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Robthomp

Model 22 vs Model 22A

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Hi,

Today I just bought a pair of Model 22's from a guy on CL. The cabinets are in beautiful condition and they sound great.   When I got home I realized that one is a 22 and one is a 22A.   He advertised them as 22A.    Does anyone know what the A designation is for and is there any difference?   I can find references online to both but no mention of the difference, if any.

The tweeter on the 22 is mounted on a white cardboard ring, the tweeter on the 22a is mounted on a black plastic ring.  The woofer cones are slightly different colors. The particle board backs have  slightly different colors.   The cabinets and grills are absolutely identical but I don't know if the grills are original or if the cabinets were ever refinished.  The serial number on the 22 is 23519 and on the 22A its 45037.

Rob

 

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Also, the letter "A" on the back plate isn't part of the original lettering on the plate - it looks like it's stenciled on or something.

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All of these KLH model numbers confuse me, but those two appear to be virtually identical from the exterior. Maybe, just maybe, there might be a slight revision on the inside?.....but enough to necessitate a change in model number? Despite your suspicions about the stenciled "A" on the back plate, the serial number sticker also features the "A", so there is some yet-to-be-determined differentiation between the two. You'll probably have to take a peek inside - -  meanwhile here are a few threads which might offer some ideas. From this first link, I suspect what you have is the original grille cloth.

http://www.classicspeakerpages.net/library/klh/klh_22_klh_model_twenty-two/klh_22_photos/klh_22_front.html#previous-photo

http://audiokarma.org/forums/index.php?threads/klh-22a-speaker-score.720273/

 

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Well, I opened the Model 22 and Model 22A.   The crossovers are different:

 

1)   The drivers appear to be identical.  The Model 22 drivers are stamped with 1968.  The Model 22A doesn't have a date stamped on the drivers, but there is a stamp on the baffle board which contains the line STY 5 21 70, which I am guessing is a 1970 date?

2)  The Model 22 tweeter is housed in a cardboard enclosure, the 22A tweeter is housed in a plastic one.

3)  The woofer on the 22 is sealed with the usual bead of white putty seal, but the woofer on the 22A is NOT sealed with that stuff. Under the rim of the aluminum frame there is just a thin ring of foam stripping.

4) The Crossovers:  the Model 22 has a simple first order crossover - a 4 muF capacitor in series with the tweeter, and a coil in series with the Woofer ( I do not know the inductance of the coil, it doesn't appear to be printed on it.)  The Model 22A on the other hand in addition to the coil,  has a 16 muF capacitor in parallel with the woofer, and an 8 muF capacitor and a 3 Ohm resistor in series with the tweeter.  I have attached drawings I made of the schematics. 

I am learning a little bit about crossover design and I'm very interested in knowing what the effects would be of this crossover upgrade and why KLH went to it.   Is it possible to generate the frequency response plots for these two crossover designs, assuming identical drivers, and compare them?  Is the modified crossover in the 22A related to the fact that the woofer didn't seem to be sealed as well? Or is the woofer on the 22A supposed to be sealed but KLH just cheaped out by using a flimsy foam strip instead of the airtight putty?

How good would your hearing, or listening training, have to be to hear the difference between these two crossovers?

 

Rob

 

 

 

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Hi,

 I think I can ask a better question: I'm recapping these speakers.  Should I replace the crossover in the 22 with the same one that's in the 22A?   If the drivers are in fact identical, then presumably KLH decided the second crossover was an improvement, otherwise they wouldn't have put it in.  On the other hand, if the drivers do not have the same electrical characteristics (even though they look the same to my untrained eye) or if the inductors have different values, then modifying the crossover in the 22 might be a bad idea.

Rob

 

 

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