Hello Integrativeservice,
I've owned several Quads, one Martin Logan, and am presently an owner of and dealer for Sound Lab electrostats.
I think that the electrostatic loudspeaker was invented long before the first Quads, but my understanding is that the Quad ESL (introduced in 1957) was the first commercial electrostat. Legend has it that when the owners of Warfedale, Tannoy, and Bowers & Wilkins (the premiere British loudspeaker manufacturers of the day) first heard the Quad ESL, they quietly made preparations for bankruptcy just in case. Fortunately for them the ESL didn't catch on as much as they feared, but for years many a manufacturer of serious high-end loudspeakers had a pair of Quads tucked away somewhere as a reference system.
The main difference between Quads and (current production) Martin Logans is that the Martin Logans are hybrids - they use a dynamic woofer for low frequencies. As in most things audio, this involves tradeoffs. The Martin Logans will generally play deeper and louder, but aren't as coherent. It's difficult to get a box woofer to blend well with an electrostatic panel for several reasons including: the box usually introduces colorations that are absent in the panel; their radiation patterns are very different; and the sound pressure level literally falls off more slowly with distance from the panel than from the woofer (meaning the tonal balance is influenced by room size and/or listening distance).
Personally, I tend to prefer full-range electrostats; that is, no box woofer.
You mentioned InnerSound and Magnepan. InnerSound electrostats are use flat panels that give extremely precise imaging but a small sweet spot. They also will play louder than other electrostats and are very dynamic and lively, but are a more difficult load than the Martin Logans or Quads. Magneplanars are not electrostats - they use a different technology (planar magnetics) even though they look like electrostats. Magneplanars are very enjoyable loudspeakers but don't have quite the inner detail and articulation of a good electrostat.
Since I'm a dealer, can't resist the impulse to plug the brand I sell. Sound Lab offers one hybrid and several full-range models, and they differ from other electrostats in giving a much wider, more uniform radiation pattern with a corresponding wide sweet spot. Their uniformity of radiation pattern contributes to correct timbre, because the reverberant sound (which significantly influences perceived timbre) has the same or nearly the same tonal balance as the first-arrival sound. On the other hand, the full-range models are large, expensive, and difficult loads for an amplifier.
In general, electrostats are finesse loudspeakers, emphasizing quality over quantity. They can reproduce music with an ease, freedom from coloration, and naturalness of tone and texture that can spoil you. They tend to excel at low volume levels, but aren't really ideal for reproducing rock-concert level in the listening room, the InnerSounds being the exception here. Electrostats typically have narrow radiation patterns and small sweet spots, the Sound Labs being the exception. The hybrids are smaller and easier to integrate into a living room, but impose some performance compromises. In general electrostats present a difficult or even downright beastly load to an amplifier, so be aware that there may be a significant hidden amplifier cost.
Feel free to shoot me an e-mail with any questions you may have. I'll do my best to give accurate information, whether about the stuff I sell or stuff I don't sell.
Best of luck in your quest!
Duke LeJeune
AudioKinesis
New Orleans
