Thanks for the delta stereophony history Dave, interesting! > Current products do not allow progress to true Delta Stereophony (DBADP)
Well conceptually it should be possible if, beyond aux mixes, you have a further layer of mixes that can comprise aux bus sends (with controllable delays/filtering/volumes) as well as input channels. A possible problem is not having sufficiently small delay increments, and not having smoothing within the device. Anyway, its worth doing some experimentation! Implementing DBAP or VBAP is fine. > DSP chips are now capable of providing it Yes, there is a Sharc DSP in the miniDSP speakers we use, and a controllable 32x2 matrix with delays/attenuation at the cross points. As you say, running Spat and a DAW is processor intensive. This was one of the reasons we have turned to using the processors in current devices to do the post-render mixing/delays. Having this capability in a speaker is great, because your processing capability grows with each speaker. Having it in an audio interface/mixing desk means that all the inputs - analog/usb/ADAT/… can have spatialisation applied to them. > On 15 Nov 2020, at 13:56, Dave Hunt <davehuntau...@btinternet.com> wrote: > > Hi Richard, > > I’ve changed the title of this topic to something more relevant. > > I still prefer the term Delta Stereophony to describe this. It seems to date > back to the mid 1980’s, and was described by Gerhard Steinke and Wolfgang > Ahnert. They were working in East Germany behind the Iron Curtain, reputedly > working with Sinclair ZX Spectrum computers and expensive AKG delay lines > somehow imported from Austria. > > It does make a great deal of sense. When digital delay lines became more > generally available and affordable (1990’s ???) they were increasingly used > in public address systems to improve coverage over a greater area, using > speakers down the length of an auditorium to augment the usual left/right or > LCR main frontal system. The feed to these was delayed by an amount that > caused the time of arrival of sound from them to match that of the main > frontal system . Sometimes the feed to a "front fill” system, arrayed along > the front of the stage to increase clarity in the rows of seating near the > stage, was also delayed to match the time of arrival of sound from its > source. Amplitudes were usually adjusted by ear, as indeed were delay times > after an initial calculation. > > These systems were more “appropriately distributed mono” than spatial. It is > impossible to get the delay/amplitude combination correct for every position > in the space with a finite number of speakers and output channels, so > compromises are inevitable. This became common practice, especially for large > scale stadium events. Digital mixing desks now commonly incorporate delays on > each output, making this simpler to implement. > > Current products do not allow progress to true Delta Stereophony (DBADP), as > the architecture does not provide delay as well as amplitude control on each > matrix crosspoint, and the market doesn’t expect or demand it. DSP chips are > now capable of providing it, as proved by TiMax, LISA, d&b’s Soundscape, > Iosono , Astro, and Meyer’s relaunched system. The market is small, and the > DSP boxes pricey. It becomes relatively more affordable for large > multi-speaker systems with large budgets. > > For the rest of us, it’s down to software. Ircam have a basic implementation > of DBAP in Spat~ for Max/MSP (or you can roll your own), and adding the delay > component is relatively simple. You can then scale the amplitude and delay > separately for each source, as seems appropriate. Using delay alone is > surprisingly effective. The variation of amplitude between widely spaced > speakers can be excessive. > > Of course you need a fast and powerful computer, and efficient programming to > do this, but that is also true with any of the alternative algorithms > (ambisonics, VBAP, DBAP, WFS etc.). None of these are perfect for every > situation, and it is hard to envisage a combination of them that would work. > > Ciao, > > Dave Hunt > > >> On 14 Nov 2020, at 17:00, sursound-requ...@music.vt.edu wrote: >> >> From: Richard Foss <rich...@immersivedsp.com> >> Subject: Re: [Sursound] Was: Recorder for ORTF-3D OUTDOOR SET >> Date: 14 November 2020 at 16:48:36 GMT >> To: sursound@music.vt.edu >> >> >> Dave, I have meant to follow up on your message for some time, because your >> ideas match what I am currently busy with - at last getting to it! >> >> Our first immersive audio implementation uses networked PoE miniDSP speakers >> which each incorporate a matrix mixer with volume and delay control at the >> cross points. The delays were a later addition, and I certainly found that >> the localization was enhanced by incorporating delays. We implemented DBAP >> for the amplitude panning, but we have implemented and experimented with >> VBAP. Given that our targeted applications will need irregular speaker >> configurations, we have settled on DBAP for now. >> >> We had an idea, similar to yours, to utilize the signal processing >> capabilities of audio interfaces/mixers. Because we owned MOTU devices, we >> tried this first on three of the MOTU devices, and have updated our ImmerGo >> software to work with these interfaces. However, it was not possible to >> implement a delay matrix on the MOTU devices, so they just have a DBAP >> implementation, not DBADP (your innovative label:)). >> >> I am now working on a mixing console implementation where I believe I can >> have delay/EQ at matrix cross points for a few channels, where there is an >> inverse relationship between number of speakers and number of channels with >> delay/EQ, although all channels can have DBAP. One does need to have mix >> buses to enable this, and also there often is the timing constraint, because >> a lot of messages go to the mixer as the sound sources are spatialized. I >> have found that the MOTU devices are very responsive in this regard. >> >> Anyway, good to have a fellow DBADP enthusiast . >> >> Regards, >> >> Richard. >> >> — >> Richard Foss (PhD) >> Software engineer/director >> >> ImmersiveDSP >> 46 Silver Ranch Estate >> Keurbooms River Road >> Plettenberg Bay 6600 >> South Africa > > _______________________________________________ > 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 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.
