amp/cab combination. Use the experience of the players here to help you - and you can ask them specific questions about a particular setup.