[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 martin.le...@stanfordalumni.org 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 e...@elcaudio.com To: sursound@music.vt.edu 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
[Sursound] 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. From: Eric Carmichel e...@elcaudio.com To: sursound@music.vt.edu sursound@music.vt.edu Sent: Thursday, June 27, 2013 4:33 PM Subject: [Sursound] Of stereo miking, Fourier analysis, and Ambisonics Many thanks to everyone for your responses and insights (re Giving Precedence to Ambisonics). I would like to comment on the following two responses: 1. from Jeff **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** and 2. from J?rn **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, j?rn** Eric C. responds The array of 2-inch speakers is reminiscent of many psychoacoustical experiments I’ve participated in: More laboratory-like than musical. Note that the clicks run in a sequence in lieu of random places. Once we perceive a pattern (e.g. L to R sequence), we begin to fill in the spaces based on patterns. At least that’s my (intuitive) notion. Also, clicks are among the easiest sounds to localize. The broadband nature of the clicks provides multiple localization clues, to include ILD, ITD, and (very importantly) pinna transfer cues. I have collected data from my personal lab to provide evidence of this latter claim, and I welcome everyone to review and scrutinize it. Listening tests were performed using 8 young, normal-hearing persons. 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., group all female participants), stimuli, listening condition (e.g., unoccluded), or azimuth/location on the fly. You can download the Excel spreadsheet here (again, it's 2.6 MB): www.cochlearconcepts.com/stats/hearing_data.xls Graphical representation of the results (using SPSS) are in the same folder, and you can see it here: www.cochlearconcepts.com/stats/Figure_6_96dpi.jpg As can be seen (and heard!), the broadband stimuli are easy to localize when compared to tonal stimuli. When participants were donning binaural stereo electronic earmuffs (net acoustic gain at ear = 0 dB, carefully calibrated to match earcups), lateralization was accurate. But discerning front-back angles on same side (L or R; e.g., 60 and 120 degrees) was nearly impossible. This demonstrates what happens when ILDs and ITDs are preserved, but pinna cues are lost. You can see spectral and time-domain analysis of the broadband stimuli here: www.cochlearconcepts.com/stats/Figure_1_96dpi.jpg I have to agree with J?rn that the example miking demonstration isn’t all that fair, and for another reason: How much low-frequency energy can a 2-inch speaker provide? Although the Fourier decomposition of a transient or *click* sound may suggest it's a broadband signal, I have reservations about Fast Fourier Transforms and clicks. My reservation is, in part, rooted in my own ignorance of math, but I’ll have to state that I don’t believe the ear works exactly as math would predict. Let me explain... Fourier series shows that an ideal impulse (Dirac delta function or Kronecker delta?) can be decomposed into sine waves, but these waves have to begin in the Paleozoic Era and end when travel to distance galaxies is a reality. 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
[Sursound] Spatial music
Are things really that bad? I need to get out more often! I'm thinking that the 99% own flatscreens by now. If a homebuilder is going to place an electrical outlet on the wall suitable for mounting a flatscreen, he might as well put in suitable-located outlets for in-wall loudspeakers as determined by the location of the flatscreen. As rooms shrink in size and skrink in number, I foresee the media room as the hub of all internet, entertainment and telecommunications of the future. Since living space will be at a premium, a wall-mounted flatscreen and in-wall loudspeakers will become all the more advantageous. --- On Sat, 4/14/12, Ronald C.F. Antony r...@cubiculum.com wrote: On 14 Apr 2012, at 04:46, JEFF SILBERMAN ambis...@pacbell.net wrote: The solution lies in getting the home/spec builder industry to integrate in-wall loudspeakers at pre-specified locations (including ceiling) in the 21st century media room which room will become the new normal much like the kitchen has certain de-facto features/standards which are now taken for granted. In the fullness of time, multichannel audio in the home ultimately will prevail because it is the last frontier. That suggestion may apply for the 1% of people, not for the 99%. More than half the people in the US live what in Europe people would simply call a ghetto, and of the rest, a lot of people are on their way to descend into that level of wealth, given that wages under the new union contracts are not sufficient to sustain what one would call a middle-class life style with secured retirement. To stick to your kitchen mataphor: the 1% have custom cabinets, Sub-Zero refrigeration units, Wolf or some high-end European appliances. For the rest, a kitchen is simply a room with a sink, a super-cheap electric stove and a second-hand fridge. They also don't have a laundry room, they have to go to the Laudromat with their dirty clothes, and I'd venture to guess that people rather invest in their own washer and drier than into a media room of the 21st century. For a technology to succeed, it can't just target those who lead the gilded life. Ronald ___ 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/20120414/96175921/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Spatial music
The solution lies in getting the home/spec builder industry to integrate in-wall loudspeakers at pre-specified locations (including ceiling) in the 21st century media room which room will become the new normal much like the kitchen has certain de-facto features/standards which are now taken for granted. In the fullness of time, multichannel audio in the home ultimately will prevail because it is the last frontier. --- On Fri, 4/13/12, Gerard Lardner glard...@iol.ie wrote I ain't objecting to HOA. I'd love to have a HOA system again for normal listening; I /have/ heard it and agree it is good. But two things argue against it: 1.) Cost for a home installation. Despite what I wrote in an earlier message today, it was hard work to assemble even 8 /good/ speakers cheaply. I got them for HOA, but I probably will not use them for it, at least not for long, because 2) Having lots of speakers on one room is not compatible with home harmony or with visual aesthetics. Sadly, that is the killer. Bandwidth, storage, processing power? Yes, they are all affordable now. Now we need to find a solution to my point 2 above - and that is not an Ambisonics problem! In practice, Ambisonics is most useful as a production tool. Only a dedicated few will use it in a home environment. Only when the speakers can be effectively hidden from view without compromising the qualities needed for Ambisonics and for serious music reproduction will it have the potential to become part of the home system. -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20120413/084cdc8b/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Transient time differences
--- On Mon, 4/2/12, Eric Benjamin eb...@pacbell.net wrote: In subsequent thinking about his question it occurs to me that the plausibility, not of the signals in the recording but of acoustic signals that enter the listener's ears, is an important indicator of whether the listener finds the reproduction to be realistic or not. If our ears receive a large number of cues that are wrong, or at least implausible, then the reproduction is unrealistic. I would hasten to add visual cues as well. Seeing a small listening room and observing loudspeakers interferes with the creation of the illusion. Listening in a pitch black room (no light whatsoever!), as silly as it may seem, is imperative to create the suspension of disbelief. Try it! ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Transient time differences
--- On Mon, 4/2/12, Eric Benjamin eb...@pacbell.net wrote: Don't take this to mean that I don't like ORTF recordings. I do like them. The best stereo recording that I have ever made was an ORTF recording. But then, I'm not a very good recording engineer. I think that one of the reasons that I like ORTF is that it introduces an artificial spaciousness which may compensate for the spaciousness that is lost in stereo reproduction. I think you might find that this lost sense of spaciousness (IACC) is attributable to 60-degree stereophony. Three-speaker stereophony (Trifield decoded) with the left/right loudspeakers subtending a 90 degree arc does not suffer from a lack of spaciousness thus obviating the need to create artificial spaciousness a la spaced-omnis in order to compensate for 60-degree stereophony. ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
