Thanks @wsrrsw: Thanks, I hadn’t seen that write-up on the TRW-17.
@uncledemp: Though "normal" recordings made in studios are limited in very low frequency content, some recordings made in very large "rooms"---cathedrals and churches, large theaters---contain very low (below 20Hz) information. That’s why you can hear the sound of the room itself (the dimensions of large spaces allow very low frequencies to propagate.). I have some EMI and Decca Classical LP’s in which the environment in which the recording was made is quite audible/evident---a HUGE space. I can only imagine what the ET TRW-17 would make them sound like!
@aldnorab: Some good questions. Here’s some answers to them:
1- Very true. That’s how I learned of the Magneplanar Tympani T-I’s (Gordon Holt’’s review of them---which was not entirely positive---had not yet appeared in Stereophile). In the Spring of 1972 I happened to visit a newly-opened hi-fi shop on the very day Bill Johnson was delivering and installing a complete ARC/Magneplanar system in the shop’s excellent sound room (Bill was a pilot and owned a plane, so flew himself and a demo system to new dealers who were located far from Minnesota). I made like a fly on the wall---keeping my mouth shut and my ears open, listening to Bill and Walter discuss all thing hi-fi. I got quite an education that day!
I had already heard the Infinity Servo-Static and Dayton Wright electrostatic loudspeakers, but was unprepared for the sound the ARC/Maggie system produced. Shortly thereafter I bought from that dealer (Audio Arts in Livermore, California, owned and operated by Walter Davies, as fine a man as I have ever known. He later created the Last Laboratories line of excellent LP and tape preservation products.) the same system: Tympani’s bi-amped with the ARC passive crossover and D-51 and D-75 power amps, an ARC SP-3 amplifying the signal from a Decca Blue cartridge mounted on a Thorens/Decca player. That was Johnson’s reference system, except he had brought along a prototype tonearm in development at ARC, which was never put into production. I remember it resembling the Weathers and Grado arms of the 1950’s and 60’s.
2- Prior to introducing the LFT-8, Eminent Technology had already marketed LFT models which were not hybrids: the LFT-3, LFT-4 (a pair of which I also own), and the LFT-6. Instead of a dynamic cone woofer, those three models had planar-magnetic woofer diaphragms, which were of course somewhat large (bass frequencies require drivers which have either large radiating surfaces---planars of course do---or considerable excursion capabilities---planars don’t---in order to be able to "move" enough air.
To make an LFT model of more modest proportions, Thigpen decided to use a dynamic woofer for the LFT-8. He readily admits the 8" woofer is the LFT-8’s weakness, but for those with a room big enough one could use the bass panels of the Tympani’s with the LFT-8 midrange/tweeter panels. Or, since the LFT-8 woofer operates up to only 180Hz, in place of it one could instead use a pair of the fantastic Rythmik Audio/GR Research OB/Dipole Subs (which---unlike "normal" subs---can be used up to 300Hz.). Or, get the new LFT-8c, which incorporates a new sealed dipole woofer. By the way, Magnepan has itself been working on their own dipole woofer for some time now, and it will eventually come on the market.
3- All drivers are made with compromises. Do the front-mounted magnets of the LFT driver cause diffraction? Remember, the more expensive Magnepans---the 20.7 and 30.7---themselves employ push-pull midrange drivers, with magnets front and rear. Which is worse: a small amount of diffraction, or a large amount of harmonic distortion? Only you can decide. ;-)