Curious to see how much love these good old CX100s are going to get xschop!

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Login to view imageI foamed (1/8" thick open-cell) the inner frames and applied 2 layers of thick polyurethane adhesive to the outer frame baskets first thing after removing old rotten foam from cones with mineral spirits. I protected the rear cones with a curled strip of bubble-wrap, and terminals with electric wire nuts. I also made fiber-cloth reinforced rubber gaskets and glued directly to frames, rubber side facing towards cabinet openings for  positive driver sealing. After polyurethane, foam glue and new frame gaskets dried, I glued the inner cone perimeter and attached new butyl surrounds there first.

After new surround is glued and dried to basket frame flange, I use just a drop off black latex paint to dampen the cones and dust cap. It dries to a miniscule added weight and rejuvenates the dried paper cones as well. I go ahead and black out the frame edges too while I'm at it....

 

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Great progress! I would measure the woofers as the doped cones will likely change the parameters causing a crossover modification.

Again, I removed more mass from the moving dust cap than what was added from the thin layer of dried latex (for cone damping). The speed increase of the lighter moving cone translates to better transients. Here's what B&O did to ameliorate the resonance of the air chamber created under the hard dust cap of their midrange, which is just the same woofer, just modified pole-piece. A phase-plug would have also solved that problem, as well as fix any center cone signal cancellations...

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If the driver with the hole in it is NOT the midrange, then B&0 factory  installed both my CX100's backwards and got the wiring WRONG....

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I'm only going by ears for the sound improvement. As I stated in another thread that YES INDEED, TS parameters were changed by going from the loose foam to the stiifer rubber. I knew so going in on the first build because it improved midrange performance at the cost of lower frequency SPL. They still went down to @40-50 HZ doing a HZ tone sweep, albeit with lower spl. It was a win-win situation, as I paired them with a passive sub that cuts off @ 200Hz any way. I'll be doing the same for this set. Just incredible midrange reproduction doing these modifications.

That said, being an experimenter with a biochem degree and many years of industry experience, I loosened these next set of butyl surrounds with  a high dilution of methyl salicylate in boiling water for 10min. This was to improve their deformation for cone edge gluing, but indeed also relaxed the butyl rubber nicely...

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The black anodizing on this particular set was damaged by previous owner, so I'll make them with the brushed alloy patina... Over the years I've used NaOH solutions, but have found heavy duty oven clean works great with 2 applications...

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