It's been shown in several measurements by different people that Quad ESL63 can have very low distortion. Final ESLs have a reputation of having poor harmonic distortion either because they use an unusual drive configuration (inverted electrostat) or because they used to use high conductivity membranes. The example of a more recent Final ESL I found a review of pretty good, though:
https://www.diyaudio.com/community/threads/inverted-electrostat-inferior-in-distortion.409322/
Just one picture (ignore the 0.5% THD which is probably THD+N, the important thing is that the HD2 is 60 dB down = 0.1% HD2)
I also had a chance to measure an Acoustat 1+1 recently. I just did a quick test at 200 Hz at rougly 85 dB / 1 m and got HD2 about 55 dB down, so not bad at all.
There were also measurements of pre-production Capaciti panels in Klang+Ton and HobbyHifi magazines which were in the 50 dB+ range.
Well, I came across this review of the purity which has a Gen 2 CSL panel (same reviewer & magazine as the Final review, but different equipment and parameters):
https://hometheaterhifi.com/reviews/speaker/floor-standing/a-secrets-speaker-review15/
1 kHz distortion at (guessing from full FR sweep further down in the articla 87 dB / 1m ) is poor at 1.36%, this time stated as THD+N. More importantly, the HD2 is only about 37 dB down.
https://hometheaterhifi.com/wp-content/uploads/2015/08/martin-logan-purity-speakers-1-khz-large.gif
That number, however, is not consistent with THD+N sweep which should be higher because of the noise included and reads more like 0.6% at 1 kHz:
Even at 10 kHz, still 0.24% which is high for an ESL
Even the integrated ICE-T amp can't be that bad. So is anyone aware of reviews or other published measurements of Martin Logan ESLs? Is there a chance the Gen. 2 with their metallic coating and clear plexiglass spacers / dampers perform worse than the Gen. 1 with graphite coating, heavier foil and foam dampers?
https://www.diyaudio.com/community/threads/inverted-electrostat-inferior-in-distortion.409322/
Just one picture (ignore the 0.5% THD which is probably THD+N, the important thing is that the HD2 is 60 dB down = 0.1% HD2)
I also had a chance to measure an Acoustat 1+1 recently. I just did a quick test at 200 Hz at rougly 85 dB / 1 m and got HD2 about 55 dB down, so not bad at all.
There were also measurements of pre-production Capaciti panels in Klang+Ton and HobbyHifi magazines which were in the 50 dB+ range.
Well, I came across this review of the purity which has a Gen 2 CSL panel (same reviewer & magazine as the Final review, but different equipment and parameters):
https://hometheaterhifi.com/reviews/speaker/floor-standing/a-secrets-speaker-review15/
1 kHz distortion at (guessing from full FR sweep further down in the articla 87 dB / 1m ) is poor at 1.36%, this time stated as THD+N. More importantly, the HD2 is only about 37 dB down.
https://hometheaterhifi.com/wp-content/uploads/2015/08/martin-logan-purity-speakers-1-khz-large.gif
That number, however, is not consistent with THD+N sweep which should be higher because of the noise included and reads more like 0.6% at 1 kHz:
Even at 10 kHz, still 0.24% which is high for an ESL
Even the integrated ICE-T amp can't be that bad. So is anyone aware of reviews or other published measurements of Martin Logan ESLs? Is there a chance the Gen. 2 with their metallic coating and clear plexiglass spacers / dampers perform worse than the Gen. 1 with graphite coating, heavier foil and foam dampers?
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Found another review by myself (same magazine, same reviewer):
https://hometheaterhifi.com/reviews/speaker/floor-standing/a-secrets-speaker-review41/
So that's even at 100 dB/1 foot, so probably 90 db/1m and finally 60 dB down (so 0.1% THD without N):
So Gen 2 panels can be good. The size of the larger panel of the Spire vs. the Purity should not really matter at 1 kHz. So how do we explain the -37 dB (roughly 1.4% HD) at a lower level in the purity vs -60 dB (0.1%) in the Spire?
https://hometheaterhifi.com/reviews/speaker/floor-standing/a-secrets-speaker-review41/
So that's even at 100 dB/1 foot, so probably 90 db/1m and finally 60 dB down (so 0.1% THD without N):
So Gen 2 panels can be good. The size of the larger panel of the Spire vs. the Purity should not really matter at 1 kHz. So how do we explain the -37 dB (roughly 1.4% HD) at a lower level in the purity vs -60 dB (0.1%) in the Spire?