I seem to recall that the Quads measured with the lowest distortion of any speaker available at the time (back in the 1960s-70s).
The Sound Labs seem to be the Sate of the Art in ESLs. The newer ones are fairly efficient- once you translate the numbers to real world, about 90dB by comparison.
Getting the older Quads and the Sound Labs to play bass is a bit of a trick- you have to have an amplifier that can make power into higher impedances. If you do, they play bass very nicely!
ESLs are different from a lot of speakers in that they work best if the amplifier can make constant power into them at any frequency rather than constant voltage. IOW an amplifier that can double power as the impedance is cut in half will be bass shy and too bright on many ESLs. The reason is that the impedance curve of an ESL is not a map of its efficiency as is common with most box speakers. That has a lot to do with the fact that there is no box and its associated resonance and also because the impedance curve of the speaker is based on a capacitance.
The Sound Labs seem to be the Sate of the Art in ESLs. The newer ones are fairly efficient- once you translate the numbers to real world, about 90dB by comparison.
Getting the older Quads and the Sound Labs to play bass is a bit of a trick- you have to have an amplifier that can make power into higher impedances. If you do, they play bass very nicely!
ESLs are different from a lot of speakers in that they work best if the amplifier can make constant power into them at any frequency rather than constant voltage. IOW an amplifier that can double power as the impedance is cut in half will be bass shy and too bright on many ESLs. The reason is that the impedance curve of an ESL is not a map of its efficiency as is common with most box speakers. That has a lot to do with the fact that there is no box and its associated resonance and also because the impedance curve of the speaker is based on a capacitance.