Ngott

KLH 6 Speakers One No Sound after not using for 2 months

22 posts in this topic

I have a pair of KL6 Speakers purchased in 1975. All of a sudden one produces no sound (the other is fine). I checked

to confirm not an issue wit the channel on my amp by switching speakers. So the speaker is not working. Is there

away to find out if it is one one the two speakers or the speaker connection mechanism in the back? How hard

would it be to fix as seems very difficult yo open up these speakers and get internal access.

 

Thanks,

 

Neil

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Hi Neil and Welcome!

I'd suggest you look at the AR-3a restoration guide: http://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/restoring_the_ar-3a/

Your KLH Sixes are very similar in some ways. You may know that Edgat Vilchur and Henry Kloss started AR in the '50s to produce the revolutionary acoustic suspension speaker and in the late '50s Henry left to start his own company, KLH, in the same town making acoustic suspension speakers.

So... It's not hard to get inside IF the woofers are screwed in place (if epoxied, that's another matter). Follow instructions from the AR guide regarding removing the woofer. It seems unlikely that both the woofer and the tweeter would fail, or that the problem involves the crossover components. I'm guessing something came loose. The wires are held together with wire nuts, which are generally reliable but you never know.

Another possibility: KLH stupidly (IMHO) mounted the metal speaker terminal screws to a metal plate. There are insulating washers or grommets to isolate the machine screw terminals but if some deteriorated rubber or a stray wire is causing a short, that would kill the signal.

btw, there were a couple of versions of the Six: One had two terminals on the back for the speaker wire and the other had three, with a strap connecting 2 of the 3. This is the way AR speakers of that era looked. What AR did NOT do is epoxy the woofers in place. If you have the epoxied woofers you cannot remove them. Is that what you have?

Here is a thread by CSP member Glenn. Maybe he will chime in here http://www.audiokarma.org/forums/index.php?threads/just-picked-up-a-free-pair-of-klh-6s-from-original-1963-owner-pics.520806/  Glenn's speakers were a real horror show and he did an incredible job of reviving the cabinets. Presumably you won't have to do that but if you have the dreaded epoxied woofers he shows how to get inside.

Keep us posted (and maybe post a photo of the woofer so we can see which version you have)

-Kent

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Hi Kent,

 

Thanks for the response. The KLH 6's I have have 2 terminals in the back with a toggle switch for change to high, mid, low etc.

The Woofer is attached by screws (after removing the cloth grill). So Your suggestion is remove the woofer

and i can get to the back and see where the control is that the speaker wires attach?

I would think there is a failure there since both tweeter and woofer are not working.

Neil

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Good. You have the "easy" one.

I agree that the problem must be in the wiring (or a short as mentioned), probably at the input terminals. So yes--take the woofer out. Follow the AR-3a guide regarding the cloth behind the woofer and the fiberglass stuffing. You will also need some sealant for when you replace the woofer.

Once you have corrected the problem you may want to do a re-cap while you are in there.

-Kent

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Thanks Kent!

 

What type of sealant and what is a "re-cap"?

Neil

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Hi Neil,

Good luck with the adventure, and pics are always enjoyed on this forum!

The sealant that Kent references is some material to "seal" the backside of the woofer outer edge to the baffle. You may find a clay like product or a foam strip and then when you screw it back in place (after done with recap and other stuff) it creates an airtight seal.

A recap is replacing the likely old and tired original capacitors in the crossover with new replacements. Off the top of my head I do not know the values needed but can easily be found. The toggle switch can benefit from a good dose of deoxit as well before sealing them back up. Take a close look at the resistors as well, KLH did use some bargain basement stuff and these are also easily replaced.

How are your soldering skills?

Geoff

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Sorry. You're new to this.

