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Dude, where's my bass? Oh, lost to stiffened rubber surrounds...who knew?

Started a thread on "Cables" re: better cables to help restore bass to my B&W CM-4 speakers...so while preparing and listening to speakers for cable evaluation, our daughter - who has very acute hearing, unlike my senior ears! - noticed sort of a "crackling" sound in left speaker, and sure enough, removing cloth speaker covers, we notice a 6cm hairline fracture in the surround of the mid-range cone.  In fact, checking the rubber surrounds of bass and mid-range cones in both speakers, there were significant areas of stiffened and brittle rubber material, which - I would presume - drastically muted the speaker responses to incoming audio signal.  So, what to do?  Can the surrounds themselves be replaced w/o impairing cone native sonic qualities?  Totally new area here for me, having never dealt with material failure or deterioration in speaker components.  Suggestions most welcome!
compass_rose
mtrot
642 posts
 
Congrats on the resurrection! 

As to the cables, don't bother and don't waste your money.   Cable is cable./s   Just wanted to get that out there before anybody else!

Actually, I stand by my recommendation in your other thread in Cables.


phusis's avatar
phusis
350 posts
 
@johnk --

... system I am running as I type uses drivers from the 1950s 60s 70s all are orignal all are in spec. They sure dont make it like they use to.

Would you expect new, more or less equivalent drivers with the same diaphragm (i.e.: paper) and surround material (pleated cloth accordion surround) to last as long as those older drivers you’re referring to? The bass horn drivers of yore are almost a breed onto their own that are rarely made the same way today (i.e.: with their typically smaller and lightweight VC’s and light diaphragms), though a few examples that are made today could be GPA, Vitavox and Crites (the K33E "clone"). Moreover, bass horn drivers are very often hidden to some degree behind the horn they’re loading, and so aren’t as readily exposed to sunlight and other atmospheric conditions. I would assume this also to be a factor in extending their lifetime compared to direct radiating units?
compass_rose OP
23 posts
 
Re: SimplySpeakers replacement surrounds:  the material of the new surrounds differs from original in color (black, slight shine), more supple, and "soft" to the touch.  I emailed SS to enquire about the composition of the replacements, but haven't heard back.  Maybe it's a proprietary formulation, who knows?  But, for all that, just great gear.
johnk's avatar
johnk
1,490 posts
 
Hard to tell how things will really age and I honestly do not think that modern drivers will age as well as some vintage has. I have modern drivers in my scrape piles many killed by foam degradation modern plastics are used in most everything and some of those as they age become gummy and break down into the VC. 
oddiofyl's avatar
oddiofyl
1,076 posts
 
I have a pair of KLH Model 2, they have to be over 30 years old and the butyl surround is still soft and supple...  so you never know....the environment plays into it too.  


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