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Refoaming problem I cannot fathom

S

Sax & Guitar

Active Member
I am refoaming the woofer surrounds on my father-in-law's Boston Acoustics A-60 speakers. I got the kit from Simply Speakers, and the first speaker was a cinch. Sounded just like it did in 1982 when he bought them (on my advice).

However, the second speaker went wrong somewhere. I was certain that I had hit the centered "sweet spot" for the cone, yet I had major buzzing when I did the play test. After talking with one of the guys at Simply Speakers, I attempted to loosen and move the attachment to the speaker frame, using the instructions he gave me. Needless to say, the foam ring tore and became worthless.

I ordered a second kit of two foams, in case I had another problem. Then I patiently removed the second speaker's refoam, and prepared it for another refoam. Again, I very carefully found the "sweet spot" where the cone would move both up and down without any rubbing before attaching the foam to the speaker frame. After waiting for a full dry of the outer frame's glue, I did my play test once again. Again, I had major buzzing, and even some cutting out of the signal.

What could be the problem? Could the speaker's cone be damaged in a hidden way? Could the connection to the speaker coil be loose or intermittent? Could the voice coil be damaged in some way? I looked at the crossover, and the components did not look leaky or damaged.

The only other thing I can add is that his basement was very humid, and that screwed up his turntable. Could the voice coil be damaged by the moisture? The other speaker plays perfectly now.

Thanks in advance for any help you can give.
 
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While the glue is still wet you need to play a 30hz test tone through the woofer. Any misalignment will be heard.
Some people cut the dust cap and shim the voice coil, but I’ve had good luck with the test tone method.

And yes the VC could be damaged somehow. How I check for that is with no surround on the woofer (old surround completely removed) I set the woofer facing cone up, and play the 30hz tone through it. You should not hear any distortion If the VC is good.

As long as your dad didn’t use the speakers a lot with the degraded foam, the voice coil shouldn’t be damaged.

Edit: I’m also assuming you are testing the woofer out of the cabinet when you get the buzzing.
 
Thanks for your input, elitopus! The buzzing takes place both in and out of the cabinet, but the intermittent cutting out of the signal happens in the cabinet. I cannot try your suggestion without removing the second refoam.
 
Check the crossover for corrosion. Also, try swapping the woofer with the other one.

Does the coil rub after the glue is dry? You should be able to push the cone all the way down into the magnet without anything rubbing or touching without power on the speaker.

You may also have some junk in the voice coil gap. Fixing than usually means removing the cone and voice coil.....

Make sure the cone is not torn or separated from the voice coil tube, and the dust cover is not loose and that there isn't something stuck to the spyder or back of the cone.
 
^+1
Hook the woofer up directly to the amp and listen for the buzzing. It rules out the rest of the speaker.
 
Make sure the spider hasn't partially separated from the coil former. Had that happen on a Advent woofer. Drove me nuts trying to figure out how I had screwed up the refoam job. I had an extra pair of Advent woofers so I used one of those but I believe I read the spider could be reattached with epoxy.
 
Buzzing

You may have a bad voice coil.
The windings have come loose from the former.
Basically a dead driver.

Intermittent

You may have a bad joint from the tinsel to the voice coil. It may be at the connector solder point but more likely where the tinsel connects to the voice coil leads on the cone. At the cone, it’s a near miracle to fix that. You need to carefully dig through the seal/glue and try to resolder the joint. You need some skill and a truck load of luck.
 
Further on what @blhagstrom wrote above me, you'll need to remove the dust cap, as that is generally where the tinsel connects to the voice coil leads. You don't really have much to lose at this point. If the dust cap isn't loose, best bet is to cut it a little above where it meets the cone. An X-acto knife is probably the best type to use. Don't try to cut it at the cone since you run the risk of hitting the wires with the knife.
 
I use to recone and foam speakers all the time and I would never attempt to do so with out removing the dust cap and shimming the voice coil for proper alignment. When you are working on big CV, Altec, JBL, Mcintosh, EV and others you can't afford any mistakes. Time is money.
 
I did an A-60 for a friend years ago. I had a similar issue. After three attempts, it was determined that the frame of the woofer was bent and unfixable. I tried my hardest, but all was to no avail. Good luck.
 
I've only done a few refoams, but i felt more comfortable shimming with index card shims than with the test tone.
 
I just did a set of Boston A70s. The clearance between the magnet and voice coil is even tighter than my JBLs. I ended up shimming them. I ussually do the foams by feel; however, for JBLs and the Boston A series I shim (Boston HD seem to have more VC clearance - I do those by feel). I've tried the 30hz sine wave, personally I'm not a fan - it doesn't do the trick for me.

One advantage to shimming is it allows you to glue the inner and outter diameters of the foam surround at the same time. One the negative side, the time is about the same because there is an extra step of gluing the dust cap. There is also the extra cost of the dust cap.

I do think you can get a better finished result with shimming, but for most speakers with gobs of VC clearance (like Advents), doing it by feel works ok.
 
Thank you, one and all, for your fine suggestions! I have given plenty of things to check out thus far, and I welcome any further contributions to this thread.
Regards,
Sax & Guitar
 
Like others have mentioned, some method of aligning the VC should always be used. Yeah, lots of people don't, and lots of people take shortcuts and never get burned.
I shim every one I do, and I have done every BA "A" series at least once. That's because it's the only way it's a guaranteed perfect alignment.
You can cut the cap like this https://www.decware.com/newsite/refoam.htm if you desire to re-use it.
 
Absolutely do not attempt to remove the dust cover on those polymer woofer cones in Pioneer HPM speakers unless you want to replace them. They WILL shatter. Never seem to break in service, but snap with almost no effort when the edge is free of the foam.

For anything else, cutting and replacing the dust cap isn't a problem, and you will also get better centering.
 
Thank you, grillebilly, for your link to the Decware online instructions. I did not know how to shim a voice coil, and this was very clear and informative. If I do it this way and still have a problem, it is likely in the voice coil or the spider, as others have suggested.

Once again, my thanks to everyone who contributed to this thread and to my education in the possibilities of what may be the problem. I will post back here in a couple of days when I see how the shim refoam system works for this troublesome speaker.

Sax & Guitar
 
check the spider before you redo any thing. its not at all uncommon for part of the spider to have come unglued
and it will cause a buzz sound more than any kind of rubbing sound
 
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