Re: [Sursound] Giving Precedence to Ambisonics
On 06/26/2013 07:02 PM, Eric Carmichel wrote: 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. If you do that, you are also recreating the comb filter effect :) Frankly, I've never been much of a Decca Tree fan for stereo. For LCR however (e.g. the frontal part of a 5.1 mix or anything with a dedicated center), it's quite useful. I've even used it for live sound amplification in theatres with a good center cluster. best, Jörn -- Jörn Nettingsmeier Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487 Meister für Veranstaltungstechnik (Bühne/Studio) Tonmeister VDT http://stackingdwarves.net ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Giving Precedence to Ambisonics
Your memory jives with mine though as I recall, the instruments did surround the Soundfield. The vocalist was not recorded directly; rather, her voice was amplified through a loudspeaker positioned in front of the Soundfield. Jeff silberman > > From: Martin Leese >To: sursound@music.vt.edu >Sent: Wednesday, June 26, 2013 10:53 AM >Subject: Re: [Sursound] Giving Precedence to Ambisonics > > >Eric Carmichel wrote: >... >>> 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. > >The Trinity Session is CD UHJ encoded, so >can be decoded to surround sound using an >Ambisonic UHJ decoder. However, when you >do this, the performers are (correctly) located >in strange places. This suggests that the UHJ >was not intended to be decoded. Instead, >decode it using the Super Stereo mode. This >keeps the performers at the front where they >"belong", while still surrounding the listener >with the ambience of the Trinity Church. > >From memory, the recording engineer has >said that the output from the Soundfield mic >went straight into a UHJ encoder, and only two >channels were recorded. If true, this means >that the recording can not exist in B-Format. > >Regards, >Martin >-- >Martin J Leese >E-mail: martin.leese stanfordalumni.org >Web: http://members.tripod.com/martin_leese/ >___ >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/20130627/a3465061/attachment.html> ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Giving Precedence to Ambisonics
May I suggest "Demonstration of Stereo Microphone Techniques," Performance Recordings #6 wherein 18 coincident, near-coincident and spaced omni (2 and 3 mic) stereo techniques are compared via a line of loudspeakers mounted at equal intervals and spanning 10 1/2 feet left-to-right. Each loudspeaker was 2 inches in diameter and the center to center spacing was 9 inches. An electronically generated tick was switched to each loudspeaker in turn starting at the center and moving full right, full left and full right again before ending in the center. The pros and cons of each technique are unmistakable... Jeff Silberman > > From: Eric Carmichel >To: "sursound@music.vt.edu" >Sent: Wednesday, June 26, 2013 10:02 AM >Subject: [Sursound] Giving Precedence to Ambisonics > > >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/20130627/63af75de/attachment-0001.html> ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Giving Precedence to Ambisonics
On 06/27/2013 01:27 PM, JEFF SILBERMAN wrote: May I suggest "Demonstration of Stereo Microphone Techniques," Performance Recordings #6 wherein 18 coincident, near-coincident and spaced omni (2 and 3 mic) stereo techniques are compared via a line of loudspeakers mounted at equal intervals and spanning 10 1/2 feet left-to-right. Each loudspeaker was 2 inches in diameter and the center to center spacing was 9 inches. An electronically generated tick was switched to each loudspeaker in turn starting at the center and moving full right, full left and full right again before ending in the center. The pros and cons of each technique are unmistakable... hi jeff, i think the test you're mentioning is not entirely fair, as much as i like coincident techniques. such a setup tests for localisation only, and with wide-band transients. it is quite clear that spaced techniques will lose, and their main advantage (better perceived spaciousness in stereo-only playback, and better LF response) is not even considered. miking is a trade-off. testing individual aspects won't tell us much about actual musical use. best, jörn -- Jörn Nettingsmeier Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487 Meister für Veranstaltungstechnik (Bühne/Studio) Tonmeister VDT http://stackingdwarves.net ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Giving Precedence to Ambisonics
I use an array which is an extented OCT array with M/S and a center and two hypercardoid mics pointed at +/- 90 degrees at aproximately 0.5 meter laterally. I have found that we have been ignoring the precedint effect in music reproduction. In the classic reproduction situation, i.e. 6 feet from each speaker and spaced 6 feet apart, you will find that the image will move to one side or the other if you move your head by as little as 6 inches. Any mixer will confirm this experience. By adding time to the recording you can keep the edges still left and right however the center will move as you move. ThomasChen -Original Message- From: Aaron Heller To: Eric Carmichel ; Surround Sound discussion group Sent: Wed, Jun 26, 2013 11:06 am Subject: Re: [Sursound] Giving Precedence to Ambisonics 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 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.
