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Trying to use KLH model 31's need to buy stuff please help

George P

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I saw a thread on here about a model 31 restoration, which gave me hope.

long story in 1 paragraph on these: I bought these forever ago like in 1998-1999 as a teen at a thrift store for $20 that included a kenwood turntable. (wish I could find deals like that again).
I put them up for sale years later (on ebay ugh) but the winning bidder only wanted the woofers (odd to me at the time but ok). Double my money back and still had like 90% of the speaker, cool.
I had purchased (better at the time) decent pioneer 3 ways. tall. big. loud etc. that came with a block party 80's LXI amp that I also pulled out and want to use today.. (don't judge just yet, it's made in japan, 190 watts and has built in 5 eq slider frequencies, that if i remember correctly worked well). 
The poor Klh sat in my room and then a basement for about the last 10 years. I pulled them out and have had them airing out on the sun porch I have in my apt.

they have gotten better but still smell musty.   Any tips on how to get this out? 
and is that fiberglass in there?  I poked my hand around and don't see any wires coming out for the speaker just yet, but now my hand feels like it's getting stabbed by a needle every so often.. ha.
The grills are in decent shape but could probably use a cleaning, any recommended sprays or process for this? Woolite spray cleaner?
Out side cabinets are presentable. I'd rather the speakers sound good then look good, if I had to choose one or the other.

Important spec questions:
So I need to order some odd size KLH 8" woofer (really 8.25 outside diameter measured not 8..) and the inside hole is 7.125"  not 7".. 
I actually found these: https://www.parts-express.com/goldwood-gw-8pc-8-8-delmar-series-heavy-duty-woofer-8-ohm--290-314
they are power hungry but they are the right size and ohm and frequency range I want. So I 'd like to order those.
the tweeters in the KLH should be fine they worked last I had them running.

I noticed that it is recommended to replace the resistors and capacitors?
that thread used:  Capacitor (2): Dayton Audio PMPC-4.0 4.0uF 250V  and    Resistor (2): Dayton Audio DNR-4.0 4 ohm 10W
would those work for me? he had vintage klh woofers to put in, I do not, I'd like to buy the ones above (unless someone has a better similar priced option?)

also what is the difference between "precision audio capacitor": https://www.parts-express.com/dayton-audio-pmpc-40-40uf-250v-precision-audio-capacitor--027-226?utm_source=google&utm_medium=cpc&utm_campaign=pla&gclid=EAIaIQobChMIn76I04fX4wIVBJ6fCh2xdAr3EAQYASABEgJk4PD_BwE

and polypropylene capacitor: https://www.parts-express.com/dayton-audio-dmpc-40-40uf-250v-polypropylene-capacitor--027-421?utm_source=google&utm_medium=cpc&utm_campaign=pla&gclid=EAIaIQobChMIn76I04fX4wIVBJ6fCh2xdAr3EAQYAiABEgLeWvD_BwE

this is the resistor that I would get: https://www.parts-express.com/dayton-audio-dnr-56-56-ohm-10w-precision-audio-grade-resistor--004-5.6?utm_source=google&utm_medium=cpc&utm_campaign=pla&gclid=EAIaIQobChMI2JDmsrTY4wIVBJ-fCh0YOQ3OEAQYBCABEgK3MvD_BwE

would I just cut out the old and solder in the new? soldering inside a fiberglass speaker box might be above me. I've only soldered a few wires before on an open guitar..
I don't even have the iron anymore I don't think. There is (amazingly) a local audio electronic repair place, I could ask them, let them do it, or watch a you tube video.


I don't know much about electronics, but I do know different resistors and capacitors work better and worse depending on what you have and want to get, so if anyone out there knows if my choices are good or bad please let me know. also if you have any suggestions on a better capacitor or resistor let me know (and maybe explain why if you have the time, thanks in advance).

I will post some pics if you want?

Thank you ! for any info or help.

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Hey George. A belated welcome!

I "had" some 31s for a while. They're OK speakers but I wouldn't spend a lot to restore them. Mine had a bad tweeter and I ended up parting them out.

Yes. That is fiberglass. Put on some gloves and pull it all out. Save it in a plastic bag (1 for each speaker). There should also be a bit of cloth in the woofer opening to keep fiberglass out of the woofer. If it's missing you can replace it with a thin layer of fiberfill (I'll find a link somewhere).

You can probably clean inside the cabinet when it's empty with a dilute solution of bleach and water. Or hydrogen peroxide. Or any disinfecting spray cleaner.

Trouble with cleaning the grilles is once wet, stain can bleed through from the fiberboard or masonite panel. You could try but I'm not optimistic. A good replacement cloth can be found at Michael's craft stores: CharlesCraft Irish Linen in "tea" color. It's in the needlepoint section. Costs $8/roll but they always have 40% off coupons. Not sure if one roll would do it.

