Re: [Sursound] OT Stereo stage width - Was: Static stereo source in rotating soundfield, possible?
Hi, I'll not copy what has already been said, as this discussion has got fairly lengthy. Perhaps "normal" stereo with speakers at plus and minus 30 degrees came about from a variety of things. The preponderance of control rooms that are rectangular, with speakers mounted near the corners of the the shorter side of the room. A sense of perspective, in that listeners were accustomed to performers being in front of them. Many orchestral recordings were done with microphones being nearly overhead to the conductor, so much closer to the orchestra than the audience with a much wider image. This would emphasise the orchestral sound over the sound of the concert hall, and result in a "clearer", if somewhat unnatural, recording. A narrower angle between the loudspeakers than between the microphone capsules (in the case of crossed cardioids) would place the orchestra more in front of the listener with reduced width, and in the listening space. Even with pop, rock or electronic "tape" music the expectation is that a performance takes place in front of you. The fact that much work in some form of spatial audio was done for cinema use, with a frontal screen of limited width. The use of a centre channel for dialogue helps enable a more consistent coverage centred on the screen throughout the cinema, without the problems of comb filtering encountered with spaced left/right speakers. Ciao, Dave Hunt ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
[Sursound] OT Stereo stage width - Was: Static stereo source in rotating soundfield, possible?
Aaron Heller wrote > Marc Lavall, Eric Benjamin, and I put together a Trifield (three speaker > stereo) plugin and demo'ed it a Burning Amp last fall. It is hosted at https://bitbucket.org/ajheller/trifield/overview > There are also some plots that use Gerzon velocity and energy localization > vectors (rV and rE) to analyze, +/-45 deg stereo vs Trifield vs +/- 30 deg > stereo that shed some light on why "the +/- 30 deg stereo triangle" works > well. Thanks for this Aaron, Eric & Marc. There's a small error in the last pic "Magnitude of Localisation Vectors +/- 30". The x-axis should be from -30 to +30. You can extend the info to -45 to +45 virtual sources by panning beyond the speaker positions and show +/- 30 is still 'better' than +/- 45 speakers. You can also show the DIRECTIONS of the rV & rE vectors are more in synch for the +/- 30 case I did a lot of this stuff in my mispent youth trying to apply Gerzons theories to stereo. Another big effect of wide speaker spacing is the frequency response of the virtual source varies a LOT more with position. It's bad enough with +/- 30 speakers. You can test this for yourself by comparing a mono source panned to the centre (or near centre) with it panned to L or R. The exact centre is also prone to HUGE comb filter effects. All these effects (image stability via rE & rV, frequency response, comb filtering) are reduced if the speaker spacing is reduced (with proper compensation via more L-R bla bla ... to maintain image width). The various Transaural / Stereo Dipole / Ambiophonic systems may be considered sophisticated variants of this. Stefan Schreiber wrote : How can rV > 1 be true??! (second last image...) Gerzon's infamous vector magnitudes rV & rE are a measure of image stability with head movement. Small magnitudes mean the image moves LESS than you'd expect in 'real life'. In theoretical 'real life' (?!?) rV = rE = 1 .. but actually the magnitudes are usually slightly less than 1.0 An rV > 1 means the image moves MORE than in 'real life'. Very large rV s are unnatural & disturbing as they are VERY uncommon in 'real life'. You can get a taste of this by listening to normal +/- 30 stereo with L-R turned up. Also some of the more naive early surround sound systems. All explained in the Appendix of Gerzon's "General Metatheory of Auditory Localisation," Preprints from the 92nd Convention, Vienna, no. 3306, 1992. He shows how his rV & rE theories model (give the same answers as) all models of auditory localisation except for the impulsive HF and pinnae colouration models. This Appendix is required reading for anyone interested in auditory localisation. please reply to rica...@justnet.com.au NOT to the yahoo address which is riddled with spam. I never look at it. -- next part -- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20160401/95398edd/attachment.html> ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
