AVS Forum banner

Status
Not open for further replies.
1 - 16 of 16 Posts

·
Registered
Joined
·
6,224 Posts
Discussion Starter · #1 ·
I have a strange situation. I have 5 TVs and all are hooked to AV systems, 4 with out any problems. One of the smaller set-ups has a reoccurring problem. I was using some old Scott speakers from the 70's hooked to a Sony integrated amp and a 20" Samsung TV. The sound was getting progressively worse and I took the grills off and saw that the foam surrounds on the woofers had disintegrated. I figured 30 year old cheap speakers, no big deal.


About 10 months ago I replaced the speakers with a pair of Mits. speakers that had the old flat panel design . These from the mid 80's, but had always been decent for non critical listening. After a few months sound was bad again, I looked and the foam on these had disintegrated too! I'd chalk it up to age but I've got some AR speakers I'm using with my bedroom system and they are from the 60's and they are fine. Is it something in the equipment that might be stressing the speakers or was it just bound to happen with old inexpensive speakers? I've upgraded to some Mission speakers from the early 90's and I'm hoping to avoid this situation happening again.


Any ideas?
 

·
Registered
Joined
·
1,058 Posts
I too have had some speakers partially disintegrate on me after some fifteen years. Yes not all speakers disintegrate equally, as you note the AR speakers you've had from the 60's are ok. But the AR's may be made with different materials and perhaps they are higher quality speakers (for its day). Also environment matters. Damp environments may encourage rot.
 

·
Registered
Joined
·
733 Posts
Another thing that can eat foam surrounds is ozone, the type that is produced by electric motors. I work with high end copier/printers. If you don't change the ozone filters frequently enough, the foam seals in them will disintegrate in less than 5 years...
 

·
Registered
Joined
·
3,188 Posts
I avoid speakers with foam surrounds like the plague. I have seen speakers with foam surrounds disolve with time, exposure to sun etc. I have some Dynaco A25's made from the early 70's that I will be using for my HT speakers - hooked em up and they still sound great and they have rubber surrounds. My sister said my dad used to have those speakers at his store and then brought them home. My dad's store was a laundry mat / dry cleaner so there was lots of heat and steam around the speakers but yet they are still standing the test of time.


I remember years ago Klipsch running customer testimonials in their ads about how their speakers get hit by lightening etc and still keep working. It is all how the speaker is designed and contructed. I was considering purchasing one pair of fairly recent speakers (last years model) on consignment made by a reputable company. I took off the grills and lo and behold - foam surrounds. I said no thanks.
 

·
Registered
Joined
·
6,224 Posts
Discussion Starter · #5 ·
So the consensus is cheap speakers? I did look at the ARs again and the surround seems to be more rubber-like, I guess that's the key. I just thought the the coincidence was too great, and the failure might be equipment generated.
 

·
Registered
Joined
·
488 Posts
things to watch for are high moisteure content in home, that would promote mold. --- i doubt this is your man, but when your looking............


also oil depleats rubber. in all the years of the speakers, there had probably been some fingers touching the surrounds, and thus introducing oil to the rubber. in time oil will depleate and destroy rubber. maybe this is the culprit added with years = composition break-down.
 

·
Registered
Joined
·
1,954 Posts
Some VERY high quality drivers such as the Lowthers, JBL LE-14, Altec 411 and various Dynaudios and Morels have used foam surrounds. The foam is an excellent surround material because it does an excellent job of damping the sound wave traveling outward along the cone to the surround and prevents it's bouncing back, such bouncing causes notches in the frequency response. But the stuff does deteriorate. Refoam kits are available from Parts Express and other driver dealers as well as from speaker repair shops. Easy job.
 

·
Registered
Joined
·
6,224 Posts
Discussion Starter · #8 ·
I had looked at the possibility of redoing the foam surrounds but the cost, though small, wasn't warranted in the case of these speakers. If it was a better speaker, like my vintage ARs I would. There seems to be a fair amount for decent name brand speakers for sale out there on various sites at reasonable prices, so that's the direction I took.


