Restoring KLH Model Thirty-One Speakers

[gelid]

I am restoring a pair of Model Thirty-One speakers and discovered right away that the woofers don't look original.

Can someone please tell me if this woofer is possibly the original for this KLH Model Thirty-One?

I don't believe it is, but I'm new to vintage speakers and know manufacturers sometimes substitute components for various reasons. Both speakers have this same unmarked woofer. No name... no number... nothing printed or stamped on them anywhere. They look nothing like what I have seen.

[dxho]

That's a replacement. The original (according to an auction listing) looks like
most KLH woofers from that period- cloth surround, big square magnet.

[gelid]

34 minutes ago, dxho said:

That's a replacement. The original (according to an auction listing) looks like
most KLH woofers from that period- cloth surround, big square magnet.

Thanks for responding!

There were two 8" x 8-ohm KLH woofers posted there by two different sellers; Last night I bought that one in your photo, and after reading this I just bought the other one.

The tweeters look original, though they didn't seem to be working. The capacitor and the other component in the wiring (sorry... I'm still learning!) both look new, and there is no physical signs of damage like on the woofers, so I'm hoping that will get sorted out when I install the original woofers and figure out the wiring.

[gelid]

I have another question: If these are 8-ohm impedance speakers, then why is there a 4-ohm resistor in each speaker?

 

[dxho]

That value of resistors is apparently a requirement of the crossover. It's not an
issue for the impedance of the speakers.

[JKent]

Hey gelid. A belated welcome!

While you're in there please take a photo of the capacitors. If they are the black Callins or Temple brand with red ends and red leads they are junk and need to be repaired.

-Kent

[gelid]

There is no manufacturer name on them (TI is all) but they are black with red ends and red leads... made in Mexico.

 

[JKent]

Yeah... they gotta go.

That kind of capacitor is notorious for leaking and going out of spec.

[gelid]

So, all the items needed for the restore project are ordered:

* Two 8-inch, 8-ohm KLH vintage woofers. One was specified as being
out of a KLH Thirty-One and the other didn't specify any model, but
except for missing the grid-pattern of sealant on the cone face, it looks
identical to the other one. If it's not an exact match, it's still better
than nothing. 

* Capacitor (2): Dayton Audio PMPC-4.0 4.0uF 250V
* Resistor (2): Dayton Audio DNR-4.0 4 ohm 10W

* Cloth-surround sealant for vintage acoustic suspension speakers.

The cabinets and grills are in beautiful condition, and need no
work what-so-ever.

I know these are the absolute runt of the KLH litter, but I hear they still sound great in a small setting, with a very smooth, unobtrusive sound.

They are what came along at the right time, and at that time seemed to need very little work. They will be perfect for what I will use them for.

I even have stands that, aside from being a bit too high, are perfect for their size. I need to cut them down a bit to add weight to the bases anyway.

[gelid]

I now have both 8-inch 8-ohm KLH woofers. The two are almost identical.

As I said before, one is definitely out of a Model 31... the other is a mystery, with a date stamped in blue ink: "JAN 27 1969"

Without seeing the voice coils, the only differences between these two are the voice coil spider. The Model Thirty-One has one more ring that the older woofer has, and the rings are shaped slightly different. Hopefully that doesn't mean a completely different voice coil. Still, it'll be better than nothing.

I don't know what purpose the grid-pattern on the cone face serves, but aside from that and the spider underneath, these look identical.

I'm still waiting for electrical components from PartsExpress so no sound test yet, but if they don't sound the same I'll still use it until I find another Model Thirty-One or Thirty-Two woofer.

[JKent]

On 3/15/2018 at 1:21 AM, gelid said:

I don't know what purpose the grid-pattern on the cone face serves

Both Ar and KLH used this cross-hatched (aka "hot cross buns" or "tic tac toe") pattern to add some damping to the woofers. I doubt you will hear any significant difference between the two woofs.

Good luck with the rest and keep us posted.

