Dan, first let me express our thanks to you for the service that you're rendering our country and extend best wishes to you and your wife for the upcoming arrival of your new baby.
Thanks! I wasn't really mentioning my sitation because I want any special recognition, I was just trying to express why the ultimate comparison is almost a year into the future. But thanks all the same!
Your plan to test the Axiom and Klipsch sounds good, but I'd suggest that the RB-61II would be a closer match to the M22 in overall size and cost. Yes, a key difference will be the significantly higher sensitivity of the Klipsch, and you're aware of the necessity for level-matching. Your setup description sounds fine, but I didn't follow why the distance settings would be different.
My current receiver (and hopefully the new one I plan to get - Yamaha RX-V1900) has an audible speaker distance fine tune (maybe it's delay) Where it plays a short tick on both fronts. Sitting in the listening position, I can hear whether it's left or right of center. The setting is adjusted so that the tick sounds like it's coming from exactly inbetween the front speakers. I figure I will do this with both sets to help eliminate localizability (is that a word?) of which pair is playing.
I was going to respond re the Crown calculator in your other thread, but was delaying because you'd indicated that you might have time to test with an SPL meter, and those results might be interesting.
Once I get home (in 5 months), and once I have get my treatments finished, I will do that test. I suspect it will be more than 3db per doubling, but less than 6db. Perhaps 4db? I know that even with just the front wall treated, there is definite absorption going on. The room is noticeably quieter. (less echoey)
Although I didn't doubt the findings of Dr. Toole and other authorities on the point, I did check for myself a couple years ago. If you'll able to do this at least at 1, 2 and 4 meters you may be surprised to find that the reduction in sound level is indeed far less than would result from applying a 6dB per doubling of distance formula, which is of course theoretically correct, but applies only to an omni-directional sound source in an anechoic environment.
What numbers did you come up with? Was this a treated room? If it was, I'd be very interested in the results.
...but unfortunately that rather key point is somewhat buried near the end under "Other considerations".
I see, a fine print error.
In brief, you appear to be too concerned with the power question. Clean power is cheap and plentiful these days and both the principles of audio technology and personal experience indicate to me that typical receivers rated anywhere in the 100-150 watt area are ample for all safe sound levels with speakers such as Axioms(even that 5 watt tube amp which Alan derisively commented on might work with those Klipsch sensitivities).
Over on the Klipsch forum, somebody did relate an experience where he drove his RF-7s with a 50W amp, and it sounded better than with a different 200W amp. The context was that it was a very very nice 50W amp capable of meeting the RF-7s current requirements. Apparently there's a point in the impedance curve where the RF-7 drops down to somewhere between 2 and 3 ohms. It's somewhere around 180hz. So for them to sound nice you either use brute force with a 300W amp capable of delivering lots of amps in the first place, or you get a really really nice low power amp from a boutique store.
An update on the comparison, the Klipsch side is throwing yellow flags on the field. The Rf-7's tweeter and horn are larger than the RB81s (1.75" vs 1"), and as such, it is crossed over at a different frequency. Whereas the RB81 is crossed at 1400Hz, the RF-7 is crossed at 1200Hz. As one user put it, "it definitely improves the clarity and impact of the midrange/treble". Another user said that the RB81s may not give me an accurate representation of the RF-7s, and that the RB-75 (discontinued) would be a better match. The RB75 had the same size compression driver that the original RF-7 had, and was meant to provide RF-7 sound to those who didn't have RF-7 space. However, the tweeter was attenuated to keep it from stomping all over the RB75's single 8" driver (after all, the tweeter was designed to keep up with two 10" woofers)
I expressed to them that I will not be looking at low frequency extension, nor would I be SPL drag racing them, as towers are certainly capable of higher outputs. But I fear they may have a valid point in that the RB81s may not be a good representative for the RF-7s sound...
