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KLH Woofer Surround Sealant


boreas

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I know this topic has been done to death but I've just finished redoing a pair of Model Seventeens and while doing so my thoughts strayed to the topic of this post. Over the years I've done a few pairs of KLHs and always used thinned siliconized latex caulk as a sealant.

It has worked well but over the years whenever I've heard the topic discussed I've never heard a definitive answer to the question of what, precisely, KLH actually used when making the woofers. That may be due in part to the fact that they used at least two different materials. In my experience I've seen surrounds treated with an opaque black substance and also a sort of honey colored material that's semi-transparent.

I think I've heard some people suggest that KLH may have used a butyl rubber material. If so, I'm guessing that's the black stuff but what about the other honey colored stuff?

Now, the speakers I just finished have the honey colored treatment and, as I was considering what to use to refinish the cabinets I started thinking about a mixture of linseed oil and turpentine.............

Linseed oil. Raw linseed oil. Sort of honey colored. Semi-transparent. Never dries completely and always stays flexible and slightly tacky. Just like the woofer surrounds. Hmmm..........

KLH must have had gallons of the stuff around for finishing the cabinets. It's certainly possible that they used it on the surrounds. I think it would work, probably really well, and it would be just like KLH to find a cheap but effective way to do the job. Anyone else have any thoughts?

Oh, also, I think this particular pair is pretty early. They have the SN's stamped into the XO plates instead of on those little foil stickers. The numbers are 012758 and 017303. Also the caps were great big duals (a 2 + 2 and a 4 + 4 wired in parallel) in cardboard cylinders rather than the smaller black & red ones. Does that make them pretty early?

Thanks,

John

KLH17.jpg

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Very nice restoration John. You should hear from RoyC, our resident sealant expert soon.

Thanks, Carl. It was fun. I love bringing this stuff back to life. I'm listening to Wynton & Branford Marsalis through them now. :)

After posting this thread I saw that RoyC has developed a black butyl-based sealant. Maybe he will have some insight into the other stuff.

John

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Thanks, Carl. It was fun. I love bringing this stuff back to life. I'm listening to Wynton & Branford Marsalis through them now. :)

After posting this thread I saw that RoyC has developed a black butyl-based sealant. Maybe he will have some insight into the other stuff.

John

Nice restoration, John!

Actually my butyl sealant is not black. It is amber and remains quite tacky. According to a former KLH employee who posted here some time ago, the original black KLH sealant may have had asphalt in it, and the base solvent was toluene.

While KLH woofers do appear to need resealing more often than, say, AR woofers, it should be noted that the original sealant is still present, and has likely stiffened a bit.. The "re-sealant", therefore, should not be too heavy or compliance will surely be compromised. I have removed old KLH sealant with toluene (a nasty job), and measured a subsequent drop in fs of 4 to 6 hz. (Presumably anything applied to a surround will decrease compliance/raise fs somewhat , however, so the drop in fs may simply reflect the untreated cloth's original properties).

Any treatment that dries or cures, even if it stays elastic, like rubber cement, PVA/white glue compounds, or latex caulk, tends to raise compliance unacceptably in my experience. My sealant has not increased the fs of any woofer by more than 1+ hz for the two years I have been monitoring it. I think Carl got it up to 3 hz or so after baking a treated woofer in an oven to simulate time. He said it was delicious. :)

I won't be making more of the stuff, as it was costly and messy, but I still have enough to share. Send me a PM if interested.

Roy

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Nice restoration, John!

Actually my butyl sealant is not black. It is amber and remains quite tacky. According to a former KLH employee who posted here some time ago, the original black KLH sealant may have had asphalt in it, and the base solvent was toluene.

While KLH woofers do appear to need resealing more often than, say, AR woofers, it should be noted that the original sealant is still present, and has likely stiffened a bit.. The "re-sealant", therefore, should not be too heavy or compliance will surely be compromised. I have removed old KLH sealant with toluene (a nasty job), and measured a subsequent drop in fs of 4 to 6 hz. (Presumably anything applied to a surround will decrease compliance/raise fs somewhat , however, so the drop in fs may simply reflect the untreated cloth's original properties).

