I like to think of natural silence as the canvas upon which other sounds are painted. (Dr. Timothy C Mullet)
MONO-STEREO SETUP FOR PARABOLIC MICROPHONE
People often debate the use of mono or stereo microphones inside a parabolic dish. This I have already mentioned here.
In summary: some prefer a mono recording for a “clean” use with spectrogram analysis, others prefer to obtain a stereo recording to have a pleasant soundscape. However, a stereo recording does not exclude the possibility of being able to use only one channel of the two to still obtain a good spectrogram.
Personally, I have always thought that the best thing would be to have both opportunities.
This is why I thought of designing and manufacturing (for my personal use) a Mono/Stereo microphone baffle to be inserted in a parabolic dish, which gives the possibility to separatly connect one of the two configurations when using a two-channel recorder, or both configurations at the same time if using a mixer/recorder with at least three channels..
Above the project drawing of the baffle and below the 3D printed realization of the microphone assembly.
Stereo capsules L-R; M = mono capsule facing towards the inside of the dish. __________________________________________________________________________________________________
UPDATE:
I performed a Mono vs. Stereo test on Common Nightingale song.
I used a Sound Devices 302 connecting channels 1-2 to the 1+1 AOM 5024 capsules stereo baffle inserted in a 53 cm parabolic dish, while to the third channel is connected the single AOM 5024 capsule (see the picture above).
I first recorded with only the channel 3 signal to obtain a mono recording, then with the two channels 1 and 2 linked in stereo mode. As a recorder I used a Tascam DR05x connected via a splitter cable to the OUT tape of the SD 302.
Common Nightingale Luscinia megarynchos song – First MONO, then STEREO
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I asked about adding the two signals Mono+Stereo to Jules Ryckebusch who replied:
“The signals are adding. So that gives you, in theory 2X signal that works out to 6dB. It’s what people do when putting four mics in an array too. The correlated signal adds 6db and the uncorrelated noise only adds 3dB so there is an improvement in signal to noise ratio”.
Here a quick audio test using a metronome
below European robins at dawn (mono + stereo – Sound Devices 302 mixer + Tascam DR05X)
Is there a reason why you choose for 3000Hz ie baffle 11,5cm? All above is recorded in stereo and all below is recorded in “mono” because the frequency goes around the baffle.
This article, particularly in Figure 4, can help
https://avesrares.wordpress.com/2016/04/28/diy-parabola/
Two questions: Do you need a mid-side to stereo convertor? Has somebody tried 2 mono capsules parallel and L+R out of phase as figure 8 side mic?
Yes, I know using for some capsules it is possible 2 mono capsules parallel and L+R out of phase, but with those I use it is’nt possible.
For the stereo converter, it depends: if I use a Zoom F8 or another similar recorder I use Rode’s VXLR+ converter to feed the capsules while the recorder is setted to Mid Side recording mode.
But for Mid Side in parabola see my dedicated page https://www.naturesound.it/mid-side-in-parabola/
Peter,
this is not a Mid Side configuration, although it may seem at first glance, so it does not require a Mid Side decoding.
Could we consider this type of configuration a sort of Mid Side without the possibility of adjusting the stereo width? It may be…
How can a stereo recording be used to achieve a pleasant soundscape while still allowing for the option of using only one channel for spectrogram analysis?
I made this setup exactly with this target in mind: to have at the same time the two option, stereo and mono. Obviously one need to operate with a multichannel recorder, at least a three channels recorder, for instance Sound devices mixpre 3, or a simply Tascam dr 70d.
If on the other hand you just have a stereo recording, to have a useful spectrogram it is sufficient to select one of the two channels, possibly the best for the target species.