How much Power do speakers really use ???????

Pragmatist: I hope you understand the point that i was trying to make as my post was not meant as an attack on you personally or the information that you provided. I thought that the effort that you put forth in responding was very kind and covered the basics quite well. What i was getting at is that math and various formulas can be very helpful in predicting accurate results, but only when you factor all of the variables into the equation.

Busaganashi: I think that most people would find a quality 250 wpc amp with 90 dB speakers to be plenty of power and capable of attaining SPL levels that are more than enough in the size room that you mentioned. On top of being a bit of a nut, i also tend to push things noticeably harder than most folks. As such, i try to figure for worst case scenario, which pretty has one covered under any circumstances.

If you have the opportunity to audition the amps that you were considering in the confines of your system in your listening room, i would by all means do so. Otherwise, i would be relatively confident that a well built 250 wpc SS amp was up to the task at hand for someone that was slightly more sane than myself. You might be able to get away with a slightly smaller tube amp due to the differences in sound quality that they produce under stress. Most SS amps tend to get hard and grainy if pushing them whereas many tube products remain musical, but get a little sloppier. The fact that your speakers are of reasonable impedance and not highly reactive also helps things out a bit : ) Sean
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None taken,Sean;I enjoy reading your posts,really.

Thanks Sean. I'll see if I can audition some stuff in my area.

It just happens that I have been making a bunch of electrical measurements as I design and set up my greatly revised system.

1. SUBWOOFERS...I have three subwoofers, each consisting of a 15" JBL LF Driver and a 12" Dayton Titanic Subwoofer sharing an 8 cubic foot sealed enclosure. (They are about half way between floor and ceiling, and they back up my three Magnepan 1.6). The two drivers in each SW are in parallel, which gives a 2.7 ohm load. Each of the SW sets is driven by an amp rated for 250 watts at 4 ohms, but they seem to handle the 2.7 ohm load without any problem. Using either a warble test signal, or organ music, the maximum voltage that I see from the amplifiers is about 3.5 volts, and since it is 90 Hz or lower I don't think we need to worry about brief voltage spikes that my meter wouldn't see.
I = E/R so I = 1.3 amps.
Power = E * I = 4.55 watts.
Of course I have three of these things going, 13.65 watts all together, but it absolutely shakes the house. With all that cone area (like the Magneplanars) none of the SW drivers is working hard, and the amps don't even get warm.

2. MAIN SPEAKERS...They are three MG 1.6, driven by ADCOM 5503, rated at 350 watts into 4 ohms. These are much less efficient and go to 12-16 volts on the voltmeter, and I am sure that an oscilloscope would show higher peaks.
16 volts would yield 4 amps, with power at 64 watts.
Remember this is 90 Hz and up, and a full range drive of the Magneplanars would be more.
However, I have driven these Magneplanars (90 Hz and up) using a smaller ADCOM amp rated at 100 watts into 4 ohms, and there is no doubt that the big amp sounds a lot better.

The most dramatic difference was noted with a set of Dynaudio Gemini small MTM speakers that measure 3.1 ohm. I never realized how good these little boxes are until I hooked them up, full range, to the 350 watt ADCOM.

I don't think it is power (watts) that does the trick. The ability to deliver lots of power (more than you ever use) IMPLIES other characteristics of the amplifier that enhance its audio performance in the low voltage range (nowhere near clipping) where it actually operates.