Model 17 and Model 20 tweeters - interchangeable?

[mrbruce4]

I have Model 17 speakers and could obtain Model 20 tweeters (for spares), but don't know if they're identical. I've looked at the spreadsheet and see that the 17s are an 8 ohm system while the 20s are 4 ohm (I believe)but don't know if the tweeters are different impedance. Help will certainly be appreciated.

Somewhat related note - Just completed a capacitor change for the 17s based on urging from a couple of members.

Thanks

[Guest MarkAnderson]

They are the same. AFAIK, the only difference between those two models is the woofer impedance (and subsequently the low-pass portion of the crossover, I'd assume) and the rear connection (RCA jack vs. screw terminals).

[mrbruce4]

Mark - Thanks for the reply. I thought they might be, and since the original post, saw something that said the difference in the speakers impedance was due to the woofer.

Appreciate the reply.

Bruce

[Andy]

A note on this topic; In the Dec. 1966 High Fidelity review of these speakers, they say, "the model Twenty has a shorter voice coil winding then the Model Seventeen to reduce impedance to 4 ohms in order to take more power from the amplifier"

I'm not sure why KLH felt they needed to do this, all the Model Seventeens I've owned seem to handle plenty of power, and The Model Twenty system only put out 50 watts total acording to a 1970 product brochure.

[Guest MarkAnderson]

>I'm not sure why KLH felt they needed to do this, all the

>Model Seventeens I've owned seem to handle plenty of power,

>and The Model Twenty system only put out 50 watts total

>acording to a 1970 product brochure.

That same amp would not have been able to produce that same 50 watts into an 8 ohm load. Changing to a 4 ohm v/c was just a quick and dirty way of wringing more power out the the amp. Course, this is mostly speculation on my part. Seems like a plausable explaination though, don't it?

[tysontom]

>A note on this topic; In the Dec. 1966 High Fidelity review

>of these speakers, they say, "the model Twenty has a

>shorter voice coil winding then the Model Seventeen to reduce

>impedance to 4 ohms in order to take more power from the

>amplifier"

>

>I'm not sure why KLH felt they needed to do this, all the

>Model Seventeens I've owned seem to handle plenty of power,

>and The Model Twenty system only put out 50 watts total

>acording to a 1970 product brochure.

A shorter voice coil winding -- all other things being approximately equal, and if they were referring to the length or voice-coil overhang -- will also result in higher efficiency (or sensitivity) for a given power input. Basically, a shorter coil in the gap means less windings left out of the gap at any given moment, and thus less wasted energy. The problem is that distortion rises as the coil becomes non-linear quicker, but unless one is driving the speaker hard, the differences would not be noticeable.

--Tom Tyson

[Guest matty g]

Don't forget that the Model Twenty was designed for and sold with the phono system. The intent was never to have it hooked to anything other than a Model Twenty phono system amp, and the amp was designed to drive that speaker system only. The distortion factor may not figure in as readily with this speaker system considering these circumstances - something about "overcoming the weaknesses inherent in a small speaker"? Anyway, it's hard to stuff all that power into a little cabinet that already has a record changer and a tuner in it - pretty damned amazing that it could be done so well so long ago!

Matt