The Klipschorn Motorboard?

[Axz Hout]

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[Axz Hout]

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[ZAKO]

In some technical letters to ashworth,,,, A special chemical was applied to the EV 15wk outer surround to lower free air resonance...Paul applied this himself,,, I don't know if this after all these years had dried out... Paul was trying to lower free air resonance to just below 30 hz,,,I don't no wicth serial number were on the units,,,Paul new about the problems in trying something smaller than 3x13 slot,,, ASHWORTH had several mounting boards in his position  6x13 ,,3x13 ,, 2 1/2 x13,,and one at 2x13...,,, After Georges death...I was allowed to recover some of these boards,, I have them in my  basement,, Plus all 155 tech letters from Paul to George... I sent copies to Jim Hunter... I haven't read them in many years,,, The additional wedges in the bass bin are a mystery to me,,,  I don't remember who ,,cant remember his name also found these wedges in the bass bin and was able to remove them..

[Axz Hout]

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[LarryC]

A special chemical was applied to the EV 15wk outer surround to lower free air resonance...Paul applied this himself,,, I don't know if this after all these years had dried out... Paul was trying to lower free air resonance to just below 30 hz,,,I don't no wicth serial number were on the units,,,Paul new about the problems in trying something smaller than 3x13 slot,,, ASHWORTH had several mounting boards in his position  6x13 ,,3x13 ,, 2 1/2 x13,,and one at 2x13...,,, After Georges death...I was allowed to recover some of these boards,, I have them in my  basement,, Plus all 155 tech letters from Paul to George... I sent copies to Jim Hunter... I haven't read them in many years,,, The additional wedges in the bass bin are a mystery to me,,,  I don't remember who ,,cant remember his name also found these wedges in the bass bin and was able to remove them..

Was the "special chemical" orange?  I think the Klipsch 15WK cone had a central orange ring that the standard E-V 15WK's lacked.  I always wondered about that.

 

Were the wedges you mention placed just above and below the 3X13 slot on the motorboard?  That's what I found inside of my '62 bass bin.  Mark Kaufman relayed a view by Jim Hunter and others that they were an attempt to raise the output around the crossover point.  A purpose obviously lost to history at this point.  As I mentioned earlier, my thread (linked above) had good pictures of all that which didn't survive the last forum software upgrade.  Again, I probably can dig up those pics if anyone is really interested.

Edited September 15, 2015 by LarryC

[ZAKO]

No it was not orange,,, But Paul was very careful not to get it on the cone ,,But on the outer surround,,, So it would not migrate further down the cone....Yes the wedges were just above and below the slot,,,.......  GEORGE ASHWORTH had a special bass bin made for him by Paul,,,,to make fast exchanges of woofers in the bass unit,,,

[Axz Hout]

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[ZAKO]

Not that one,,,

[ZAKO]

Remember the woofers at that time had fe of at least 40.... Paul needed to get tham down to around 30...

[BeFuddledinMn]

Mach1 and Zako,

This is great information! It seems that we are getting closer to unraveling some mystery here.

Zako - in the material you have, is there any reference to the installed impedence of the EV 15wk woofer in the old klipschorns? The impedence plot that Mach1 has provided looks to be that of the early Alnico model based on the high sensitivity - looks like a crossover impedence around 7-8 ohms, which would be about 2-3 ohms higher than the installed impedence of a k33e around the crossover point of 350-450hz. If that is an installed vs installed comparison - does that difference make sense given the nominal 16 ohms and 4 ohms ratings of these two woofers?

Again, thanks much to all for sharing their knowledge and experience. The upcoming tests should help as well.

-BeFuddledInMn

[LarryC]

This is the *orange" surround used on K EVs

YEP!  That's what I was referring to!  I thought it made the Klipsch 15WK look more iike what it was supposed to!

