Film-Tech Forum ARCHIVE: Good speaker surround glue?

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Posted by Eric Robinson (Member # 2966) on 06-10-2009, 11:55 AM:

In my earlier post:
"How to find a bad driver?"
I did find the bad drivers X2.
These are EV 15" subs which the cone and cardboard surround have come unglued from the basket edge, thus creating a nice flapping sound at 61Hz.
The cone surround and cardboard are still in good shape. It looks like all I have to do is glue it back together. I have installed new surrounds on speakers before using some white glue provided by the company I bought the surrounds from. Does anyone know what the most reliable type of glue is that I can use?

Posted by Jim Cassedy (Member # 4115) on 06-10-2009, 01:53 PM:

This doesn't exactly answer your question but I'm not
sure how reliable a 'home made' speaker repair will
hold up. I'm not questioning your ablility. It's just
my gut feeling about speaker repairs.

Since you're located here in Northern CA, I can highly
recommend a company called Orange County Speaker Repair,
in Los Angeles. They were recommended to me by a couple
of local audio techs several years ago when I needed to
have some Altecs re-coned.

They can do the entire job for you at a very resonable
price and if I recall, they also sell kits which contain
the proper glue & materials so that you can do an
"expert" cone-edge repair yourself.

Their web address is:
www.speakerrepair.com

Check out their website and see if they have what you need.

If you decide to have them do the repair, I can tell you
I've used them several times and they do excellent work.
Turn-around time was amazingly fast too.

Posted by Monte L Fullmer (Member # 2797) on 06-10-2009, 03:59 PM:

True. It's best to have the speaker reconed.

For if you do it yourself, the cone has to be dead center in the basket, otherwise, you'll have a rasping sound due to the speaker windings rubbing against the magnet.

Posted by Frank Angel (Member # 248) on 06-11-2009, 08:16 AM:

I have done a number of these repairs, and I must say, after the daunting first few, it really is a relatively easy job. The cone is held dead center by separators that are supplied which are the exact size of the gap and they hold the coil centered while you apply the glue to the spider. If the surround material is foam rubber, you best use the replacement that comes with the kit because that stuff disintigrates after about 10 years (more or less depending on the harshness of your environment). I know of what I speak because we had 16 speakers ALL with foam rubber surrounds that just fell apart and had to be replaced.

The repaired speakers with these kits sound every bit as good as the original and I even think the bottom end is more solid than before. I can drive them to quite hard and there is no sign of breakup or distress.

Quite a few years ago an older tech once showed me a treatment for paper speakers that was pretty impressive. He said that you can extend the bottom end response of older paper subwoofers by "doping" them with rubber cement. You paint the entire speaker cone with a coating of the cement as evenly as possible and supposedly this will increase the damping. I've never done it, but he did one while I watched on, and I actually heard the before and after results with its response in the 40hz to 60hz range; where it doubled prior to the treatment as he increased the level, it was able to deliver more sound pressure after the rubberized treatment before it began to double. It was pretty impressive. I would like to have seen a full spectrum chart before and after to see how it affected the overall response, but to the ear it was pretty sweet. If I get a chance I'd like to try it on an old speaker and really seriously test the effect. We've got some old speakers into which it would be nice to be able to pump some new life.

Posted by Mark Gulbrandsen (Member # 72) on 06-11-2009, 09:11 AM:

quote: Frank Angel
He said that you can extend the bottom end response of older paper subwoofers by "doping" them with rubber cement.

I wouldn't do that in any theater in this area... the cone would be stuck full of popcorn, candy wrappers, and other items in just a short time period.... [Eek!]

Those dam blowers the janitors use.... [Mad]

Mark

Posted by Robert Minichino (Member # 3495) on 06-11-2009, 10:19 AM:

Adding rubber cement to a paper cone won't help the cone's stiffness (it might even hurt due to the increased mass), but it will retune the speaker so that the resonance is at a lower frequency. The effects on the Thiele/Small parameters of the driver by adding mass:

Fs (resonant frequency) decreases by the inverse square root of the mass
Q (quality factor, inverse of damping) increases proportionally to the mass
n0 (efficiency) decreases with the inverse square of the mass

So by adding mass, you get a driver with a lower resonant frequency that is less damped (boomier, looser, etc.) and much less efficient.

Posted by Frank Angel (Member # 248) on 06-11-2009, 02:07 PM:

quote: Robert Minichino
So by adding mass, you get a driver with a lower resonant frequency that is less damped (boomier, looser, etc.) and much less efficient.

That, plus like Mark said, the popcorn stuck to it would have to make it even LESS efficient! Then again, one big explosion and all that stuck popcorn goes flying back at the audience! [thumbsup]

Hmmmm....amazing what techie myths abound.

Posted by Jack Theakston (Member # 4484) on 06-11-2009, 02:54 PM:

If the speaker is worth anything, don't risk f***ing with it and take it in to have it re-coned.

DO NOT DOPE IT WITH RUBBER CEMENT, ELMURS GLUE or VARNISH (another myth). Many audiophiles recommend this, but in my experience, the added brittleness and uneven nature can and will cause damage over the years. The less weight you put on the cone the better.

If you're going to use any glue, use the real stuff- LocTite 410 Prism Instant Adhesive. It's a black rubber-based adhesive that is far more flexible than the other suggestions.

Posted by Eric Robinson (Member # 2966) on 06-11-2009, 04:09 PM:

I think I'll just send them in for a new surround service to Orange County Speakers. I was just going to glue the loose edges, but, the more I think about it...I don't want to have to work on these again when the surround craps out. Its no fun as you all know trying to remove these from a cabinet way up high with cakes of dust and other unidentifiable materials.

The Loctite 410 does look like a good product though. Thanks for the tip.

Posted by Jim Cassedy (Member # 4115) on 06-12-2009, 09:33 AM:

quote: Mark Gulbrandsen
the cone would be stuck full of popcorn, candy wrappers, and other items in just a short time period.... Those dam blowers the janitors use....

Hahahahaha- ain't that the truth!

One theater I worked at had the sub woofer at floor level
behind a skirt under the screen. I constantly found pieces
of sticky carmel popcorn the theater sold stuck to the cone.

I considered putting a screen over the cone but figured
that a metal screen would just resonate at the low freqs.
and actually the damn carmel corn would only wind up
sticking to either a metal screen or a fabric mesh which
I also considered putting in.

We moved the sub back a bit and were able to raise it a
few inches without having it get blocked by the screen
frame superstructure.

It wasn't a perfect fix. I'd still occasionally have
to crawl under the skirt and brush off the carmel corn
or we'd wind up with a carmel cone. [Roll Eyes]