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Belles versus fortes?


Fido

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That Belle pamphlet is a little confusing, 400-6000 crossover points? 16 ohm rating? Bass down to 40hz? Its rating is 45-17.5 but bass response is 20hz higher than the Klipschorn on the low end, wouldn't that equal 52hz? I thought crossing over a horn below its rated response would cause distortion?

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PWK had a series of exponential horns going.

 

K-400 for the K-Horn and LS (length with driver is just under 24 inches)

K-500 for the Belle (and maybe Valerie) length with driver is about 18 inches because that is the depth of the Belle.

K-600 for the CW

K-700 for the Heresy.  (It seems this is now used in the CWIII because the molds for the 600 were lost.)

 

I can't say that they are all scaled entirely, accordingly because they all used the 7/8 inch exit K-55 driver. Therefore the throat was not scaled.

 

The suffix most likely gives the working low frequency in PWK's thoughts. 

 

By my calculations, the actual fc of the K-400 was about 271 Hz.  That is based on a doubling in area every 2.75 inches given in PWK's article on the K-400. 271 = 13500/(2.75*18.1)

 

For whatever reason, PWK used the length to double (the Hebrew lamed) in place of fc.  The cutoff wavelength is 18.1 times the length to double area.  You see this in his patents on bass horns. (I suspect he was tired of being dogged by non-engineering critics and therefore expressed the cut-off in a term which only the sophisticated would understand.)

 

A fair guess is that by the time the K-400 gets up to 400 Hz the acoustic load is purely resistive.

 

If you look at the ratio, it is about equal to square root of two or 1.4.  Back in the day there was some thought, I believe, that it was a rule of thumb that a purely resistive load was accomplished that far above cut off.  With the K-400 he was looking at getting the midrange horn to work as low as possible.  His K-5 horn wasn't going quite as low as he liked.

 

WMcD

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1 hour ago, Weber said:

There is more from which to select. Have you had the KLF? The Chorus is the Forte's big brother.

I love my fortes - - all tricked out, fits perfectly in our living room, sounds amazing, and they were my dads pride and joy. Also my wife loves them. Those Belles just looked rad but they couldn't bring part of my dad into our home. I miss my mom and dad! 

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3 hours ago, Weber said:

The Forte are keepers for sure. They are all that's needed and more. Sorry about your folks, keep doing them proud :emotion-21:

 

 

Do you have any other place for speakers: Garage, basement, etc...? We can help you spend your money. :D

I live in a small townhouse and this is the only place for speakers - I used to have a pair of Cerwin Vegas 380 SEs. They are probably the best speakers CV ever made but they took too much room in my garage - my nephew is borrowing them now - if I had a place for them I'd get them back - I do appreaciate the forums help spending my $$$$, though:P

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