-Kent

[gelid]

On 3/16/2018 at 12:11 PM, JKent said:

Both Ar and KLH used this cross-hatched (aka "hot cross buns" or "tic tac toe") pattern to add some damping to the woofers. I doubt you will hear any significant difference between the two woofs.

Good luck with the rest and keep us posted.

-Kent

As you stated, Kent, I did not notice any difference between woofers, significant nor other.

I finally received the resistors and capacitors from PartsExpress yesterday, so after work last night I swapped those in, then mounted the stock woofers and whamm! what a beautiful sound!

I am more than pleased with these Model Thirty-Ones. They sound... smooth, like a Shure V15 phono cartridge. The tweeters are the dominant component here. There is more mid-tone coming from them than there is from the woofers, from what I hear, and they sound sooo good.

As luck would have it, immediately after my previous post I spotted a new posting on the auction site. It was for a single Model 32 speaker, working great, and for $20.00. Got it.

It arrived this morning. I swapped the mystery woofer with this 32's woofer (I know for sure these are the exact same woofers) and I now have a complete, correct pair of KLH Model 31 speakers, serviced and looking and sounding great.

Posted the donor Model 32 on the auction site, specifying the substituted woofer, for $25.00 or B.O.

[gelid]

Thank you everyone here at The Classic Speaker Pages forums. I could not have done this without you. What a wealth of info you have here!

Restoring these KLH Model Thirty-Ones has been a rewarding experience, to say the least.

I started out with very good looking exteriors, but non-funcioning tweeters and non-KLH woofers with disintegrating foam shrouds. I think they were also tripping a safety-circuit on the Pioneer's amp, as the sound was cutting out, then in after a few minutes of listening. Yeouch! Didn't leave it on long enough to track that one down.

I obtained two original woofers and replaced the capacitors and resistors (one in each cabinet). No soldering, just wire nut connections. I simply duplicated what was there.

Getting two woofers from two different sources, I was skeptical they would sound similar, but they are well matched. I also bought some sealer for the cloth surrounds, thinking I would need to re-apply. Turns out the sealant on them was still tacky, so I didn't use it.

All I have to compare them to are my Klipsch R-15m 85w bookshelf speakers, as they are what I normally run with the big Pioneer system (SX-850 receiver, PL-71 TT). I don't know the rated wattage of the KLH 31's. Although I know they are very entry-level for the KLH line, I really don't know what brands and models ("class") they should be compared to. 

The first thing I listened to was "All Through The Night" by Cindy Lauper. (Don't judge me! It's just what was on the radio when I turned it on!) Turns out, it is a pretty good test song as there is a wide dynamic range, and lots of stereo action (little keyboard action on the left.... drum or other effect on the right...) After that it was "Beat It" by Michael Jackson. Still impressed with my new speakers. Next, I put on some vinyl: the Brothers In Arms album by Dire Straits. Side one, beginning to end.

All three listening tests were of similar results: The KLH Model Thirty-One's are a very good speaker, worthy of restoration.

It's my perception that they are a warm but precise speaker. Typical to what I've been reading, the bass is just a little bit light. It's all there... just that I hear it more than feel it. It's not an annoyance, just an observance. The mids and highs are pleasingly well-balanced.

I was most impressed with the soundstage, second only to very detailed mids, as the music actually felt three-dimentional. I wasn't just hearing the music, I was experiencing it. It was materialized there in the space in front of me, between the speakers.

So there you have it. My restoration and review of these budget KLH Model Thirty-One speakers. They sound great and were worth the time and effort I put into them.

I will be pairing them with my KLH Model Twenty-Seven stereo receiver, and Philips GA-427 turntable, which is my next restore job.

[JKent]

Nice write-up of a worthy restoration. One suggestion would be to do the woofer-push test to check for air leaks. Put 3 fingers on the cone, just outside the dust cap, and push in. The cone should return slowly. If it pops right out you have an air leak (which could decrease the bass) and may need to use that surround sealant.

