@bdp24 Dipole subs do not work well, I have built and tested them. No matter how heavy you make them they shake and the cancellation effects along with room modes create wild frequency response aberrations. The problem for line source users is to match the radiation pattern of a line source with a subwoofer system. Using the same math above subwoofer drivers need to be spaced less than 1/2 the wavelength of the highest frequency they are to reproduce and the array has at end at barriers, either side walls or floor and ceiling. I chose side walls for my system using 8 drivers to cover a 16 foot wall.
@pindac 57s hate making bass. They will do it at the expense of reliability and Doppler distortion. One of the reasons we were blowing 57s all the time with the HQD system was the crossover point to the woofers was too low. The problem was we only had slow analog active crossovers in the day and even John Curl can't work miracles. The HQD system was driven by all Mark Levinson equipment. With digital crossovers you can run much steeper slopes bringing the crossover point up as high as 100 Hz while still keeping the subwoofers out of the midrange. Given the System you have you really should look at the DEQX Pre 8. It is a digital preamp with a fully programmable 4 way digital crossover. It is a DIY speaker maker's dream. https://www.deqx.com/ The are still selling Beta units at 1/2 price.
@richardbrand The first indestructible ESL was the early Acoustat series, not their amp, just the ESL panels. Then there is the Sound Labs which are totally indestructible. I have tried desperately to kill these speakers and the only things I succeeded in killing were two JC 1 amplifiers and two bass transformers. You can turn up the bias supply and "spark" the diaphragms without any damage whatsoever. I have no experience with later Quads as none of them meet my specification being point source speakers. You can stack them but they still will not become a line source as the active part of the elements is too far away. Peter Walker is a plagiarist. He essentially copied Edward Kellogg's 1929 design, an American working for GE. Arthur Janszen patented the first ESL design in 1955 two years before the 57. Arthur also designed the KLH 9 in 1957 arguably a better design than the Quad, but very large and hard on amplifiers. By itself the Quad 57 is a midrange driver for apartment dwellers. To obtain a reasonable output suggestive of a live performance an ESL must be a line source and be crossed over to subwoofers. This leave us with the Dayton Wrights which take second place for the worst speaker design ever. First place goes to the Hill Plasmatronics.
There is something about the Shure V15 V that I do not like. I have not put my finger on it yet. I have to make recordings of the same records with various cartridges for AB purposes.
