90 watts, and your 1909 would be slightly conservatively rated, as is common with HT receivers, would provide for a 104-105dB level at your 12' distance. Increasing that number by 1-2dB would hardly be a significant increase. Enjoy the great sound(when you play great material)through your 1909 and M80s.
John, I'm lost again. Alan's article says that to reach 106 without distortion with M80s you would need more than the 90 undistorted watts available. Moreover, while the amp will produce more than 90, it will start to distort the signal much lower (e.g, my 3300 list at 110wpc, but begins to distort at 74.) Assuming a similar situation here, won't he have significant distortion long before he gets to 104? A test of the 1909 says that at 50w into 4 ohms you have THD above .3%.
1909 Bench Test As the author notes, "THD+N vs. Frequency is shown below for 8 ohms and 4 ohms. The 20 volt at 4 ohms graph line suggests that this receiver may not do very well with 4 ohm speakers (because distortion stays relatively high all along the graph line)." By the time you reach 90, the amp has to be clipping hard, and you have not reached 105 for the damned peak yet.
I'm just missing something here, and I can't figure out what it is. Your rational for 90 being plenty makes sense, but Alan's article makes the need for 200 compelling, if we are talking about that volume range of 100-106db for un-clipped peaks. (not sustained - kids don't try that at home.) And the test bench implies you won't get 90 clean out of the amp with M80s. I need to take a night class on amps to i can get this stuff under control.
a full orchestra and chorus in a concert hall will measure 106 dB, and a rock group, 120 dB SPL. Now let's try and get our peak speaker sound levels to 96 dB, "twice as loud" as our 86-dB listening level. That isn't that difficult because right now we're only using 1 watt per channel to drive the M80ti's to 86 dB. So we'll need ten times as much power, or 10 watts, to reach 96 dB. Big deal. We've got lots more.
But things begin to change, and rather dramatically. Let's push the M80ti's to what we might experience from a solo grand piano, 109 dB. We're at 96 dB with 10 watts per channel. Let's go to 106 dB. So that requires 10 x 10, or 100 watts. Close, but not quite there yet. Just 3 dB more. Remember, we have to double the power for a 3-dB increase in sound level. So 100 watts becomes 200 watts. Yikes! Our receiver has only 110 watts maximum output! We've run out of amplifier power!
