KLH cloth surround leaking & sealing

[DaveD]

The last time I used my KLH Seventeen pair, about a year and a half ago, I didn't think they sounded so good. They had been in storage for several years, and I had re-broken them in. I was surprized that the bass was weaker than that from my Cambridge Soundworks Model Six pair.

Over the years, I have looked at the black coating on the KLH woofer surrounds, which is very unevenly applied. It seems to be fading away in several places. This is described as "synthetic rubber" in the KLH sales brochure.

Lately, I have seen that these are selling for $20-$35 on eBay, almost constantly. Sometimes they are in very nice cosmetic condition. Why so cheap? Maybe they start to sound bad because of leaky surrounds destroying the acoustic suspension.

The photos on eBay prove a dramatic variation in the application of the original black sealer. Some are very black, some are merely light gray and mottled. Very early ones are not coated in black, but a clear coating.

The KLH surrounds which are still very black may be sealed well, I don't know. I have seen this variation in the sealant on other KLH models on eBay. The Sixes and Twenty Threes I have

seen tend to be darker than many of the Seventeens.

I found a speaker designer and technician 80 miles away who works on vintage gear. He said that these surrounds are often very leaky. He likes to re-cone, but not me. So, I researched all of the flowable silicones from Dow, coating them onto cloth swatches. And, one other product, sold as Surround Glue by Oragne County Speaker. This is the one I chose as being the most flexible and adding the least mass. Its seal against air is complete, applied in one thin coat.

Bryan Sunda of Orange County Speaker describes the product (also available is an 8 oz. bottle):

Hi David.

I am not sure what the material was they used in the old days, but it has

not been available for about 15 years. We do have the new version. It used

to be an MEK base coating. Now it is a water base. It's got latex in it and

it will dry clear. It is not as tacky as it used to be. But it works just as

good (or probably better). We sell it for $10 per 1oz bottle. Shipping is

$4.95. The part number is XL49. You will need to call us to order it. We

don't have it on our website.

If you would like to place an order, please give us a call. We accept Visa,

Master Card, Discover, and AMEX. Or you can email me your full name,

address, phone number, credit card number, and the list of items you would

like to order.

Regards,

Bryan Sunda

Orange County Speaker, Inc.

12141 Mariners Way

Garden Grove, CA 92843

800.897.8373 M-F 10am to 6pm Pacific Time

714.554.8520 M-F 10am to 6pm Pacific Time

http://www.SpeakerRepair.com/

This product has been applied in two thin coats to the front of the KLH surrounds, and the technician tells me that he is very pleased with the result, and that it sticks well to the remnants of the old black sealant, although I expected that it might not. Those places with remaining heavy amounts of the black stuff were still well sealed, so this is not critical. It was very easy to see light through the leaky cloth, upon inspection.

I have yet to pick them up, but expect that the sound will be much improved. So, the unimpressive sounding $35 pair could be brought back to their original glory on the cheap. Yes, I could have done this myself, but I wanted an expert to replace the original capacitors and maybe improve the connections. Two surprizes here! The original caps were polystyrene on this 1974 pair, made in Mexico. Still close to spec, but modern ones will be better. Electrolytics were expected. Also, no inductor at all. Simple, but no simpler, as Einstein used to say.

[Guest Gerg]

Dave,

How do you like the sound of your refurbished 17s? What capacitors did you use? Did you replace the internal wiring too?

Thanks, Gerg

[DaveD]

I have just gotten them back. I am in the process of listening to a bunch of used LPs while I can still return them. Frequent lightning storms are slowing me down.

I will post after I have a chance to listen to the Seventeens.

All capacitors were within their original tolerance, and were not replaced. No wiring was replaced.

DaveD

[Guest frleand]

Hi, Dave - 20-35 $ cheap? You'd be really surprised if you knew how little a speaker driver cost to manufacture. And why so reluctant to re-coning? Think about it: Your 17 woofer today is totally different from what it was when it was new. Applying layers of coating at uneven intervals doesn't make it any better. Reconing is a highly approved method in professional circles. I have several Altec speakers which have been reconed. One pair is of the original 604 duplex from '44 (made in "Hollywood"). Now they sound great (relatively)!

And you just have to face it - compared with today's "better" speakers the modell 17 (and its contemporaries) sound "wooly".

Best Regds

Fred

Norway