KLH Model 6 restore (kind of)

[RockinRonnie]

I have been looking for a pair of Model 6's for a while.... and while I was down in the Tampa area soaking up the heat and hiding from winter I saw a local and fellow Audiokarmia member had a pair on facebook with a problem driver but great cases etc. Might have over paid at $125 but they really don't come up often and I rarely get to thrift shops etc and in my area good stuff well priced goes FAST. Brought them back to the cold and dug into them and sure enough as he described.... no continuity or anything out of one driver. I am medium handy and good with the woodworking side. My soldering skills are beginner at best but I am learning.

Question for the brains trust: Is it worth trying to troubleshoot the driver/bring it somewhere? There are two drivers on fleabay right now that look good for $79 plus shipping. Rest of the speakers sound good if very flat (which I hope new caps will fix). Attaching pics. Other than the caps and the bad driver (and one badge) I am hoping they will come back to life with light sanding, tung oil, and cleaning the speaker cloth. Thanks in advance for any advice. Hoping these will kick my Dynaco A25's to the basement.

 

[Dswankey]

.. a pair of Model 6's ... with a problem driver ... no continuity or anything out of one driver.

Question for the brains trust: Is it worth trying to troubleshoot the driver/bring it somewhere?

Thanks in advance for any advice...

Congrats on your new to you acquisition, they're are big fave here on AK with lots of folks having very good knowledge with regards to repairs, restores and woodworking.

Be patient and they'll be along shortly to address the main issue of the driver and what could be the problem and hopefully a solution.

 

[KJ244]

Hi RockinRonnie,
Welcome to AK and congratulations on your Model Sixes. I think they are great speakers and are worth the effort to restore.

A couple of questions/observations. Which driver is out? Bass or tweeter? I would confirm whether you have resistance on the suspect driver with a DVM before purchasing a new one. I've done several restorations on Model Sixes, and the 8uF capacitors have been bad on at least one set, which resulted in no sound out of the tweeters when I first got them. If it is a tweeter that is not providing output when hooked up to the cross-over, but you have resistance on it when you measure outside of the cabinet, I would suspect the 8uF capacitor or one of the 2uF capacitors. I suggest you bench test your tweeters with new 8uF caps before buying drivers off of the bay if you get a resistance on them. I've also had bass drivers that were bad on Model Sixes and I have just gone ahead and purchased replacements on the bay. There seems to be more bass drivers available at times then tweeters.

New cross-over capacitors and a reseal of the bass drivers are a must. VintageAR on the bay has the has the recommended sealant, which was perfected by RoyC - an AK guru.

I also suggest you consider updating the cross-over resistors with at least 10 watt resistors. I've used 12 watt Mills resistors. Other just leave the original resistors and just replace the capacitors. I also recommend cleaning the cross-over switch with deoxit.

Based on your photo, it looks like you may have ASV serial numbers. I believe the V stands for Vinyl, which KLH used in their later models. I think yours may have vinyl not walnut veneer. The cabinets look to be in decent shape, so I would just leave them alone. If they were walnut veneer, I would suggest Howard's Restore based on their good condition. I have not done a vinyl removal, but there are others on AK who have if in fact yours have the vinyl veneer.

You can find replacement KLH badges on the bay as well.

If the grill masonite backing pieces are broken (they sometimes break on the sides around the bass drivers), I've glued balsa wood shims on the back sides to reinforce them and that has worked great as a fix.

Good luck,
Kevin

 

[alteclipsch]

Which driver, woofer or tweeter? If tweeter, many can be awakened with new capacitors. If not, it could be a repairable wire under the metal grill, a fairly straightforward process if done with care, I'm not expert and I've done several. Or it could be toast.

If it's a woofer, check behind the cone to see if either lead is broken, they can also be repaired (although I've never been faced with that). Also the push test on the cone to feel if severe rubbing or scraping is present, could be a burned or deformed voice coil, which IMO means toast.

At any rate, disconnect the driver from the circuit and test with a meter.

And yes, good luck. Great speakers.

Below is a Twenty Three tweeter I repaired a while back, I soldered a tiny jumper wire across the break. Very similar to a Six tweeter.