Any treatment that dries or cures, even if it stays elastic, like rubber cement, PVA/white glue compounds, or latex caulk, tends to raise compliance unacceptably in my experience. My sealant has not increased the fs of any woofer by more than 1+ hz for the two years I have been monitoring it. I think Carl got it up to 3 hz or so after baking a treated woofer in an oven to simulate time. He said it was delicious. :)

I won't be making more of the stuff, as it was costly and messy, but I still have enough to share. Send me a PM if interested.

Roy

Thanks, Roy. I've done six pair of KLHs now, as well as a few others, and continue to learn. One of these days I may get it right :)

Your butyl compound sounds like quite the stuff. At this point I'm not even sure I want to reseal these particular woofers. They look as if they need it but sound as if they don't. The last pair of Seventeens I did sounded fine after a recap but I redoped them anyway. The bass went missing so I'm a bit gun shy about doing another set. That being said, I will definitely be PMing you if I decide to go ahead with this pair.

So, I guess my bright idea about linseed oil may not have been so bright. :) Still, I wonder whether it would work. It's pretty benign stuff too and actually used to be employed to preserve rope so it would have beneficial effects on the cloth surrounds, especially if, as I believe, they're linen. (Linen and linseed oil both come from the flax plant.)

Asphalt and toluene! <<shudder>> ;) Which raises the question, would it be advisable to remove what remains of the old material before applying the new? I'm thinking yes, although I've not done that previously.

Thanks for the great info and offer!

John

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Thanks, Roy. I've done six pair of KLHs now, as well as a few others, and continue to learn. One of these days I may get it right ;)

Your butyl compound sounds like quite the stuff. At this point I'm not even sure I want to reseal these particular woofers. They look as if they need it but sound as if they don't. The last pair of Seventeens I did sounded fine after a recap but I redoped them anyway. The bass went missing so I'm a bit gun shy about doing another set. That being said, I will definitely be PMing you if I decide to go ahead with this pair.

So, I guess my bright idea about linseed oil may not have been so bright. :) Still, I wonder whether it would work. It's pretty benign stuff too and actually used to be employed to preserve rope so it would have beneficial effects on the cloth surrounds, especially if, as I believe, they're linen. (Linen and linseed oil both come from the flax plant.)

Asphalt and toluene! <<shudder>> :) Which raises the question, would it be advisable to remove what remains of the old material before applying the new? I'm thinking yes, although I've not done that previously.

Thanks for the great info and offer!

John

I'm not a big fan of re-sealing the surrounds unless they absolutely need it. Too many folks are destroying the attributes acoustic suspension speakers are known for by slathering stuff on the surrounds.

It is not necessary to remove the old sealant unless measurements indicate your woofers may be out of spec due to increased compliance. (Solvents like toluene can also dissolve the glue that bonds the surround to the basket, so it is not something I would recommend doing routinely.) My stuff has toluene in it as well, which tends to soften the old sealant when it is applied. Some woofers have actually become slightly more compliant immediately after treatment.

Roy

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I'm not a big fan of re-sealing the surrounds unless they absolutely need it. Too many folks are destroying the attributes acoustic suspension speakers are known for by slathering stuff on the surrounds.

Yes, having trashed a pair of Seventeen woofers that way, I'm with you. This particular pair sounds fine so i'm inclined ot leave them alone. Maybe in another 45 years (when I'm 110 ;)) I'll do it.

It is not necessary to remove the old sealant unless measurements indicate your woofers may be out of spec due to increased compliance. (Solvents like toluene can also dissolve the glue that bonds the surround to the basket, so it is not something I would recommend doing routinely.) My stuff has toluene in it as well, which tends to soften the old sealant when it is applied. Some woofers have actually become slightly more compliant immediately after treatment.

Roy

Not knowing the type of glue KLH used to attach the surrounds to the cones and baskets, I wasn't sure but I did wonder about the toluene "disassembling" the woofer.

Thanks, Roy!

John

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Not knowing the type of glue KLH used to attach the surrounds to the cones and baskets, I wasn't sure but I did wonder about the toluene "disassembling" the woofer.

Thanks, Roy!