 

After I had a Model T Shorthorn for several years, I put its innards into a utility model K-horn, where they sounded wonderful, and then bought a then-current new utility K-horn for stereo.  VERY disappointing!  The bass and lower middle range almost dropped out.  I complained, and was sent a newer ceramic magnet 15WK.  It lacked body and sounded very weak in the bass.  I remember that it's cone was crudely sawed through along the surround's edge, and the orange stuff crudely applied as in the above picture; obviously the historical skill was not applied in that woof.

 

You can imagine my deep disappointment that I couldn't match the superior original 15WK in the "T".   You're lucky to have a pair of the originals if that's what you have!

[ZAKO]

I don't know who would saw through a   woofer surround edge,, Paul certainly would not do that........I found the tech letter from Paul about what was applied to the outer surround of woofers ... EV and Jenson woofers,,,  IT was dibutylphalate,,,... a small amount of shellac was applied at the cone edge near outer surround so no migration would creep into cone,,,From what I saw everything was clear not orange like the EV WK,,,Thats a different cone surround,,

[LarryC]

don't know who would saw through a   woofer surround edge,, Paul certainly would not do that........I found the tech letter from Paul about what was applied to the outer surround of woofers ... EV and Jenson woofers,,,  IT was dibutylphalate,,,... a small amount of shellac was applied at the cone edge near outer surround so no migration would creep into cone,,,From what I saw everything was clear not orange like the EV WK,,,Thats a different cone surround,,

It certainly seemed like the crude cut on my substitute had been handed off to someone, perhaps at E-V but probably not Klipsch.  Anyway, it sounded terrible, and I expect Klipsch knew they couldn't make it the equal of the older 15 WK.  I recall the original in my "T" looked exactly like the pic posted above by Mach-1.  I saw a different pair of E-V 15WK's without a different colored surround.  I didn't think it sounded as good.

Edited September 16, 2015 by LarryC

[ZAKO]

This all changed when Stevens  made a series of woofers to pauls specs,,,..and Paul didn't have   apply the chem,  to lowerFe... Now  Eminence hasthe code,,,,,,, I don't think EV would have done that ,making that crude cut...,,, Some one passed a lousey woofer on to you...

[LarryC]

This all changed when Stevens  made a series of woofers to pauls specs,,,..and Paul didn't have   apply the chem,  to lowerFe... Now  Eminence hasthe code,,,,,,,

Very interesting.  I have current K-33 models; should these have the "treatment" done?

 

Or is that only for unmodified vintage 15WK's or Stephens's?

 

Thanks,

 

Larry

Edited September 16, 2015 by LarryC

[ZAKO]

Current K33 do not need treatment..Stevens do not need treatment,,,,,, EV ??????

[Axz Hout]

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[ZAKO]

No nothing else was applied by hand... I have one of the CTS  K33....That goop was part of that design,..... JBL has that on some of their outer compliance ring,,,,,  It gets grungie... Don't mess with it....

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[boom3]

Coming in late (as usual) on this thread...the "mystery pyramid" in front of the bass driver is really called a splitter bar. Paul told me long ago that this improved the response at the top of the bass bin's range. My interpretation is that at the frequencies involved, and with the geometry of the motherboard, this acts somewhat like a phase plug at the very top end. Recalling that the purpose of a phase plug is to make the path length from all parts of the diaphragm to the throat the same; at the frequencies of interest here, the effect would be the same. Also bear in mind that this area is the zone of highest pressure in the horn (or any horn). This is why Klipsch put a vertical brace in the middle of the first expansion. At this part of the horn, we may think more in terms of  hydraulic flow, not neat little sound waves marching along. My visualization of this is that without the splitter bar, there would be a region of pressure that would not "flow" correctly and contribute turbulence, upsetting the horn loading scheme.

 

It would be interesting to introduce some colored smoke into the plexiglas Klipschorn at the museum and using high-speed photography, watch the flow from throat to mouth. Of course, this can now be approximated in software but there's no substitute for trying on the genuine article.