This might be OT, however, what is the current thinking about the best speaker polar response?
My Polk T15s are typical bookshelf speakers in their polar response (and suitable for my downstairs Quad system).
Electrostatic panels are by default dipoles and the ESL-63 simulates a point source sound source.
If a point source still represents current thinking, digital technology could be easily used to provide the small time delays for an ESL-63 type speaker and a combined speaker and specially designed amplifier(s) [to cope with the unusual electrical characteristics of electrostatic speakers] would solve the problem of finding an appropriate amplifier.
Maybe Involve Audio could build an updated ESL-63 type speaker combined with an amplifier.
Kirk Bayne
Hi Kirk
Really good question!
But first to discuss the issue of the point source as advocated in the Quad 63's . I never really understood the industry wide obsession that the perfect sound radiation source is the dot point. There are many issues that I would argue indicates that it is the opposite of what you want!
1 Not a lot of sounds are emitted from a point source....piano, orchestra, harp, drums, more a bunch of point sources possibly. This is quite unnatural.
2 It makes it very easy for the human ear to directionalise the distance to the point source.....meaning typically puts the sound stage 6 to 10 feet in front of you
3 The energy radiation from the point source is omnidirectional (good start) but it infers an inverse cube relationship with displacement with respect to distance.....meaning its bloody loud near the driver and real quiet say 3 meters out.
Back at my old factory 20 years ago (Vass Electronics) we were developing several electrostatic speakers....one was the ELS 3 as shown in Robs ER Audio site. We invited around 10 persons from the Melbourne Audio society to participate in a shoot out between the Quad 63 and our ELS 3. The result was 8 preferring our ELS3 and 2 preferring the Quad 63! Of the 2 that preferred the Quad, one was the owner and the other was an older lady with a hearing aid !!!!! All remarked that the ELS3 had a much deeper "image".
My verdict on the Quads was they are a very good speaker but suffered badly from being as flat as a tack on the depth of the apparent image and had a maximum SPL of a puny 96 db. So much for the magic of the concentric ring delay line point source myth.
Around 12 years ago Dave the ***** and I investigated "What makes a good loudspeaker sound bad and a bad loudspeaker sound good" And we did a 76 page report on it chock full of every known plot, THD, IMD, Impulse decay waterfall, frequency response etc. The result was totally unclear with often speakers with the poorer plots actually sounding more "real" and visa versa.
The end result..............................Roll drums.....................
A concentric Dipole (Bipole second best). It is not subtle, it really is dramatic. When compared to the crud being sold today (99.9%) nonconcentric monopoles no one preferred them . Comments were all like sharpening the image and position , like putting on a pair of glasses on a vision impaired person. We constructed very good instant A/ B test jigs so in a blind manner and me with my best polka face could instantly switch between non concentric monopole/ concentric dipole/ concentric bipole. I still have the jigs.
The dipole has typically a figure 8 polar pattern but can also be an omni (as in the Naka Dragon)
Another feature of the electrostatic is that it creates a planar wave (imagine an infinite number of point sources in an array - think of the Huygens principle). This effectively gives the listener no ability to triangulate distance, if you walk up to a large electrostatic panel with your eyes closed you will end up whacking your nose! Hence the creation of artificial depth.
Now I can feel an argument coming on, I might hide in my bunker.