Walter Knapp wrote:
>Two photos:
>http://frog_recordist.home.mindspring.com/naturerecordists/QuickParabolic1.jpg
>http://frog_recordist.home.mindspring.com/naturerecordists/QuickParabolic2.jpg
>
>I did this in about a hour, this is what the drawing I gave below looks
>like. I did not mount the mic inside the end cap, and it's all just
>slipped together (you would want to glue the handle to the T, but
>probably not the rest). This one is made with 3/4" PVC pipe. The
>reflector is my spare Telinga one, the same design would work with
>others like the one available from Edmond Scientific:
>http://www.scientificsonline.com/Products/DisplayProduct.cfm?productid=2135
>Note the Edmond one is polished for solar cooking, it would have to be
>painted to keep from cooking your mic.
I don't like the look of the tube and the end cap area where the mike
has to be. There is so much obstruction. You want the mike to sit in
a spot where, pointing back toward the reflector, it can see the
whole surface of the reflector without obstruction. I see no reason
for having such a heavy structure there. Imagine something like a
lampshade harp.
-Dan Dugan
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>From Tue Mar 8 18:22:44 2005
Message: 2
Date: Mon, 23 Sep 2002 01:28:21 +0200
From: Klas Strandberg <>
Subject: Re: Re: Your homemade quick parabolic mic.
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".
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.
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.
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.
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
>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. 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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