Any classic KLH 8" 8 ohm woofer should be OK and will give you more authentic KLH sound than any aftermarket replacement. I'll attach a photo of the originals. I think the Models 22,, 24, 25, 26 and 31 and 32 (maybe) all used 8" woofers (The 10" seem to be much more plentiful). Be sure the woofers look like the ones below: brownish cones and cloth surrounds. Also ask the seller to check the outside diameter. You said yours are 8.25" O.D. KLH speaker sizes were kind of creative. The so-called 10" woofers were under 9" IIRC. There's a Model Twenty woofer on ebay right now, described as 8" but the Model Twenty woofer was what KLH called 10". And although there is an "index of classic KLH products" in our Library, it has some inaccuracies. Here's a list that's pretty good: http://www.aphenos.net/electronics/speakers/klh/all_klh.htm and a lot of useful info here: https://audiokarma.org/forums/index.php?threads/klh-speakers-reference-thread-original-models-1957-1977.765372/ Here's a quote from that thread: "The Twenty Two, Twenty Four, Twenty Six, Thirty One, and Thirty Two systems are very similar, available from the late 60s to the early 70s. There were differences in rear connectors, tweeters, and cabinet finish." So they all used the 8" woofer.

Resistors don't go bad. Re-use the old ones.

Either of those Dayton caps will be perfect. There is no appreciable difference.

I don't have a pic of the crossover but yes--take out the old capacitor and solder in a new one. If you aren't sure about soldering you can use crimp connectors or even small wire nuts. Post a photo of the xo if you can. Resize it to about 100K-ish.


KLH31woof back.jpg

KLH31 woof front.jpg

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hi! thanks for the info.

I didn't see any model 20  10" woofer listed as 8" on ebay.   do you mean this one?:  https://www.ebay.com/itm/Nice-Pair-KLH-Model-20-Woofers-Very-Original/333140637789?hash=item4d90bab85d:g:PH0AAOSwe9VcTtH4

I took pictures but then realized you probably meant the back plate stuff where the speaker wires from the amp go to.?   I was not 100% sure what you meant about cross overs.
I know what they do and the function but have never seen or looked at one. ha.

once I get a better pair of gloves and some proper sized bags, I should be able to see everything I'm guessing.

I'm not against searching for a 8" KLH woofer set, I'm also not against buying a new (non KLH) woofer either. As I remember they were a little muddy and lacked some bass.
maybe a recap would help that?

I also noticed a little black hexagon stamp on the back, I can faintly make out a KLH and a 16? 19? I dunno I never noticed it before, ever see one?
and this webpage seems to auto rotate my pics.. which is not good because I already rotated them correctly. Appears it is set to have the longest side = horizontal axis  automatically I guess, which for some of my pics is not correct, bear with the neck turning. Also the white cloths are there.

thanks again

inside 1.jpg

inside 2.jpg

inside 3.jpg

out 1.jpg


out 3 label.jpg

stamp on back.jpg

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The ebay listing was "Vintage KLH 8" Woofer & Tweeter & Crossover For Model 20". The 20 used a 10".

Your pics do show parts of the crossover. The crossover consists of capacitor(s) and resistor(s). Maybe an inductor, too. Once you pull out all the yellow fiberglass you'll see it better. And save that off-white cloth.

That black capacitor is junk. The resistor is 4 ohms/5 watts. I usually replace 5 watt resistors with 10 watt but the one you linked to is 5.6 ohms/10 watt. I'm having trouble pasting a link, but search Parts Express for "4 Ohm 10W Resistor Wire Wound 5% Tolerance" You probably don't need it. Most respected members here say the 5w is fine but for less than a buck apiece, I usually replace the 5w with 10w.

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22 hours ago, JKent said:

The ebay listing was "Vintage KLH 8" Woofer & Tweeter & Crossover For Model 20". The 20 used a 10".  

ok found it. (thank you), but $65.00 for only 1 woofer is not exactly what I want to do. I can get the 2 new ones for that lol.


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1 hour ago, George P said:

ok found it. (thank you), but $65.00 for only 1 woofer is not exactly what I want to do. I can get the 2 new ones for that lol.

My point was, the Model 20 woofer is being incorrectly described as 8”. Be careful if you buy a used KLH 8" woofer. Recent ebay sales show 8" originals went for $20 and $25 each.

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The 8-inch woofers from my KLH Thirty-Two's have the following measurements:

* basket, outer diameter: 8-1/4"

* screws, center-to-center: 7-3/4"

* cone, outer diameter: 5-1/2"

* DC resistance: 4.7 and 4.8 ohms

There is currently a pair of these woofers (online auction), dated 1969, for sale in New Jersey with a starting bid less than a Hamilton. Seller notes them as 6-inch, but that's probably a cone dimension estimate. Take a look, ask for more info from seller, and see if you can negotiate shipping expenses.



woofers ebay.jpg

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On 8/2/2019 at 11:54 AM, ra.ra said:

The 8-inch woofers from my KLH Thirty-Two's have the following measurements:

* basket, outer diameter: 8-1/4"

* screws, center-to-center: 7-3/4"

* cone, outer diameter: 5-1/2"

* DC resistance: 4.7 and 4.8 ohms

There is currently a pair of these woofers (online auction), dated 1969, for sale in New Jersey with a starting bid less than a Hamilton. Seller notes them as 6-inch, but that's probably a cone dimension estimate. Take a look, ask for more info from seller, and see if you can negotiate shipping expenses.


yes my cabinets measure about the same! I thought these were 8ohm speakers tho ??
THANK YOU for the ebay heads up, I did email the seller just now about dimensions and shipping.
I'm not too far away from that spot in NJ but far enough from there like 4 hours to be unmotivated to pick up item.  ha



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4 hours ago, George P said:

I thought these were 8ohm speakers tho ??

