Re-foaming bass speakers

[engrssc]

Found an interesting indoor (constructive) project to do on these cold wintry, snowy days. That being to replace the rubber surrounds of some original (4024) Realistic Mach One 15" bass speakers. The original surround had aged rendering the speaker system worthless. A replacement surround is readily obtained from one of several on-line sources. (Found the price can vary widely).

The time consuming part of the project is to remove the adhesive and residue of the original installation. Installation of a new surround is relatively easy.

This model speaker is said to have been individually hand built for Tandy (Radio Shack) by Thompson (others say this speaker was made by Foster/Fostex). This was back in the early 80's. These were the first speakers I ever bought and believe they would compare favorably with most anything on the market today (personal opinion, of course). While the surrounds held up quite well until now, they have developed cracks and need to go to their well deserved place of rest. I was reluctant to replace the surrounds as the only replacement surrounds that are available now are the foam variety. But, finally after waiting 2 days for the adhesive to dry, the first one sounds just as good as it ever did. Even tho the power handling capacity is low by today's ear popping standards, I have no doubt they will hold their own in our music room.

Curious how many have even heard of a Mach One, let alone owned one? No doubt there are some, as almost 30 years isn't all that long ago, or is it?

Rgds,
Ed

BTW, I have no urge to buy (or even listen to) any of R/S's current line of speakers. Come to think of it, I can't remember the last time I was in a R/S store. In those (old) days, I used to wait for the mail (person) to deliver the new R/S catalog. Then, brilliantly, their marketing dept dropped catalogs along with quality.

[BarryG]

Thanks for posting this, Ed.

Once again, this forum (and Google) have led me to a solution to a problem that I had assumed would be very difficult/expensive to fix, and I can do it myself! I have a pair of great old '70s era Advent speakers (Maestro's?) that a friend gave me when he upgraded his home theater system. One has a tear in the surround of the woofer, and subsequently rattled a bit on the low notes from Hauptwerk. I worked around the rattle by routing low notes through my sub and thence to the Advents, giving the latter only those higher than the rattle point. But fixing the surround is the real solution!

I found several relevant sites quickly, but haven't spent time with them yet. Any particlar favorites or most useful from your experience, Ed?

Barry Gerken

[engrssc]

Try this site, http://www.myaudioaddiction.com/ . I've had very good results from him. Very reasonably priced products and good customer service. All I needed.

Rgds,
Ed

[engrssc]

A couple pointers I found to be useful. As I mentioned, removing and cleaning the residue of the old surround is probably the biggest task. I found the surround separated from the paper cone quite easily. The adhesive on the speaker (metal) frame was a bit more work. Suggestion is made to use a razor blade. I found a combination of a small (1/2") file and a stubby screwdriver to work as well. The suggestion to use alcohol works to some degree, but I found using either Goo-B-Gone or Goof-Off dissolves the adhesive much better. I was careful not to let these soak the paper cone. A soft paint brush (along with a shop vac) is useful to clean away the debris.

After cleaning, I put the new surround in place. It, of course, needs to be carefully centered. At this point, I placed a small dab of the adhesive between the paper cone and the new surround at intervals. I used the speaker mounting holes as a guide. In other words, I wanted to anchor the surround to the speaker cone (with these "dabs") before gluing the entire perimeter. Takes about 2 hours for the "dabs" to dry. (The white liquid adhesive appears to be a latex based product that dries clear). I let the final "gluing" dry over night.

The rest is pretty easy. Glue the edge of the surround to the metal frame, let dry and finish re-assembling the speaker. BTW, there is a suggestion to connect an amplifier to the speaker and play (music) at a very low level to insure that the voice coil stays centered. I didn't find this to be necessary as these 15"ers are quite (self) centered. (Not stuck up, mind you ).

The supplier I mentioned has other items in addition to surrounds such as surround adhesive, replacement (cardboard) gaskets that fit around the edge and (center) dust caps. While the process takes a bit of time, I felt it was well worth it. Prior to investigating this as a DYI project, I found prices anywhere from $90 USD (per speaker) and up to do the job. Overall, I figured (as a newbie) it took me approx 3 hours per speaker (broken up into shorter segments).

Rgds,
Ed

[BarryG]

Thanks for the additional information, Ed; it'll undoubtedly save me some mistakes and time.

Barry

[David Pinnegar]

Hi!

There can be an alternive to refoaming. I have a magic potion which has got me out of difficulties - provided the structure of the foam is all still there, cracks and all but still there, then you can paint it with IsoFlex special primer for roofs - its a really flexible transparent rubber that stays flexible. It soaks into the foan and gives it a new structure . . . and it works!

I bought a pair of good Realistic 3 way speakers with 15 inch bass units and the units were on their way . . . This stuff has saved them and they work beautifully now.

Best wishes

David P

[engrssc]

Hi David,

Is the material you mentioned a UK product? The only IsoFlex I've heard of, over the pond here, is a dietary supplement such as http://www.gnc.com/product/index.jsp?productId=3465588&CAWELAID=367517309, probably not what you referred to.

In my case, the surround(s) were missing pieces. I would think such a product as you mentioned would be good at prolonging the life of a speaker surround as well.

If I'm not mistaken, I read somewhere that a person coated the entire paper cone with a similar product and "created" a speaker with, understandably, completely different characteristics.

Rgds,
Ed

[David Pinnegar]

Hi!

Yes - it's not a dietary supplement!

http://www.isoflex.ie/prodshowind.asp?g ... intext=int
http://www.diy.com/diy/jsp/bq/nav.jsp?a ... =266946591

There are other discussion threads where people recommend it as a varnish on latex or even as a substitute to latex in making theatrical weapons! It's brilliant stuff - fine as long as you have structure there. Painting it on a cone would increase mass and remove midrange so yes it could alter a driver's properties. But ideal to convert a rotting foam into an elastic material again. The other alternative is the product for damp proofing car ignition systems - "damp start" but personally I have found IsoFlex brilliant.

Best wishes

David P

[engrssc]

Thanks, David, appears to be an excellent product. Appreciate the info, cheers.

Rgds,
Ed

[BarryG]

Ed (or anyone),

I've just ordered the foam replacement kit for my Advent Maestro with 10" woofer. Only one of the speakers has a tear in the foam, the other looks like it's in perfect shape. Should I replace only the torn one, or is the other likely to "sound" differently from the repaired one, so both should be replaced?

(I also ordered a kit for a pair of Boston Acoustics A60s, another gift from a friend recently, with both foam surrounds completely disintegrated, but if I can reclaim them for the less-than-$20 kit price, plus a little labor, should be a good addition to my "oldies but goodies" Hauptwerk system speaker collection.)

Thanks for any advice,

Barry Gerken

[engrssc]

I brought 2 pair of surrounds good for 4 speaker systems all of approx the same vintage. With 3 of them, no question - replace. The 4th is hanging in, maybe on it's last big bass note, but so far it works. Go figure. But, I do have a replacement ready to go whenever.

Rgds,
Ed