--- In Klas Strandberg <> wrote:
> Rich:
>
> This is my "model" for thinking about parabols:
>
> The focus is a "ball" of energy. The higher the frequency, the
smaller the
> ball. Consequently: The higher the frequency, the narrower it gets.
> When the frequency is 10.000 Hz, the "ball" is about 30 mm, and you
can move
> the mic +/- 15 mm without much change and you can move the parabol
aside of
> the bird until the "ball" doesn't hit the membrane anymore.
> This also means that the size of the mic membrane is important for
the
> directionality, as general design. An omni is much
more "forgiving".
I recall your Globe viewpoint and have kept it in my thinking as it
is useful.
>
> As a matter of facts, most recordists who are familar with the
Telinga since
> many years back, prefer to put the mic a bit out of focus. The
alternative
> is to point a bit aside, or below, the bird. This is especially
true when
> the song has a lot of overtones. General advice is that you don't
find the
> "best" sound when you come near, or focus perfectly, but that is a
matter of
> taste.
I am not buying into the idea that the best location is outside the
globe yet as a ultimate fix to a problem. I wish to experiment with
sound absorbing baffles to make the dish appear to be an oval shape
sound wise to accomplish the same without loss of the center of the
focus.
>
> The bigger the parabol, the bigger the mic membrane - the better the
> amplification. Big glass fibre dishes (the old Roche 1200 mm + a
good
> tripod!) with a big dynamic microphone (like the old version of
Beyer ME88)
> perform fantastic, if you just can get rid of the electronic noise
(A
> perfectly matched transformer and very careful design of the mic
amp)
> However, such monsters are mostly left under the bed, back home,
and not
> much recording is done.
>
That is part of my problem in using my dish in the woods at night as
I am dealing with a much larger dish than yours. I did not take into
my thinking the size of the mic element in the angle of capture and
that is likely why I see my dish as a lot more narrow than yours as I
run a larger element. By the way your construction is great as my
dish is larger but has less gain. The bigger dish has its advantages
though but part of that is personal preference as well.
> Finally: There is very little difference if you put the omni facing
out of
> the dish or facing in. Facing out of the dish means that the
microphone body
> doesn't stick out of the dish. It's more practical. Walt
wrote: "You are
> dealing with a pressure variation, it's not light and not a water
wave. The
> focus is actually a small volume in which the pressure
> variations from sound are pretty even. You have to do a fair amount
to mess
> it up. At least for the kind of frequency response of a inexpensive
tie tac
> mic."
> Which I agree with.
My dish is setup to handle focus faced in or out with an omni. I
have to admit that I just favored in because of the directionality of
an omni on the high freqs. I should take the time to test the mic
out arrangement which I never have done.=20
What do you consider to be the minimum distance for placing a pink
noice sound source and testing the gain and charector of a
parabolic? Is it the same as the in focus minimum distance of a
binocular at the infinity setting?
>
> Klas.
>
>
> At 02:12 2002-09-22 -0000, you wrote:
> >I prefer not to walk in the woods at night with my parabolic and
that
> >seems to be when I enter for deer. It is a pain. For deer and
for
> >stalking I pickup my shotgun mic. But the types of sounds you are
> >after you may prefer a omni. Keep in mind your minidisc recording
in
> >mono is 160 mins. You can locate the prime location setup in a
tree=20
> >and leave. That likely will get you better results.
> >
> >A salad bowl can be used to achieve a 45 degree viewing angle but
is
> >not a parabolic. Consider it more like a shield for back noise if
> >you want to use one.
> >
> >The Telinga dish and other good parabolics have to have their mold
> >made from a computer manufactured model. My dish seems to have a
5
> >degree viewing angle and maybe Klas will tell us exactly what his
is
> >designed as, but it seems to be a bit more friendly and around 15
> >degrees.
> >
> >Keep in mind what you lack in equipment right now you can make up
for
> >with the experience you have from spending time in the field.=20
Since
> >I've been recording my stalking and tracking skills have improved
> >many fold.
> >
> >Rich Peet
> >
> >--- In "deer2me22002" <>
> >wrote:
> >> Dear Walter
> >> I am very delighted with your pictures of the
homemade
> >> parabolic mic you made, and am intending to try to build one
myself
> >> to use in the woods next month. I have a few more questions on
this
> >> mic if you would not mind answering them. My first question will
> >> probably sound very off the wall to you, but i was wondering if
> >using
> >> a large plastic salad bowl or similar desighn for a reflector? I
> >was
> >> also wondering what kind of foam you were refering to when you
> >> metioned using it in your mic, and also would you fill in the
whole
> >> handle and T with this, besides in the cap with the mic, and
just
> >> leave the peice of PVC with the cutout holes empty of this foam?
> >How
> >> do you go about finding the focus point of the reflector to be?
> >Should
> >> i cement all the caps , including the mic cap? Also were the
holes
> >> already inthe pvc pipe or did you cut them yourself, if so what
did
> >> you use to do this so neatly? Would the part with the holes in
it
> >be
> >> cemented to the T, or another way? And lastly, how would the mic
be
> >> mounted in the cap with foam?
> >> Thanking you greatly:
> >> John E Parks..
> >
> >
> >
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> >
> >
> >
> >
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> >
> >
> >
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>
> Telinga Microphones, Botarbo,
> S-748 96 Tobo, Sweden.
> Phone & fax int + 295 310 01
> email:
>
> org. no SE440130067001
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