Hello forum followers,

I recently picked up a pristine set of Sony 007AV mini-apm full range speakers.  Prisitne, yes, fully working, yes...as advertised...but some bassy music and, you guessed it...the ~30 year old foam surrounds cracked and produced horrible sound...within 20 minutes of play.

Was I disappointed, yes, yes I was.  After searching for square surrounds, I could not find anything for these little beauties, but remembered seeing an interesteing method, translated from Japanese to English, here: http://homepage2.nifty.com/k-ooki/apm/edge1a.htm

I don't know who posted that information, but ALL of the following credit goes to this person.  In short, the method works, and works very well.

Assuming you have read that gem posting on how to repair apm speakers, I will cut right to the results with a few comments first.

1) Likely the most difficult thing required for this repair is to find the starch.  I finally found a spray on kind, which seems to have worked.  I was tempted to make my own, and this is possible using potato or corn starch, but I don't really know what concentration.  Maybe someone here will give it a go!

2) Cleaning the old apm...be careful on the corners, on one of mine, the thin foil lifted off of the honeycombs, ever so slightly.  So go slowly, and if you get frustrated, STOP, go have a beer or other pleasant relaxant, and try again.

3) I used non-acetone nail polish remover to get rid of the old foam and glue.  What worked well was taking some flat cotton bits, and soaking them in the solvent, and laying them diectly on top of the glued bits (after scraping off the foam and some glue beforehand).  Let it sit 1/2 hour, and that old glue swells and is really easy to remove.  See here the result:

In the next picture, you can see my template which consists of some wooden plant stalk holders which were cut and glued (glue gun).  The leather chamois was soaked thoroughly before pressing into the mold.  The yellow foam square (courtesy of my 2.5 year old's "learn some letters" kit), fit perfectly inside to keep the inner shape (pressed down with 1 glass of water for weight).  I used flat table coasters to meet the outer edges and keep the shape (pressed down with 4 glasses of water for weight).  Then sprayed the hell out of the exposed "bulge" with starch, followed by some savage hair-dryer action (to cook the starch a bit).  Let it dry in place over night (what you see here is the next day after I took my template apart).

 After an initial cut, I got this (note it is fitted inside the speaker frame),

And some cloth dye action next

 After this, one needs to measure and cut out the inside bit.  I could have done a nicer job, but wasn't going for looks really, although I think one could carefully make these to perfection with some practice.  And the final product:

 Couple more notes.  I used a 1.5V AAA battery hooked up to the speaker connectors to keep the "cone" in place, from the first gluing til it was dry (seems to have worked).  I also used some silicon gasket sealer (high temp) as my glue.  So, you see what you can get: maybe go with a clear silicon, as you can see some red poking through, although a cotton swab with some of the nail-polish remover worked well for goof-ups.

And, the sound?  Well, these are full range speakers, and they have very detailed high end, and pretty decent base.  I was concerned I would lose high-end after my repairs, but I didn't.  These things sound great!  The bass is there, and the high end is very clean.  I've been listening to JJ Cale, and now Ravi Shankar, it all sounds great (and my fully restored Aiwa HS-PL50 with BBE and amorphous HX-head of course helps with the sweet sweet sounds!).

OK, well, there you have it.  I thought this repair would be beyond my capabilities, but actually, once you gather all the gear required, and commit to the job, it wasn't that bad.  I just share this here to encourage anyone to repair those old apms.  I could say in the end it was quite easy, and I am seriously pleased with the results!

Cheers!!

Very useful tutorial, I have several APM speakers, so far they are working great but I will keep that in mind.

You could use leather already painted black...

Ya, I have some on an FH-5 and they are fine, but I have read many have gone to dust by now.  And yes, black would have been nice, but, I have never seen a black chamois cloth...not sure how well this would work with other less soft leathers...

Thanks GWD for the link and the hands on experience with that method.

I have an FH-10W that waits me to finish other projects to deal with it.

You can see it here:http://REPLACEMENT ERROR/topic...ite-and-more-stories.

If you notice you'll see that the foam on the right speaker has started falling off!

So for for me is an answer before I ask.I hope in the near future to add a report .

Another common problem with the early FH Series is that if you get one then you can't stop!!

OK, I took a look, yes nice unit!  Yes, I understand how this business becomes an addiction quite fast (I have an FH-3 and an FH-5)!

By the way, did you know there are available pre-formed foam squares on ebay for FH series?  Not so expensive either.

I can report that it is only about a month since I did this work, and they are quite fine, so I can attest the method really does work.  I am curious how they will sound in a year, but I think they will still sound great!

Good luck and keep enjoying the apms!

Cheers!!