SpeakerTalk

[Lee in Montreal]

My Calindas, Cantatas and 105/2s have perfect woofer surrounds, despite being 25 to 30 years old. Any B110, B200 or B300 is in new condition despite their age. On the other end, you got 104/2s and 107s with rotten woofer surrounds. What separates them? Rubber surrounds on one hand and foam on the other.

I just bought four 1985-vintage B300B and the surrounds are like new. I wiped the membranes and surrounds with alcohol to remove grim and dust and they look like I just bought them.

So, the big question is: what quality of cocaine were the designers at Kef snorking at production meetings (remember the mid-1980s?) when they decided to use foam surrounds on woofers when they already had proven rubber surrounds already in production?

We want the name of whoever approved that...
_________________
Current line up
2 sets basic Kef 104/2
2 sets bi-wire Kef 104/2
Plenty of KEF components for a few fun builds

[proffski]

Surround compliance is part of the complex design criteria.
Just about every famous loudspeaker manufacturer has suffered this problem, I doubt if the foam rot was forseen or anticipated.

The surround has more duties than merely keeping the cone in place.
If you can find a copy of "High Performance Loudspeakers" by Martin Colloms it is explained well in laymans terms.

Most amateur DIY loudspeaker builders I know own this veritable bible as of course does yours truly.

http://www.amazon.ca/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=High+Performance+Loudspeakers&ih=20_9_0_0_0_0_0_0_0_1.124_171&fsc=-1

The price range of the book on Amazon Canada is amazing!
_________________
I contend that for a nation to try to tax itself into prosperity is like a
man standing in a bucket and trying to lift himself up by the handle.
-Winston Churchill

[audiolabtower]

we talked about this in a previous thread, and I made much the same point. They came in with coupled cavity loading, and Speakerguru explained that this form of loading needed a lightweight diaphragm with low resonance freq - hence the foam surround with paper cones. They were all taken by surprise at how relatively quickly the foam deteriorated compared to the previous generation pvc surrounds.

Do any models still use foam surrounds nowadays?

[proffski]

I still have a pile of original Son Audax foam surround drivers and the foam is perfect.

But, they are still in their boxes with no sunlight creeping through or household vapours, and they are in room with no central heating either!

Now I'm curious as to how long the ones I used in my friends centre speaker will last as well as the ones I made for the schools physics department?
_________________
I contend that for a nation to try to tax itself into prosperity is like a
man standing in a bucket and trying to lift himself up by the handle.
-Winston Churchill

[audiolabtower]

[proffski]

I have seen foam rot inside loudspeakers a plenty, including KEF!

By far the worst were other makers units using reflex tuning in a household full of smokers, they reeked! The foam just turned to crumbs.
_________________
I contend that for a nation to try to tax itself into prosperity is like a
man standing in a bucket and trying to lift himself up by the handle.
-Winston Churchill

[audiolabtower]

that's interesting, smoke must be an accelerant? My speakers have never seen smoke from new, so eventually age must be the eventual limiting factor. Interestingly the Spendor grill foam is much softer than the internal damping foam, presumably this makes it more vulnerable in comparison since the BC1s are also reflex and open to the surroundings.

I see that few Kef104s (which I once had) have their grills intact either.

[TL 200]

[rossalator]

Hi people, im a newby here.

Just a quicky on the subject of foam rot, i have this pair of dantax "studiopower metal cone" speakers, well aware they are awful sounding , i brought them for £2 off a boot sale in awful condition, i basically needed a speaker i dont care for to use with my electronic drums.... these things have two 8" with foam and a 4" also with foam, the cabs had been in a very damp place and the boxes all swelled, still wet inside...with the bottom of one flapping open ...

i basically bodged the boxes, glue and screws to hold them together so they dont fall apart while i use them..... had them a year and decided to replace the tweets and sort out the terrible crossover, they sound alright now and 3 years down the line the foam is still intact ! they take some stick as well !

i dont get it, if any surround should have rotted it should be these !?!

[audiolabtower]

Hi, have you any idea how old they are? Maybe age is the primary factor, but secondary factors like smoke and chemical vapours act as accelerants. If the foam is relatively new (compared to the 20 or 30 years we are talking about here) maybe moisture and "clean" water vapour does not affect that badly in the short term? Still an interesting story

[Pyrrho]

[ColinR]

I would suggest foams from Speakerbits of Melbourne Australia.
_________________
This post or any other information supplied to this website or any other by myself is not available for any form of commercial purpose i.e. to hi-fi magazines or as sales and marketing material for sleezeBay or Audiodogging pimps and the like.