I agree your configuration gives a good stereo image of off axis
sound. If you always want the lead singer to be front and center it
is the way to go. I prefer being able to reach into a flock and get
the flock recorded from within it.
970kb download.
http://home.comcast.net/~richpeet/stereodish.mp3
The catbird is only about 10 degrees off of the meadowlark. At the
time I was actually recording the Henslows. Both the catbird and the
meadowlark are more than 75 yards away. I recall them as over 100.
My sound room is taken apart to far for my trip so I can not scope
this now but, if you have a second. Phase reverse a channel and sum
to mono and listen to what happens to the distant trucks and the
distant dog. I think you can think of a few uses for that technique.
Around here somewhere I have a number of distant auto driveby
recordings that have the vehicle drive through the entire sound
field. Probably the kind of thing you are looking for as an example.
Rich Peet
--- In Lang Elliott <>
wrote:
> Rich:
>
> I will be interested in hearing some examples from your setup.
>
> What we might want to do is some standard test, like a person
talking
> directly on axis and then slowly moving 90 degrees to each side,
talking all
> the while and describing the location with respect to the axis.
That way one
> can determine the accuracy/quality of the spread of the stereo
soundfield,
> and one can also look at the phase changes of one channel with
respect to
> the other.
>
> The Telinga barrier design does yield very nice stereo with the
parabola
> completely removed. Thus, the stereo soundfield is not dependent
upon
> reflections from the parabola.
>
> For all parabolic mike setups (monaural or stereo), the sounds
arriving
> directly at the microphones will not be in phase with the same
sounds
> reflected off the parabola back to the microphone. For on-axis
sounds, it is
> assumed that on-axis reflected sound is so much louder than the
direct
> on-axis sound that the interaction between the two is
insignificant in
> practical terms.
>
> Lang
>
> I will try and put some examples up later today. I am packing for a
> few days recording outing and trying to tie up some other ends.
>
> I will also scope my examples to determine if they are mono
> compatible. I believe mine are mono compatible but will double
> check. I more often phase reverse one channel and sum to add
> additional noise reduction than attempt to combine the two channels
> which results in an overall drop in dish gain.
>
> If you start your barrier at the mic diaphram and only project it
> back away from the dish, then you will still have your cows in
> stereo and try a 1" seperation of the diaphrams for your dish. For
> mine I use 3".
> You would then be using the whole dish for each microphone rather
> than having reduced it to half. Also with separated mics your
> targets at a distance will sound like wide separation stereo even
> though they may be only 10 degrees separated. The down side is two
> fold this way. One, the amplified stereo sounds will be fliped in
> image from the off axis stereo sounds. Two, if you are slightly off
> aim on a variable freq bird such as your grousebeak then the high
> notes will be lower volume from the low notes which occationally
> makes the location of the bird in image flutter from side to side.
>
> Not better, just a different flavor.
> Rich
>
> --- In Lang Elliott <>
> wrote:
> > Yes. My setup is basically the same as used in the Telinga Stereo
> Dat Mike.
> >
> > http://www.naturesound.com/telinga/telinga.html
> >
> > Rich, what is it you "hear". I believe that you prefer spaced
> mikes with no
> > barrier. Do you have any good examples for listening?
> >
> > Lang
> >
> > By my ears it appears that you run a partition between the two
mkh-
> > 20's, correct?
> >
> > Rich
> >
> > --- In Lang Elliott <>
> > wrote:
> > > Re: Stereo Parbolic recording
> > >
> > > I've been doing lots of recording using my custom stereo
Telinga
> > MKH20
> > > setup. Go to the address below to listen to a recording I made
> > last weekend.
> > > It features a Rose-breasted Grosbeak plus the sounds of some
> other
> > animals,
> > > big critters of some sort. Maybe someone in this group can tell
> me
> > what
> > > creature so rudely interrupted my grosbeak recording. Be sure
to
> > listen
> > > using headphones so that you can fully appreciate the marvelous
> > stereo
> > > effect:
> > >
> > > http://www.naturesound.com/mp3/rbgroby.mp3
> > >
> > > Studying the waveforms of my various stereo parabolic
recordings
> > on the
> > > computer, I've discovered the following important fact. Unless
> the
> > target
> > > bird is exactly focused, with the bird's song being identical
> > amplitude in
> > > both channels, there is often a resultant phase difference
> between
> > channels.
> > > This occurs even when the target bird is "slightly" off-axis.
> > >
> > > This can cause major problems when one desires a monaural
> > recording and sums
> > > the two channels to obtain it. Phase cancellations then reduce
> the
> > amplitude
> > > of the target bird's song, and may also result in other
> anomalies.
> > For this
> > > reason, it is not a good idea to mix the two channels to
> monaural.
> > It is
> > > better to choose the channel where the target bird is the
loudest
> > and use it
> > > as your monaural source.
> > >
> > > This negates my earlier conclusion that the stereo parabolic
> setup
> > produces
> > > a monaural recording superior to that of a monaural parabola.
> This
> > is true
> > > in theory, but only if the target bird is perfectly focused and
> > there is no
> > > phase variation between the two channels. In actuality, it
turns
> > out that
> > > this is rarely the case, unless the target bird is in direct
view
> > and
> > > focusing becomes foolproof. When the bird is not seen and one
> > focuses the
> > > parabola "by ear", it seems to be the norm that it will end up
> > slightly off
> > > axis, with phase differences evident.
> > >
> > > It follows that if one chooses the loudest channel in a stereo
> > parabolic
> > > recording to produce a monaural version, then this will
produce a
> > result
> > > that is somewhat inferior to that produced by a monaural
> parabolic
> > setup. I
> > > haven't tested this in a controlled situation, but I expect
that
> > using only
> > > one channel will result in a loss of signal-to-noise of 3-5 db
or
> > so. Maybe
> > > one of you tech-heads can tell me what would be expected in
> theory.
> > >
> > > I expect that the Telinga Stereo DAT mike exhibits the same
> > behavior as my
> > > custom setup. A quick preliminary test revealed that this is
> > indeed the case
> > > (I noticed similar phase differences between channels).
> > >
> > > In spite of this potential "problem", I am totally sold on
stereo
> > parabolic
> > > recording. If you listen to the mp3 I've posted, using
> headphones,
> > then
> > > you'll hear why. The listening experience is far more
pleasurable
> > that one
> > > has with mono. Off axis sounds come from their proper
directions
> > and the
> > > sense of spaciousness is superb. Listening at home becomes a
real
> > joy, and
> > > monitoring while recording in the field is much more exciting.
> > >
> > > Lang
> >
> >
> >
> > "Microphones are not ears,
> > Loudspeakers are not birds,
> > A listening room is not nature."
> > Klas Strandberg
> >
> >
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> > [Non-text portions of this message have been removed]
>
>
>
> "Microphones are not ears,
> Loudspeakers are not birds,
> A listening room is not nature."
> Klas Strandberg
>
>
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