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KLH Model Twenty

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I was asked to refurbish these Twenties and eliminate the RCA jack. Haven't got around to the cabinets yet--that will wait for better weather. Grilles are a little stained so they may need new cloth.

Tackled the crossovers today. Crushed the RCA jacks and pried them off then attached wood paint stirrers to provide a stable backing and non-conductive mounting for the 5-way binding posts.

Caps are one 8uF Ulta-Cap and two 2uF Swedish Rifa Miniprint caps per xo The Rifas were from an AK member at Glenn's 2018 Blue Mountain Lodge gathering. FWIW, the original Rogers LS3/5a speakers used Rifa Miniprint capacitors.

I did check the old caps. They're the familiar black & red. Not Callins but Whale. I was amazed to find every cap was within spec. I think the worst one was a 2.0 that measured 2.3uF. But they're little ticking time bombs and for the approximately $5 per speaker cost I'm happy to have nice new film caps in there now.

More photos will follow when the cabinets are finished.

P1110470.JPG

P1110471.JPG

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🤔 hmmm...I have a pair of these stashed. Never tried them out. How might they compare to something like the Lg. Advents? 

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Similar I suppose. A little less bass. And they're 4 ohms.

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8 hours ago, fran604g said:

🤔 hmmm...I have a pair of these stashed. Never tried them out. How might they compare to something like the Lg. Advents? 

I suggest you try them out. You might be surprised.

I have a pair of Model Twenty's that I recapped and added binding posts, similar to what JKent did. I also have a pair of OLA and had a pair of NLA and Advent/1 and Legacy II. I like the 20s better, even if the OLA may dig a bit deeper.

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9 hours ago, JKent said:

Similar I suppose. A little less bass. And they're 4 ohms.

 

5 hours ago, RTally said:

I suggest you try them out. You might be surprised.

I have a pair of Model Twenty's that I recapped and added binding posts, similar to what JKent did. I also have a pair of OLA and had a pair of NLA and Advent/1 and Legacy II. I like the 20s better, even if the OLA may dig a bit deeper.

Thanks guys, I think I found my next speaker project.

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Finished.

The cabinets still have some scratches (patina 😉) but I don't want to sand the veneer too aggressively. Filled chips and corner dings with epoxy/Mixol 22. Used Howard Restor-a-Finish Mahogany to even out the color on the cabinets and when that was thoroughly dry (a couple of days) I used 2 coats of Watco Danish Oil, Walnut.

The woofer surrounds got a coat of Roy's goo per Service Bulletin 60 http://www.classicspeakerpages.net/library/klh/other/klh_schematicsservice/klh_service_bulletin_60.pdf  That really improved the "3-finger" test.

I tried to clean the grilles with upholstery spray cleaner and oxy-clean but the stains didn't come out and new ones were created where the black scrim cloth bled through so I replaced them with some nice Irish Linen. Spray painted the Masonite black first, both to mimic the original appearance and seal it. The Masonite is too thin to staple so I glued the linen on with Aleene's Tacky Glue. No scrim--why put extra layers of clothe between the drivers and your ears? After the glue was dry I sprayed the linen with water, dried it with a hair dryer so it's nice and tight. Then gave it a coat of Scotchgard. Finally installed a pair of my reproduction logo plates.

I'm happy with the result and they sound good!

KLH-20 9.JPG

KLH-20 4.JPG

KLH-20 6.JPG

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Nice work! 

Has anyone actually measured the impedance of a KLH 20 to see if it is different from that of a 17?  Perhaps the woofers are different even though they look the same. 

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3 hours ago, Martin said:

Perhaps the woofers are different even though they look the same. 

Yes. The 17s are 8 ohm, the 20s are 4 ohm. Tweeters and crossovers are the same. Only the woofers are different.

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