The acoustic suspension cabinet has to be air-tight. Your woofer is sealed around the perimeter. They probably used Mortite caulk (I'm not sure about the Six--I've worked on the 5, 12, 33, 20, 17 and others). You can use one of several things:

  1. Duct Seal, available at home centers in the electric dept. It's cheap. It's like working with children's plasticene "modeling clay." You make a 1/4" diameter "snake" for the seal. https://www.lowes.com/pd/Gardner-Bender-1-lb-Pug-Duct-Seal/4595233
  2. Parts Express sells essentially the same thing, but already formed into the little snakes. http://www.parts-express.com/parts-express-12-speaker-sealing-caulk-box-of-72-pcs--260-400
  3. Parts Express makes very nice gasket tape http://www.parts-express.com/parts-express-speaker-gasketing-tape-1-8-x-3-8-x-50-ft-roll--260-540
  4. You may be able to get foam tape, similar to the PE stuff, in a home center. Just don't get anything too thick or wide http://www.frostking.com/install-foam-tape-weatherstripping-windows-doors/

A "re-cap" means changing the capacitors. This may sound daunting for a first-timer but it's pretty easy and will probably improve the sound. Your capacitors are 40+ years old. Capacitors ("caps") leak and go out of spec. Early KLH speakers often used Callins or Temple brand caps that were made of black PVC with red ends. Those are especially prone to leakage and should be replaced.

Here is a very good step-by-step write-up by Larrybody (also a CSP member) http://audiokarma.org/forums/index.php?threads/klh-model-six-restoration.632555/  He has the earlier type Model Six, which is much harder to get into, but the principles are the same. He used Dayton capacitors, which are good. He also replaced the resistors, which is not necessary. Resistors rarely go bad.

Your capacitors should be marked, something like "2uF" or "2 MFD". Those are 2 microfarad caps. It looks like the Model Six uses two 2uF and one 8uF per speaker. It's sometimes confusing with KLH speakers because sometimes they used double caps or parallel caps, so it may look like you need two 4uF caps when you really need one 8uF. Here's a thread with a schematic http://audiokarma.org/forums/index.php?threads/upgrade-crossover-for-klh-model-6.677433/

PE (Partsexpress) has these 2uF caps http://www.parts-express.com/dayton-audio-dmpc-20-20uf-250v-polypropylene-capacitor--027-414  and these 8.2uF caps (8.2 is close enough) http://www.parts-express.com/dayton-audio-dmpc-82-82uf-250v-polypropylene-capacitor--027-426  or you could do as others have mentioned and wire up some 4uF caps in parallel, but that's not at all necessary http://www.parts-express.com/dayton-audio-dmpc-40-40uf-250v-polypropylene-capacitor--027-421

Another good source for capacitors is Madisound. Their Carli caps are good and they're inexpensive. Here's the 8uF https://www.madisoundspeakerstore.com/carli-capacitors/carli-mylar-8-mfd/ They don't have a 2.0 cap (well, they do have a 2.0 surplus cap, which is fine but the leads are frustratingly short). You could use a Carli 2.2uF but that's 10% over spec. I'd probably use two 1.0uF caps in parallel.

All of these caps described above are film caps. They last longer than electrolytic caps and are generally preferred when it comes to these smaller values.

Hope this helps and doesn't fscare you off.

-Kent

PS: Looks like Geoff answered while I was typing. Good tip on the switch. Deoxit is also available from PE

 

 

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Here's another thread. This one shows newer crossover, like yours http://audiokarma.org/forums/index.php?threads/klh-model-six-rule.193462/ Look at post #23 in that thread. He gives a good explanation of replacing the "double" caps.

Notice the shiny metal plate. This is the culprit that can short things out.

In this thread, the writer used Sonicaps. Good caps but expensive and not worth the cost IMHO. He also left the original resistors (attached to the switch). Geoff is correct--KLH sometimes cut corners on resistors (IMHO) but as long as they are 10 watt (10W) and show no signs of scorching or cracking they should be fine. I have found some  5w resistors in KLH speakers and always replace those because I've seen 5W resistors that were scorched or even burned! Resistors are very cheap, so when in doubt replace. These are fine: http://www.parts-express.com/cat/wire-wound-resistors/303?N=19851+4294967118+4294963632&Ne=10166&Nrs=collection()%2Frecord[endeca%3Amatches(.%2C"P_PortalID"%2C"1")+and+endeca%3Amatches(.%2C"P_Searchable"%2C"1")]&Ns=P_BestPrice|0&PortalID=1

-Kent

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Kent and Geoff:

 

Thanks guys I will give it a try. To answer Geoff's question about my "soldering Skills", I used to build Heathkit equipment (if you remember that company). Built a color TV and my first stereo amp from Heath kit but that was a long time ago. But I never made  cold solder joint so we shall see!