You are correct - - the nominal impedance rating for this speaker model is 8 ohms, but actual DC resistance measurements for individual drivers are typically less. I believe that auction listing shows a measurement of 4-something ohms in one of the pics, which is reasonably consistent with my notes above. Additionally FYI, my tweeter measurements are 6.3 and 6.7 ohms, and all drivers function properly.

Good to know you may try to nab these, because if you didn't, I may know someone who would. :ph34r:

Keep us posted.

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  • 2 weeks later...

yea someone tried to bid them up, but I still won for a decent price.
they have arrived and are in working shape as far as I can tell


I took the tweeter out of the one so I can get better access to twist new capacitor in.
I am fortunate to live in an area with a lot of electronic manufacturing so my city has not 1 but 3 electronic stores..
I was able to get all the pieces needed for under $5.00 locally (includes twist cap wire things and NY tax, not bad at all and instant, maybe I should have got the crimp joiner things now that I'm looking at it).   There is some white powder caked onto the back of the tweeter, I can't tell what it is.
There was some thin foam/Styrofoam pieces to protect the tweeter from the wood cab and top paper piece thing.. interesting.


I wiped the box out with bleach and paper towel.. it still smells musty..  any other ideas?

Also I need help rewiring them.. since I had no woofer to take out and look at for reference.
(now all of a sudden all of the pics are vertical aligned on this post... so time to cramp your neck)



so.. There is a big round thing and it looks like it is wrapped in copper wire.
There are 2 bare copper wires coming out of it. 1 goes to positive incoming line which then goes to a capacitor and then to the tweeter. So I'm guessing the incoming positive signal comes in and meets the 1st bare copper wire and that brings the signal to the big wound up thing and then the 2nd bare copper wire goes to the positive on the woofer?  (I'm guessing here),   then the same signal is also sent through the capacitor to the tweeter positive.

The ground is coming in and twisted to the resistor and then after the resistor it is twisted to go up to the tweeter negative ground terminal. should this bundle before the resistor go to the  woofer negative ground or should the incoming black wire go to the resistor 1st then the woofer and then up to the tweeter?

I find it odd that it is already capped off. I did not do this. I just cut out the woofers and mailed then out as far as I remember.

It's possible but unlikely I put these black wire caps in here but I do plan to use them and maybe return the ones I bought at the store.

That said, I only have about an inch (less than an inch) of spare wire coming out of the woofers I got on ebay to connect them. This may or may not be enough to put one of those caps to. Can I just twist it together and leave it as is?  What is the danger in that, if any?

thanks for any info on wiring.

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The white powder "may" be cadmium dust so be careful with it.

The foam behind the tweeter is a gasket and it's probably too compressed so you'll have to use either foam gasket tape from PE or duct seal or cut a new gasket from a foam sheet from a hobby store like Michaels.

The big round copper wire coil is the inductor and it should not be changed. The bare wires are not bare--they are lacquered for insulation. Be sure the lacquer is scraped or sanded off at the ends to make electrical contact.

The black wire is common (ground). The wire splits before the tweeter. The wire to the tweeter goes through the resistor (not the woofer).

You need the caps on your connections so the bare wire doesn't short against metal (like the woofer basket).

The drawing below "may" be accurate. I'm hoping ra.ra or others will comment.



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10 hours ago, JKent said:

The drawing below "may" be accurate.

As far as I can tell, Kent, your schematic looks entirely accurate. The speakers I worked on were model Thirty-Two, but very similar. My schematic is attached, and while you can see minor differences, the basic circuit construction is the same as the Thirty-one, and my sketch shows wire nuts just like yours. My speakers used an iron core inductor, but did not include an added resistor for the tweeter. Instead, my tweeters have alnico slug magnets and originally used some external fiberglass damping to tame or shape certain driver characteristics. 

11 hours ago, George P said:

....but I still won for a decent price.

Glad to hear about this, George :) - - I was following that auction and had mistakenly thought that you were outbid. For the cabinet interiors,  you've probably done enough - - now just let them air out a bit before re-stuffing them. For the powder dust on tweeter magnet, I usually wipe down with paper towel dampened with white household vinegar. About the (extremely) short woofer wires, you'd be well-served to solder on a couple longer ones. And for re-wiring crossover, I can't follow all of your observations and comments, but if you re-wire per Kent's diagram, you should be just fine.

Please report back with progress or additional questions.  

KLH 32 schematic.jpg

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