Vifa DQ25 Phase Shield removal surgery ...! - diyAudio
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Old 7th June 2011, 04:39 PM   #1
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Join Date: Dec 2007
Location: Melbourne the sunny city!
Default Vifa DQ25 Phase Shield removal surgery ...!

I'm building a rigid cone version of my dipole panel and decided to use Fountek FW146 and Vifa DQ25. While I immediately fall in love with FW146, the same cannot be said about the popular DQ25. It sounded "hard" for the lack of better word.

I suspected the phase shield is the issue and is a compromise between trying to maintain flat on-axis respose vs. other anomalies. So I removed one and measure it just to see.

Click the image to open in full size.

On axis response

Measured from about 20cm on-axis, here we can see the effect of phase shield. It brought back the dip of typical rigid cone tweeter, but overall cannot remediate it fully. I'd say it's marginally useful.

Click the image to open in full size.

Off-axis response

Things gets more interesting here. Now we see the compromise, which is poor off-axis response. No phase shield is better by miles.

Click the image to open in full size.

Burst decay

This one is I think the real reason why original DQ25 won't sound smooth. It's all the resonances, stored energy, and reflection of that hard phase shield.

Click the image to open in full size.

So I proceeded to remove all the phase shield of the 4 tweeters. The subjective impression is more mellow sounding tweeter and a bit loss of "immediacy" as in steel guitar strings

In case you want to try, be careful in removing the shield as it is very close to the cone. I managed to dent one of the 4 tweeters ...
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