In building a closed-box system with a Selenium 12PW5-SLF 12" woofer, I discovered that the cloth surround of the woofer is very lossy. I know that because I tried attaching some 3/8" dia. poly foam caulk saver in front of the surround next to the woofer's frame with (what else?) duct tape. As soon as I did that, my maximum impedance reading for the woofer (at Fc, of course) increased dramatically. As mechanical Q of the box system relates inversely to the system losses, and impedance at resonance is according to the ratio of Qmc to Qec, the max. Z reading gives me a quick indicator of box losses.
What I'm wondering is if any one here has found a way to permanently reduce leaking (losses) of a cloth surround without significantly raising free air resonance Fs? I would like to permanently reduce the leaking of the Selenium woofer's surround.
My thought was to apply rubber-based contact cement, but I don't know if this would work or really ruin the woofer.
Why do I want to do this? The Selenium woofer has a very high Qms/ Qes that I would like to preserve as much as possible in a closed-box system partly to prevent Qtc from being significantly less than Qec. Qts of this woofer equals 0.31, and I don't want a really small box in order to get Qtc equal to about 0.7.
Come on, if nowhere else, there must be someone here who has treated a cloth surround to stop the leaks, I guess.
Thanks if you can share your experience,
Pete
What I'm wondering is if any one here has found a way to permanently reduce leaking (losses) of a cloth surround without significantly raising free air resonance Fs? I would like to permanently reduce the leaking of the Selenium woofer's surround.
My thought was to apply rubber-based contact cement, but I don't know if this would work or really ruin the woofer.
Why do I want to do this? The Selenium woofer has a very high Qms/ Qes that I would like to preserve as much as possible in a closed-box system partly to prevent Qtc from being significantly less than Qec. Qts of this woofer equals 0.31, and I don't want a really small box in order to get Qtc equal to about 0.7.
Come on, if nowhere else, there must be someone here who has treated a cloth surround to stop the leaks, I guess.
Thanks if you can share your experience,
Pete
I selected the Selenium driver for its extraordinarily high ratio of Qms to Qes. You are certainly right, this driver was designed for a vented alignment- Qts = 0.31 is very low for a closed-box system. I also worry about whatever treatment I might think would work; that's why I'm asking for advice.
CLS,
By any chance are you referring to PVA glue? By looking at other similar threads here at diyaudio.com ( I missed them before starting this thread), I discovered "PVA speaker foam edge sealer" from simplyspeakers.com, their part # MI-1291FG. Their "part" is a very high-priced 1 OZ. of the stuff.
From Wikipedia, PVA is polyvinyl acetate, a rubbery synthetic polymer. Further PVA is a component of widely used glues such as white glue, carpenter's glue, school glue and PVA glue.
Simplyspeakers.com is selling PVA for sealing foam surrounds (CLS's favorite), but it maybe would do a good job making a cloth surround less air-leaky.
Thanks for the replies, hope that this is of interest,
Pete
Sorry, I don't know the exact ingredient of that (sticky) glue I described above. I'm not sure if any combination including PVA would work or not.
What I know about PVA glue is the white stuff commonly used in woodworking. I've been using it (diluted) on paper cones, not surround. It stiffens and damps the cones when dried. I don't think its the right property you need.
Have you search here? ADHESIVE SPRAYS & CEMENTS from Parts Express ship same day and come with 45 day money back guarantee. Free Shipping Available. Order free 10,000 product catalog.
Or this might be a reference, too: Wharfedale Super 8
(scroll it down) It doesn't say what the coating is, though. You might try to contact the web page owner.
And, you know, almost all such mods on driver are not reversible, so you got to take the risk. If I were you, I'll search for any glue that remains soft when cured, and find the right solvent to dilute it a little, apply as thin as possible...
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BTW, why does a foam surround need sealing? It should be close-cell, no?
What I know about PVA glue is the white stuff commonly used in woodworking. I've been using it (diluted) on paper cones, not surround. It stiffens and damps the cones when dried. I don't think its the right property you need.
Have you search here? ADHESIVE SPRAYS & CEMENTS from Parts Express ship same day and come with 45 day money back guarantee. Free Shipping Available. Order free 10,000 product catalog.
Or this might be a reference, too: Wharfedale Super 8
(scroll it down) It doesn't say what the coating is, though. You might try to contact the web page owner.
And, you know, almost all such mods on driver are not reversible, so you got to take the risk. If I were you, I'll search for any glue that remains soft when cured, and find the right solvent to dilute it a little, apply as thin as possible...
--------
BTW, why does a foam surround need sealing? It should be close-cell, no?
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CLS,
Simply Speakers (Simply Speakers - Official Speaker Repair Page - Speaker Parts and Repair Service) claim that the foam edge sealer slows down the process of bacterial attack on the foam. Go to their website to get the full description of their product part #MI-1291FG. The company location is Florida, US.
Speakerdoctor,
Thanks for the tip to contact an Ebay seller about a sealer.
Just now I read an email reply from Simply Speakers saying that their foam edge sealer will also prevent air leakage of a cloth surround.
