Hi John--
I didn't realize the separation distance change was recent. It would
be fun to experiment with some of the variables. Good diffuse field
Hz response appears to be one of the strengths Jecklin points to
which is very relevant to our applications. One would need to dive
into the papers of course, most of them in German, but here are few
traits that stand out to me:
Perhaps the 13 - 3/4" diameter dish prevents sound waves higher in
frequency (shorter) than ~1000 Hz from passing around the dish (speed
of sound =3D 13600 inches per second / 13.75 inches =3D 989 Hz). As Eric
Benjamin reminds often reminds us, our brains can use time of arrival
differences only up to 1000-1100Hz-- so it seems the "off-side"
timing differences would NOT be blocked while the off-side
frequencies above 1000 Hz would be.
One can imagine "shadowing" or diffraction around the dish creates a
potential of directional cues. The shadow formed by a sound wave
would be different depending on angle of incidence and frequency.
Unlike our ears, the spread between the mics affects how far into the
"shadows" the mics extend.
Simply adding some padding to hard surface doe not eliminate
reflections. On-side lower frequency sounds coming from the right and
left (between ~1:30 to 4:30 and 8:30 to 10:30 o'clock) will reflect
back to the mics from the baffle creating potential phase relations.
From my own attempts at blocking sound from the rear for surround mic
arrays, I found that I had to place heavily treated barriers at least
2 feet away or I'd hear the affect on the mics frequency response.
The closed-cell, rubbery boundary and baffle materials that some
people are experimenting with can change coloration as well.
As far as I can tell, very little of the designing, testing and
theorizing audio engineers do takes into consideration "diffusion" to
the extent that we engage it when recording ambience in "quiet," very
large, non-geometric spaces. We've been doing this almost long
enough so that we can start looking for ties between arrays that do
things we like. For example, the SASS uses a partial baffle. Rob D.
=3D =3D =3D
At 9:09 PM +0000 9/26/10, hartogj wrote:
>Hi Kevin,
>
>Baffled arrays, including the Jecklin disk, are definitely
>appropriate for nature recording. I have found that a baffle can
>establish accurate left to right imaging independent of chosen angle
>between axes or polar pattern of the microphone capsules. Such
>flexibility allows for explorations of a variety of interesting
>perspectives of the natural soundscape. The basic Jecklin disk
>design is certainly elegant where function meets simplicity.
>
>I notice Jecklin recently published an update that more than doubles
>the ideal spacing between capsules, the original was 16.5 cm, but
>now it is 36 cm. That seems quite a big shift. It would be
>interesting to hear the difference.
>
>John Hartog
>
>--- In
><naturerecordists%40yahoogroups.com>=
m,
>Kevin Colver <> wrote:
>>
>> Rob,
>> I've made my own Jeklin disk with about $25 of materials (not
>> including the microphones) and used it this summer. Your comments
>> about the Jeklin were fairly positive. I'm wondering if others in the
>> group have found the Jeklin useful for nature recording?
>>
>> Kevin J Colver
>> Soundscapes for Birders - a Podcast of Natural Sounds
>> www.7Loons.com
>>
>>
> >
>>
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