Hi John--
I'll keep working at finding better samples for
the indoor testing. I included 7 HF sounds in the
test and this one worked the best. The
repetition does become fatiguing. After
determining the samples you want to concentrate
on, it can help to pull out the just those
sections and pair them up for shorter
run-throughs and give your ears frequent breaks
Tying to maintain concentration for a whole
minute or two is taxing.
I'm not sure whether it applies to others, but
I've stopped using headphones for stereo imaging
evaluation because the horizontal spread across
the field is portrayed by many headphones as over
the top of my head or through my head. It takes
additional mental work to push the illusion out
in front me whereas the spread naturally resides
across the front with speakers. If the imaging
works on speakers, it sounds good on all my
headphone models 90% of the time. The reverse is
much less true. Stereo imaging on speakers is
more demanding and this lessens some the
perceptual work.
Of course, the darker coloration at 90 degrees
comes from squeezing the lobe-shaped polar
patterns inwards to provide more gain and HF
response in the center of the field. I'm after
apparent presence and tonal _symmetry_ from front
to back. Many stereo arrays produce hot spots
around 2 and 10 o'clock and gain dips in the
center. I'm trying to achieve maximum presence in
the center of the field, even phantom locations
and smooth tonal change from crisp across the
front to progressively warmer states starting at
2:30 or 3:00 to 6 o'clock. For me, symmetry
presents better depth cues and eliminates doubts
about whether a sound source is in front or in
the rear-- such as at 5 o'clock or 1 o'clock.
One can argue that being able to detect "front"
from "back" is not as important and getting as
much HF clarity from as many angles as possible.
Maybe we'll be able to hear some examples of this
in my next test. The studio test was to determine
if I could get more symmetrical HF imagery.
Compelling spatial imaging of distant subjects
and location ambience relies a lot on lower
frequency behaviors so I don't have a clue how
the spaced boundary rig will work.
As long as there's some hardness beneath the
covering on the baffle, I would think that at
least some lower frequency reflections would
occur. Seems odd to encourage onside reflections
and and then diffuse them but there's probably no
single layer material that will completely absorb
all the sound waves only 3" from the baffle.
Maybe that's one advantage in the greater mic
spacing? To find out more, one could start off
with a hard, smooth surfaced, circular baffle and
add increasingly absorptive materials and then
different angling/edges to hear the changes. One
could use pink noise at 15 feet in the first run
through to "see" the effects/trends with sonogram
assistance and then repeat the most promising
factors in an outdoor location with distant sound
sources. Rob D.
=3D =3D =3D
At 1:06 AM +0000 9/28/10, hartogj wrote:
>Hi Rob,
>Actually I have no idea when Jecklin updated his
>OSS scheme, I misinterpreted the description on
>the Josepheson web
>site(<http://www.josephson.com/tn5.html>http://www.josephson.com/tn5.html)=
>where it mentions 2009, and I now see it does
>not directly refer to the date of publication.
>The paper referred to is dated in the footer as
>2003/04.
>
>Anyway, it would be interesting to experiment
>with that spacing variable sometime. In my own
>baffled arrays I have kept distance between mics
>more or less head-spaced. Having them closer to
>the baffle is certainly more convenient for wind
>screening and for portability, but if wider
>spacing proved to be noticeably superior in a
>variety of situations, then I might be inclined
>to adopt that configuration.
>
>Of course there are many variables worth
>exploring as you have pointed out. I have
>strayed away from the smooth, flat, and
>perfectly circular characteristics of the
>Jecklin design. There is some crazy idea in my
>head that if the baffle must be reflective to
>some degree, and if those reflections can cause
>phase issues, then the baffle should at least be
>shaped to scatter those reflections as much as
>possible. I don't really know what difference if
>any that makes, but I do it anyway.
>
>Getting back to the SASS-like boundary arrays
>you have been testing. I think there is a lot to
>learn from your latest comparison
>(<http://diystereoboundarymics.blogspot.com/>http://diystereoboundarymics.=
blogspot.com/).
>I like the squirrel, however I am afraid that
>the same as with the old clock tick tock, it
>might still cause insanity if listened to one
>too many times. One thing I find interesting is
>how off-axis coloring of the 90 degree source in
>the flat or angled-in configurations give the
>illusion (headphones) of a source slightly from
>the rear =96 that may or may not be desirable
>depending on the circumstance.
>
>John Hartog
>
>--- In
><naturerecordists%40yahoogroups.com>=
m,
>Rob Danielson <> wrote:
>>
>> 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 Eri=
c
>> 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><naturerecordists%40=
yahoogroups.com>
>> >Kevin Colver <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 th=
e
> > >> 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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