B&W CM-2 Speakers Rock Hard Surrounds

BJJB Jr.

Active Member
Just got a pair of 2001 hand me down Bowers & Wilkins CM-2 bookshelf speakers. They are in pristine condition. Then I hooked them up to give em a listen. Horrible. No bass at all, very tinny sound. After a few minutes of ugly, I took off the grill to reveal beautiful ivory surrounds and Kevlar woofers. Nice. Then I touched the surrounds. Hard as a rock. Might as well of had a plastic surround. Hard to believe a 16 year old high end speaker would have such hardened surrounds. My guess is that they hardened because they were ivory in color, but am not sure. I am going to replace with black rubber surrounds, but thought i would ask for any insight as to others in this situation. Anybody?
 
Bought a pair of Wharfedale Dovedales with black rubber surrounds on 12" woofers. The one surround I checked at time of purchase was fine but I soon discovered the other was petrified. Pieces broke off it like it was a wafer of dried clay or plaster. A long established, well know specialty speaker repair shop advised using foam surrounds because obtaining replacement rubber surrounds that were compliant enough was doubtful or at least uncertain. They said it would turn the woofers into mid-ranges.
 
Found a single B&W CM-something at recycling, same issue, surrounds had turned rock hard. Strange as i've had the CM-C and smaller CM-series bookshelf speakers and they were fine. Could be because they were left in direct sunlight for years?
 
Yeah, could be something about the material they used for the white surround on the CM-2. The other B&W speakers from the 90s that I've seen with black surrounds are typically soft, rubbery, and as-new.

Dan
 
I pulled one speaker out to begin the process. The surround just chips away easy up to the point of glue. The rubber was fairly thick compared to other rubber surrounds on my RSL and PSB speakers. The outer edge was bonded with a double sided tape ring. The inner is bonded like cement to the Kevlar cone. Gonna be some tedious work to clean. I ordered rubber vs foam replacements, though I will have to see if they are compliant before committing. I'll take a few pics during the process.
 
Heres a few pics of the progress, I got the rubber surrounds, along with a black contact cement product. Finally got both woofers cleared, btw no solvent i own would touch the old glue up on these babies, acetone, men, lacquer thinner, adhesive remover, nada. Had to do a very delicate Dremel sanding job down the bare sight of kevlar. Also fwiw, the sun / air was probably a major factor in the fossil process, as under the aluminum bezel, the edges of the surround were still rubbery. So any who, phase one glue up complete (inners), tomorrow phase 2 outers and centering.IMG_5717.jpgIMG_5718.jpgIMG_5719.jpg
 
Today is another day, and the second glue up went well. Here is an update picture finished. They will have to sit another day till I tip em up and play em.

Another FYI - The woofers are substantial in these, and weighed in at 4 pound 5 ounce each.IMG_5745.JPG
 
You can't see it in the picture, but the aluminum trim ring left a small gap between the woofer rubber that looked unfinished. I glued up thin o-ring around the outer edge of the surround to take up the exact thickness. Now there is no more dust pit around the outer surround and behind the aluminum edge. Nice.
 
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