KLH model 6 tweeter

[KeithD]

In the process of rehabbing a set of "sealed" cabinet KLH model 6's. First one went great with recapping bringing back the tweeter, which had no sound before.

However, tweeter in other speaker did not come back with re-capping. Measured the resistance of the tweeter and got 4.6 MΩ, so no surprise I have no sound. Can these be reconditioned, or do I need to replace it? If i need a replacement, what KLH models used the same tweeter? I cut the speaker cloth to access the front to see what I have, and it is the screwed in version of the tweeter.

 

[alteclipsch]

Others will chime in here, but they can sometimes be repaired. Removal of the front mesh will show if there is a broken fine wire. If this is the case, there may be enough wire at each end to put a tiny glob of solder to rejoin them. I and others here have been able to do this repair and salvage a great tweeter. If it's the voice coil it's probably curtains. The fact that there is a reading at all suggests (to me at least) a partial connection, which IMO points to the voice coil. I would take off the mesh and have a look. I've done several over the years with good results.

Here's a shot of a wire from a Seventeen that had broken at the solder joint where the wire is embedded in the bezel. I maneuvered both ends to a connection, soldered them, and re-bedded the result. Worked slick. I've wondered if the break happened at the factory since it was a bedded connection, or a corroded joint.

 

[spark1]

How did you measure the resistance?

 

[alteclipsch]

How did you measure the resistance?

I should have asked that before suggesting a repair effort!

 

[Dswankey]

Thread title say KLH Model 6, your initial post says 5 you might want to edit that so there's no confusion.

On another note the grill cloth does not look original for those early model Six's.

 

[KeithD]

How did you measure the resistance?

I disconnected the wire on the tweeter that connects to post A and the woofer, then measured resistance between that wire and the other one that connects to the 8 µF cap.

 

[KeithD]

Thread title say KLH Model 6, your initial post says 5 you might want to edit that so there's no confusion.

On another note the grill cloth does not look original for those early model Six's.

Thanks, made that correction. Working on too many speakers at once!

As far as the grill cloth, it is two layers. The black you are seeing is the bottom layer, the top layer is a cream color, very open weave.

 

[KeithD]

Others will chime in here, but they can sometimes be repaired. Removal of the front mesh will show if there is a broken fine wire. If this is the case, there may be enough wire at each end to put a tiny glob of solder to rejoin them. I and others here have been able to do this repair and salvage a great tweeter. If it's the voice coil it's probably curtains. The fact that there is a reading at all suggests (to me at least) a partial connection, which IMO points to the voice coil. I would take off the mesh and have a look. I've done several over the years with good results.

Here's a shot of a wire from a Seventeen that had broken at the solder joint where the wire is embedded in the bezel. I maneuvered both ends to a connection, soldered them, and re-bedded the result. Worked slick. I've wondered if the break happened at the factory since it was a bedded connection, or a corroded joint.
View attachment 2295756

Does the wire mesh just pop off, or how does one get that off? Just don't want to damage it.

 

[alteclipsch]

The stuff they used to attach the mesh doesnt give up easily. Some folks use heat at the edges to soften it, I scored it with a knife and pried it loose all around the edge. Its really soft and does deform, but its so malleable that it will smooth out perfectly. I used an espresso tamper to reform it and bedded it in mortite rope caulking.

Here it is after reforming:

 

[Dswankey]

As far as the grill cloth, it is two layers. The black you are seeing is the bottom layer, the top layer is a cream color, very open weave.

That's right!, my bad

 

[KeithD]

Since I was able to unscrew the tweeter, I pulled it out and measured resistance completely disconnected.



As you can see, I was reading 17 MΩ and rising. It just kept going up continuously.

 

[KeithD]

Not seeing any broken wires on the tweeter, but one has some kind of green corrosion (?) where it is glued down on the tweeter (?). Any advice on this would be appreciated. Just wondering if there is something I can do to salvage the tweeter?

 

[KeithD]

Had time to take a closer look at the corrosion on that wire. I just moved it slightly and the wire came right off at the corrosion point!

I was able to scrape some of the "glue" off that area where the break occurred and find the other end of the wire. Put a dab of solder on there, and the tweeter measured 4.2 Ω.

Hooked it back up and I've got sound through the tweeter! So it appears the wire was not completely detached, but corroded enough to greatly increase the resistance.

I'll mount the tweeter back in and then re-seal the woofer. Then the challenge will be re-attaching the grill cloth. I'm thinking I will stretch it from the opposite side that is still attached and attempt to glue it down with some craft glue. Then I can stretch the top & bottom and glue them in. Might need to do the black under cloth first and then repeat the process for the cream outer cloth. I'm open to other ideas if anyone has some. Anyone done this before?

 

[alteclipsch]

Well, there you have it, good on you! Always great to hear of a timepiece rescued .

