1gdw wrote:
> Rich,
> I must have done too well in ID'ing the dish issues because I have
> had very little response to my questions on this list or the
> MicDIYers list. Perhaps the answers are evident to the experienced
> users, and not to me.
Here's specifics to your original questions.
>>>I have no experience with building microphones but would like to
>>>make a parabolic using the Telinga dish. I have been thinking
>>
>>about
>>
>>>both a Stereo and Mono design, following the previously posted
>>>diagrams for a home made unit.
>>>For the Mono setup;
>>>If I use a mono mic such as a ME-62 ( I have a K-6 power unit),
>>>would I be compromising the microphone efficiency if the mic was
>>>orientated to point away from the dish? The reason for that
>>>orientation would be to accommodate the K-6 element of the mic
>>
> and
>
>>>keep the unit within the lip of the of the dish.
>>>For the Stereo;
The focus point of the Telinga dish is inside the lip of the dish. No
matter which way you mount them, the diaphragm must be located inside
the lip. According to Klas, 5.5 inches out.
>>>I will be using nosier lapel electric elements.
>>>First idea: Would there be any benefit if I used a small 1 1/2
>>
> inch
>
>>>boundary (mounted perpendicular to the dish axis ) and mount the
>>>elements as a PZM.
It may, or may not work well, purely experimental. Though I'd make the
boundary larger. Also don't center the mic elements on the boundary. The
Telinga DAT Stereo mic element is a PZM design using multiple capsules.
>>>Second idea, if the PZM idea has no merit: Would you expect the
>>
>>pick
>>
>>>up field of a cheaper omni to be uniform in shape? Should I
>>
> face
>
>>>them into the dish or away from the dish .
A omni, by it's definition, picks up evenly in all directions. So, a
perfect omni it would not matter.
However, the ME-62 is not a perfect omni. Above 6khz or so it gets more
and more directional. If faced out you would get considerable falloff of
the high frequencies compared to faced in. The MKH-20's Lang is using
also have such a falloff, though not as steep.
So, even high end omni's are not even in pickup shape.
>>>A second thought about the stereo parabolic. You folks have me
>>>confused about using a barrier in the dish, is the barrier in
>>
>>Lang's
>>
>>>most recent photos acting as a PZM? Is the barrier simply
>>>reflecting the wave to a new path and the mic diaphragm is large
>>>enough to gather all the semi focused wave? Perhaps the setup
It's acting like a boundary mic, but not a very efficient one. The
diaphragm is too large, most of it is too far from the boundary to make
much difference.
If you wish to do proper boundary mic in this sort of setup put the mics
perpendicular to the barrier, either spaced closely from it or through
it with the diaphragms even with the barrier surface on each side. When
I get some time I'm going to machine up such a setup to test using
MKH-20's. I've a few more complexities to it as well.
>>>relying on the efficiency of the mic to offset any loss of gain,
>>>since the mic is not at the focus point. How far from the focal
>>>point can you move the mic elements?
No more than a inch or so either way. Unless you are recording close
subjects, then you can go a bit more out. At least that's my experience
with the regular Telinga mic elements.
Walt
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>From Tue Mar 8 18:23:25 2005
Message: 18
Date: Sun, 09 Mar 2003 19:29:15 -0500
From: Walter Knapp <>
Subject: Re: Success-frogs
Neville Recording wrote:
> Hi Walt;
> Congratulations on recording the last missing species. I find it hard to
> imagine you have so many frogs. I would love to buy a copy of your frog CD ,
> if you could tell me how to get it. We only have two frogs in this region (
> British Columbia Canada Gulf Islands). You can hear the croaks of Pacific
> Tree frogs in any month of the year . The males, at lower elevations, started
> proclaiming about two weeks ago " ribbit, ribbit". The red-legged frog is
> very quiet and I have never encountered one. I shall come to Georgia one day
> looking for Walter's frogs.
> Sincerely
> John Neville
The frog CD is still "in process". I'll post a notice once DNR has sales
set up. Expected to be real soon now. It's really out of my hands at
this point.
Walt
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