Not quite right, I think. Mike noise doesn't exactly sum because of it's
random nature; there is some natural phase cancellation that would occur.
Klas could probably shed some light on this.
Remember too that there is probably a slight PZM effect introduced by using
a barrier and keeping the mike elements close to the barrier. Far from a
perfect PZM, but perhaps there would still be some additional noise free
gain.
I think if you use very low noise mikes to begin with, such as the MKH20's,
then stereo parabola is the way to go. If you then find it necessary to sum
to mono, the result will sound extremely close to a mono parabola using the
same mike.
At least that's my conclusion. Maybe I'm wrong.
Klas?
However, for stereo recordings the signals are not summed, they are kept
in separate R and L channels.
If you decide (for a mono recording) to sum the signals but keep a
barrier between the mics, the R mic receives the sound from the right
half of the dish and the L from the left. Your mechanical magnification
from the parabola will be cut in half. By summing the 2 signals you
will sum the mic noise along with your desired sound, achieving the
desired total magnification but with twice the mic noise. Thus for mono
you are better off using a single mic and concentrating the entire
parabolic force into one mic. Recall that the parabola magnifies
without adding electronic noise while the mics (especially 2 summed
together) magnify with a bit of electronic noise added. This should cut
in half the electronic background noise.
Kevin
-----Original Message-----
From: Lang Elliott
Sent: Thursday, February 13, 2003 11:01 AM
To:
Subject: Re: [Nature Recordists] Dream Systems?
Kevin:
I don't entirely agree. For instance, if you sum the signals from the
two
mikes, then the "on-axis" signals from each mike should be exactly in
phase
and they would combine to produce a louder signal, rivaling that
produced by
a single mike.
At least I think this is true. If it is, then stereo parabolic
recordings
could simply be summed to mono when necessary.
Lang
I've used a similar system of 2 mono mics mounted in a parabola with a
barrier between. It works fairly well, however it has less magnifying
power than a single mic because each mic in the pair only receives the
amplified sound from 50% of the parabola surface area. Thus it has a
bit less "reach" than the single mono mic. The stereo effect is more
pleasing however, and you will need to get a bit closer to your sound
source.
Kevin
-----Original Message-----
From: Lang Elliott
Sent: Wednesday, February 12, 2003 3:47 PM
To:
Subject: Re: [Nature Recordists] Dream Systems?
Rich:
I'll try photographing my setup next week and then posting photos of the
parts-and-pieces on my website.
I did copy Klas's setup, using a plastic boundary and two Shure foam
windscreens trimmed and glued to the boundary to hold the two mikes,
pointing forward and separated by the boundary.
You'll have to look at the photos to get the gist of what I did. I
enlarged
the hole in the Telinga parabola and used plastic PVC pipe fittings to
attach the mikes to the parabola.
Again, you'll have to look at pics. It's too difficult to describe with
words. I'll try to get to it next week sometime.
In any event, the results sound really nice. Very low noise stereo
parabolic
recordings, much like Klas's stereo setup, but at least 6 db quieter.
lang
Lang, you have given us so much to work with in the past, but I again
have a request.
Would you be willing to share with us on what your stereo
configuration is with the MKH-20's and a dish. Do you also run a
barrier like the Telinga? Is it a PCC configuration or a PZM? Did
you also choose a plexiglass barrier if you used one. Is there a
need for it to be buffered as the Telinga is with foam? I will be
setting my 32" dish for stereo for the spring but would love to avoid
the pitfalls that you already fell through.
--- In Lang Elliott <>
wrote:
> on 2/12/03 10:30 AM, Kevin Colver at wrote:
>
> > Here's a question for the group;
> > What equipment would you purchase (recorder, pre-amp, mics, ect.)
for
> > your dream system in the following categories?
> >
> > 1. Stereo ambient sound, price $1000 - $2000
>
> SASS with two MKH 20s - about $3000 for whole setup
>=20
> > 2. Stereo ambient sound, price $4000 - $5000
> >
> > 3. Stereo ambient sound, price $10000 - $12000
> >
> > 4. Directional mono recording, price $1000 - $2000
>
> MKH 70 shotgun microphone with zepplin (for mono shotgun recordings)
>
> or Telinga Parabola retrofitted for STEREO recording using two MKH
20s for
> about $3000 total. Why use a mono parabola when you can get a nice
stereo
> recording, plus all the benefits of the parabola?
>
> >
> > 5. Directional mono recording, price $4000 - $5000
> >
> > 6. Directional mono recording, price $10000 - $12000
> >
> > Thanks for your opinions.
> >
> > Kevin J. Colver
> >
> >
> >
> > To unsubscribe from this group, send an email to:
> >
> >
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> >
> >
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