XT25TG30-04 distortion cancellation - diyAudio
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Old 2nd July 2009, 07:36 AM   #1
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Default XT25TG30-04 distortion cancellation

Hello all,

Time has come to finish up a project I started a few months ago. It is for a 2-way floorstander which should use a combination of the SS 18W/4531G00 midwoofer and the Vifa XT25TG30-04 ring radiator. The midwoofer shall be placed into a separate curved enclosure, sealed. The enclosure is almost done with curved side pannels made of sandwich of plywood and mdf with total thickness of 40mm, top and bottom plates made of 50mm mdf and front and back panels made of 50mm mdf. I am going to use a 2nd order for both drivers and no impedance neither baffle compensations ( the front baffle will be cut and there will be very small planar radiating area around the SS midwoofer which will be covered with leather to reduce difractions and to make it look better ).
What I was looking at is the Vifa Xt25TG - it is based on the old Revelator and is a magnificent tweeter. The only problem with it is the high distortion when crossed too low. I will be crossing it at 2Khz and distortion will be a problem.
This tweeter has no ferrofluid and there is a resonanse peak close after its Fs. I am under the impression that if this resonanse is smoothered with a notch ( as far as I see from the tweeter freq. response graph, the peak is at 730-760Hz ) the distortion of this tweeter will go much lower.
Has anyone tried this and with what effect? Any other suggestions?
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Old 2nd July 2009, 09:03 AM   #2
bjorno is offline bjorno  Sweden
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Hi,


Tip: Design a shallow waveguide for the XT driver like :

http://www.jantzen-audio.com/downloa..._v2_ja_web.pdf

You will gain a couple of dB around 2-(4-5) kHz before equalizing or notching the driver to a flat response down to 2 kHz, mount the driver as close as in the .pdf .

This will keep the distortion at an acceptable level by lowering the excursion substantially around 2 kHz and lower.

b
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Old 2nd July 2009, 10:38 AM   #3
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Hello Bjorno,

Thanks for the input

I was thinking about a wooden waveguide as wood sounds very natural, what I was concerned of is that the waveguide will move the tweeter further upwards and the acoustic centers of the midwoofer and the tweeter will be too far away one of each other, as at the crossing freq. the wavelenght is about 17cm. I am also going to align the acoustical centers by placing backwards the tweeter on its separate enclosure on the top of the woofer enclosure.
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Old 2nd July 2009, 03:16 PM   #4
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XT25 will easily play down to 1khz in a waveguide.
you'll get up to 10db boost in tweeters lower frequencies.
then after you pad it down to match woofer's FR, tweeter's distortion is not an issue. look for SP Tech speakers reviews.
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