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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Or not. posted by Bill Fitzmaurice on April 21, 2004 at 06:08:18:
[ While I don't disagree in total the fact remains that the effects of edge diffraction and the baffle step frequency are inexorably intertwined. ]No, no they are not. They are actually two separate things, that can be looked at individually. The woofer and the tweeter can be affected by both issues.
[ It's no coincidence that in enclosures of typical dimensions edge diffractive effects above the frequency of the baffle step, 2kHz on average, tend to run on the order of 2dB or less, while below the step frequency glitches of 4dB and more are common. ]
While you may have made such an observation (I am not arguing the numbers, even though my own experiences do not mirror these figures, they show larger deviations for both frequency regions), that does not validate your statements or claims.
[ While rounding of the cabinet edges can be beneficial as far as HF diffraction is concerned, it's no panacea, as many of the same studies you mention note that the nearby presence of the mid-bass driver(s) cause far more diffractive effects than the baffle edge, effects that cannot be significantly ameliorated shy of mounting the tweeter separately of the mid-bass baffle. ]
This holds true ONLY if you do not use an absorptive barrier or ring, as the original post was discussing. Use of such an absorptive barier, WILL reduce the problems with tweeter energy diffracting off of the mid-bass or woofer. Radiusing the edges will further reduce the remaining amount of tweeter energy that does reach the baffle edge.
[ There is also the contention that the most effective method of limiting HF diffraction is the relocation of the tweeter to an off-center position, and that the benefits of so doing render additional efforts via edge rounding to be rather insignificant by comparison. ]
Whose contention? Mounting the tweeter off-center will stagger the difraction arrivals at the listener, but it does not actualy reduce them for each edge, or eliminate them, only spread them out in time, relative to a circular bafle, where ALL the tweeter energy would be edge diffracted at the same time for a center mount tweeter.
Radiusing the edges on an offset tweeter location will still provide the benefit of reducing the AMOUNT of tweeter energy diffracted from each edge.
[ This is not to say that large radius edge rounding has no benefit with respect to frequencies above the baffle step, just that the benefits so gained are going to be minimal, while below the baffle step frequency far greater benefits will be obtained. ]
This is still just plain WRONG. The tweeter diffraction will occur at the same strength for a given distance, whether or not it corresponds to a given 2 Pi to 4 Pi baffle step response frequency.
You are still confused.
Jon Risch
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Follow Ups
- Re: Or not. - Jon Risch 04/21/0422:29:19 04/21/04 (0)
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