I have a pair of A3. At one moment I’ve had this kind of problem on one speaker. It turned out to be a moisture issue. The speaker was close to the open window on rainy days and picked up some moisture from the outside. After exposing it to the heat of the sunlight for all day long the problem disappeared by itself. It may not be the same issue on your speaker. Dr. West will certainly know the best.
I’ve moved from Quad ESL 2912 to Soundlab A3. I’m very happy with this evolution of my system. Soundlab are much better in every possible way. I’m looking now to upgrade my amplification. If some of you have Atma Sphere MA-1 for sale, keep me posted please.
I would recommend Atma Sphere as well. I have recently purchased Soundlab speakers which I run with Atma Sphere M-60 + MP-1 right now. I live in Paris. We have many fine tube amplifiers here in Europe. But I largerly prefer Atma Sphere gear over any other tube amplifier which I have listened so far. That should tell you how good these are.