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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: the mid pod has effectively a 90 degree edge with very little rounding, so diffraction will not be smooth. posted by Timbo in Oz on November 12, 2010 at 10:59:15:
B&W bothered to get it right for mid frequencies, with as small a driver, The distances involved / frequency? Diffraction happens at edges.
Diffraction happens at edges, sure. But diffraction is frequency dependent. The smaller the baffle, the higher the frequency at which this occurs. The midrange is not only directional at the relevant frequencies here, reducing the intensity of illumination, but they are likely high enough in frequency to be outside the midrange passband.
If you look at this mid pod it's hardly any better than the tweeter pod, the curve radius at the edges, for the frequencies involved. The radius of the curve on that mid pod will not help smooth the pod's diffraction behaviour. It will be just as poor as the tweeter pod's, not enough of a curve.
You're not considering the operating bandwidth or directionality here. The tweeter pod is not the issue so much as the flange is. There is no corresponding flat section on the midrange mounting. This flat section creates the distance required to make diffraction an issue. Tweeters with tiny little flanges would be less sensitive here, as in the tweeters you see top-mounted on the Nautilus series.
On B&W's mid pods, a far greater radius curve begins at the driver's edge, and are you saying they shouldn't have bothered?
I'm not saying they shouldn't have bothered, but it's a design difference that doesn't really make much difference in the real world- both designs will be low diffraction, the B&W setup will have a little more on-axis output at the low end of its operational band as you're receiving reinforcement from the slightly larger apparent baffle size, but because it's so well rounded, it's a minimum effect. Fractions of a dB.
And, why didn't AR just restrict the blanket to the tweeter on the AR9 and all the later models? They did it to damp out the Mid (and HF) waves travelling towards the sharp edges, so that they would be weak at the edge, and their diffraction there less audible.
Yep, I like felt on baffles. The AR baffles had sufficient distance from the drivers to illuminate the edge. The transition from 2pi to 4pi is based upon the size of the baffle in traditional box speakers. With a "baffle" so small, the transition is determined by the directional characteristics of the driver itself, the edge diffraction is not an issue.
Lastly, the ear is much more sensitive at mid frequencies.
Yep. But since the "baffle" is not being significantly illuminated by the mid here, it's a non-issue.
Bass is supposed to sound big. 6.5" is not a woofer size.
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Follow Ups
- RE: the mid pod has effectively a 90 degree edge with very little rounding, so diffraction will not be smooth. - badman 15:23:55 11/12/10 (0)
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