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Tweeter Diaphragm Material


BEC

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This is a little test I have been meaning to do for awhile. This test looks at the difference in performance with a change of diaphragm material. The driver is a K-76 tweeter out of a Heresy II. It was tested with a sweep of 3k to 25K with its original phenolic diaphragm (red trace) then with a replacement diaphragm of the soft poly type (blue trace) and again with a replacement titanium diaphragm (green trace). All test conditions remained the same during the three stages of the test with the only difference being the change of diaphragm.

Looking at these traces, I think I would pretty much disregard what is seen below around 6khz. I was feeding the signal through a type A crossover that happened to be lying around. Also, my mike only claims to go to 20khz, so what we see above that is suspect.

The diaphragm for this K-76 is the same one for a bunch of the non-heritage Klipsch speakers.

k76diaph.jpg

post-9312-13819260073076_thumb.jpg

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Bob,

What do you make of those peaks and valleys? They seem to be at a regular "beat" of about 2500Hz. Also, what is your feelings about the "suck-out" at 16KHz?

Actually the pheonolic is the best. That's suprising but not really as that driver was designed for the pheonolic diaphram was it not?

Rick

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D-MAN,

Yes, I was surprised at how well the phenolic does. I had listened to phenolic compared to the soft poly and I thought I could hear a difference there with the phenolic sounding better. I haven't listened to the titanium yet, but looking at the spectrum analyzer, I think it is a better replacement for the original phenolic than is the soft poly. The phenolic is no longer available.

Bob

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Rick,

Yes, the phenolic was the original. Also I may get around to testiing the three diaphragm types in some of the other drivers that use it. Some of them have larger horns and larger magnet assemblies. I just have to believe that the titanium will show an advantage in some of them.

On the peaks and valleys and such, probably some reflections. This was done with the driver just lying on a workbench with the mike about 6 inches in front of it.

Bob

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Yes, the diaphragm for the K-77 has been and is now phenolic. The "newer" type tweeters, which include the K-76, K-75, K-79, K74 and a long list of others, originally shipped with a phenolic diaphragm. The replacement diaphragms for those at some time changed to the soft poly type. I think the titanium is a better replacement for the original phenolic.

Bob Crites

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