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12 inch Woofer Surround fix


Dchristie
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Hi folks, I recently restored a pair of AR 11 speakers which I bought off CL several years ago. The seller told me he had re-foamed the bass drivers and also indicated that he used the proper surrounds. Well, after getting everything back together the speakers are very satisfying except for the bass response. I am afraid that the wrong surrounds may have been used for the re-foam. The current surrounds are quite stiff and I believe they should be more compliant and supple as they are on my AR 5 re-foamed 10 inch drivers. They also do not have the bass response that I would expect from an AR 3a, AR 11,  or any other of the AR speakers using the classic  12 inch bass driver.

Although I have re-foamed about a dozen or so speakers the past couple of years, these were always old drivers that had deteriorated surrounds with old glues/etc. I have never tried to re-foam a driver with new surrounds already attached. I am thinking that if the seller used the water-soluble white glue, I may be able to carefully apply a small amount to those areas where the surround attached to the cone and frame and slowly loosen up the glued area. However, if some other  type of adhesive was used, I may have to use another procedure.

So, I am looking for any advice from anyone who has some experience in re-foaming a re-foam.

Thanks in advance for your assistance!

Dean 

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Yes, always do a polarity check (for the drivers only) prior to replacing the drivers in the cabinet and also check the wiring/etc after they are attached to the xover. I also play the drivers while connected to the crossover but not in the cabinet for proper phase/etc. 

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40 minutes ago, Dchristie said:

Yes, always do a polarity check (for the drivers only) prior to replacing the drivers in the cabinet and also check the wiring/etc after they are attached to the xover. I also play the drivers while connected to the crossover but not in the cabinet for proper phase/etc. 

Your  post doesn't  explicitly state that you replaced the surrounds while It also reads as though the bass was at one time satisfactory before you opened the box.  Even If you used surrounds that were merely adequate  the bass would not drop off that much so you could have a leak or they are connected to the amp in opposite polarity to each other.  If you have already tried reversing the polarity at one of the amp connections or speaker terminals and didn't hear an improvement then check for a sealing problem around the woofer.   I am assuming everything in your system before the speakers is set correctly and is operating properly

Aadams

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Thanks for your response. You bring up some good points with regards to poor bass response from a pair of speakers. 

To clarify, the Seller replaced the surrounds just prior to my purchase. When I 1st listened to the speakers at the Sellers place, I listened at relatively low volumes only to make sure all drivers were functional. Brought the speakers home and played briefly once again with normal volume acoustic music and did not like at all what I heard but did not check for bass response as such. Everything sounded wrong ( ended up needing all new caps) and so I placed the speakers in storage for a couple of years because I was fairly certain that I would need to restore at some point and they were not my main speakers, so time was not of essence. So, this Fall, I completely restored them and they do sound very good except for the weak bass response. I also did the "sealed cabinet response test" where the bass driver is lightly pushed in and you observe the return of the cone to normal. They passed this test as well. I am well aware of what an out of phase speaker sounds like and with the bass driver in the AR 3a and 11 operating well into the lower mids , this would be also very obvious on these speakers. Not only would the bass be poor but the imaging would also suffer greatly  because of the upper bass and lower mids being out of phase as well. I actually sent a pair of Cello Amatis back to the manufacturer for just such an issue (the 12 inch bass drivers only were wired out of phase).  So, I know this can happen but I try to be especially careful to make sure this doesn't happen on my rebuilds. 

Also, the surrounds appear quite stiff and this is not what I would expect of the proper surrounds for this speaker driver. Realizing that good bass response in any speaker is somewhat subjective since we all differ in our priorities for what is a good sounding speaker, but  my Cello Amatis,  KLH 5s, and the AR 3a speakers that I have heard all were much better with deeper bass compared to what I am hearing. So, this leads me back to the surrounds. I am willing to replace them with what I know are the correct ones but looking for a little advice on removing the new ones already on the speakers.

Dean

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When I got my first set of AR3a's I ordered a surround kit from a well known supplier in St. Petersburg. When I received them they seemed rather stiff to me. I went ahead and got another set from Rick Cobb and the difference was like night and day. Rick's surrounds were not only more compliant, but also had a slightly wider roll. I still have the first set, but always choose to go with the better quality surrounds.  The original set are on the left and Rick's are on the right.

