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Response curves run by PWK


garyrc

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I've heard that, when AR (acoustic research) got good reviews of their early acoustic suspension speakers (AR-1? AR 3A?) that PWK ran curves on them, and they were not as flat as they were cracked up to be.  Do you have these?  Can you share them with us?

 

A 1977 brochure describing the Klipschorn read, "...And we test every speaker that makes a serious claim to quality reproduction."  It would be fascinating to see some of those test results -- can you help?

 

I also heard that PWK and Edgar Villchur had some debates -- were these in print or transcribed?   Love to see them!

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I wish had copies, but I did see the curve PWK ran on the AR-3A. Yep, it was not nearly as flat as AR claimed, and it had a pronounced fall off above about 8 Khz. I think that AR's published system curves were all anechoic curves of the individual drivers spliced together

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Yes, Paul tested everything he could get his hands on.  The Altec A7 was the "target" when designing the LaScala. The museum has about seventy 3-ring binders chock full of curves going back to 1960.  It is certainly a goal AT SOME POINT to sift thru them and make some available. 

 

PWK and Vilchur "went at it" in the October 1957 edition of Radio-Electronics magazine.vilchur.thumb.JPG.e020687ba59360e051c822c41c5c8729.JPG

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Reading that article reminded me of something I heard Paul say 20 or so years later, when he presented the curves he ran, including the AR 3A curves. He called Edgar Villchur "Edgar Vulture." I read somewhere (gee I hate that phrase) that in the 1930s Tannoy experimented with what Villchur later patented as "acoustic suspension" and gave up on it. At that time amplifier power was very costly and making low-efficiency speakers seemed counterintuitive. 

 

In a Dope From Hope, ("Whats a Watt?") Paul stated that 1 acoustic watt, radiating into "corner space" would equate to about 118 dB.  Klipsch Heritage can handle that level with ease, although I daresay most listeners and rooms are overwhelmed long before that. I do know that my 4 Corn set up can produce an average of 102 dB with peaks as high as 106 dB in my rom, and that't the level at which my room and I cry Uncle.

 

If you consider the best commercial audio reproducing chain that was available in the late 1950s, the Klipschorn was the component in the chain that, aside from the preamp, had the lowest distortion. I was not listening to Klipschorns then, but I bet that the audible differences between the Klipschorn and most other speakers were even more marked then than they are now.

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Jim,

 

It was Allison and Villchur that wrote a JAES article on how modulation distortion isn't audible ("The Audibility of Doppler Distortion in Loudspeakers," AES 70th Convention, October 1981). 

 

This 2004 Stereophile article by Keith Howard pretty much reverses their views in favor of PWK on the subject of FM distortion...and no one since has apparently taken the ball on the audibility of AM distortion in woofers beyond what PWK did in the late 1960s.  Since the two modulation distortion sources produce the same effect (significant higher order modulation sidebands).  I assume that the Keith Howard's article also applies to that type of distortion source, too (AM distortion).  The Klippel papers on measurement of nonlinear loudspeaker distortion will show those that are curious how these types of distortion are related.

 

I particularly like the comments on the "edge" that FM distortion adds to musical sounds in the linked Howard article, above, even at very low levels...apparently at much lower relative levels than Allison & Villchur stated in their 1981 JAES article.

 

It's still amazing to me how far other loudspeaker designers will go to defend small loudspeakers and the use of "long throw" woofers. 

 

Chris

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I was just reading this article, which I think is apropos to the subject:  https://www.technologyreview.com/s/610012/the-tricks-propagandists-use-to-beat-science/

 

I can bet what Mr. K's reaction was to the Allison & Villchur article.  I've got the picture of how he reacted in my mind right now...( :pwk_bs::pwk_bs::pwk_bs: ).

 

Chris

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  • 2 weeks later...

in his "Audio League Report" 1955,  I believe Julian Hirsch was using the AR-1 as a reference as it would play a reasonably clean 30Hz sine wave on the oscilloscope much cleaner than most of the high efficiency speakers (and the AR-1 was just as efficient at 30Hz as many of the larger speakers whose 30Hz response was quite a bit down from their flat passband sensitivity)  The small box did make way for acceptable sized stereo installations.   (fwiw, I do like Henry Kloss' KLH work a lot.)

 

I've got great respect for PWK and personally think the K-400 is a better horn than sometimes gets credit.

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FYI,

 

For others that might not be conversant, it's modulation distortion that is the issue...not harmonic distortion that is seen in the type of tests that are described above.  In order to see modulation distortion, two tones must be played at the same time:

 

 

Chris

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35 minutes ago, babadono said:

Right in the middle of PWK's article there's a tube amp by Joseph Marshall. Is that the Marshall of Marshall Guitar amps?

I believe that you're looking for Jim Marshall

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