How good are the Sony APM speakers ?

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.

 

My thoughts are if they were actually superior, why did Sony themselves cease making them?

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.

 

There are so many APM designs that it is hard to generalize. The ES line from SONY had a very controlled, detailed, unforgiving sound. The lower range APMs could be a bit too harsh and boxy.

On the other hand, the 2-way APM-22ES which was bottom of the ES line has a refined, detailed quality that I admire. And wonderfully musical, convincing bass. Their build quality is first rate.

The APM-615 is 3-way. I am listening to a pair now. The brass is most convincing. But the bass is a little boomy and the high end is very ordinary sounding. BUT they can play amazingly loud!

My strong suspicion is that Sony chose to under-damp the cabinets to get more bass volume. If one recalked all the inside seams and added foam to the back panel and then stuffed then full of cotton-poly fluff, I bet they would sound much much better. Perhaps even gaining the control and subtlety in the ES line. Also, I am tempted to try a diffusion ring around the tweeter. Because the 615 has a lot of promise and is basically a very good idea but the details are implemented crudely.

thanks for the responses so far

Sony made two speakers for the Esprit line which used APM drivers in the early eighties. One was a large rectangular monolith which was a four way design I think. The second model was a two way design also very large but with rounded sides. They cost $12,000 and $8,000 respectivly. They sounded good especially the two way. Other speakers I had listened to at the time were the Hill Plasmatronics, ESS Transar, and the original 801's. The Hills were $10,000 and most other exceptional speakers at that time were less. This APM is an example of trickle down technology, sounding great in the Esprit but leaving much to be desired in their mid-fi brethern. APM drivers are also hard to repair because of their unusual surrounds and multiple voice coils.

not very good...even then.