 

[KeithD]

Used a flathead screwdriver to flatten the edges of the tweeter wire mesh, then used a hard roller to smooth out the whole thing flat putting a shop cloth over the mesh.



Cleaned out the gulley around the tweeter where the old caulk had been, then used one rope of Mortite to seal in the mesh.



Reinstalled the tweeter and put the rest of the insulation back in. Screwed on the back plate with a foam seal.

 

[hornbostel]

Thanks, made that correction. Working on too many speakers at once!

As far as the grill cloth, it is two layers. The black you are seeing is the bottom layer, the top layer is a cream color, very open weave.

Yes. Outside looks like this, my pair, ~10k earlier SN as the OPs. When I got my 6s neither tweet worked. Recap through the back brought them back to life. I haven’t redoped the woofer surrounds because I just don’t want to cut into that grill fabric!

 

[KeithD]

View attachment 2297997
Yes. Outside looks like this, my pair, ~10k earlier SN as the OPs. When I got my 6s neither tweet worked. Recap through the back brought them back to life. I haven’t redoped the woofer surrounds because I just don’t want to cut into that grill fabric!

Yes, I'm still mulling this over. It will be easy to reattach the black cloth as it is stiffer, and really does not need to be stretched. Any small gap would be concealed anyway. I'm thinking I will either glue the edges or staple them every several inches. I think this mostly needs to be done along the top and the side. I don't see any need to attach it at the bottom.

The outer cloth is a bigger challenge. I think there are two options. My wife suggested making a small frame that will fit inside the cabinet frame to hide any frayed ends and any gap between the cloth and edge. What I'd prefer to do is carefully glue the top edge down to the black cloth/front baffle. Then work my way along the side, stretching and gluing down. This might leave a gap on the bottom, but maybe that will be less noticeable than if it were at the top or the side. It will be tricky, but I don't have anything to lose. The alternative is to cut the cloth out completely, buy new material and either glue that in, or make a backer board with the requisite holes for the woofer and tweeter - pretty much like the later versions of the 6. The other speaker came to life with just a recap from the back, so that grill cloth is in tact. I re-sealed the woofer on the one I cut the grill cloth. I'm not noticing a significant difference in sound, so as of now I'm not planning to cut the first grill cloth to re-seal that woofer. Wish me luck!

 

[GD70]

Yes, I'm still mulling this over. It will be easy to reattach the black cloth as it is stiffer, and really does not need to be stretched. Any small gap would be concealed anyway. I'm thinking I will either glue the edges or staple them every several inches. I think this mostly needs to be done along the top and the side. I don't see any need to attach it at the bottom.

The outer cloth is a bigger challenge. I think there are two options. My wife suggested making a small frame that will fit inside the cabinet frame to hide any frayed ends and any gap between the cloth and edge. What I'd prefer to do is carefully glue the top edge down to the black cloth/front baffle. Then work my way along the side, stretching and gluing down. This might leave a gap on the bottom, but maybe that will be less noticeable than if it were at the top or the side. It will be tricky, but I don't have anything to lose. The alternative is to cut the cloth out completely, buy new material and either glue that in, or make a backer board with the requisite holes for the woofer and tweeter - pretty much like the later versions of the 6. The other speaker came to life with just a recap from the back, so that grill cloth is in tact. I re-sealed the woofer on the one I cut the grill cloth. I'm not noticing a significant difference in sound, so as of now I'm not planning to cut the first grill cloth to re-seal that woofer. Wish me luck!

Or, just look for removable grills from slightly later models on fleabay. That’s what I have on mine, exact fabric as the original.

 

[KeithD]

Or, just look for removable grills from slightly later models on fleabay. That’s what I have on mine, exact fabric as the original.

That's definitely an option. For now I stapled the black under cloth in a few places just to hold it in place.



Then stretched and hot glued the outer cloth grill as best I could. It went ok, not great, not terrible. Certainly looks "used", but could be worse.



For now I am just going to enjoy the sound. I'm A-B comparing these mid-60's model 6 with the later ones I have. I agree the sealed woofer models have a bit more bass. In either case the sound is amazing! Well worth saving. My friend was either going to take them to the dump or cut them up and re-use the wood from the cabinets! So glad he passed them on to me. It was a great project this past week! I used the caps I had purchased to re-cap the later 6's, so now I'll have to order another set to do those.

 

[Bodyblue]

I have a later set of 6s. One of mine was blown apart by a dying STK module so I had the woofers rebuilt by a local guy who works his magic......he rebuilt them with modern foam and they sound great. But the gross old speaker fabric really bugged me so last year so I ordered grill cloth from an online store that sold fabric for guitar amps. It is black and gold but looks greenish with sparkles. I ordered a new set of badges from ebay and they came out nice I think.