 

[RockinRonnie]

Thanks both of you for your thoughts! It is the woofer (thought term driver referred only to woofers). I have removed it and looked closely at the leads and they look intact. There is no continuity across the contacts nor at the solder points on the back side of the cone. Did the push test and hear not so much a scrapping as a clicking sound so something is touching something Will get the woofer goop and apply. The grill backs are intact but slightly warped. Will glue some shims as suggested. Glad for the heads up before I tried to bend them to straighten them. Will deoxit the cross-over switches and consider new resistors (my soldering skills are marginal). Is it easy to remove the whole cross over to do the swap on a bench?

Didn't know about the vinyl but I can see it now. It is in good enough shape that I suspect I will leave the vinyl with touch ups.

Looking into new capacitors from parts express and thinking I want to spend a little more on them than the entry level ( part numbers 027-338 and 027-324). Leaning towards the Jantzen Audio 8.2uF and 2.2 uF 400V Z-Standard Capacitors. Is there an issue not getting the exact same values of 8.0 and 2.0 ones?

Lastly it is looking like I need a replacement woofer. I think I read on here that the 10" KLH woofers vary from model to model in specs. Should I only look for ones from a model 6? The two on fleabay are a bit pricey at 79 I suspect. If these sound better than my Dynaco's I will be amped....(apologies for the pun). Cheers, Ronnie

 

[alteclipsch]

I'd stick to the Model Six woofer (verify before buying). Woofers from the 17 are too small, and the 23 is too big and has a bigger magnet. KLH stretched the truth a bit in their marketing literature when talking about woofer diameters.

The cap values you quote are fine IMO, they're within tolerance range.

The Six will probably beat the A25, it's a beefier speaker with greater depth and chest-feeling bass. I do love my A25s however; they did end up beating my KLH Seventeens.

 

[Dswankey]

.. Which driver is out? Bass or tweeter?

... It is the woofer (thought term driver referred only to woofers).

You're correct, disregard that question

 

[RockinRonnie]

The cap values you quote are fine IMO, they're within tolerance range.

Thanks alteclipsch, ordered the pricier caps...figured in for a dime. What I have learned in 2 days is remarkable. Spoke to the Speaker Shop in Toronto.... very knowledgeable and helpful and not; repairing the voice coil would be $120 US and he thinks he has a used $45 Model 6 woofer... but he moved and if he has it call back in a month or two.....lol.

Just found the problem; looking closely at the wire going down the back of the cone there is a break in the wire epoxied to the back of the cone. I was able to get a probe through the epoxy to the wire to test for continuity and got a reading of 860 ish. Doubt I have the skills to fix that but will investigate further with Speaker Shop.

 

[alteclipsch]

Looking closely at the wire going down the back of the cone there might be a slight break near the solder point from the lead. Going to see if I can get some more solder on it or even or even just get a probe through the epoxy to the wire to test for continuity.

Are you able to get a photo of that spot? That would be a stress point since there's no flex in the joint. I hope someone else chimes in on that. Be careful with heat back there, I've always put a little aluminum foil around vulnerable areas when I'm soldering.

 

[RockinRonnie]

Upon closer look the break wasn't anywhere near the solder point....went to a bay window and in bright sunlight spotted a lifted piece of the paper cone that broke the thin wire. As I am all thumbs when soldering I am going to turn it over to a pro to repair.... but since the woofer looks pretty good otherwise I might be in luck. I made it slightly worse getting the multimeter probe on it but it told me the voice coil should work.

 

[alteclipsch]

Sure would like to see a pic...hell, I'd be in there with a sharp soldering iron.

Could that paper be what causes the click you described?

 

[RockinRonnie]

Just added a pic with the break circled. Possible with the click... not sure. It didn't seem to always click. No scrapping or binding that I could feel with the push test. Do you think that is a relatively easy fix? Here is a second pic of the problem area.

 

[alteclipsch]

If it was me, (and I takes risks with this stuff), I would lift the two ends away from the cone, stick a piece of foil under the break, scrape the varnish away from the wire ends, add a strand of wire from thin speaker wire, flux it a little, and solder it together with as little solder and as little heat as possible. Then I'd remove the foil and apply a little bead of clear epoxy to the fix to attach it to the cone. Then pop a beer as I settle into a recliner to listen to the results (with a bit of luck). The caveat here is that click you've been hearing.