The Model Twenty-Seven is a nice receiver

• FM-AM receiver, all transistor; AM/FM vernier dial tuner.
• Designed by Henry Kloss in the mid 1960s.
• Power output was rated at 30 watts RMS per channel.
• List price was $325.
• This was Kloss's first attempt which led to the Advent 300

I've had 2 of these and based on that admittedly limited sample I'd say they have age-related issues. I sold the first one but took the 2nd one to Tim at Bristol Electronics in Ho-Ho-Kus NJ (HIGHLY recommended technician!) for the electronics work. I think it will be an excellent receiver to use with your Thirty-Ones.

If you now have the KLH bug you may want to look into the Model Seventeen, Twenty-Three, Five and Twelve (in ascending order of preference). The Seventeen is another nice 2-way. The Twenty-Three is a step up with its a bigger cabinet and bigger woofer. The Fives are among my favorite speakers, designed to compete with the AR-3a. Twelves are basically Fives in much bigger cabinets with a cool external adjustable crossover "Contour Control". Model Twelves can sometimes be bought very cheap because they are cumbersome to move and have a low WAF.

Here's my Twenty-Seven atop a Twelve.

[gelid]

On 3/18/2018 at 11:57 AM, JKent said:

One suggestion would be to do the woofer-push test to check for air leaks. Put 3 fingers on the cone, just outside the dust cap, and push in. The cone should return slowly. If it pops right out you have an air leak (which could decrease the bass) and may need to use that surround sealant.

Here's my Twenty-Seven atop a Twelve.

Thanks for the tip. I pushed in the cones like you said, and they pop right back out. I found a Youtube video of someone performing this test, so now I know what it should look like.

Your Twenty-Seven looks great! I can't find a photo of one in decent shape... they are either all banged up, missing the sides, or have missing and/or substitute knobs.

Mine was (and still is) immaculate... like the previous owner kept it in the box for decades. There isn't even any dust on the inside, and that is remarkable given the very porous grill that is the whole top panel! Here's my photo album of the whole thing, front to back: https://flic.kr/s/aHskuP1BoR

[JKent]

Wow! That's the nicest Twenty-Seven I've ever seen! Congratulations!

-Kent

[gelid]

Update: Sealed the woofer surrounds.

I ordered two larger-size bottles of the stuff recommended for just this application.

I did note that one speaker needed more than the other to pass the "push test". That's no suprise though, given they came from two different sources. They do have similar responses to the test now.

Let it be said for the record that this did change the sound. It improved the base as expected, but I also noticed a softening of the treble. Before sealing, I had stated that mids and highs were well-balanced. After re-sealing the woofer surrounds, I cannot say that for sure. I can only assume I had the tone controls at neutral before, but I'm not 100% positive.

No worries, though. I just turn the treble knob up to +3 instead of +1 where it normally was. After all, these are the runt of the KLH line.

It is a real treat to listen to these. I ended up keeping them with my Pioneer SX-850 receiver because they sound so sweet together! I like the look of the whole setup, too. I do need to build a shelf to set the turntable on, as I need to stack them due to the larger width of the Thirty-Ones.

These Thirty-Ones have come a looong way, but it was worth it all!

[JKent]

7 hours ago, gelid said:

These Thirty-Ones have come a looong way, but it was worth it all!

Nice job!

[ra.ra]

Hi gelid, that was a nice little project, and I'm happy to know they turned out so well. Not sure how I had missed this thread, but I just noticed you did make a comment in the thread about my KLH Thirty-Two's from a couple months ago. Very similar speakers - - sort of like first cousins.

Two other not-so-common small two-way models I'm interested in are the Thirty-Three (left) and the Thirty-Eight (right), shown in pic attached.

If you look at the end of this thread, you'll see a set-up with the Thirty-Three's and some Pioneer components very similar to your rig. 

http://www.audiokarma.org/forums/index.php?threads/klh-model-thirty-three.130713/

[gelid]

Thanks JKent

...and thank you, ra.ra! 

I'm studying very closely that photo you pointed me too. Specifically, the rack that person is using for the components.