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How important is a roundover on the top and bottom?

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  • #31
    Re: How important is a roundover on the top and bottom?

    Originally posted by Zilch View Post
    First rule of thumb is that the distances should be unequal.
    I'll second that. I don;t know of any "golden ratio/rule" kind of thing. Depending on the baffle size (width and height) and position there will be some ripple. The amplitude, number and positions of the ripple(s) changes as you move the tweeter around. Sometimes, it is better to live with one ripple/hump that you can easily clean up with a notch filter than to try an minimize everything.

    -Charlie
    Charlie's Audio Pages: http://audio.claub.net

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    • #32
      Re: How important is a roundover on the top and bottom?

      http://sound.westhost.com/articles/waveguides1.htm

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      • #33
        Re: How important is a roundover on the top and bottom?

        Looks like Zaph agrees also:

        http://techtalk.parts-express.com/sh...50#post1615850

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        • #34
          Re: How important is a roundover on the top and bottom?

          I don't know if I dare to tread where giants walk, but one thing I haven't seen mentioned is how the baffle diffraction effects change as one moves off-axis. When working with the BDS (and in my own measurements), I've noted that the majority of the on-axis hash reduces or goes away when the measurement is taken even just 10 degrees off axis.

          It seems to me that a speaker utilising a tweeter with good dispersion would allow you to ameliorate the worst of these issues just by fiddling with the amount of toe in. I'm not the horney-waveguidey type, but that dispersion is probably another advantage to them.
          nothing can stop me now

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          • #35
            Re: How important is a roundover on the top and bottom?

            Originally posted by Dirk View Post
            I don't know if I dare to tread where giants walk, but one thing I haven't seen mentioned is how the baffle diffraction effects change as one moves off-axis. When working with the BDS (and in my own measurements), I've noted that the majority of the on-axis hash reduces or goes away when the measurement is taken even just 10 degrees off axis.

            It seems to me that a speaker utilising a tweeter with good dispersion would allow you to ameliorate the worst of these issues just by fiddling with the amount of toe in. I'm not the horney-waveguidey type, but that dispersion is probably another advantage to them.
            The advantage to using diffraction control (chamfers/roundovers/felt) is that as one moves off-axis, the variability may be greatly reduced. If you design for some specific off-axis with no diffraction control, then you may be locked into that axis for optimal response. Flexibility of room arrangement may be more limited.

            Another problem with designing on any specific axis, whether on-axis or at 10 deg. or some other, is that there is the power response that should be considered. When that is considered, the response on some single axis may be somewhat at odds with a smoother power response.

            Use of diffraction control helps in optimizing for a wider listening window (more flexibility as to axis) and may help the power response as well. But if for nothing else, it makes design easier due to that reduction in off-axis variability.

            dlr
            WinPCD - Windows .NET Passive Crossover Designer

            Dave's Speaker Pages

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            • #36
              Re: How important is a roundover on the top and bottom?

              Originally posted by Zilch View Post
              I think it's worth a direct quote:

              Originally posted by Zaph
              Related to the directivity benefit is the fact that a waveguide is not affected by the baffle it's on. Baffle diffraction is a non-issue compared to a standard dome mounted in an enclosure. In a waveguide system, you will not see the lower treble "ripple response" present in typical box systems.
              I don't think this is any surprise considering what a waveguide/horn does. Zaph had empirical evidence as he measured the waveguided 27TDFC on both infinite baffle and a cabinet baffle (Waveguide TMM).

              Jay

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              • #37
                Re: How important is a roundover on the top and bottom?

                DXT has elements of a constant-directivity waveguide.

                Perhaps Mark would post his polars here?

                [I don't have access to Praxis, alas.... :( ]

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