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KLH Model 6 high range questions


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I've downloaded the brochures available on this page and it looks like these are sealed units, but..I just bought a set of KLH model 6 speakers and have been doing some internet research on them - looks like they are great early high quality units - Problem is they don't seem to have much high range,

and adjusting the high-freq switch on the speaker backs doesn't make any

discernible difference. I can hear some output from the tweeters if my

ear is right against them... but I would expect more. Same deal on both

speakers. From what I have read the speakers are fiberglas and epoxyed

onto the speaker face and then the face is glued onto the rest of the

enclosure. Meaning you have to cut the woofer out to access the

crossover network?! I've done a fair amount of

repair, but none of it having to do with speakers - not even positive

there is a problem - both work the same ... If I remove the "bonding link" between screw terminals B and C and put speaker power to them individually the big speaker is quite loud and the little guy can barely be heard - what might the problem be? crossover? Both tweeters blown? Fix?

Any wisdom or tips you could pass along would sure be appreciated -

Thanks, Tom

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Hi Tim:

Looks like you have the same dilemma I have. No, not the tweeter problem, but how do you get into these things??!!

See my post dated April 6th? Nobody gave me a useful answer.

A guy GAVE me three of these speakers. Now I know why. I think it was a cruel trick. I've worked on a lot of classic speakers but haven't seen the likes of these!. Henry Kloss just didn't want anybody mess'n with these. I don't know what to do.

Even if you knew what was wrong with your tweeters you probably couldn't fix the problem anyway. I tried going thru the back side where the nameplate is located along with the binding posts and the switches. I pried it up, pulled out the nails at each corne and lifted the whole thing and guess what I found? More epoxy - that's right, 'ol Henry K. sealed up the back side as well.

If you find a way into these buggers short of an M80, let me know; no, let the world know!


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Yup. I did read your message, and am glad to read about you trying to go through the "connector plate" area. That was going to be my next area of attack. As I read the brochures on this page, the face fabric is also glued on before gluing - under pressure yet - the faceplate/speaker assembly to the box. The only repair discussion I have seen involved CUTTING the woofer felt out to access the interior of the cabinet and then refelting. Chance of this being cost effective? nil. Of course, I read that the speakers are epoxyed in anyway so how is one to fix a speaker?

I think the best and highest use involves playing old black guy blues on them, with them behind me at the keyboard. Very few pesky high notes, good muffled mellow sound. Or maybe car stands - they arer sure tough enough!

Thanks & keep me posted if you find a good solution - Oh, I did find 1-800-225-9847 Cambridge speakers(?) recommended for repairing and helping restore early KLH's. They weren't working last weekend and I'm not likely to ship these anywhere for repair so I would feel a little bad about calling them, but if you wanted to pick their brains I would sure like to hear what they had to say.

Thanks for the reply, Tom

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This is just a thought, I've never laid my eyes on a set of these speakers.

I take it you can get to the woofer and that it is epoxied in.

I would try this approch if you are brave enough.

3M make some pretty good adhesive remover. You can find this in just about an auto-body supply store. I would try some of that to loosen the adhesive or epoxy. Then maybe some heat from a heat gun. One the adheasive loosens you should be able to pry the woofer out of the case.

Best of Luck,

Mike W.

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  • 2 months later...

Here's the deal: Henry Kloss could not afford to buy OEM drivers when KLH was formed in the very late 1950s. After several unusual models, such as the KLH-1 and KLH-2, the KLH-4 emerged as a competitor to the already successful AR-3. Then, in approximately 1960, Kloss introduced the Model Six, soon to become one of the most famous and successful speakers of the era.

Because of Kloss' adsence of funding, he decided to completely fabricate the drivers completely from scratch. He wound the voice coils, made his own cones, but did purchase the inner suspension ("spider") and the outer suspension ("skiver"), but fabricated the speaker basket, magnet assembly, etc. Remember, KLH speakers were acoustic-suspension speakers, so the cabinet needed to be sealed (acoustically, not hermetically), so the cabinets were glued together on all sides, and not accessible. Before glueing together, however, the front baffle board with its woofer hole and tweeter hole, was laid face down. Three pipes were epoxied to a coffee-can affair filled with epoxy and the woofer's magnet, and the cone, voice coil and such were attached, and the entire affair was permanently affixed (epoxied) to the baffle. A similar treatment was done for the tweeter. Then this affair was wired to the crossover, and the front baffle board was glued to the cabinet. Sealed for life.

This configuration worked extremely well, but was simply not field reparable. The speakers had to be returned to the factory, where repairs were made by ripping out the cone, reaching in the cabinet, making whatever repairs were needed, then putting a new cone, voice coil and such in place and re-glueing.

The lack of treble response probably relates to the poor quality caps used in the crossover. Many of the early KLH speakers failed due to this problem, as though not enough power was getting to the tweeter. If there is only a small output from the tweeter, most likely it is the crossover. To fix it, you can possibly cut a hole in the back of the cabinet, reach in and remove and replace the crossover components, and then re-attach and seal the piece from the hole. It is an ugly solution, but the only choice if the drivers are still good.

Later, KLH went to front-mounted replacable drivers like the rest of the industry, and this problem went away. The caps were improved, as well.

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With all of the discussions about gaining access to the inside of the KLH6 speaker, I thought it might be of interest for people to read Henry Kloss's original patent pertaining to the construction of a speaker without a conventional frame. The patent number is 3,150,441, issued Sept. 29, 1964 and filed May 6, 1959. Go to www.uspto.gov and search under patent numbers. It may be necessary to download a tiff viewer in order to see it.


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Kloss' patent 03150441 does show the nature of KLH's in-house fabrication of the woofer frame and magnet assembly. It seems to be an appropriate method to rigidly mount the magnet, voice coil and related moving parts, but it was extraordinarily inconvenient with respect to field repair. It came about partly because of necessity and partly out of the innovative mind of Kloss to solve a problem in his mind. Some might classify this as "a solution for which there is no problem."

I understand that some people are capable of "reconing" the early KLH-4's, KLH-6's, KLH-7's and KLH-12's that had the epoxied-frame woofers. One was the previous plant manager of the old KLH Research and Development Corp. There were some older models before the first 4's and 6's that apparently also had this style woofer, but these speakers are seldom seen.

--Tom Tyson

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