As I mentioned earlier, my concern was if some part of the equipment chain was causing the problem.
 

·
Registered
Joined
·
728 Posts
Surround foam rot is typically mold related. Although great acoustically, the manufacturers back in the '70's and '80's never thought that the natural foam that they used would die of Foam Fungus. And it _is_ contagious- it doesn't help that modern homes are so well sealed that spore levels can build to very high levels. Note that this is _not_ the mold that can lead to Deadly House Syndrome.

The Butyl surrounds (Sticky Black Stuff) of some speakers of that period are mostly impervious, while paper surrounds die of mechanical failure- they flex themselves to death.

Non-organic or treated repair foam kits are available, but be aware that the replacement task may be simple- when done badly. A good job requires patience and attention to alignment, and the frequency response and damping chracteristics _will_ change; if you're doing one woofer, do them all, so at least they match.

(I've got a pair of old AR 90 towers to do when I have time; four Woofers, three of which are fungified.)
 

·
Registered
Joined
·
648 Posts
Flesh, I mean Foam eating bacteria.
 

·
Registered
Joined
·
1,954 Posts
APG---Good thing I'm into old Altecs and JBLs, those corrugated linen surrounds are very reliable, I've a set of early 1960s Altec 605s and mid 70s 515Bs that work and look like new, also some nice mid 70s JBL 15" woofs. I have 2 1957 Altec 15" woofers with the rolled paper surrounds, one has cracks but the other is fine. Nice thing is that you can still get Altec stuff ("real" Altec I mean, not the computer stuff) fixed with new, original type parts made on the same machinery by Altec's last head engineer who bought the stuff when Telex killed off the real Altec.
 

·
Registered
Joined
·
195 Posts
Foam rot isn't a "cheap speaker" problem, and I don't believe it's a moisture/fungus problem, either. I live in one of the driest climates on earth and every foam-surround speaker I've owned for more than 15 years has disintegrated, even $500 JBL woofers. Fortunately, reconing is usually less than half the price of a new driver.


Dave
 

·
Registered
Joined
·
235 Posts
I upgraded my 9 year old Hsu subwoofers because the surrounds were made of foam. Regardless of price I have found the stuff usually starts rotting. I thought of the repair kits but I can not believe the change would not alter the original sound of the speaker. Now I just buy speakers with the butyl rubber surround including my Hsu tn1220ho's.


Frank
 

·
Registered
Joined
·
728 Posts
Tom Brennan-

Oops! I didn't mean to say that mechanical failure in paper surrounds was inevitable; just that it was the normal failure mode. I have a pair of Wharfedale W90s that are entering into their fourth decade, and they are still fine, (But a little deaf on the high end...), plugged paper woofers and all.

David Milne-

You don't need a lot of moisture to have a mold/fungus problem, but it certainly helps. The degradation of natural (rubber) foam due to mold/fungus is well documented- and not just in speaker surrounds. This is how rubber naturally breaks down. (Or the tropical forests would be treetop tall with dead, mummified rubber plants...)

That, and heat. (Failure mode for tires- rolling resistance creates heat, which oxidizes the rubber into (Mostly) CO2. (Or the highways would be treetop tall with tire dust.))


Butyl (Synthetic) rubber will fail as well, eventually, Probably from all the smog produced by those decaying rubber plants and disintegrating tires.
 

·
Registered
Joined
·
6,224 Posts
Discussion Starter · #15 ·
Hmm, the comment about moisture caught my attention. A few years ago I replaced my humidifier with a much better one. since then I have maintained my humidity at 45-50%. I wonder if that level was enough to cause the foam to rot. The house is certainly more comfortable, but it may have a cost.
 

·
Registered
Joined
·
7,136 Posts
Matt,


I doubt you'd want to keep your humidity any lower then that... 45-55% is the recommended range for comfort, wood furniture, electronics, etc. Any lower and you'll probably start to notice static problems...


Kal
 
1 - 16 of 16 Posts
Status
Not open for further replies.
Top