Low power tube amp for Sonus Faber?

According to a lengthy email exchange I had with Roger Sanders --over 40 yrs of ESL experience -- the jist of what he explained to me is that speakers with a 4 ohm rating will not actually perform at their state SPL range.    a 91 db rated speaker will be somewhere in the 80's.     The discussion I had revolved around a pair of Decware speakers rated at 94db..   Roger's calculation indicated that they were more like 86 db or something to that effect.   If Im not mistaken has to do also with not being 1 watt @ 1 meter.   Im sure someone here that posted remembers better than I.  

wolf

tell me more about these " drunken dance festivals "..... also a location would be helpful................and some dates......and times.......

According to a lengthy email exchange I had with Roger Sanders --over 40 yrs of ESL experience -- the jist of what he explained to me is that speakers with a 4 ohm rating will not actually perform at their state SPL range.   a 91 db rated speaker will be somewhere in the 80's.

Yes. 91 db and 4 ohms will be 3 db less, or 88 db. I mentioned this earlier:

The speaker efficiency is about 88 or 89 db 1 watt/1 meter; on paper the speaker is rated with the sensitivity spec of 91 db. But because its nominally 4 ohms, this means that the voltage into the speaker will be more than one volt; hence the lower efficiency.With tubes, the efficiency spec is a lot more useful!!

The Evolution 845 is the amplifier I was hoping to suggest and it looks like it is already on your radar.  The Compact 845 is an excellent amplifier, but might not be right for every situation.  In this case, I do think the Evolution 845 would be the top contender.  The price is much higher, but so is the performance.

Like Charles has hinted at, the transformers are massively beefed up in the Evolution 845, bringing the weight up from 75 lbs to 117 lbs.  I have had a few speakers in house where the Compact 845 was just not the right bill and for every one of those speakers, the Evolution 845 lit them up.  

The Evolution 845 is a statement piece that I have yet to find a poor match with.  I'm not saying they aren't out there, but they haven't presented themselves yet.  Even on Martin Logans, the amp has performed magnificently.

Audiothesis,
Thanks for the additional amplifier information, it confirms what I suspected. All design and built parameters of a power amplifier have to be considered. 50 watt amps of the caliber of this Mastersound Evolution can manage speaker loads that some higher wattage amplifiers can druggie with. Just saying that ’X’ amount of power is sufficient doesn’t account for the entire picture/scenario.

I recall a situation described by an Audiogon member Raquel ( former TAS reviewer I believe ) several years ago. At a demonstration a 750 watt VTL was having a very tough time driving a pair of speakers. They replaced the big VTL with a VAC Renaissance 70/70 (65 watt) amplifier that easily drove the same speakers. Obviously this suggests very different design aspects of the two tube amplifiers.

The VTL wasn’t a bad amplifier by any stretch, just a poor match with these speakers despite the very high rated power. Power supply and transformer quality are crucial considerations in the big picture with regard to tube amplifiers.
Charles