KLH Model Thirty-Two Loudspeaker

[ra.ra]

I'm wading into relatively unfamiliar territory here (the KLH forum), but am just posting this for general interest, information, curiosity, analysis, and/or critique.

Walking home a week ago from the bus stop one block away, I spotted a heap of discards in the front yard of a house six doors down from my home, which included these speakers sitting on a dry spot amidst the remaining piles of snow. I do not need any more speakers - - and besides, I'm mostly an AR guy - - but there was no way I was about to pass on these freebies.

These are the simple KLH Thirty-Two model, two-way speaker with an 8" woofer, circa 1973. Serial numbers: 97725 and consecutive 6. For size reference, see pic here adjacent to AR-6 and AR-4x. The cabinets were nearly entirely intact and the no-badge grilles showed only aged discoloration and some minor damage, so I tucked one under each arm and trudged them off to a new home. 

With the cooperation of a couple of mild weather days, I was able to get these to nearly full restoration within a couple days. Complete disassembly, rear terminal repaired, cabinets sanded and partially refinished, baffles painted, woofers re-doped, crossovers re-capped....and so on, with a few details omitted. 

The original crossover had a single 4uF (Temple) cap in the tweeter circuit and what I believe is a 1.0 mH coil for the woofer. The internal wire is very light gauge, and connections are made with wire nuts. There is no tweeter control or switch. Cabinets are robust but very basic construction with good quality veneer, no T-nuts, and are densely packed with pre-sized fiberglass batts. Woofer appears to be typical KLH design - - stamped metal basket, inverted heavy cloth surround, square magnet, yellow-brown appearance with eight screws. Cone tweeter measures about 2 inches and seems of good quality, originally installed with outer fiberglass damping and wire mesh protective screen.  

When I first hooked up the restored speakers, I was somewhat disappointed, particularly with HF output. Soon I realized I may have a small problem with my 80's NAD pre-amp, since I was hearing this scratchy, static-y, grating noise behind the music. But after re-wiring the pair to a 26-watt early 70's Sherwood receiver, I was pleased to discover that these are extremely good yet humble speakers. The bass output from the 8" woofer is indeed impressive, and I'm still trying to determine the best use of the tweeter damping concept. Right now I'm playing them "naked", but I think I can foresee adding some external damping material in the future.  

The performance observations noted above were confirmed, and even enhanced, when I hooked these up to a very beefy and gorgeous (but modest wattage) early 70's SONY receiver that is on loan to me from a friend.

Just a couple questions:

* any idea if this tweeter was used in other KLH models?

* not unlike the AR-2ax tweeter, the exterior tweeter damping clearly has an effect, but exactly what is the concept here?

* cabinets: did KLH ever use threaded T-nuts for driver attachment? 

* anyone know the fiber composition of this grille cloth (top)? (shown here next to typical AR cloth, bottom) 

[ra.ra]

Additional "progress" pics attached. Each cabinet had six pre-cut batts of FG fully stuffed (!). Revised crossover uses a generic 4uF film cap. "New" frontal pic. And the last pic, I suspect most of you restorers can identify with this image.

[dxho]

Yes the tweeter is known to also exist in the Thirty One, Thirty Eight, and some
late manufacture Seventeens.

Damping? Seems like you answered your question.

My Model Ones have t-nuts, but I don't recall seeing them in the Model
Seventeens. The only other KLH I own are Fours, with epoxied woofers.

[ra.ra]

39 minutes ago, dxho said:

Damping? Seems like you answered your question.

 

Thx for reply, dxho. Re: tweeter damping, I'm still not sure what to do. The on-axis and off-axis perception has not yet offered a decided solution to me with regards to an obvious and definitive application of external fluff, but I've even wondered if a half-damped tweeter might  be a preferred solution. I just dunno yet.  

