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K-400 Throat and Washers


JohnA

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The discussion, "Modernize the Klipschorn ....", brought out a point that the K-400 throat and driver may be mismatched. It got me thinking about my own La Scalas. I bought them used and I am probably the 3rd owner. If I remove the K-55-V I have a red rubber washer in the throat and its i.d. is less than the i.d. of the horn and less than the o.d. of the screen protecting the phase plug of the -V. I'm pretty sure my speakers were monkeyed with before I got them, I just don't know how much. What size washer is correct? Shouldn't its i.d. be a smooth fit with the i.d. of the throat?

John

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Dear john, The washer may have been distorted by excess pressure for too many years. The ID should match up within a few thousands of the throat hole for the horn. The screen on the K55V is a "fooler" as I remember it rests on a hidden step beneath the screen. So the actual working throat of the Atlas driver is smaller than it appears from looking at the protective screen. I critically measured all of this long ago when cutting up K400s' to use bolt on drivers but unfortunatly I don't have immediate access to those notes(15 yrs. ago) but once everything was taken into consideration I don't believe we discovered anything that mis-matched. Plus, just about got my scanner issue sorted out so the Klipsch "packet" should be ready to fly by 28/Jan.

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  • 6 years later...

John,

I don't think the mateing of the driver to the throat is very critical when it will only be used to 6 Khz. Some of the K500 sand-cast horns even have lumps of metal in the throat path. The ones in my Belles did. I cleand it out and heard no difference. I also have jurey-rigged k55 drivers on to the end of Altec VOT horns using simple flat particle boards. That's .7 inch flat into a 1 inch throat hole. The response measurements were ok. I think you can replace that little washer with anyhting you have. I use cut up foam place mats to mount inductors on the boards of my crossovers. I think that material would do nicely.

Al K.

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Al is correct; the wavelengths involved at the operating bandwidth are too long, comparitively, to be concerned with tiny changes such as the types mentioned above.

The gasket "gap" would introduce a very small capacitance being that technically forms a cavity. However, again, because of its size, it would only effect frequencies much higher than the operational bandwidth.

I think you're quite safe and even with a new exactly sized gasket, you would not be able to determine a sonic difference, either with your ears or with a measuring device.

DM

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Just measured a bunch of this stuff.

Rubber washer ID is 0.72 inch

K-400 throat is 0.70 inch

K-55V (push term) outlet is 0.85 inch

K-55V (solder term) outlet is 0.80 inch

K-55M outlet is 0.72 inch

Bob

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""interesting...2 year old thread getting dug up.""

There are a bunch of old threads that floated to the top yesterday as a result of a bug in the forum software.

the bug

if you have your view set to newest first

then open the first active thread

once opened

select next in the upper right

you wind up 5 years back instead of the next active thread.

various post were made about this glitch.

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