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KLH Research Ten Series, Model CL-4


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Howdy fellow forum members. Newbie here. Did not know this forum existed until I started looking for replacement mid-drivers for my KLH speakers.

I've gone thru all 500+ postings in the KLH forum and found no references to my particular speakers that I can tell. Nor have I found any listings on internet searches. Actually, that is how I found this forum,

Just like the topic title says, they are "KLH Research Ten Series, Model CL-4" -- that is directly from the label. They are serial-numbered, but I don't have that info presently. I have a pair of them from around mid 1970s, as best as I can remember. Main thing I am wanting to do presently is replace the mid-range drivers. The cone surrounds are getting poor in shape. They are not foam-surrounds -- are some kind of "rubberized" fabric it seems.

I replaced the woofers a couple of years ago, and that is the 2nd replacement from what I remember. I do plan to replace the foam surrounds on the "1st replacements" which I still have.

Here is some info for those who would want to know:

They are 3-way speakers: Woofer is 10-in (outside rim dia; cone >8"), Mid-Driver frame is 5"x6" in a rounded square shape (cone is 4" or so), Tweeter is cloth dome type measuring 1-1/8 inches across dome (frame is 5-5/8 x 3-1/8 inches, rectangular shaped)

Speaker box is 26-7/8 H x 14-1/4 W x 12-1/4 D. There is a front vent which is 1-3/4 inches in diameter. Have not measured its length. Lots of pink fiberglass batting inside the box. Trim is oiled walnut. Has removable dark brown cloth (original) speaker cover that fastens to box with velcro. Kept the original boxes for years, but I think they got trashed after the last move.

It would not surprise me that the capacitors in the crossovers need replacement too. I have not dug into that yet. Speakers still sound great though!

I was going to download the "history spreadsheet" that I saw was available to see if this speaker type was listed, but regrettably the computer I am presently using does not have Excel on it! Durn it! LOL!

Do any of you know any details of the original speakers and/or the crossover used in these speakers? If nothing else I would love to find out what the original power rating was.

Thanks bunches - Watson

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I tried to add a reply with some additional information and have not seen it posted. I may have done the "Quick Reply" incorrectly. So, here is a repeat using the Reply feature.

I measured the vent tube length and it is 8 inches long.

Also, I forgot to mention in my original post that there are two 3-position switches on the box back at the speaker terminal plate for adjusting frequency compensation. There is a switch for MID and HIGH with DEC -- FLAT -- INC settings.

Thanks -- Watson

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These speakers are not considered from the classic era, the focus of this board. The KLH spreadsheet has no information on the Research Ten series, because they are too new.

I had a pair of Research Ten CL-8, I believe. They were 2 ways, with a 10" woofer. I sent them on; the KLH 17s and AR-2s I have sound less harsh, have more presence, etc.

Please don't let me dissuade you, though, if you enjoy them. You're right; there's just little to no information available on these speakers. I'm guessing it's because they sold very few.

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  • 3 weeks later...
Main thing I am wanting to do presently is replace the mid-range drivers. The cone surrounds are getting poor in shape. They are not foam-surrounds -- are some kind of "rubberized" fabric it seems.

I'm not familiar with those particular speakers but if the only problem you have at the moment is the condition of the surrounds you might want to consider repairing them. What is it about their condition that concerns you?

Early KLH speakers "from the classic era" often had coated cloth surrounds. As a rule, they never go bad but they do need to be periodically (3 times per century ;)) resealed. There are a number of preparations that people use but the original material is essentially butyl thinned with toluene.

If the problem you're having could be remedied by resealing the surrounds you might want to research the forum for threads on the subject of resealing them.

Oh, and welcome!


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