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refoaming issues

Guest radkrisdoc

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Guest radkrisdoc

Hi all....here's another aspect of vintage AR's that keeps bugging me. I'm sure this question has been raised many times here. Issues with refoaming, or

1. Does refoaming bring a driver back to original specs? I thought that even the amount of glue that goes on a speaker affects its Thiele/Small parameters, that is, more glue will increase a cone's mass and as I understood, increase in mass will decrease efficiency and the resonance frequency. A whole new speaker should be born.

2. Replacement foam quality. Who manufactures these foams? Anyone with the right knowledge or some no-name company from taiwan? If correctly sourced, are there almost-original-u-cannot-tell foams available? If so, what is the source?

Since there are so many of us out there, we ought to work out a way to solve this problem. Maybe identify a lab which can measure and compare characteristics of foam surround A to B. I dont know how feasible this idea is though.

I have tried contacting AB Tech several times, by email and through several phone calls, but the answers and replacements I've received are not satisfactory. I will "air my grievances" sometime soon. Thats why the refoam idea and how good/bad it is.

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I do loudspeaker refoaming and know that some surrounds are available in a limited range of stiffnesses (sort of like soft, medium and stiff). My parts source supplys only 1 stiffness for the st'd 11 inch AR3a woofers amd I've done a number of them with very satisfied customers.

So, you don't have a lot of choices available and I doubt if anyone knows exactly what stiffness/compliance characteristics the original build woofer's surrounds had. Even if anyone had an original one they probably would have had to store it in a vacuum to preserve it and prevent the deterioration that is so common with 10-20 year old foam surrounds.

The bottom line is, unless you only listen to the bass with the mid and tweeter disconnected, you won't notice any difference in the musicality of the AR3a with a typical refoam job done today.

If you're interested in my services and pricing, write me at


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Good topic!

It would seem the larger, thinner and least porous (the originals were sealed with a rubber compound) the better. Many parts suppliers and repair folks have no clue or are unwilling to share info when asked. I have tried a couple of different sources with OK results, but still feel there may be a better product out there. No matter what, refoaming an old woofer in good repair has produced better results for me than the standard "replacement" woofer.

Who knows, maybe they are all being manufactured in the same place these days.

I have been thinking about ordering from several other sources to compare. Maybe this thread will provide insight.

Roy C.

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Guest radkrisdoc

My dear friend Roy, looks like its just the two of us and a lot of silent lurkers (who I am not including by the way :P ) who are game for this discussion and the lab measurement idea. Carl here wants to refoam speakers right away, thank you for the offer, but Im anal about my audio stuff. I'd be happy if my eyes were pleased as well, with driver T/S parameters and half space measurement results.

I also have a pair of Polk LSi9's and this weekend I might try to compare between the AR's and the Polks. Got some time on my hands, there is no better way to spend it. :)

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>1. Does refoaming bring a driver back to original specs? <

The answer is that it would depend on other things and we really don't know. We don't know because we don't have a brand new AR speaker of any sort that isn't aged to measure and test against.

BUT, we do know a couple of specs and one of them is Fs of a Norwood production 12". It's 18Hz as quoted in AR literature.

Some time ago I sent Ken Kantor six such woofers, four were refoamed, or completely reconed, or re-spidered and refoamed by Tri-State Loudspeaker, two were refoamed by Simply Speakers in FL.

Ken ran a lot of tests on those AND on a newer 12" driver like those he used in the AR-303 he designed.

All of the Tri-State speakers came back with Fs in the upper teens, and were very much alike; not identical. The Simply Speakers pair came back with Fs in the mid-twenties and increased efficiency. The four non-Simply Speakers drivers were very much alike and in many respects like the newer driver Ken tested.

You can find a link to the data and graphs somewhere in this forum, but I don't know the right search-term to tell you to use.


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I found the right message, but with the view I had I didn't see a message number to point to. So I'll just quote Ken Kantor's original message below:

"I've placed a great deal of data on repaired AR 12" woofers at the following URL:


Over the next few weeks, I will be uploading more information, and trying to editorialize about what it all means. For now, some notes:

1- Eight woofers were tested for their small and large signal parameters, and for axial response in an infinite baffle.

2- The data is divided into 8 subdirectories, one for each driver.

3- A PDF file in the top directory shows an overlay of all the woofer responses.

4- Unit #1 is the 12" used in the 303a. Others are all some form of refurbished Norwood production, as described. None are stock, unfortunately.

5- Parameters are very accurate, but the acoustical responses seem to suffer from some consistent anomolies related to the jury-rigged baffle used. This will be corrected in future uploads. For now, best not to archive this response data.

6- There is a spread of about 5 dB in overall sensitivity, and a midrange responses do vary somewhat.


Ken Kantor




If you have excel or something that will open xls files and will "save target as" from here


you are likely to find-out everything you ever wanted to know about some 12" AR drivers.

Unfortunately, we don't have numbers from a stock driver to know what we are comparing to, really.

And we're missing Tonegen-like driver information. As I said, Ken got even more super-busy than usual about this time.

If I had this all to do-over, I would have sent two Tonegen-like drivers, two Millersound repairs, two TriState repairs, two Simply Speakers repairs, and begged someone to provide a "stock" unit for comparison. Then Ken would have been so overwhelmed that he would never have talked to any of us again.

Tom Tyson provided a "standard cabinet" as a baffle.


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Guest radkrisdoc


Im elated. Smiling ear to ear, maybe a feeling of euphoria. Bret, your post has made my day. Kudos to you all!

There is way too much info there for me to look at in one night, though I really would love to browse through all of it right now!He's used a standard box, probably near field measurements for the woofers. Just the way to go, after all, noone can doubt these measurements coming from someone like Ken. That's awesome stuff you have posted, Bret.

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