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Acoustic Suspension Seal Video


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Two videos to demonstrate the acoustic suspension seal. I had the tweeters out of my early AR-3a's for rebuild, so I thought it would be a good demonstration of what a seal should look like. The first video does not have the tweeter installed therefore there is no seal. The second video is after installation of the tweeter with a properly sealed cabinet. 

 

 

 

 

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Thanks, I have some of Roy's sealant, but Roy himself said that 12 AR inch woofers rarely needed it, so I didn't apply it. Anyone have any other thoughts or experience on the cloth surround 12 in woofers of 3's or early 3a's?

 

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Those do pass the push test but the sealant looks kind of dried up and flaky to me. I re-sealed my own AR-3 woofers. I remember the KLH Service Bulletin in our library that told service centers to always re-dope (KLH) cloth surrounds regardless of the reason for service.

Kent

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Using a small brush, apply a thin coat to the entire cloth surround and the dust cap. Here's a link to the KLH instructions. KLH called the cloth surround a skiver

http://www.classicspeakerpages.net/library/klh/other/klh_schematicsservice/klh_service_bulletin_60.pdf

apply goo.jpg

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On 7/13/2022 at 7:25 AM, jnolan5784 said:

Thanks, I have some of Roy's sealant, but Roy himself said that 12 AR inch woofers rarely needed it, so I didn't apply it. Anyone have any other thoughts or experience on the cloth surround 12 in woofers of 3's or early 3a's?

 

The AR woofer's surround always looks like that, and is different than the KLH surround. The original sealant does not flake off or disappear from either of them. Many KLH woofers were simply insufficiently treated at time of manufacture, prompting the KLH technical service bulletin recommending additional sealant. AR woofers were usually pretty well treated at the time of manufacture, especially the 12 inch AR woofer. Accordingly, my sealant is is deliberately thin and intended to only be supplemental to the original treatment.

When my sealant is used on cloth surrounds of AR woofers, I recommend a very light application. The toluene in the sealant softens the original sealant, which may be somewhat beneficial, but if it is applied too heavily it can collapse the roll of the AR canvas-like material. For this reason I don't recommend using it at all if an AR woofer passes the "push test". On the other hand, the inverted cloth roll of KLH woofers is made of a different (more porous) material and is not prone to this potential issue. KLH woofers almost always require a couple of additional applications.

Roy

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Thanks Roy. Learn something new every day! So jnolan was right. I was not aware of the difference between AR and KLH cloth surrounds.

Kent

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5 hours ago, JKent said:

Thanks Roy. Learn something new every day! So jnolan was right. I was not aware of the difference between AR and KLH cloth surrounds.

Kent

Hey Kent,

I learned some of this along the way as well. I suspect the KLH material was too soft to be made into a roll, making the inverted installation necessary.

Roy

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