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Picked up a pair of KLH Model 20's at an estate sale last weekend...

Treker

Treker

Super Member
I picked up a very nice pair of KLH Model 20 speakers at an estate sale this past weekend for only $10.00! I figured that even if the speakers were cr@p, that it was worth $10.00 just to get the beautiful cabinets.

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I hooked them up when I got home, and unfortunately they sound absolutely terrible, especially compared to my Dynaco A25's.

After doing some research here on AK as well as on the Classic Speaker Pages web site, it sounds like they definitely need a recapping, and then quite possibly a redoping of the surrounds. Here are a couple of pictures of the 10" woofer, one being a close up of the cloth surround.

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Now, I have read quite a few opinions on both web sites as to first, whether it is a good idea to re-dope the surrounds, and second, what material should be used for this. My question is is there a consensus among the vintage speaker experts here on AK as to what, if anything, should be done to these surrounds?

My plan is to first recap the crossovers and then to listen to them before doing anything to the cloth surrounds. I don't want to potentially ruin what by all accounts is a wonderful sounding speaker once restored.

Opinions?
 
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If you notice a lack of low end, and you thinks its due to the cloth needing re-doped. Try it. It is a acoustic suspension loudspeaker.
 
Well, they sounded very muddy, lacking in both the lows and the highs. That's why I assumed a recapping would be in order to restore the highs, and a redoping of the woffer surrounds would probably be necessary to restore the low end. I just want to go about the redoping the right way.

However, I have read about several different products being used for redoping old cloth surrounds, I was just wondering if there is a current consensus as to what is the best product to use in order to restore the surrounds to as close to their original factory condition as possible, as well as restoring them for longevity and long term performance. Any input would be greatly appreciated.
 
Treker said:
However, I have read about several different products being used for redoping old cloth surrounds, I was just wondering if there is a current consensus as to what is the best product to use in order to restore the surrounds to as close to their original factory condition as possible, as well as restoring them for longevity and long term performance. Any input would be greatly appreciated.
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I just picked up a pair of KLH 22's that will probably have the same issue (I need to make an adapter for the RCA input). I am very interested in what the consensus is for wha to use on the surrounds.
 
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Nice score...I have some KLH 6 and KLH 19 speakers so am interested in how doping the surrounds works out for you. Good luck!
 
Pull the driver and check to see the crossover. KLH used wire nuts to secure the connections. I have seen more then one vintage KLH with open connections in the wiring.

I also never like the tweeter much. The drivers are nice though.

Barney
 
I know someone who worked for Market Speaker (my dad), that told me that the material that they use to repair the doped cloth was Permatex High Tack Gasket Sealant. When it cures, it remains sticky, and very flexible. The original doped material on my 20's was like that, so I'm guessing that this is extremely similar to what they used originally.

I am in the process of restoring a pair myself, and my three biggest tips are these: replace the caps with Dayton caps, which are available from parts-express, use rope caulk to re-seal the woofer (which is what was originally used), and re-seal the tweeter.

I'm sure that there are several ways you can seal the tweeter. Personally, my dad and I went with a closed cell foam, as the hole had to be cut big enough to fit the square magnet through, which on one speaker, left a physical air gap around the tweeter.

As for the Permatex High Tack Gasket Sealant, it comes in a metal can with a brush. Dad said to thin it down and spray it on (make sure that you tape everything off), but I would think that if you're skilled with a brush, you could achieve good results by brushing it on, but make sure that you don't put it on too thick, as it will change the characteristics of the surround, which could possibly change the sound.



-Jason
 
Hmmm if memory serves the Model 20 speakers are designed specifically for the KLH Model 20 and Model 20+ receiver/turntable.

Mine are put away but I believe they may be 4 ohm impedance speakers.

I wouldn't do anything until i recapped those speakers though. My Model 6 speakers improved dramatically with new caps.
 
visman said:
Hmmm if memory serves the Model 20 speakers are designed specifically for the KLH Model 20 and Model 20+ receiver/turntable.

Mine are put away but I believe they may be 4 ohm impedance speakers.

I wouldn't do anything until i recapped those speakers though. My Model 6 speakers improved dramatically with new caps.
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Yes, they are 4 ohm speakers, and from what I understand, they were originally from the KLH 20 turntable/amp system.

I have also noticed that the KLH name plates are missing from the front of the speakers, but it appears that they may actually never even been present. Maybe someone knows if they were actually originally included or not.
 
The speakers on my Model 20+ did have name plates. Here is what it looks lke ...

I'll see if I can find a close up of the label.
 

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I have three pairs of old KLH speakers from the 60s & 70s that look like that. They are all untouched and sound great with plenty of bass. If your speakers sound bad, I'd suspect caps or blown drivers.
 
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The caps KLH used were very cheap and needed replacing when they left the factory. I used Daytons on my model 32s, they were a huge improvement. I redoped the surrounds with a 3M neoprene contact cement. It worked great and helped the low end quite a bit.
 
visman said:
The speakers on my Model 20+ did have name plates. Here is what it looks lke ...

I'll see if I can find a close up of the label.
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Just curious, but how are the name plates attached on your speakers? My speaker grills do not have any indications of screw holes or adhesive residue, so that is why I said it appeared to me that none were ever actually on these speakers. I also believe that the grill cloth is original. Either that, or someone did a VERY good job of replacing them, but I don't think that that is the case.
 
They are glued on - I replaced the grill cloth on mine and just used some fabric glue.
 
visman said:
They are glued on - I replaced the grill cloth on mine and just used some fabric glue.
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Hmm... That's interesting. I'm not really sure mine actually ever had any then. The reason I say this is that there is no glue residue on the grill cloth, and it appears that the grill cloth is original.

Thanks for the feedback though. It is helpful information. I suppose it is possible that some of the Model 20 speakers shipped without logos. Maybe someone reading this thread knows the answer to that question.
 
I've owned 3 of the model 20 systems (not the 20+ though) and none have badges. My wife's father had one bought new and she says they didn't come with badges.
 
kirk57 said:
I've owned 3 of the model 20 systems (not the 20+ though) and none have badges. My wife's father had one bought new and she says they didn't come with badges.
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Thanks for the feedback. That confirms what I suspected about these speakers. They did not originally come with badges. Mystery solved.
 
Do a search on ebay for "ACOUSTIC RESEARCH CLOTH SURROUND WOOFERS SEALANT KIT, ALSO KLH " Supposedly this is the proper stuff to use on the surrounds. Haven't tried it myself yet, but I have some 17's that need it.
 
I ordered some KLH cloth woofer surround doping material from a user over on the Classic Speaker Pages.net web site, RoyC. This is also apparently the same material that can be purchased from ebay seller vintage-ar. From what I understand, this material is very, very close to the original material that AR and KLH used on their speakers, and does not change the compliance of the cloth surround with time as the Permatex Gasket Sealant has unfortunately been found to do. I also have a new set of caps on hand, and hope to get these speakers redone in the next week or so. I'm going to do one at a time, and then do an A/B comparison of the sound between the restored speaker and the unrestored speaker. I'll report back my findings.
 
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