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Need some advice about KLH 20's

mash35231

mash35231

Member
I found a pair of KLH 20's cheap. They sound ok for a pair of speakers 40 years old! I opened the cabinet to recap the crossovers and I found something very interesting in both cabinets. The woofers are connected directly to the speaker inputs. The woofers aren't connected to the crossovers. My original intention was to replace the woofers to get more bass. The tweeters have a 8 uf in series with a 2 uf in the circuit depending on the position of the tweeter attenuation. The crossover is a 1st order (I think) for the tweeter and no crossover for the woofer. Is the crossover for the tweeter around 3500-4000hz? I'd like to keep the tweeters and replace the woofers. Is my uneducated guess about the tweeter crossover point correct?
 
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Should be closer to 2500 Hz.

You can use any of the many on-line crossover calculators to figure it out,
here's one:

http://www.erseaudio.com/CrossoverCalculators/First-Order-2-Way

BTW the impedance of the model 20 woofer is 4 ohms and the tweeter is 8.
and yes, there is no inductor, the woofer just rolls off without one.

I wouldn't assume that replacing the woofer is going to yield more bass; that's a function of the cabinet size and the T/S parameters of the driver.

Maybe you already know this....
 
more bass? with no power to the speaker, press the cone in and hold. then release. does it come back quickly, or slowly? slowly, you've got a good acoustic seal. quickly, you have air leaks, and should check to make sure the woofer and tweeter frames, and the back plate are sealed well to the cabinet. use rope caulk or plumbers putty to seal. repeat the process, if they still spring back, the woofer surrounds might need to be redoped. search for redoping threads of KLH and AR drivers for more info.

beyond that, you could try a heavier fill of fiberglass to extend the bass a little.

or you could alway sell the guts on ebay, and then with some of the proceeds, build a pair of these with the cabinets:

http://www.audiokarma.org/forums/showthread.php?t=204850
 
The woofers in both cabinets move "back out" quickly. I sealed the enclosure at the joints on the inside. I went to Parts Express and bought 2 Pyle woofers and used the online crossover calculator to figure out a 2nd order Butterworth crossover. Oh yea, I spent the extra money and bought Jantzen 18 gage inductors along with Auricap capacitors (ouch says my pocket book) and I like the results! Bass is tighter and less muddy sounding. I can't put another ounce of batting in the cabinets. I was going to leave the wood cabinets alone because they have character. I think I'll refinish them now.....
 
From everything I've read, redoping the speaker is not recommended and generally raises the speakers Fs. Also too, an air leak would have to be fairly big before it resulted in reduced bass.

I'm actually shocked that the Pyle woofer sounds better than the original, but who knows.

I have KLH Model 23's and the woofers sound decent.
 
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