John--
I've always admired the way dishes can isolate details-- getting more
stereo "liveliness" would be a great plus.
Just to be sure, your dish is divided in half vertically, correct?
It sounds like the highway(?) is on the left in the recording. Is
that that correct orientation, field-wise? I noticed the right
channel of the sound file is showing more resonance between 250-500
Hz than the left and I was trying to explain this flip.
http://ad2004.hku.nl/naturesound/RobD/Hartog-SB-Left-Right-Channels.jpg
The gain is also lower on the right channel so the difference in
resonance is probably more pronounced than this.
Regarding stereo localization in a dish. If the back of the dish is
more responsible for the most, on-axis "centered" sounds (like the
water splashing in the take-offs), then one could surmise that that
the sides of the dish are more involved with (moderate) off-axis
pick-up. When I look at the geometry, it seems like the (moderate)
off-axis sounds coming from left of center would be
reflected/amplified a bit more by the right side of the dish and
vice-versa. The effect gets greater as you move towards the sides. If
your rig defeats this flip-phenomenon, that result could be
unexpected.
As for reducing some of the resonance in the two dish halves, did you
try some higher density foam or other deadening material on both
sides of the divider? It could be that facing the capsules towards
the dish works better in dealing with the resonance from the two dish
enclosures. As Curt says, one would expect the centered sound to be
clearer with the capsules directed towards the back of the dish (the
focus point). As the dish only has one focal point, all stereo
imagery is an "enhancement," so I'd also try placing the capsules
directly on the divider (or foam).
For greater stereo "side" imagery with a dish, your project makes me
think that one could also use 4 mic capsules (2 in series for each
channel) and place one capsule of each pair outside of the dish
(left-right crossed) and pointing hard left and hard right. This
would surely create phase issues but the arrangement might add width
and liveliness with less ill-effect on the tonality and localization
of the off-axis sounds. Thanks for sharing this project. Rob D.
At 5:31 PM +0000 1/16/08, John Hartog wrote:
>Hi Curt,
>I have tried it with the mics pointing to the dish, out from the dish
>and now toward the boundary. All three ways sound slightly different
>and previously I had preferred out from the dish because I thought the
>off axis sounds sounded better.
>
>I was concerned however that having the mic membranes perpendicular to
>the boundary might be causing some funny phase cancellations. Until
>now I hadn't come up with a good way to accurately mount the capsules
>facing the boundary. So, a lot of the reason for facing the boundary
>is for the sake of experimentation, but my hope is it will maximize
>the free gain in the pressure zone where the boundary combines with
>the parabolic reflection.
>
>As far as the severe separation. I notice that too, but maybe it is
>the location more than anything. Will have to test it out in a quieter
>setting. Maybe panning both channels slightly toward the center in
>post will fix it - I'll give that a try.
>
>I'm late for work. So until later...
>
>-John Hartog
>
>--- In
><naturerecordists%40yahoogroups.com>
>Curt Olson <> wrote:
>>
>> Excellent work, John. I find it interesting that you chose to face the
>> mics toward the boundary and not toward the parabola. Can you 'splain?
>>
>> Stereo separation seems a wee bit severe to my ear at this point, but
>> you're definitely on to something very clever here!
>>
>> Curt Olson
>>
>>
>> John Hartog wrote:
>>
>> > Hi group,
>> >
>> > You may remember that LP I was using as a barrier for wl-183's in a
>> > Telinga parabolic dish a couple years ago. Well I finally reworked
>the
>> > idea and came up something that definitely has promise. I put a few
> > > photos and a sound clip up on a page on my website.
>> >
> > >
><http://www.rockscallop.org/how/spba/spba.html>http://www.rockscallop.org/how/spba/spba.html
>> >
>> > I gladly welcome comments.
>> >
>> > -John Hartog
>>
>
>
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