[gelid]

I briefly had a single 32 speaker, and I compared it to one of my Model 31's and I can say that the 32's tweeter, pink fiberglass front and all, was very bright. The 31 was more balanced, and without the fiberglass over the tweeter.

Based on this audible difference I thought they were different tweeters, but then it could just be a difference in the crossovers. They were definitely wired differently. The Thirty-One has a single coil, with a 4uF capacitor and a 4-ohm resistor. I think I remember the Thirty-two having two coils and one capacitor.

[stupidhead]

hey Robert, I too would have not been able to leave them on the curb.

as for the damping, I would think experimenting with varying thickness' of material would be in order and relatively easy to apply.

as always, enjoy your work.

[ra.ra]

11 hours ago, gelid said:

...but then it could just be a difference in the crossovers. They were definitely wired differently. The Thirty-One has a single coil, with a 4uF capacitor and a 4-ohm resistor. I think I remember the Thirty-two having two coils and one capacitor.

Thanks, gelid. You have been inside of both models and I have not, but your description of the Thirty-One crossover components is entirely consistent with information I have dug up. Your notes about the Thirty-Two crossover do not jibe with what I found - - mine have only one coil and one cap, as shown in pics above. 

11 hours ago, gelid said:

Based on this audible difference I thought they were different tweeters

Pics of KLH Thirty-One shown below - - tweeter looks identical from the front (sans external padding), but magnet structure is very different. It's interesting to note that the Thirty-Two tweeter has the external damping (is this mostly about dispersion?) while the Thirty-One tweeter uses an in-line resistor to tame the output. The two models have very similar cabinet sizes, but the Thirty-One has a beveled front profile and appears to be vinyl clad.

7 hours ago, stupidhead said:

....as for the damping, I would think experimenting with varying thickness' of material...

Thanks, Geoff - - yeah, I'll probably just play around with various configurations to find my own preference. I'm still playing them 'in the buff', and I wouldn't necessarily disagree with gelid's observation - - the tweeter is quite noticeable, but I'm thinking that that is mostly a virtue. Maybe a bit "hissy" on-axis with no padding, but I'm just not sure yet. Right now I am playing them A-B-C style from the aforementioned period SONY receiver against some AR-4's (not 4x) and AR-6's, and I am developing different opinions depending on the style and musical range of program material being fed to them. It's all good fun, even if I don't always trust my own listening lab set-ups for absolute judgments.

[JKent]

Nice work, Robert (as usual)

I "had" a pair of Thirty-Ones for a while but gave up on the resto because one tweeter was bad, grilles were ripped and the cabs were crappy vinyl. Your Thirty-Twos OTOH look great.

My 31s did not have the "sculptured acoustically transparent foam grille" mentioned in the add above--they had cloth. It was probably boucle IIRC and I believe that's what yours are but I don't know what the fiber is (cotton? wool?).

As you know, I have reproduced badges for these so if you want a pair email me.

-Kent

[ra.ra]

Thanks, Kent - - - if I end up getting these grilles looking good, I may be contacting you for a pair of badges (I might need some AR repros, too). I was asking simply before I tried to clean or lighten them. BTW, it seems like KLH badges did not have a consistent placement - - sometimes left, sometimes right, yes? And I did find this image (first pic) of Thirty-Ones like yours with boucle fabric  - - good thing that sculpted look didn't last long. 

The thin grille frames were originally attached with a number of nasty little hidden nails (pic 2) - - I will replace with velcro or discrete staples. One excellent little detail with these speakers is the thin black reveal (about 3/16") between fabric and walnut. (pic 3) 

[ra.ra]

Ooops....almost forgot - - I just wanted to share this pic of the sweet, modest, age-appropriate electronics I've been testing these with.

Top: Sherwood S-7100; bottom SONY STR-7055.

[JKent]

Yes--KLH was a little inconsistent with speaker badge placement, even on the Model Eight radio.

Those are some nice receivers. I have little experience with Sony but really like Sherwood: Made in Chcagoland!