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

Dear @richardbrand   : " My Velodyne 18" subwoofer is ..."

Wel, you can be sure that 2 subs always is better than only one listening at the prefered seat position.

I own Velodyne too but with better wooferbuild material: pulp/paper.

R.

@mijostyn   : Velodyne comes with the high-pass filter as the one that use richard.

R.

Ah, so much to take in.  Yes, my Velodyne has stereo high pass digital filters which is how I relieve my Krell / Quad ESL-63 / ESL-2905 of having to play low bass.  It is also old enough to have a pulp/paper cone but if the servo mechanism is good enough, who cares?  The only things stopping me adding more are: the cost; the space; the fragility of my home; the fragility of my partner; the neighbours and ROI.

The original Quad ESL is often known as the ... ESL.  But it is totally different in concept, design and implementation to the later Quad ESLs which have factory designation not less than 63.

The original ESL, aka ESL-57, uses a curved panel (much later this was apparently "invented" by Sound labs) to give an approximation of a line-source, albeit horizontal.  Like modern stadium systems, these can be stacked vertically.  Stadium so-called line source systems are curved in the vertical dimension to get them to emulate a point source!  It is of course rather hard to bend a flat panel in two dimensions simultaneously.

The ESL-63 and later models use fancy electrics and shaped electrodes to get a truly flat panel to emulate a point source.  It makes no sense at all to stack them, nor to remove the electrics which are their unique raison d'etre in my opinion.

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.