Amp's nominal power rating - any use?

Kijanki, it is difficult to disagree that music has varying loudness, but 45.9%? I don't think your calculation is nearly accurate enough to claim a number with such precision. For one thing, the dynamic range of music varies so much by music type and recording, though I suppose someone with a SET and minimonitors is unlikely to be listening to Kayne West.

Regardless, I'm still not bought into the efficacy of your calculation.

As for Magfan's comments about adding capacitance or inductance into the power calculation, "next to nothing" seems like a big exaggeration. But considering we're talking about a tube SET here, which is going to be the most sensitive design to load variance, amp and speaker matching is of more importance than usual, I'll agree. Once you're in SET territory, I think the only practical way to tell if an amp is compatible with a speaker is to listen. No one publishes enough specs to make a worthwhile prediction, and even if they did, very few of us could probably do a reasoanble interpretation.

Irv,
I just reread my response and will pretty much stand by it.

Just for an unreal example, a phase angle of 90degrees will result in ZERO power making it to the load. Using the 4foot fluorescent tube next to my workstation as an example, it draws about 1/3 amp. This lamp is consuming about 40va or 32 watts....the power factor is 0.8 and the phase angle is about 37 degrees. The math? PFxVA=Watts.

Tube amps do not like some reactive loads. An 8 watt SET working into a 60degree phase will deliver HALF its rated power to the load. SS is subject to the same limits. But, the amp may not even do that well....half is the upper limit.

I have not seen enough data, but would go out on a limb and say that many amps, even some highly touted ones, won't even do as well as a straight theory calculation (cosine of phase angle x power) says it should.

http://stereophile.com/standloudspeakers/807sonus/index4.html

Stereophile measures of recent version of the SF Guerneri.

Original speaker....from the 90s.

http://stereophile.com/standloudspeakers/487/index5.html

Magfan, the phase angle discussion you're trying to have is frequency-dependent, which you've ignored, so "next to nothing" still seems a stretch to me, which was my point. Since most listening, even on the OP's speakers, will be done with the first few watts, the effective frequency response will be the most important determinator of the sound.

Couple of points....and some agreement.
Yes, phase and impedance ARE frequency dependent.
I think the main take-away would be that a large phase angle coupled with an impedance dip is an amp stresser....(is that a word?)

Also.....and I don't remember which, Tube amps simply do not like a very reactive load. Capacitive? Inductive? don't 'memeber which.
Their is a good reason for this to do with transformers, right?

I don't believe 'next to nothing' is a fair characterization. Given that the PAIRING is a most important aspect to choosing amp/speaker combos, you can't simply ignore phase/impedance characteristics of the load and the amps response TO such loads.

Overcome a 'weird load' with simply more amplifier power? A solution, of sorts. I've heard talk of 'cheap watts' which is one answer. Another approach is the rational design of speakers.... We've all heard of some of the wacky stuff out there which apparently need something from Lincoln or Miller to drive.
I'll leave that decision up to YOU!

Now, about a proposed amp test? I think I'd like to see some data before I simply tossed that out. A resistor may be a nice, standard way to test an amp, but has little or nothing to do with real world conditions. Even my panels have reactive elements, though the impedance curve is pretty flat with only a rise at the crossover frequency. I'd love to see amps tested for power with real world reactive loading. A simulated speaker load could be agreed upon. The worst loading should be below....say 1khz, where most of the amps power goes, anyway, in real music.

And as for the OP's speakers. Fine stuff. Pricey and apparently worth it to some. I can't possibly criticize that choice. But, I would caution the owner to look at the pairing amp carefully. A large phase angle load, regardless of impedance, will still eat into amp power. Large impedance swings also, IMO, kind of defeat the purpose of tube amps. The more recent stereophile test of the similar SF speaker says you may want to use the 4 ohm taps, even though a straight look at the impedance curve may indicate the8 ohm taps.
If I wanted tubes with that speaker, I'd for sure try both.
The OLD test by stereophile did not measure such phase data. The new test indicates moderate phase and impedance curves....probably not a bad load for tube OR SS..

Perhaps it's a starting point without direction?