Thanks Rich,
Hearing you have not had any noticeable issues with standing waves
with your dish is encouraging.
John Hartog
--- In "Rich Peet" <> wrote:
>
> As you may recall I use a 32" dish with the focal point being close to
> the rim.
>
> Do not worry so much about standing waves.
> If cavity resonance is noticable to you than you can easily dampen
> that. My windscreens dampen it well.
>
> Ideal in my eyes is setting the focus at the rim or just outside.
> On occation I do use a mic above the dish as a noise cancellation
> device and if standing waves were a large problem with my dish I would
> hear it.
>
> More often I use two close mics without a barrier. One is on target
> and one is off. I am not a fan of ever having the target partly out of
> the focus. Because I am recording with two mics and hearing one that
> is always out of focus I understand focus fairly well. Using my two
> mic setup a Song Sparrow can appear to be moving as it gives its song
> when the ideal focus is between the two mics yet closer to one.
>
> The focal length a dish is designed for does change the flavor of the
> recorded sound. Randy Little who did the math on that, I recall, also
> ended up recommending a 1:1 ratio of focus to depth. Klas does not
> agree and that is simply another flavor.
>
> Rich Peet
>
> --- In "John Hartog"
> <hartogj_1999@> wrote:
> >
> > I must be nuts to bring this up again, but I still have some burning
> > unanswered questions -so here is one.
> >
> > Regarding the focal point (and I know it is not really a point), what
> > is the ideal distance inside the rim. I am hearing different
opinions.
> > One from a Cornell page suggests if the mic is positioned inside the
> > dish there would be a distortion from cavity resonance (or something
> > like that) off the sides of the dish.
> > Conversely, a few of this group suggest a standing wave at the rim
> > opening would cause distortion, so the mic is best put inside the
dish
> > somewhere below the level of the rim.
> > Is the standing wave only exactly at the rim level or does it extend
> > somewhat into and out-of the dish? If so how far each way? Would
the
> > optimal position of of the focus be at a certain ratio of the dish
> > depth?
> >
> > If anyone can bring a little more light to this problem or steer
me in
> > the right direction, I will be sincerely grateful.
> >
> > John Hartog
> >
>
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