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KLH Model Six

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So I was at Kutztown and saw a pair of Sixes. They looked kind of sad so the seller said "The cabinets are rough and the tweeters don't work. Five bucks". So I couldn't resist ;)

Got them home (no easy feat: 3 hour drive in a 2-seater) and had to tear into them. Some initial impressions:

  1. These are NOT the epoxied-in versions but they are fairly early (SN 95544 & 99166) so they do have the 3 terminals on the back.
  2. Cabinets may not be that bad: water marks, a few chips, corner dents and what look like scorch marks. All can be fixed.
  3. Both Masonite grille frames are broken but the nice cast badges are there.
  4. Both tweeters work! :D
  5. Crossover is not like the one shown in the Model Six manual (in the Library). I've only opened one but it has an inductor, one 3 ohm resistor and one 8uF cap (well, the cap is actually a double 4uF, typical of KLH). It's a crappy old paper cap so I suspect that's the cause of the non-working tweeter although the toggle switch may also be the culprit.

Has anyone seen a crossover like this in a Six? I don't even understand how it works; if there's only one cap and one resistor what does the 3-position toggle do? Seems to me there should be some more caps and/or resistors.

edit: This IS like the crossover shown in the manual. See follow-up posts below.

So the plan is to patch the dings in the cabs (probably with brown epoxy), replace the caps with some 8uF "Ultra Caps I got a while back from Apex Jr, squirt some De-Ox-It in the switches and fire 'em up. Will post pics and progress.

-Kent

xo.jpg

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Kent,

Did you happen to see the Model Twenty-One with the center mounted power switch?

IMG_2589 edit.jpg

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Is it possible there are resistors or caps hiding inside the epoxy? I can't see any but that is how KLH did it in the earliest Six's..

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22 hours ago, JeffS said:

Did you happen to see the Model Twenty-One with the center mounted power switch?

Nope. I didn't see any of the stuff ar_pro mentioned either :(

Also didn't see your AR coffee cup.

 

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On 5/13/2018 at 5:42 AM, jessiAV said:

Is it possible there are resistors or caps hiding inside the epoxy? I can't see any but that is how KLH did it in the earliest Six's..

RIGHT YOU ARE!

I should have known that. Even though I couldn't see any components in that chunk of epoxy I chipped away at it and it broke like ceramic. Embedded in there were 3 more resistors and a double 2uF cap. And the caps are bad. So in addition to the 8uF "UltraCaps" I'll throw in some Madisound Surplus 2uF Mylar caps.

Getting the plate off was a nuisance and getting it back on (and retaining the airtight seal) will be a chore. I HATE those metal plates KLH used. Each of the THREE terminal screws has to be isolated with rubber shoulder washers. Just a stupid design.

Will be posting some photos eventually.

Thanks Jessi :D

-Kent

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hi Kent,

 

         I couldn't agree more about the rear plate. My solution to sealing was to put a bead of sealant inside cabinet hole where the wood and metal plate meet, but I'd be really curious how you will do it.

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I cut a gasket out of some laminate floor underlayment and attached the plate with some small brass pan head screws.

45O18qWl.jpg

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Changing /removing KLH Model 6 caps

Any suggestions on removing the epoxied caps and resistors besides brute force. I would appear to be easier to just bypass the small caps and add new resistors to switch out the small ones as long as one can get to tie in to the terminals? It is very messy banging away on the epoxy block.

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13 minutes ago, ADC/AR_F400 said:

Any suggestions on removing the epoxied caps and resistors besides brute force. I would appear to be easier to just bypass the small caps and add new resistors to switch out the small ones as long as one can get to tie in to the terminals? It is very messy banging away on the epoxy block.

Welcome!

I think brute force is the only way, since you have to get at the lugs on the 3-way switch. Since my woofer is NOT epoxied I was able to get inside through the woofer hole and use an old screwdriver (a junk chisel would probably work even better) to chip out the epoxy. It shatters fairly easily, like ceramic. It's just messy. And wear eye protection!

Kent

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Thanks for your quick response. I bought the replacement caps ( from looking at the CSP crossover diagram) before removing the woofer on one of my pair, but have been frustrated by the relative toughness of the epoxy used. I thought it would break away more easily. but not so. I'l  try a chisel but I have been afraid of damaging the terminals or putting a hole through the metal plate.

Hence the concept of bypassing that whole crossover segment and just changing he larger cap I had changed the caps on a pair of KLH 24's to excellent effect and expected the KLH 6's to go as simply. I expect the resistors to get damaged and was wondering what specs (wattage) would be needed for the apparent wire wound resistors used. Do all of the Parts Express ones work?

 

Thanks

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18 hours ago, ADC/AR_F400 said:

I expect the resistors to get damaged and was wondering what specs (wattage) would be needed for the apparent wire wound resistors used. Do all of the Parts Express ones work?