881rBix.jpg

 

 

I have replaced fairly new surrounds on speakers I have purchased for a number of reasons. One set of woofers were not aligned correctly and had some voice coil rub, another set was just a sloppy job with glue spread everywhere, and one set of woofers had surrounds that were cut down to fit. The tricky part is getting the glue off without damaging the cone. The best advice I can give is to go slowly and don't get too greedy. Sometimes it helps to walk away for a few minutes and don't be afraid to try different techniques such as applying heat to soften the residual glue. I try to stay away from solvents as much as possible. Good luck on your replacement. 

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Or..... Do what I did.

I bought a pair of nice AR-91s a few years ago and the woofers had been very sloppily re-foamed. The glue was the solvent-based stuff and it was glopped all over. Also, the roll was pinched. So I packed them up and sent them to Bill LeGall at Millersound. I had them back in no time at a very reasonable cost and very professionally done. Perfect. 

Although I've re-foamed many speakers, whenever I have something difficult and/or valuable (Cizek KA-1s), I send them to Bill.

-Kent

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19 hours ago, Aadams said:

I will be watching this thread.  I have a similar issue that I have been putting off i.e. two good foams to remove and replace, .   I was going to use water or goo gone but first I was going to PM Roy C.

Adams

If you have the solvent, the solvent based glue is somewhat easier to remove than fully dried water based pva (white) glue, for which I have not found water or a solvent to be helpful. In any case it is not easy to remove new glue from a cone without damaging it. I have had to repair a fair number of failed foam replacement jobs for some "no shim" or "30 hz tone" method folks in the past few years. In some cases I've had no choice but to glue the new surround's cone edge on top of the existing edge. In other cases, the foam was able to be coaxed to peel off the cone with a razor knife.

Roy

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On 12/14/2017 at 12:35 PM, Dchristie said:

I am thinking that if the seller used the water-soluble white glue

I would recommend that you contact the seller and ask about the exact glue product that was used.  You could also get the specifics about the source of the surrounds at the same time.  Knowing what glue was used would be invaluable to how you proceed.  Edit: I just reread one of your earlier posts and realize that it has been some time since you purchased the speakers and it might be a long shot to contact the seller for information.

I agree with Roy that you would be lucky if the seller used a solvent based glue.  These are the rubber cement type glues.  They are relatively easily reversed with a variety of solvents.  Small amounts of solvent applied with a cotton swab, working on a small area at a time, is usually how I attack this situation.  If you are unlucky, the seller used a PVA or CA glue.  I don't know of any solvent that will effectively dissolve/release the glue without damaging the cone.  I agree with Roy that mechanical removal is usually the best way to proceed.  In addition to the razor scraping method, I've had success with light sanding.  It all depends on the condition of the old glue.  Dried PVA glue is a thermoplastic.  You might have luck with applying heat.  I haven't had the need to use this method, but it is something to think about if all the other methods fail.

On 12/14/2017 at 3:16 PM, Aadams said:

I was going to use water or goo gone

I would not use either of these "solvents".  Water won't be effective on (almost) all glues.  Goo Gone is a citrus oil based solvent that will leave a residue on the cone.  I wouldn't expect that any new glue would stick to the cone after it was contaminated with citrus oil.

I recommend that you use a rubber/solvent based glue when you install the new surrounds.  I have a "collection" of glues that were sold as "speaker surround" glues.  I ran a series of tests on the glues which included things like hold strength, reversibility, soak-in, etc.  My "go to" glue is a black rubber based glue that was the easiest to reverse.  My thoughts are that I want to make it as easy as possible for the next guy that replaces that surrounds.  This is probably because the "next guy" will likely be me ;).  This is also helpful if you use one of the "no shim" methods and your results aren't acceptable.

I cringe every time I hear someone recommend using a PVA glue for installing speaker surrounds.  I understand the desirability of some of the characteristics associated with this glue (i.e. long open time, low fumes/toxicity, etc.).  However, IMHO, the drawbacks outweigh the benefits. 

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