The Shure V15 V with a Jico SAS/B stylus VS The Soundsmith Hyperion MR and Lyra Atlas SL

I am not certain, but if the Quad 57 is curved at all, it is curved in the vertical plane, not in the horizontal plane.  And anyway, Sound Lab ought not to claim to be the first to curve an ESL in the horizontal plane, because Martin-Logan did it first with their flagship CLS model, albeit in a problematic way.  (They used curve stators with the diaphragm suspended inside a curved "sandwich"; thus when the diaphragm moves toward the listener it wants to stretch, when it moves away from the listener, it is looser than in the rest position.)To be fair to SL, I doubt they ever did claim to be the first to curve an ESL.  Sound Lab uses flat facet segments arranged in a curved array, thus avoiding the inherent issue with the M-L CLS but also perhaps fairly described as not a true curve.. Also, "ESL" is a generic acronym for ElectroStatic Loudspeaker.  In my lifetime, I never heard the Quad 57, so numerically named for the year of its introduction, referred to as an ESL57, but I certainly can be wrong on that. We just say "Quad 57".

On the "line source" descriptor, it was my impression that Peter Walker incorporated time delay into electronics mounted inside the speaker so as to create the radiation pattern of a point source, not a line source. Again, I would be happy to be corrected if that is bad info. Whether that was a good idea or not is also open to question.

@lewm Yes, the Quad 57 (your nomenclature) is indeed curved in the vertical dimension, which effectively focusses the sound on a horizontal line behind the speaker.  Most other speakers claiming 'line source' have a virtual line which is vertical!  

We now recognise the 57 as having three panels in a d'Appolito configuration, though unusually this is horizontal with a central treble flanked by two bass panels. Get off-center, and the bass panels start to differ in path-length, meaning there is a very small sweet-spot.

When the Quad 57 was re\eased in 1957 it was just the ESL.  Sound Labs "The Complete White Paper" states "The electrostatic speaker art was in its infancy when Sound Lab started business back in 1978" which is a bit rich considering Quad sold 54,000 pairs of the original 57, starting 21 years earlier.  I have many other quibbles with the white paper, especially when it groups dynamic speakers as point sources, which most certainly aren't.

Only the ESL-63 and later had the radiation pattern of a point source.  Whereas the 57 has a very small sweet-spot (sideways!) speakers that emulate a point source have a very large listening area.  The ESL 63 is often reported as the world's most accurate speaker, since it has a very light diaphragm, effectively no cabinet coloration, no crossover colouration, and a coherent radiation pattern with no cancellation / reinforcement interference patterns if reflections are ignored..  The 2905 has amplifier-like distortion measurements.  And if it doesn;t play loud enough for you, you can just sit closer!

Note that I am not claiming it is the world's best speaker, just very accurate.  Peter Walker's perfect amplifier is "a straight wire with gain".  The 63 and later aim for the same neutrality "If you don't like what comes out, pay more attention to what goes in" he said.

@lewm See, you learn something everyday. I've still blown out more Quads than you:-) We both own extremely similar loudspeakers, I suspect for a reason. Acoustat 2+2s driven by one big transformer and crossed to subwoofers at 100 Hz sound exactly like our speakers except their horizontal dispersion is worse.....much worse. I also believe it is the job of the step up transformer to convert current to voltage. IMHE, and we both use OTL amps, the amps that drive ESLs best are SS amps with HUGE power supplies. For whatever reason, the Bricasti M28's do a better job of it than the MA2s. I like the MA2's midbass better, but I tend to push them hard the result being a steady drain on my tube supply. They are great amps suited to a less stressful existence. The Bricasti amps are the most bullet proof amps I have ever used. If they do not like something they simply turn themselves off. Reboot them and you are good to go. They also are amazing at protecting loudspeakers. If they detect any clipping either their own or any other unit in the chain they turn themselves off immediately and this includes digital clipping. I burned out two transformers clipping the MA2s.  I do believe Acoustat was the first to curve an ESL in the horizontal plain. The X which came out in 1978 had three panels angled about 15 degrees to each other giving a horizontal dispersion of 30 degrees. The 2's and the 2+2's only had 15 degrees of horizontal dispersion, but it was better than 0 degrees (at high frequencies)

@rauliruegas You are correct! The Digital Drive Plus series has a high pass filter.....a 1st order one. Definitely better than nothing...if it is being used. I use a digital 8th order filter on both low and high pass sides. @richardbrand are you using the high pass filter??  I agree that Roger West could have stated that position more accurately. Dr West did advance the art of ESLs. ALL dynamic drivers are point sources unless you stack them in a linear array with the right spacing between drivers and that has never worked well in home HiFi systems. It has been tried unsuccessfully 3 or 4 times by Infinity, Nearfield and others. This results in a big impressive sound lacking in fine detail and image specificity. Most line sources, like Maggies, Apogees and many ESLs are crippled because they are not tall enough to extend the line source behavior below about 250 Hz. A proper residential line source has to extend from floor to ceiling or it loses it's line source behavior at the frequency matching the wavelength of the speaker's height. The power projection stops at the frequencies it is most needed. Now, what you are talking about is a co-axial point source which has absolutely no advantage over non co-axial point source speakers that are spaced closely together until you are a foot from the loudspeaker. In doing the variable diameter point source Quad was trying to improve dispersion characteristics at high frequencies. My assessment of modern Quads is there are dynamic speakers that outperform them in many ways resulting in a better listening experience particularly at levels above 85 dB. 

Funny how coincidences happen. As i read this, I was going through a box of interconnects and found two unused Shure V15-IV MRs. I was given when I worked at a studio. We had purchased several of the "new" Shure CD players for doing transcription work and they came with these carts. Just wondering, my bedroom system has a Music Hall classic w/an Ortofon 2M Bronze that has around 250 hrs on it. Does anyone have an option if the Shure may be a worthwhile replacement? 

This thread has evolved as if the Shure V15 was the sine qua non of vintage high output cartridges. It’s surely not that, in my experienced opinion. Far from it. But if you try it, give an NOS cartridge that must be minimal 30 years old at least several hours playing time before you judge

Mijostyn, if you’re talking about the Sound Lab OEM backplate on a Sound Lab speaker, with its power robbing parallel resistance and its very low midrange impedance, then yes perhaps an SS amplifier is better suited to overcome those handicaps. But if you want best sound, you remove those kludges, then Z and efficiency go way up and an OTL kicks ass. If you don’t agree, that’s fine, but please stop telling me what I would like.