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do these T-S numbers look right for a K-33?


Tom Mobley

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D-Man,

Thank you for your comments.

I agree that the numbers don't work out right for theoretical mid band matching of these drivers. Also, reactance annulling is not quite as theory predicts either.

However, I also think that there is a lot more to consider.

This is mostly an appeciation that we have to look at the conditions of a finite length horn. Down around Fc the resistance is dropping. Also, the reactive component is wiggling around quite a bit and goes into -j in places. It is very untidy. Question: what are the optimal annulling conditions? And, what is the optimal resistive match?

I get annoyed in reading papers by Edgar and Leach where they assume that we've got perfect horn conditions and a back chamber should be of a given size to balance the j from the horn.

My guess is that that the wacky conditions around Fc and below have to be optimized. That is where things are most unfavorable. We can compromise the midrange of the bass horn to keep things working down there.

I have done a little experimentation with my Bigger than a Belle unit. When the hatch is removed the system resonance goes way down. That may show that the horn is still giving a mass reatance or +j.

I'm not quite sure how this all works out.

Gil

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Bob, those numbers look really good. Of course, that's not too

surprising seeing as who had them made and for what. have you

tested one in your 2x2x2 box? really go that low?

Those numbers really look good. Anybody with bass box pro able to

run a design on them? Look good in a Cornwall size cabinet?

about 6 cu ft, 165 l.

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Tom,

I have been using the prototypes for a couple of months in my Cornscala boxes. They work very good there in a Cornwall size box. Go noticable lower than the new K-33Es but have not done much formal testing on how low. Mostly just comparison between the new K-33Es and these new woofers and some old square magnet K-33Es. I think they sound about the same as the old K-33Es in my boxes.

Bob Crites

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"...according the the engineer at Eminence, these things will perform exactly like the pre-1985 K-33Es that they made for Klipsch."

New BEC
Fs 25.5, Re 3.4, VAS 302, QM 5.9, QE 0.31, QT 0.30, SPL 95dB, Xmax 7mm

Klipsch Old (available specs)
Fs 27.9, Re 3.5, VAS 343, QM 8.5, QE 0.69, QT 0.63, SPL 92dB, Xmax 4mm

Warren, old (measured)
Fs 24.0, Re 2.7, VAS 348, QM 6.6, QE 0.27, QT 0.26, SPL 97dB, Xmax 4.7mm

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The Warren (old, measured) parameters seem to indicate a surprising manufacuturer production variance compared to the Klipsch (old, avail specs). One might conclude that the new BEC's are "within spec", but which of the parameters' deviations will make the biggest difference in sound once horn loaded? That Xmax is huge. How much can be used?

Paul

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John measured a good condition old driver, I don't know what happens to a driver over time. At any rate, with what little I do know about this stuff, I believe the most important things to look at would be QM, QE, QT, and Fs. Bob and Eminence did good it seems to me.

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The woofers do change some with age apparently. Here are the results I got when testing a pair from a set of 1974 Khorns. Notice the numbers are quite a bit different even though both of the old woofers seemed to work great. Also on this PDF is results of the same series of tests run on a new fresh K-33E.

Bob Crites

TStest1-1.pdf

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