Why do Maggies need a lot of power?

Excellent detective work, Schubertmaniac.

Yup, Magnepan plays the numbers game a bit in quoting 86 dB for a 2.83 volt input. You see, 2.83 volts into 4 ohms is 2 watts, not 1 watt.

One additional factor is compression. I don't have access to dynamic compression measurements on Maggies, but let's assume they compress about as much as the average 83-dB effienct movng-coil speaker (all moving coil speakers are subject to thermal compression, and in general the lower the efficiency the worse the compression). Suppose we have a 200-watt peak musical impulse, which we would expect to give us 106 dB from our 83-db/1 watt efficient Maggies. But taking compression into account, I would estimate that 200-watt peak input to give us about 101 dB output, and possibly less.

Note that electrostats also suffer from dynamic compression, but it's mainly determined by the transformer's internal properties and has a less direct correlation to overall electro-acoustic efficiency.

Schubert, the power requirements for the Maggies doesn't follow conventional point-source theory as you increase the listening distance. Maggies approximate line sources, and benefit from the significantly more gradual fall-off with increasing distance.

Theoretically, in anechoic space, sound pressure level falls off by 6 dB with each doubling of distance from a point source, but only 3 dB with each doubling of distance from a line source.

I took some measurements in my room to get a handle on the real-world implications of line source vs point source radiation. I measured a conventional point source speaker and a line source speaker at 1 meter and then at 8 meters (the practical limit of my room), using pink noise. The point source speaker's output fell off by 11 dB going from 1 meter back to 8 meters, but the line source speaker's output only fell off by 4 dB!

In my mind, this is one of the things Maggies do very well - you see, the kind of sound field set up by a line source speaker more closely approximates the sound field you encounter at normal listening distances at a live performance. I think this is one reason the Maggies generate such a lifelike "feel" (along with their utter lack of distracting boxiness).

Audiokinesis: you are correct about the line source vs point source. But then there is the tubewatt vs sswatt. I can drive my Spectral amps into a tizzy with the Accoustats and they have 225 watts and 380 watts, respectively into 4ohms. But my 100 watt ARC D-115, it keeps chugging along.
I did make a mistake, those measurements 3000/6000 are cubic feet not square feet. Has anybody heard the rumor about the new Maggie model which will be somewhere in between the 3.6 and the 20.1?????

I dunno about this "needs a lot of power" thing. I seriously auditioned Magnepan 3.6s in this last round of speakers. They were poewred by a Conrad Johnson MV55 power amp and while the room was bright it was also huge (20,000 cubic feet, or around that). They played plenty loud enough for me, and they sounded excellent, too. The MV55 delivers 50-60 wpc, so it is NOT one of the earth-shattering ones.

I really ended up not going with them only because the center channels were terrible, and also that the setup (CJ LS16 + MV55 + 3.6s) is also VERY unforgiving of poor recordings, of which I have plenty. But power consumption wasn't one of the issues at all.

I can confirm the fact that 3.6's need POWER to come to life. I tried a few amps of lower power before stepping up to a 450 watt per channel high current amp and now I have much better low level dynamics and much quicker lower bass, before the bass was barely noticeable now it actually feels like it is moving some air. I was skeptic when I bought these things and I tried using my 60 watt per channel tube amp and thought it sounded good till I tried more power and then I realized the bass and dynamics these speakers are capable of- they will produce good sound with vitrually any power but don't come to life till they get LOADS of power and current to spare. It would only make sense to assume that the 1.6's don't need as much power as the 3.6's after all they are a little smaller but I wouldn't try anything under 200 watts into 4 ohms and I wouldn't hesitate to try a lot more power. I am not a technical person I just know what works from my experience with these speakers, so I won't even try to explain why, I'll let the much smarter people before me due the splainin'

Hmm... one of my issues with those maggies was the obviously lacking lower bass. It didn't really bother me because I knew that if I bought them they 'd have to double duty in HT, where I'd have a sub anyway. But for some reason I didn't figure in that the amp might not be supplying the juice, and of course with a 60wpc amp that's quite possible...