Tri-amping Qs:

Doubling of distance does not reduce output by 6dB, that’s if you were in free space (so more applicable for live sound setups); For residential setups, the loss is 3dB to 4dB, almost the inverse of doubling wattage.

Note that I stated several times that I was ignoring the effects of room reflections.

Also, combing it both speaker outputs nets 3dB. 6dB is never gained. You may be confusing that with crossover design, where they have them intersect at -6dB to sum to zero, but that’s due to vector addition.

I was not thinking of crossover design, and I believe that my reference to a 6 db gain under the specific conditions I stated was correct. My statement was:

... two speakers will be in use, which will add 3 to 6 db to the maximum SPL produced by one of them. The 6 db figure would apply if the listener is equidistant from the two speakers, and they are both reproducing the same signal.

At various points in the room, if the two speakers are reproducing identical signals and again putting aside the effects of room reflections, the addition of a second speaker will cause SPL to increase by amounts ranging from minus infinity (i.e., no sound) to 6 db, depending on whether the phase relation of the two outputs at a particular vantage point causes them to sum constructively, destructively, or somewhere in between. Averaged throughout the entire room the increase will be 3 db, of course, corresponding to the doubled amount of power that is supplied to the speakers.

Some years ago I read a particularly excellent paper written by some folks in Australia which explained exactly this, in greater detail. I can’t find the link, though.

Regards,
-- Al

Gentlemen,
Thanks for your responses. I appreciate them very much and I appreciate you taking the time to write those long answers. I can now go looking for an amp that will have enough headroom @ approximately 75-100w.

Al: Thanks for your two responses. That was thoughtful. Your answers gave me a way to think differently about my questions and gave me a basis to compare amplifiers.

mzkmxcv: Thanks for taking the time to respond. Your answer added more to my knowledge and provided an answer to what power I would need to deal with headroom and also extended my understanding of how to determine how powerful an amp should be to drive particular speakers. Now I know, in the future, that I double the wattage as a good rule of thumb.

When I said "peak," I should have said, "On my chintzy iPhone-based dB meter, A-weighted, the needle infrequently taps105dB," usually in orchestral music. The EP 2.3s have an onboard DSP, so I can use your information about that. I also appreciate your opinion about tri-amping. That will save me a pile of cash and allow me to put more money into a higher quality single amp. I guess it's the geek in me that thought tri-amping would be better than using a single amp.

Again, thanks to you both,
GP

You’re welcome, Gary. Glad I was helpful.

Upon re-reading my previous post, to be precise I should make a slight tweak as follows (the words shown in caps have been added):

From: "At various points in the room, if the two speakers are reproducing identical signals and again putting aside the effects of room reflections, the addition of a second speaker will cause SPL to increase by amounts ranging from minus infinity (i.e., no sound) to 6 db, depending on whether the phase relation of the two outputs at a particular vantage point causes them to sum constructively, destructively, or somewhere in between.

To: "At various points in the room, if the two speakers are reproducing identical signals and again putting aside the effects of room reflections, the addition of a second speaker will cause SPL to increase by amounts ranging from minus infinity (i.e., no sound AT SOME FREQUENCIES) to 6 db AT SOME FREQUENCIES, depending on whether the phase relation of the two outputs at a particular vantage point causes them to sum constructively, destructively, or somewhere in between.

Regards,
-- Al

iPhone-based dB meter, A-weighted 

Being A-weighted would cause a discrepancy, C-weight should be used. On my iPhone I use the SLA Lite app, I have a calibrated mic but I haven’t compared the two to see how off the iPhone is.

mzkmxcv,
Thanks for clearing that up for me. 
GP