Electrostats

To play loudly, you have to move a lot of air. To produce low bass, you have to move a lot of air. Most E-stat's by themselves lack both the surface area and the excursion necessary to do either of the above. The only E-stat's that i know of that "might" be able to do this, and this will vary depending on room size, spl levels required and amount of bass that you want, "might be" the big Soundlab's. I have my own "personal doubts" about that though.

As such, most designers resort to "hybrid's" i.e. E-stat mids and tweeters with dynamic ( cone ) woofers. In order for the cones to blend with the e-stat's, they must be very fast, low Q at resonance and low Qms. The result of using a driver / alignment like this is that you have minimal overshoot and ringing and the driver is both very well damped and easily controlled at or near resonance. Any type of poor transient response or "tubbiness" will stick out like a sore thumb. Obviously, special attention to the crossover is required or all the hard work selecting drivers and cabinet design will go out the window due to improper "blending" of the drivers where the two different types of radiators overlap each other.

Even if one can get all of this "right", these types of speakers typically have limited dispersion patterns and produce a pretty narrow ( i.e. "beamy" ) sweet-spot. Some e-stat's have been characterized as having a sweet-spot that works well so long as you "hold your head in a vice" i.e. not move it around at all.

Having said all of that, i would say that mass produced E-stat's are not really "ideal" rock and roll speakers. Yes, many of them will "rock", but most won't "jam". I know that others that own E-stat's may want to crucify me for saying that, but this is strictly my personal opinion. The commercial designs that i've heard simply will NOT play loud enough to produce "sustained concert level" spl's in a medium to large sized room. If you try to do something like this, the mylar is either going to stretch badly and / or you'll arc the panels. You can get around this somewhat by going to a hybrid design, but i've yet to hear a hybrid that really worked "well" in terms of blending the drivers together at various spl levels. Most hybrids work well together in a specific spl range but the differences in driver characteristics become more apparent as you try to vary the output levels quite a bit. This is due to the fact that cones require excursion to produce output due to their limited surface area while e-stat's require surface area to produce output since they lack excursion. Finding a good blend between the two is VERY tough. Believe me, i know as that is what i'm "trying" to do with my main system. Sean
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Sean,

You're talking a lot of theory and generalities, which says to me that you don't have specific experience with the InnerSound Eros Mk-III that Driver raved about above.

So just FYI, the Eros can play VERY LOUD without strain (I'm sure it's pretty clean up to 115 dB or so). Roger Sanders tests the panels by playing them for extended periods of time at SPLs exceeding 100 dB for an individual panel. And the panels produce about 98 dB at one watt, so they are robust AND efficient. The can reproduce kilowatt peaks without stretching the mylar or melting. So, yeah, they pretty much can reproduce a symphony orchestra playing full tilt in mid- and large-size rooms; and I've heard them do it.

Yes, they are beamy (very!), and it seems that the bass and the mids and highs blend properly at only one distance from the speakers and that is because the ESL line source maintains its loudness further out from its diaphragm than the point source woofer which falls off in dBs more rapidly as the distance to the listener increases.

I owned a set of the Mk-IIs, which are similar, and was sorry to let them go due to a move across country. Sean, if the ESLs you are trying to build perform half as good as the Eros, then I'd say you are doing well.

Now, for the first time in years, I'm using a dynamic speaker as my reference -- the Audio Physic Virgo II. My new room is smaller than my previous basement listening room and the Virgos seem to fit and work well in the smaller space. I still miss some of the dynamics and scale that the Eros presented so well, but the Virgos are not too far off the mark and are endearing in other ways. Certainly they have a larger sweet spot. I use them with a subwoofer, just as I had done with the Eros and that seems to fill in the last half octave of very low bass nicely.

Perhaps one day I'll return to E-stats, but from what I understand, the ultra-low humidity here in AZ is not the best environment for ESL panels.

Driver, if you can deal with the Eros' narrow sweet spot then they may be just the speaker for you.