John

The KLH surround glue actually appears to be fairly resistant to toluene. I just wanted to offer some caution regarding its use. MEK is the solvent to be very careful with. It is usually able to quickly dissolve surround glue, as well as most other types of glue used in the construction of speakers.

Roy

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Boreas;

Your 17's look great and are indeed early ones - with SN's 12758 & 17303 this puts them in the first year of production, 1965.

I figure KLH made at least 35,000 units a year of the model 17. They were produced until about 1970 -1 and I've seen serial numbers as high as 180,000.

The 17 was repackaged into models 38 & 56 (basically the lighter 10 inch woofer which dated back to the model 10 of 1961).

The last act of this superb woofer came with the model 56, circa 1976.....it sounded good, but the cabinet was a sad afair....thin mdf wrapped in vinyl.

By this time, Radio shack was selling much nicer acoustic suspension speakers then KLH.

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Boreas;

Your 17's look great and are indeed early ones - with SN's 12758 & 17303 this puts them in the first year of production, 1965.

I figure KLH made at least 35,000 units a year of the model 17. They were produced until about 1970 -1 and I've seen serial numbers as high as 180,000.

The 17 was repackaged into models 38 & 56 (basically the lighter 10 inch woofer which dated back to the model 10 of 1961).

The last act of this superb woofer came with the model 56, circa 1976.....it sounded good, but the cabinet was a sad afair....thin mdf wrapped in vinyl.

By this time, Radio shack was selling much nicer acoustic suspension speakers then KLH....all that ws left to do is sell this historic company to an Asian firm, which happened by 1979.

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Boreas;

Your 17's look great and are indeed early ones - with SN's 12758 & 17303 this puts them in the first year of production, 1965.

I figure KLH made at least 35,000 units a year of the model 17. They were produced until about 1970 -1 and I've seen serial numbers as high as 180,000.

The 17 was repackaged into models 38 & 56 (basically the lighter 10 inch woofer which dated back to the model 10 of 1961).

The last act of this superb woofer came with the model 56, circa 1976.....it sounded good, but the cabinet was a sad afair....thin mdf wrapped in vinyl.

By this time, Radio shack was selling much nicer acoustic suspension speakers then KLH....all that ws left to do is sell this historic company to an Asian firm, which happened by 1979.

Thanks, Andy. I had fun doing them. I thought they were pretty early, given the "zero" first digit and the SN stamped directly into the XO plate.

I've recently learned that the Seventeen was also reincarnated a number of times. First, still being called a Seventeen, with the same cabinet, same or similar woofer and a 2.25" Peerless cone tweeter. Then with a different 10" woofer and the Peerless tweeter in a wood grain vinyl wrapped cabinet. Last as a 317, same speakers as the vinyl Seventeen but in a black cabinet. These must date from the Singer era. The XO plates declare them to be Cambridge made.

Also, as to the Radio Shack speakers, if you look at my photo in the OP, behind the Seventeens you'll see a Realistic Nova-10. It's an acoustic suspension speaker with 8"woofer, 8" passive radiator and a 2.5" cone tweeter. Pretty nice, actually, but definitely not up to the classic KLHs.

John

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It is not necessary to remove the old sealant unless measurements indicate your woofers may be out of spec due to increased compliance.

This has got me thinking. These Seventeens appear REALLY susceptible to TT rumble. The woofers pump like crazy with equipment and in locations that don't affect any of the other speakers I've tried for comparison's sake. Not only multiple speakers but multiple turntables and amps with the Seventeens. The subsonic filter on my amp defeats the problem so the speakers are usable but I was wondering whether this could be due to too much compliance.

Thanks,

John

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The spiders and surrounds may have 'loosened up' over the years resulting in more flexing with lower register notes or TT rumble. Re-sealing the surrounds might help a bit.

Thanks, Carl. That's what I was wondering. It seems to be rumble as opposed to just low registers. The pumping only occurs when I'm using the turntable. All other sources are fine.

John

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Thanks, Carl. That's what I was wondering. It seems to be rumble as opposed to just low registers. The pumping only occurs when I'm using the turntable. All other sources are fine.

