Uh, is it just me? I don't see anything in particular about the ESL57 in the OP- just Quads.
So ESL63s or any later model like the 989 could be in the mix.
My experience with the Quads has been that you really have to watch it with the ESL57 because it really can't take much power. I've also seen updates that include protection circuits.
The ESL63 could take more power. We found that right about the point that our MA-1s were going to overload was also the point that the original protection circuit would energize. We also found that due to the way the amp interacted with the impedance curve, it could drive the ESL63s with greater volume than any other amp we tried.
The later Quads have been used with both our M-60s and MA-1s. Only the ESL57 has the low power limit issue.
Now if you are worried about the speaker no longer being made or that sort of thing, the ESL57 and 63 have a lot of support in the aftermarket- new diaphragms, power supplies and the like are available through various rebuilders. But you also have other alternatives like Sound Lab who arguably makes the state of the art in ESLs.
So ESL63s or any later model like the 989 could be in the mix.
My experience with the Quads has been that you really have to watch it with the ESL57 because it really can't take much power. I've also seen updates that include protection circuits.
The ESL63 could take more power. We found that right about the point that our MA-1s were going to overload was also the point that the original protection circuit would energize. We also found that due to the way the amp interacted with the impedance curve, it could drive the ESL63s with greater volume than any other amp we tried.
The later Quads have been used with both our M-60s and MA-1s. Only the ESL57 has the low power limit issue.
Now if you are worried about the speaker no longer being made or that sort of thing, the ESL57 and 63 have a lot of support in the aftermarket- new diaphragms, power supplies and the like are available through various rebuilders. But you also have other alternatives like Sound Lab who arguably makes the state of the art in ESLs.