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Preserving foam surrounds- ideas anybody?

here's my Marantz Model 7 MKII's still in original boxes, lol! They are mint and the foam surrounds are still as they were when new! I haven't taken them out of the boxes for years. Alot of people don't know but the Mids & woofers are EXACLY the same drivers used in the earlier 920, 940, HD770 & HD880's! I also have a pair of HD 770's!

Specs of the MKII's are:
1 12" woofer
1 5" Midrange
1 1&3/4" wide dispersion cone tweeter
Frequency response-35Hz to 20kHz +-3dB
Crossover points- 800Hz to 2.5kHz
Nominal Impedance- 8 ohms
SPL 88dB @ 1w/1m
Power handling- 100 watts continuous/ 200 watts peak
Weight-40Lbs
Production years-1978 to 1980
 
here's my pics

oops forgot pictures, lol!:smoke:
 

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hi every one. ill chime in here with another question.

is using the old ebglish lemon oil also suitable for this application. as id like to try it on a pair of marantz speakers. mid 80s brand.
 
budgetaudio6 said:
hi every one. ill chime in here with another question.

is using the old ebglish lemon oil also suitable for this application. as id like to try it on a pair of marantz speakers. mid 80s brand.
Click to expand...

No no no, do not use lemon oil, it is acidic and will break down the foam faster than a speeding bullet! You can use it on the veneer if it has it, but not on the drivers or foam:(

Charlie:nutz:
 
the bottom one is more complete. darn it i forgot to buy the silicone spray from work. was looking forward to using it.
 
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whew thanks for the heads up. although a pair of bpc bookshelf units arent going to be so lucky. oh well i wonder how long theyll last. now im not posting this to encourage the rest of you guys about using lemon oil. its too late for these little muddy speakers. it did seem to soften the foam on them. i also got the little woofers for good measure. now im wondering..... hope the voice coil doesnt short out. will be interesting for me to find out. in case youre wondering how much i used on them i put gobs on them they are upside down right now so hopefully the oil will gravitate more towards the bottom. but you know how liquids creep up no matter the gravity.:stupid:

WHOOPS!
 
Hey Big Tuna,

Someone mentioned ozone as a culprit. You mentioned the Marantz's were in sealed boxes for years. I'm wondering if the foam dries out for a number of reasons, ( is attacked by pollution, or if its humidity, direct sun, etc. )
Did you wrap the speakers in a sealed plastic bag in the box?
What do you think of this diluted PVA treatment as others have mentioned?
Anyone else been doing this diluted PVA treatment?
TJG
 
What about using like the Black Magic trim detailer for cars?

I've often used it on things like weather stripping to rejuvenate the rubber...actually, did it on a set of speakers where the surrounds were dry (but not rotted) and it seems to have worked well.
 
Foam "rot" is somewhat of a misnomer, afaik.

The searching I've done seems to indicate the primary cause of foam deterioration is basically evaporation of the plasticizer chemicals that make the foam flexible.
 
well, in case any of you are wondering, foam surrounds are made of rubber with certain types of flex agents to allow for flexibility, not plasticizers at all. It is, shall we say a form of rubber, in a severely diluted sense. Closed cell of course. It is mainly the other stuff that is added to the rubber that deteriorates and the rubber cells degenerate as a result, leading to the rot. Oxygen is the main culprit of rot. Ozone is miles above the earth protecting us from the suns harmful UV rays, so how can it have anything to do with foam rot? My family was third generation Drycleaner and we used an ozone machine to purify and preserve clothes that had been moisture or smoke damaged.
 
Those of you considering adding PVA coatings or other preservatives, keep in mind the coating will affect the flexibility of the surround, which can affect its response and therefore its sound.

That’s the same reason you should not replace rubber surrounds with foam, and vice versa.

For the effort and cost of replacing a rotted surround, I’ll stick with replacement as needed.

Re-treating cloth surrounds to reseal and restore them to their original condition makes sense, but doing anything that affects the surround’s flexibility, does not.
 
Glad you wrote in on that. Not only was I wondering about what to use, but I wondered whether it would alter the performance.
Perhaps a treatment of a liquid (like Armor All) would be best as opposed to painting on diluted glue that would dry and probably alter the flex.

On top of this, now I understand that there are replacement foam surrounds of varying quality and flex . This, along with inexperience in doing the replacing just stopped me in my tracks.
But I feel I'm not alone in this.
Thanks,
TJG
:scratch2:
 
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