Help! Discovered small cracks in the rubber surrounds on my Avid 102a's - what to do?

I posted this on the vintage asylum but it seems pretty quiet today so I thought I'd try here. Apologies if you've seen it over there:

I've had these things for about a week and a half and I just noticed that there are small cracks on the outside of the rubber surrounds (where they attach to the plastic ring, not the cone). The cracks are intermittent and maybe 1/2 inch long. I can't see through them, but I they are apparent if I poke the surround. The speakers sound good, but this is bothersome.

Will these numerous tiny cracks affect the sound? If so, any recommendations on what to do? I've never done any work to a speaker, but I can work with tools - is it more difficult to repair a rubber surround than foam? Are there kits available? Any ideas on how much this would cost for someone else to fix?

Looking closely I can see that the surrounds are not 100% centered - I can see a little more of the "flat" part on one side than the other (the part that goes under the outside ring). Would they come from the factory like this, or is it likely they have been "re-rubbered"?

One of the reasons I got these was because of the rubber surrounds which supposedly last "forever" (Ha!). When I first got them I looked them over quickly and thought they looked OK, since I didn't see obvious holes like with foam rot.

There are a lot of ?s in there, but any help is appreciated as usual.

 

If you can't see through the cracks, that's the main thing. The purpose of the surrounds is to centre the cone/coil to the magnet, and you would have to be very careful in repairing them, as you could later the compliance at one part repaired. All speakers are "broken in", and makers tell you generally that they sound better after a hours, as the rubber basically "creases in" and the resistance is less. I think personally I would simply keep an ear and eye on them. If they are not fully enclosed, ie if they are ported, the pressure will be far less. You could maybe try a repair kit carefully if they ever gave out and failed, nothing lost then as it were, but I'd get expert advice, in the meantime avoid poking at them!!, and really just enjoy them. I think they will be OK myself.
Good luck,
Richard.

 

Hi! Yes, rubber can deteriorate, and you are seeing the most common failure mode of rubber, cracking. It will likely worsen with time/use. Especially if you listen at elevated SPL. This causes air to attempt to "blow" past the surround through the cracks and hastens the destruction. Along with the mechanical fatigue. Two solutions, A. Seal up the cracks. Use a compound of rubber cement or silicone you can cook up, and dab the cracks closed. This is possible due to the location of the cracks, not being on the "roll". Cheap and likely temporary, but can work. B. Total surround replacement. Best and most expensive and biggest hassle. Also, yes, the original surround can be off center from the manufacturer, this is not unheard of, and, if slight, usually won't effect the performance. I am an experienced re-surrounder, almost all I have done are "foam" surrounds. I have a stock of surplus foam surrounds of ''standard" sizes. As a forum group member, I will send you a pair to try at my cost plus US postage. (size determined) I don't know if or what will happen when rubber is replaced by foam. I think it will not be advised. And I no longer have any source for rubber surrounds. As a hobbyist, I would charge about $20 per woofer if I were to do them, including the foam parts. Most repair services are higher, If that helps you out.

 

"If you can't see through the cracks, that's the main thing. The purpose of the surrounds is to centre the cone/coil to the magnet, and you would have to be very careful in repairing them, as you could later the compliance at one part repaired. All speakers are "broken in", and makers tell you generally that they sound better after a hours, as the rubber basically "creases in" and the resistance is less. I think personally I would simply keep an ear and eye on them. If they are not fully enclosed, ie if they are ported, the pressure will be far less. You could maybe try a repair kit carefully if they ever gave out and failed, nothing lost then as it were, but I'd get expert advice, in the meantime avoid poking at them!!, and really just enjoy them. I think they will be OK myself."

Good luck,
Richard.


Thanks for the reply. These are Acoustic Suspension (sealed) 10" two-ways, so sealed surrounds are important. I guess I never really thought about what the surrounds were for! It is intuitive (for me anyway) to think that they are pulling the cone back into place as it moves in and out, but of course that is not happening - as you say they are preventing it from moving from side to side.

I am assuming that the main issues then would be that they are in fact holding the cone in place laterally (which I'm pretty sure they are) and that air is not escaping (cracks are small hairline ones so I can't imagine it would hurt the sound much as they are now).

If I don't hear a dissenting opinion I guess I won't mess with them. It might be quite a while before they turn into large rips.

 

I would prob. keep an eye on em.. and dab some rubber cement along the crack radius. No cost, and prob will stave off the day of re-coning till later, maybe forever. That's the lazy man's (most of us) way to go..

 

Thanks a lot for the offer! But as you allude to, I really don't want to replace with something other than what it was designed for.

The cracks are where the roll meets the flat part that attaches to the outside ring (makes sense - this is where the stress would seem to be as the cone moves in and out). Can you recommend a good repair sealant? By "cook up" do you mean a mixture? Is there a good one straight from the bottle? I've never repaired a speaker.

 

You can have new surrounds installed for a low cost. I would do it soon. An acoustic suspension system needs to be sealed. If any air can make it in and out of the cabinet, the woofer will not have the proper restoring force that it needs, causing it to bottom out.

 

Cook Up?

Yep, I've seen that exactly. What I did, was, got my GC electronics black "RUBBER TO METAL CEMENT" (item # code 10-352) bottle and mixed it with a little Naptha to thin it a little, added a dose of Elmer's "NO-WRINKLE RUBBER CEMENT" and applied with small brush to the cleaned area of the crack, filling in the space. Cure for 24 hours. Almost invisible, It worked for about a year.. 18 months... Good luck, RE