How good are the Sony APM speakers ?

APM 8, APM 4 esprit, APM 6 esprit, APM 22ES (2-way), APM 77, APM 66.

Surrounds may have gotten bad after all these years but they can be fixed. Crossovers should be fine, at least for the first three, for they did not use any electrolytics. APM 6 if you can find one (2- way, probably the best of them all), and APM 4 are really good ones. APM 8 is the first one, the biggest and can take a lot of power, APM 4 and 77 shared same drive units (4 is the better one).

Something to note that even Sony then said that flat drive units are not necessarily better but different. But they made them so good.

Few years back i had the chance to listen to FAL C90EXW using flat drivers also, same great dispersion and linearity.

Usual Sony (we can do it and then do something else) and because they were expensive to manufacture. I do not know and cannot guess failure rate.

Anyway, they discovered that a flat and rigid square diaphragm drove in at least 4 points was the best design to bypass split vibration and have the breakup frequency much higher with a distortion grade much lower on the full spectrum and that is heard.

In APM 66ES they even used 8 points making a woofer sounding flat up to 4Khz.

But all this is now history. Still the better ones of the series are worth looking for.

Some drive units pics

even Sony then said that flat drive units are not necessarily better but different.