Ron Streicher has written about using a Soundfield as the middle mic in a Decca tree
http://www.wesdooley.com/pdf/Surround_Sound_Decca_Tree-urtext.pdf and Tom Chen has a system he calls B+ Format, which augments first-order B-format from a Soundfield mic with a forward ORTF pair. I've heard it on orchestral recordings at his studio in Stockton and it sharpens up the orchestra image nicely. Aaron Heller (hel...@ai.sri.com) Menlo Park, CA US On Wed, Jun 26, 2013 at 10:02 AM, Eric Carmichel <e...@elcaudio.com> wrote: > Greetings All, > I have a friend who's an advocate of the Decca Tree mic arrangement. Many > of his recordings (a lot of choir and guitar) sound quite nice, so I looked > into aspects of the Decca Tree technique. For those who may not be > familiar, the *traditional* Decca Tree arrangement is comprised of three > spaced omnidirectional mics. A center microphone is spaced slightly > forward. From what I've read thus far (Spatial Audio by Francis Rumsey, > Focal > Press; and selected articles in the AES Stereophonic Techniques > Anthology), the slightly advanced time-of-arrival for the center mic > stabilizes the central image due the precedence effect. However, the > existence of the third (center) mic can result in exacerbated > comb-filtering effects that can arise with spaced pairs. So, to avoid these > filtering effects, bring on a Soundfield / Ambisonic mic...?? > As I understand, Ambisonics already takes into consideration known > psychoacoustical principles, and is why shelving is used to *optimize* ILDs > and ITDs above and below 700 Hz, respectively. But as many readers may > know, there are some nearly unpredictable ILD/ITD effects at approx. 1.7 > kHz (for example, see Mills, 1972, Foundations of Modern Auditory Theory). > Creating a virtual Decca Tree seems straightforward. To move the center > channel, or a virtual mic *forward* would require little more than offline > processing. I wonder whether anybody has tried the following: Slightly > delay all channels except the signal (or feeds) that make up the > forward-most (central) channel. Using an Ambisonic mic would eliminate > combing effects. I realize a number of Ambisonic plug-ins have built-in > crossed-cardiod, Blumlein, and spaced omni functions, but not sure I've > seen any of them give *precedence* to the precedence effect or Decca Tree > arrangement. > Two-channel playback (both convention and binaural) is here to stay for a > while, so optimizing Ambisonics for stereo is desirable to me. In fact, one > of my favorite recordings from the late 80s was made with the band (The > Cowboy Junkies) circled around a Calrec Soundfield mic. I've never heard > whether the Trinity Session recording was released in a surround format, or > if the mic's hardware decoder converted straight to stereo from the get go. > That particular recording made me aware of the Soundfield mic, though > surround sound wasn't an interest for me at that time. > If anybody I had attempted the Decca Tree using an Ambisonic mic (even > with addition of a separate and forward omni mic), I'd be interested in > knowing what your experiences were. > Many thanks for your time. > Best, > Eric C. (the C continues to remind readers that this post submitted by the > *off-the-cuff* Eric) > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > https://mail.music.vt.edu/mailman/private/sursound/attachments/20130626/535efc06/attachment.html > > > _______________________________________________ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound > -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20130626/1de5eaf1/attachment.html> _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