Best Regards,
Pete
Simply Speakers (Simply Speakers - Official Speaker Repair Page - Speaker Parts and Repair Service) claim that the foam edge sealer slows down the process of bacterial attack on the foam. Go to their website to get the full description of their product part #MI-1291FG. The company location is Florida, US.
Speakerdoctor,
Thanks for the tip to contact an Ebay seller about a sealer.
Just now I read an email reply from Simply Speakers saying that their foam edge sealer will also prevent air leakage of a cloth surround.
Best Regards,
Pete
I haven't tried the SS sealer, but do know a guy who's tried just about everything to seal vintage KLH and AR woofer surrounds. He developed a non-hardening sealer which he shared with Vintage-AR. I've tried it and tested it with aging studies and know it works. FWIW.
If you want to preserve the bass extension of your woofer you must get something that doesn't stiffen up over time. Most of the white sealers sold and watered down silicone bathtub stuff will stiffen with age and it's measureable as elevated resonant frequency.
good luck!
If you want to preserve the bass extension of your woofer you must get something that doesn't stiffen up over time. Most of the white sealers sold and watered down silicone bathtub stuff will stiffen with age and it's measureable as elevated resonant frequency.
good luck!
You want "speaker dope". 
There are compounds made for the industry that are designed for "doping" cloth surrounds.
There are two main types, the older solvent based and the newer "water" based. They come in a variety of viscosities. Finding them is another matter. They will prevent the air from getting through the cloth.
The "Altec" stuff is one of the solvent based ones.
Most speaker recone shops will have some on hand, and the PE offerings may include some, not sure.
There are compounds made for the industry that are designed for "doping" cloth surrounds.
There are two main types, the older solvent based and the newer "water" based. They come in a variety of viscosities. Finding them is another matter. They will prevent the air from getting through the cloth.
The "Altec" stuff is one of the solvent based ones.
Most speaker recone shops will have some on hand, and the PE offerings may include some, not sure.
Thanks for sharing
Yes, foam surrounds degrade over time, eventually rotten or even 'disappeared' (people use their speakers with grilles on always hear before they see those rotten surounds... ). A shop once told me that the ordinary life span is only 3~5 years under the hot and humid weather over here.
For this, I've tried silicon oil on several drivers and it seems very good.
I owned a pair of EV woofers with foam surrounds, bought them back in '95. Had used them for several years, then I heard silicon oil might work, so I tried. They live on very well with a brand new looking (and touching) surrounds all these years. I sold them 2 years ago and haven't heard any complain from the buyer.
Not bad at all
I think this is what a few people are using over at the classic speaker site--
View attachment www-permatex-com.pdf
View attachment 80062.pdf
View attachment klh_service_bulletin_60.pdf
View attachment www-permatex-com.pdf
View attachment 80062.pdf
View attachment klh_service_bulletin_60.pdf
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Thanks again to speakerdoctor suggesting a possible source of sealer. Vintage-AR in responding to my question about it says that he doesn't have the sealer, but can get it for me. It is kind of expensive, but then again so also is the Selenium 12PW5-SLF woofer. The Selenium woofer is the most expensive driver that I've purchased to date and very pricey by my standards anyway.
Oh, and vintage-AR says that the sealer he has is the original formulated by Acoustic Research. Coming from AR I think that I would trust it.
Regards,
Pete
Oh, and vintage-AR says that the sealer he has is the original formulated by Acoustic Research. Coming from AR I think that I would trust it.
Regards,
Pete
I doubt strongly that AR ever formulated their own "sealer".
These compounds were in wide usage in the 50s, and they were made by industrial companies that supplied the stuff to the "big" makers like Altec and JBL, as well as lesser companies like Jensen, etc...
Of course, they may have done so, but it's unlikely.
_-_-bear
PS. the other thing is that the Permatex stuff is mostly Rosin... Rosin will sooner or later stiffen up and harden... I wouldn't use it myself. The "water based" speaker dopes that are sold are a type of PVA, but not quite the same as white glue or diluted caulks...
These compounds were in wide usage in the 50s, and they were made by industrial companies that supplied the stuff to the "big" makers like Altec and JBL, as well as lesser companies like Jensen, etc...
Of course, they may have done so, but it's unlikely.
_-_-bear
PS. the other thing is that the Permatex stuff is mostly Rosin... Rosin will sooner or later stiffen up and harden... I wouldn't use it myself. The "water based" speaker dopes that are sold are a type of PVA, but not quite the same as white glue or diluted caulks...
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RoyC at the classicspeakerpages.net forum, posted 28Nov2007 reporting on experimenting with different sealants and giving a good report on the Permatex #80062. However he states that the Permatex is suitable for cloth surrounds only, not foam.
He also reports that he experimented with the sealant sold by Simply Speakers, giving it a thumbs down. He says that, one month after coating the surround of a 3A woofer with the SS sealant, that fs of the woofer had doubled.
That AR formulated a sealant was an unwarranted embellishment on my part that vintage-AR did not communicate to me. But who knows to what extent they used an existing compound off the shelf, or slightly modified an existing one, or came up with their own mix? What is important is that they very likely did a lot of extensive testing of the compound that they ultimately decided to use commercially.
Regards,
Pete
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