Hello David,
> Mike,
>
> First off what planar transducers are you using? What's the specs?
They are headphone transducers from Fostex. A flat printed coil between an
array of bar magnets:
http://www.fostexinternational.com/docs/products/RP-Series.shtml
http://www.urlme.net/blog/?p=1881
They did make a flat planar ribbon microphone years ago using the same
principle but lately only the RP series of headphones.
Limited in the highs > 8Khz and low end needs EQ compensation.
However they are very robust compared to a traditional ribbon mic or the
expense of shures roswelite. For loud natural sources that is, I wouldn't
advise using these in a quiet setting due to low sensitivity (estimated at
5.6mV/PA after a 1:20 transformer)
> I like listening to experimental stuff. It checks out the theory and
> my prejudices. :-) I predicted that the wooden spheres would give a
> mainly HF stereo effect and that the stereo on the parallel
> bidirectional pair would be reduced.
>
> On listening I am surprised at the quality of the Faulkner. It had a
> clarity which was lacking in the spheres, which sounded a bit -
> sorry - wooden. :-)
LOL - by clarity is there a specific frequency band or general muddy area that
can be identified?
> The stereo image of both was limited and the
> traffic noise was nebulous and "phasey". Don't know why - just not
> focussed.
Could be due to the source direction which varies with the traffic. Also
thunder in this area tends to exhibit a delay like phase sound depend on its
location,eg sounds going around the house are very poor.
There is a hedge directly in front of both rigs, behind and above the porch
which overhangs. In theory this would create a rather large cavity with open
sides. But enough to over? emphasise the floor and roof reflections. Ive
noticed 1 Khz is +3dB compared to not recording under the porch. Its a rather
convenient location for simple tests due to it being out of the rain.
> I would suspect reflections between the inside of the
> windgag blimp and the spheres. We pay three zeroes for our mics and
> then put them inside a babygro. :-) I know, I invented the original
> outer Brinisock.
Ive often thought what effect the hexagonal structure in the rode blimp brings
but never thought to measure it. Im sure it would be of interest to others also
- Ive not seen such data from Rode either.
>
> With the Faulkner, I didn't expect a wide image angle, and it sounded
> limited to about 45 deg either side. Time Stereo does need a bit of
> help from amplitude stereo as well, but the front stereo image was
> much better than I expected. 20cm is wider than dummy head spacing but
> how wide are the transducers themselves?
around 20mm square
If they are significantly wide, some of the theory goes out of the window. :-)
>
> For analysis. I derived M and S signals (thanks for making it
> downloadable) The S signal from the spheres was mainly mid to high
> frequencies, leaving the bass end to the M. The overall effect was a
> limited stereo width, a bit of muddiness and some out of phase
> backgrounds.
Interesting Ive often made such analysis from dummy head recordings, its
surprising how much information can be pulled out in mid/side.
>
> The Faulkner S had quite a lot of bass in it, giving a bass spread in
> the stereo image. Good thunder. The M was nice and clean, especially
> with the thunder. Rain and foreground sounds were sharp and well
> placed with background noise - traffic - fuzzy, but not a problem.
The taffic din is behind the rig which is obstructed by the house.
> think a 45/45 Blumlein pair would have given a wider image, so objects
> at 45 would map to 90 ie full left or right, but it would also have
> given a 360 deg pickup with out of phase sides.
Ill try that.
>
> The directionality of the Faulkner is limited to a vertical doughnut
> of reduced sensitivity, but this may have limited the tree noise and
> ground reflection and improved the overall clarity. The good news is
> that the rear pickup remains mainly in phase. There is a general bias
> in the stereo towards the left - is this the tree or trees?
More trees on the right, the rig was also at a slight angle to the road passing
on the left.
> The thunder is well placed, so I assume that was left, mid and right as it
> sounded.
>
> To see what the object/image relationship is like, do a walk-around
> like my shaking peanuts test, or use s fixed multi-frequency source
> like a running engine and rotate the mic rig slowly. I'd predict that
> the image angle would generally be smaller than the object angle (for
> example a 180deg spread comes out as a 90deg spread) and
> that the sensitivity would fall off from about 70 deg each side.
>
Will do this.
> The Faulkner rig defeated some of my prejudices, but remains best
> heard binaurally. It gave stereo on close speakers, but was better on
> cans. I doubt if it would work as well on a room hi-fi setup. The maim
> snag I can see for wildlife use is its rear sensitivity.
I think the rear response is partially attenuated by the house, which sadly
isn't very a portable object to carry in the field :)
I will test it in open space, specifically if there is a front / rear confusion
in headphones.
> Indoors it is
> going to pick up a lot of unwanted reverb.
>
Thank you for your comments,
-BR
Mike.
Off topic: A diy pip powered M/S mic into Sony D50 which is lower noise than
the dynamic transducers.
http://soundcloud.com/urlme/mid-side-bike-pass
> David
>
> David Brinicombe
> North Devon, UK
> Cogito cogito ergo cogito sum - Ambrose Bierce
>
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