enough watts to drive these speakers? Help?

I use a 90db efficient speaker.I was happy with the InSound/Omega Mikro 10 w/ch prototype V amp,but settled on a set of Viva Verona XLs {26w/ch,pure class-A}.
Your first watt will produce an 89db SPL,at 10 watts you should yeild a 10 db increase in SPL.Doubling the power will add 3db.
I would be more concerned with the impedance presented by the speaker and complexity of the crossover.

Your calculations assumed that your friend would be listening at 1m (3.3ft) from the speaker in his bedroom. Would that really be the case?
If not, one loses 6dB when one moves back from 1m to 2m. Then one loses 3dB when one moves back from 2m to 3m. If your friend is 3m (~10ft) from speakers, the 89dB efficient speaker yields 80dB SPL at his listening position using 1W. To get 90dB SPL, he'll need 10X the power i.e. 10W. At this pt. the amp runs out of gas. There'll be a 3dB increase in SPL owing to 2 speakers i.e. stereo music. Room can re-inforce to some degree but it is hard to tell.
Ill designed xovers in the speakers can eat up some watts.
If he's willing to not crank it up, 8-10W/ch should be fine if everything else has a reasonable design (a bit nebulous but I hope that you can understand what I mean).

Bombaywalla, wouldn't moving back from 1 meter to 2 meters result in a 3 dB loss, not a 6 dB loss?

Bombay pointed out an important factor i.e. seated listening distance vs apparent spl. Having said that, one can't calculate the reduction in spl based on distance without knowing what type radiation pattern the speaker makes use of. Some speakers "project" sound into the distance in a more linear manner than others.

As a side note, the first receiver that i ever had was rated at 12 wpc driving speakers that were around 88 dB's or so. While it wasn't the cleanest ( not by a LONG shot ), this little "beast" could play pretty loud. This was with highly compressed hard rock i.e. "demanding" music that put a steady strain on the amp / power supply. Given that tubes tend to clip in a much more "usable" manner ( SS sounds like HELL ), and the dynamic nature of most classical and jazz music, even with "conventional" front firing boxes, i think that he'll be okay. That is, so long as "moderate" is all that is required. One would also have to assume that this is a secondary system since it is going in the bedroom. Sean
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My listening room at home is just about the same size as your friends. My current system there is Soliloquy 5.3 speakers which are 90db floorstanders, paired off with George Wright Mono 10's which are 10 watt monoblocks (push-pull 2A3 based amps). Plenty of power for the size of the room, but as has been said, don't expect chest-pounding bass. My system can play at very 'satisfying' volumes and remains engaging at low volume as well. YMMV depending on which amp and which speakers you end up pairing off. Being a 2A3 based system it is all about midrange and leaves a bit to be desired in the low end. I've tried in the same room pairing off 8 watt 300B SET amps with 89db Silverline SR-17 monitors. Though they did sound wonderful at very moderate volumes, this combination did not work at all well when the volume went over about 88db (I'd guess). Numbers don't always tell the whole story. But I think the general speculations and expectations given his taste for jazz is a good bet for a nice solution if done with care and consideration for synergy.

Marco