But that's just me. I've done it to quite a few tweeters, but not woofers. YMMV

 

[RockinRonnie]

If it was me, (and I takes risks with this stuff), I would lift the two ends away from the cone, stick a piece of foil under the break, scrape the varnish away from the wire ends, add a strand of wire from thin speaker wire,

Cheers for the input Alteclipsch.... it is tempting and I am going to have one of those beers and listen to my A25's and think about trying it. I really am a novice solderer and no one ever suggested I consider being a surgeon so that gives me pause. That said it always feels better when you push your skills. I sent an email to the speaker shop asking for a quote with the pic.... going to see what they say. Either way it is a win because the speaker lives again! Will update when the caps come in and I have looked closer at the repair. But your step by step is massively helpful and likely what the shop would do. The break is kind of hard to get to deeper into the cone. Also I can shunt this aside and see how my soldering chops improve with the caps..... also I could do something crazy like practice and get so holding clips....lol.

 

[alteclipsch]

Good luck with it. I'd love to see what other folks here would do with this. And if you do get a replacement, you've got nothing to lose trying a repair yourself!

 

[GD70]

If it was me, (and I takes risks with this stuff), I would lift the two ends away from the cone, stick a piece of foil under the break, scrape the varnish away from the wire ends, add a strand of wire from thin speaker wire, flux it a little, and solder it together with as little solder and as little heat as possible. Then I'd remove the foil and apply a little bead of clear epoxy to the fix to attach it to the cone. Then pop a beer as I settle into a recliner to listen to the results (with a bit of luck). The caveat here is that click you've been hearing.

But that's just me. I've done it to quite a few tweeters, but not woofers. YMMV

This is exactly what I would do. pretty easy repair.

 

[GD70]

Cheers for the input Alteclipsch.... it is tempting and I am going to have one of those beers and listen to my A25's and think about trying it. I really am a novice solderer and no one ever suggested I consider being a surgeon so that gives me pause. That said it always feels better when you push your skills. I sent an email to the speaker shop asking for a quote with the pic.... going to see what they say. Either way it is a win because the speaker lives again! Will update when the caps come in and I have looked closer at the repair. But your step by step is massively helpful and likely what the shop would do. The break is kind of hard to get to deeper into the cone. Also I can shunt this aside and see how my soldering chops improve with the caps..... also I could do something crazy like practice and get so holding clips....lol.

If you opt to have the speaker shop do the repair, it should be pretty cheap. It's a 15 minute repair.

 

[RockinRonnie]

Thanks GD70, one place got back to me and want 40-65 Canadian..... free if it fails. Seems a bit much. Waiting on another. Glad I don't have to pay $79 US plus customs and border shipping for one of the two 10" woofers on fleabay right now. For now will try to order some of Roy C's dope..... clearly worth it. Also if I wait till May I have a neighbor at our RV park who is a master solderer who worked for Nortel (others opinion.. not his). That would reduce my cost to beers....

 

[GD70]

Thanks GD70, one place got back to me and want 40-65 Canadian..... free if it fails. Seems a bit much. Waiting on another. Glad I don't have to pay $79 US plus customs and border shipping for one of the two 10" woofers on fleabay right now. For now will try to order some of Roy C's dope..... clearly worth it. Also if I wait till May I have a neighbor at our RV park who is a master solderer who worked for Nortel (others opinion.. not his). That would reduce my cost to beers....

Roy's sealer is a must. Remember to seal the dust cap as well.
My first set of Six's were just like yours, with the vinyl clad cabs. They were my first recap project, and woofer surround sealer.
Sold them and have a much earlier set from 1963, and another beautiful set waiting in line for a recap, and cab refresh from 1968, dates on the drivers. Both drivers are removable, Walnut cabs, but crossovers in the epoxy tub. Six's are great vintage two way speakers.

 

[RockinRonnie]

Good to know, I wouldn't have thought of that (the dust cap). Just looked at them and they are already black. Any chance they were already "doped" by someone in the last 50 years? Or did they come that way? That epoxy tub removal and the full sand down of the old veneer you did sounds like a rewarding challenge. Looking forward to hearing them when they are all done! I had two sets of speakers that I spent a lot more on than my Dynaco A25's.... when I A/B'd them the A25 beat both pairs and a lot of AK er's have posted the opinion the sixes are significantly nicer than the A25's.