John

Instant gratification got the better of me and, rather than waiting for Roy's "Secret Sauce" I went ahead and applied a VERY thin coat of diluted caulk. I couldn't stand not knowing whether that would be the solution to the pumping woofers.

To a large extent it was. There's still some to be seen but it's significantly less than before and I think within safe limits of excursion (1/4" or less). It occurs only when playing the lead-in grooves and the first inch or so of the playing surface of an LP. Of course, a warped record has a noticeable effect but it's there to a lesser degree even on nice flat ones.

Most importantly, the addition of the sealant has tightened up the bass to a noticeable degree. I thought it was acceptable before but now it's quite nice. Adding another coat of sealant might further reduce the woofer motion but it also might start to degrade bass response so I'm inclined to call the problem solved.

Now, to get a replacement for one tweeter that has an occasional buzz.

Thanks, all!

John

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  • 1 month later...

Hi guys,

I'm working with four drivers from two sets of KLH-31's. Two of them have suffered the Permatex High Tack treatment and I'm trying to reverse the problems that this purple sticky stuff has caused. One of them makes a loud pop in the low Hz regions, the other has an occasional buzzing sound. The treated surrounds are very prone to distort with light and temperature. I used some acetone and cotton balls to strip the high tack and old butyl away and now have super soft/compliant surrounds. Although very few pinholes are noted, this is far from ideal! Please correct me If I'm wrong, but a function of the surround is to hold the edge of the cone steady enough to keep the voice coil from lateral interference with the pole piece. If the compound used on the surround doesn't have a 'memory' it won't work, the cloth is only there to hold the butyl rubber/asphalt combination in place! I've discovered Red Devil Blacktop & Roof Repair Caulk #0636 has a butyl/asphalt combination and it is thinned with mineral spirits. I've prepared one by removing its dust cap and shimming the coil. I'm now waiting for shipment of this stuff. Stay tuned..

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  • 2 weeks later...

Instant gratification got the better of me and, rather than waiting for Roy's "Secret Sauce" I went ahead and applied a VERY thin coat of diluted caulk. I couldn't stand not knowing whether that would be the solution to the pumping woofers.

To a large extent it was. There's still some to be seen but it's significantly less than before and I think within safe limits of excursion (1/4" or less). It occurs only when playing the lead-in grooves and the first inch or so of the playing surface of an LP. Of course, a warped record has a noticeable effect but it's there to a lesser degree even on nice flat ones.

Most importantly, the addition of the sealant has tightened up the bass to a noticeable degree........

The tighter bass is what I would expect as a result of sealing what is essentially an air leak in an acoustic suspension loudspeaker.

The symptom itself (woofer pumping) indicates that your cartridge and tonearm may not be well-matched. The woofer excursions

almost certainly represent flexing of your cartidge's cantiler, amplified.

As to the doping of the surrounds, I wish somebody could tell us what CTS used. I have several of their woofer from the same time period as the KLH's. They have thin cloth half-roll surrounds with a thin coating of something that is still tacky, highly flexible, and airtight after 40 years!

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The symptom itself (woofer pumping) indicates that your cartridge and tonearm may not be well-matched. The woofer excursions almost certainly represent flexing of your cartidge's cantiler, amplified.

That's possible, I suppose but for it to be true in this case it would have to mean that I had 2 tables with poorly matched cartridges and tonearms. I had the same problem using a Pioneer PL-560 with a Shure M97xE and a Sanyo TP 626 with a Shure M91ED, both with the OE stylus fitted. Meanwhile, with both these turntables and with a pair of Realistic Nova-10s placed in the same positions as the Seventeens, there wasn't a hint of untoward movement in the woofers.

John

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  • 6 years later...

On linseed oil: in Sweden it is used to preserve wood like on houses like forever, BUT: needs to be reapplied about every 5 years. There are pine windows in Old Town in Stockholm that were made in the 1500's, and they're still there, still original, still re-oiled every 5 years. So, if you don't mind re-doing it every 5 years... Raw linseed oil is the one that "never dries". However it oxidizes (and on a painted outdoor panel or window the pigment will at that point begin to be released from the oil) - thus the need to re-oil. Thinning linseed oil for outdoor use here is correctly done using gum terpentine, though this is probably only relevant for wood.

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