Quote Originally Posted by RGA
It's not about the watts and it's not strictly about the sensitivity rating. Plenty of speakers at 93db sensitivity and are not the least bit friendly to low powered amps. SET amps like stable loads - nothing wrong with a 4 ohm load if it doesn't dip and rise too much. My speakers are rated as 6 ohms but never dip under 5. If I remember correctly the 2.83V, 1m spec needs to be subtracted by 3db to be the same as the 1 watt 1 meter spec (not 100% sure so check on that). Remember for every 3db gain you need twice the amplifier power.
Nah, the 2.83 V is just used because 2.83 V into 8 ohms is 1 watt. But almost all speakers that use the 2.83 V number for sensitivity will have lower "real" sensitivity if measured with 1 watt fed into them. You do subtract 3 dB if your speakers are 4 ohm, because that'd be the same as running 2 watts into 4 ohms (sort of).

Many efficiency/sensitivity numbers I've seen on speakers aren't done in anechoic conditions, and use room gain to jack that number up a a bit. That ticks me off. I see this with $300 or cheaper speakers that boast 90 or 91 dB efficiency. It's often a few dB's less. Not a big deal, but I think a stricter standard needs to be enforced.