My instinct says the capacitors went bad as I recall from old days those things had paste in them and prone to dry out.

Will give it a try meantime so I can listen to my jazz, ordered some Klipsch Bookshelf speakers (online). Not the best way to buy speaker without listening but no more stereo stores exist at least in NY. I wonder and will find out now if new speakers are better than the old ones but KLH has a nice audiophile warm sounds like my vinyl compared to my CDs.

Much appreciate the advice and information.

Neil

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Hi Neil

With your experience you will have no problem troubleshooting the speakers and re-capping. Although I'm sure the caps are out of spec I don't believe that would cause a sudden failure of both the woofer AND the tweeter. Of course, the tweeter may have gone a while ago and you didn't notice. Nonetheless, I'm convinced a wire is separated or shorted.

-Kent

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Through the front. Just remove the woofer & FG stuffing.

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Am I seeing Model six with RCA connections?

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9 minutes ago, DavidDru said:

Am I seeing Model six with RCA connections?

No. Follow the link to AK. The owner of those speakers replaced the terminals with banana jacks.

-Kent

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Ah, I was under the impression the photos were of Neil's speakers.

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Hi All:

 

First Happy New Year to all!

SO about my one KLH 6 not working. I unhooked the speaker wires, Toggled the back volume switch

re-connect and it started working again! Been working for a week. Anyone have any thoughts about this?

Neil

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26 minutes ago, Ngott said:

Been working for a week. Anyone have any thoughts about this?

Let sleeping dogs lie ;)

I'm going back to my original thought (post #2) that there is a short. The toggle switch "may" have some corrosion but that should only affect the tweeter. If removing and replacing the speaker wires caused it to go from no sound to sound I'm thinking there is an intermittent short, probably something touching that damn metal plate. Stupid design. It's possible one of the rubber insulating washers for one of the 8-32 machine screw speaker terminals is cracked or deteriorated, and sometimes the screw makes contact with the metal. Or some wire inside is touching the metal on an intermittent basis. Hate to sound like a broken record but if both drivers are cutting out it has to be a break or a short at or near one terminal screw. Any other culprit such as a bad driver, switch or capacitor would make only one driver (usually the tweeter) go out.

-Kent

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Kent:

 

Think you are right... both speakers went when stopped working. Now both working. Must be a short or corrosion back there. I noticed when I moved the speaker

it went out again. waited removed it toggled the switch and back on both tweeter and woofer are working. So I think your diagnosis is correct!

Thanks!

Neil

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On January 2, 2017 at 1:16 PM, Ngott said:

Kent:

 

Think you are right... both speakers went when stopped working. Now both working. Must be a short or corrosion back there. I noticed when I moved the speaker

it went out again. waited removed it toggled the switch and back on both tweeter and woofer are working. So I think your diagnosis is correct!

Thanks!

Neil

Hi Neil!

Great speakers and well worth the effort to get them restored and reliable.

Time to dig into these. Did you order the caps and woofer surround sealer yet? Two very important pieces of your project besides tracking down that short. When you check the wiring where it's screwed to the terminal plate, make sure those little fiber washers are between the plate and wires loop ends. When I restored my first pair, I forgot to put them back in and upon the first test, no sound! Discovered they were missing, replaced them, and all was good.

BTW, I'm in Westcherter as well, in Peekskill, where are you?

Glenn

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Hi Glenn:

Thanks for the advice. I just bought some Polk Floor Speakers and they atuall sound good and pair well with my wall speakers.

So I might "retire" the KLH 6s after 40 years. As much as that is a big change for me to do! I am over in White Plains.

Neil

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Might want to think twice about retiring those Six's. After several months of having mine on the sidelines(I bought a pair of AR 3's, then a pair of 3a's, and that 4some became my regular setup) I decided to put them back in tonight paired with my McIntosh MAC 4100 receiver. Wow. Just as buttery smooth as I remember. Lovely presentation, different but not less then either of the big AR's. I will never give them up. 

I would heartily recommend that you to get your's checked out and restored. I'm sure the Polks are very nice, but the Six's are something special, and when right, not many speakers sound better, imo. 

 

0114171734.jpg

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Agreed, and with a restoration (caps and sealant) the six's may very well get back to a level you didn't realize had eroded over time.

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