That's a slightly controversial question. The common wisdom is that wirewound resistors don't go out of spec so you may as well leave them. My concern is this: The originals are 5w while most speakers (other than KLH) use 10w resistors. I have seen burned 5w resistors in KLH Fives and Twelves so I advocate replacing them with 10w.

Yes, the standard wirewound resistors from PE, 10w rating, are fine. You don't need "non-inductive".

Having said all that, I "may" leave the original resistors in my Sixes. We'll see.......

-Kent

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Well, they're coming along and I should have some pics soon. For now, here's the finished xo. I used two 2uF mylar surplus caps from Madisound (maddeningly short leads but only 0.35 each). The 8uF is a poly "Ultracap" from Apex Jr. I violated my own rule and left the 5w resistors. 

The cloth surrounds on the woofers were pretty porous and failed the "push test" so I sealed them up with Roy's goo. Initial listening impression: Great!

Larrybody--your gasket looks good. I went a simpler route and used some very thin double-faced foam tape (the kind used to attach plastic signs to office doors) and re-used the original brads. I'm sure that made an airtight seal but just for good measure I squirted quite a lot of hot melt glue on the inside where the original epoxy potting had been. No hot melt on the caps--those are held in place with automotive trim tape (2uF) and ny-ties on blocks (8uF).

Today I re-covered the grilles. The Masonite panels were broken at the thin part next to the woofer. I rewired them with epoxy and brown coffee filter paper. The new cloth is "Irish Linen" cross stitch fabric by Charles Craft. It's about $8 a roll and I use Michael's 40% off coupons so 2 rolls--enough for 2 speakers--ends up costing about 10 bucks. Guess I'm a cheap so-and-so. The total cost for these speakers was about $20, plus a lot of work.

 

crossover.jpg

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Finished!

I was surprised how good these sound!

Cabinets were patched up with brown epoxy where needed, After sanding with #220 grit I used Howard Restore-a-Finish: One coat Mahogany followed by one coat Dark Walnut. A couple of days later I applied a coat of walnut Watco Danish Oil. I "planned" to finish it off with Minwax Antique Oil but discovered my supply had coagulated. I had a can of Watch Teak Oil and figured it's probably similar so that's what went on as a final coat. When dry I buffed it with a white Scotch Brite pad to knock down the gloss a bit and I'll probably repeat the teak oil and buff.

The serial numbers are 95544 and 99166. The earlier one has a plywood back while the later one has a particle board back. I sprayed the backs of both brown.

Sorry for the crappy cell phone photos.

Kent

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Man those look good. My original one owner 1963 set that I did 4 years ago is still at my sisters. I have three other sets. One 1958 with blonde cabinets and 12 ply marine grade plywood yet to be restored. Two sets with the removable grills, one in vinyl that I took the grills from when I cut the 1963 set to re dope the woofers and the other set in walnut with one tweeter black and the other bare metal finish. I have been debating to find another matching metal finish tweeter or just paint the other black. I have listened to this set with a Yaqin 13S tube amplifier which produces a suburb.listening experience. The flagship set at my sisters uses a Marantz 2270. I tried to swap her out with some new large Advents, but she wanted the sixes back. Great sounding two way speakers.

 

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I've been auditioning them with my reference speakers--AR-91s. They compare VERY favorably! On a few  recordings with VERY deep bass--the kind you feel more than hear--the ARs are clearly more capable but for most recordings the KLHs are pretty amazing. Claimed bass response is down to 32 Hz and more importantly, vocals and instruments sound great. Aren't these the speakers Henry said he "got it right" on?

I no longer have Advents but after I restored some OLAs with top quality capacitors and inductors, following PeteB's guidance, my impression was that compared to the AR-2ax speakers I had at the time, the Advents were, well, meh. I sold the Advents and had no regrets so I'm sure I agree with your sis ;)

Coincidentally, I just finished up some KLH Fives--some of my favorite speakers. I'll be interested to A/B them against the Sixes (and the AR-91s).

Thanks for the positive comments.

Kent

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Nice restore as usual.  Did the earliest versions have grille frames, or was the fabric glued on?

Looking forward to hearing about your speaker comparison.  I think I'd favor the 6's over the Fives, but that is going on memroy.

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15 hours ago, alkermes said:

Nice restore as usual.  Did the earliest versions have grille frames, or was the fabric glued on?

Looking forward to hearing about your speaker comparison.  I think I'd favor the 6's over the Fives, but that is going on memroy.

Thank you!

The earliest Sixes had epoxied-in tweeters and woofers, and the fabric was wrapped around the front baffle. Virtually impossible to get into. Thank goodness these are later ones!

Of the speakers currently on hand I'd rate them:

  1. AR-91
  2. AR-3a
  3. KLH Model Five
  4. KLH Model Six

But it's a pretty close race.

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On 6/27/2018 at 12:22 AM, DonT said:

Great job. I hope my fives look that good when I am done.

Me to. I just got done with the crossovers in mine and they sound great. Now to make them look good.

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