Re: [Sursound] Giving Precedence to Ambisonics
On Thu, Jun 27, 2013 at 01:52:55PM -0400, Thomas Chen wrote: > By adding time to the recording you can keep the edges still > left and right however the center will move as you move. The center still moves, as by symmetry you can't use delays there. The edges will stay put even without delays as they are only reproduced by one speaker. Using delays to keep something fixed in between the center and the edges seems at least as unstable as using amplitude differences alone, unless the delays are so large that they will pull such sources to the edges anyway. So what is the point of using delays ? Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Of stereo miking, Fourier analysis, and Ambisonics
wn to mono for non-stereo broadcasts. There are two additional Excel files in the aforementions stats folder. One is titled keyboard: www.cochlearconcepts.com/stats/keyboard.xls This file merely generates piano keyboard note frequencies for any arbitrary A4. Throughout history, I believe A4 has changed (e.g. A4 = 376 Hz in lieu of 440 Hz). I had developed this spreadsheet because of a discussion that goes way back. I am not a musician, but am learning music theory from books and CDs. The last Excel file has to do with Ambisonics: It was my speaker positioning calculator based on the corner of a room being the origin of a Cartesian coordinate plot. Units are English because my tape measure is in feet and inches. Instead of using a compass, radians, and the center of a circle, I used basic (x,y) coordinates relative to walls to accurately position loudspeakers. Probably not worth explaining further, as this calculator is somewhat specific to my listening room. But if anybody can use it, please do so. Kind regards, Eric -- next part -- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20130627/0c874042/attachment.html> ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Corrections to recent post (10 min. ago)
Greetings, I just checked links to my recent post, and discovered that "stat" must be a forbidden file name (I assume intended for gathering stats on a site?). Anyway, I created a new folder, statistics, and Excel docs and jpg images can be found using links below. Eric C. responds... A rather large (2.6 MB) Excel spreadsheet contains all the data. I designed this spreadsheet to provide descriptive statistics for any combination of listeners (e.g., all female participants), stimuli, listening condition (e.g., unoccluded), or azimuth on the fly. Download spreadsheet here: www.cochlearconcepts.com/statistics/hearing_data.xls Graphical representation of results (using SPSS) are in same folder, and you can see here: www.cochlearconcepts.com/statistics/Figure_6_96dpi.jpg You can see spectral and time-domain analysis of the broadband stimuli here: www.cochlearconcepts.com/statistics/Figure_1_96dpi.jpg There are two additional Excel files in the aforementions stats folder. One is titled keyboard: www.cochlearconcepts.com/statistics/keyboard.xls It merely generates piano keyboard note frequencies for any arbitrary A4. The last Excel file has to do with Ambisonics: It was my speaker positioning calculator based on the corner of a room being the origin of a Cartesian coordinate plot. www.cochlearconcepts.com/statistics/big_array_calculator.xls -- next part -- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20130627/e234ba70/attachment.html> ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Of stereo miking, Fourier analysis, and Ambisonics
gt;There’s something about the time domain aspect of *real-world* sounds that is >missing. So how does the ear respond? >Imagine the inner ear is comprised of contiguous filters. Perhaps the ears >inner hair cells (IHCs) are akin to the reeds of a resonant reed frequency >meter (which can have very fine frequency discrimination ability). Regardless, >how would such filters respond to click sounds or similar transients? A click >in itself doesn’t last long, and certainly the click's period much shorter >than a fraction of a low-frequency sound’s period. But yet, we rely on IRs and >maximum length sequence (MLS) stimuli for response characteristics as well as >hearing demonstrations. Back to 2-inch speakers... >At least the low mass and confined acoustic centers of tiny speakers make them >ideal for transient bursts, but then what instruments aside from a woodblock >does this represent? There always seems to be trade-offs when it comes to >miking, and some of these have to do with mixing down to mono for non-stereo >broadcasts. >There are two additional Excel files in the aforementions stats folder. One is >titled keyboard: > >www.cochlearconcepts.com/stats/keyboard.xls > >This file merely generates piano keyboard note frequencies for any arbitrary >A4. Throughout history, I believe A4 has changed (e.g. A4 = 376 Hz in lieu of >440 Hz). I had developed this spreadsheet because of a discussion that goes >way back. I am not a musician, but am learning music theory from books and CDs. >The last Excel file has to do with Ambisonics: It was my speaker positioning >calculator based on the corner of a room being the origin of a Cartesian >coordinate plot. Units are English because my tape measure is in feet and >inches. Instead of using a compass, radians, and the center of a circle, I >used basic (x,y) coordinates relative to walls to accurately position >loudspeakers. Probably not worth explaining further, as this calculator is >somewhat specific to my listening room. But if anybody can use it, please do >so. >Kind regards, >Eric >-- next part -- >An HTML attachment was scrubbed... >URL: ><https://mail.music.vt.edu/mailman/private/sursound/attachments/20130627/0c874042/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/20130627/ae9b413b/attachment.html> ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Of stereo miking, Fourier analysis, and Ambisonics
Hello Jeff, I wasn't criticizing the preferred miking technique; just saying the demo itself had inherent limitations. One of my favorite mic techniques is the Blumlein arrangement, but this isn't terribly popular in the US. The disadvantage of the Blumlein is that sound sources from the rear of the mics get reversed. For ambience recording, this goes unnoticed. The technique assumes that the live source is *stereo* too; that is, a stage ahead of the mics with musicians aligned in rows that have L-R orientations. My work has a lot to do with hearing and the perception of environmental sounds that have random spatial orientations (or moving sound sources)--and sounds come from all directions (at least above ground level--usually): I guess that's why I like to experiment. A lot of music recordings are hyper-real (as I like to put it) in that the clarity and spatial imaging is better than what I experience in most live venues. Recording is an art, and I encourage novices and professionals to explore. I've created a few listening demos to showcase certain mic techniques, but I'm aware of the shortcomings of the demos (nothing's perfect). Best regards, Eric From: JEFF SILBERMAN To: Eric Carmichel ; "sursound@music.vt.edu" Sent: Thursday, June 27, 2013 7:32 PM Subject: Of stereo miking, Fourier analysis, and Ambisonics I agree with your criticism, of course, but the demonstration is nonetheless instructive as it highlights the localization deficiencies of spaced techniques apart from the obvious other advantages. I readily acknowledge miking is a trade-off, but I fear that too few recordists fully appreciate the advantage of coherent localization NOT to spoil the listener's suspension of disbelief in the illusion of stereophony as do incoherent "spaced mono" techniques. -- next part -- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20130627/00851048/attachment.html> ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
