Which is more efficient and requires less power?

Duke's qualifier is interesting:

Note that a few amplifiers might still be happier
with the lower efficiency 6 ohm speake.

This is telling, and why I posted the question. The 94db speaker is the
obvious choice, but the more difficult load of the 94db speakers kaes
the answer not so cut and dried, IMO.

Thanks guys. I suspected the answer would not be easy.

The question of imedance drop is important. The 6 ohm speaker dips to 3 ohms. I don't know about the 4 ohm nominal speaker, which conceivably could dip lower than 3 ohms.

The idea is to use a PP triode tube amp with a power output of 50wpc or less.

I sit 8 feet from the loudspeakers in a 19x16x8 foot room. I listen
around 89-90db, and occasionally crank to ~101db. Classical to jazz to
heavy metal. At the loudest volume, I'm using around 32 watts. My
present speakers are the 89db/1w/1m in the example above.

It seems 91db, 8 ohm speakers would be a more significant change from
what I presently own in terms of efficiency and driving ease than would
94db, 4 ohm speakers.

05-04-06: Gs5556
Regardless of the speaker nominal impedance, impedance curves, or phase angles, what you will need at your listening position of 8 feet for an SPL level of 89 db is 90 watts for the 94 db/W-M speakers and 285 watts for the 89 db/W-M speakers. This is assuming 15 db peak headroom which is reasonable for classical and jazz.

I don't follow.

I have measured the SPL from my listening position, and according to the chart Elevick provides, I am using 1 watt to produce 89db and 36 watts to produce 101db...far below your 90watt/285watt requirement. Furthermore, I reach 101db with the volume control on my preamp at about 2 o'clock. My speakers are 89db/1w/1m 6 ohm nominal. My tube amp is 110 wpc.

My real world experience does not agree with your numbers, Gs5556,
because when I'm listening to Metallica measured at 101db (not at peak)
at 8 feet from the drivers with an SPL meter, I have plenty of headroom
remaining, and my PP tube amp is 110 wpc. Your numbers would
indicate this is an impossibility, since according to your calculations, I
require 285 watts to produce only 89db at 8 feet. Yet not only is it
possible, it's real well beyond what your numbers tell you.

Perhaps it's the 15db headroom allowance that is the difference. I have
never experienced a peak of 104db when the average listening level was
89db. I can say for certain that with an average reading of 101db on the
SPL meter, peaks are generally no higher than 105db. With readings
around 90db, peaks are no higher than about 95 or 96db.

Interesting. I'm awaiting delivery of a pair of 200wpc SS mono blocks,
and it would seem they are 50% underpowered for my needs.

Also, I wonder if it would be beneficial to run Zero Autoformers on my
loudspeakers to double the 6 ohm nominal impedance to 12 ohms? Oh,
and the speakers have 89db/1w/1m SENSITIVITY not efficiency. Thanks
for explaining that, Duke.

Thanks, Duke. I've only shopped once at Bust Buy. Everything was paid in $1 bills.

I'll email you privately regarding the amps in question, if you don't mind.

Would it be beneficial to double the 6 ohm nominal impedance to 12 ohms via Zero Autormers, in your opinion? Or, is this unecessary if the amps have 4 and 8 ohm taps and/or high current delivery?

Thanks, Duke. I've emailed with some system specifics.