No. Ambi Super Stereo isn't just feeding the stereo into a UHJ decoder. This is a post from 2006. I'd recommend a "Width" control so you can decide how wide you want your stereo.
All the decodes here are basically the same with different "Width" settings. Only minor differences, with preference in Barton 82. I distinguish between WXY which is strict FuMa and W' X' Y' which already have Shelf Filters applied. Stereo, SuperStereo use the same Shelfs as FuMa. ie normal B-format Shelfs as described in BLaH3. UHJ will need different ones which are in Fig 3.3 "SHELF FILTERS for Ambisonic Decoders" _____________________ Michael's solution circa late 80's and used in most Ambisonic decoders of that period. MINIM W = 0.3667 M + j 0.3586S M = L + R S = L - R X = 0.529 M - j 0.404 S Y = S >From examination of the simple Minim circuit on RKRs >http://www.geocities.com/ambinutter. "Strict" B-format The next 2 are from http://www.geocities.com/ambinutter/UHJ_and_Ambisonic_equations.html Two approaches, from WW 1977 INTEGREX W' = 0.717S - 0.291jD 1.23 M - j 0.4991 S Stereo X' = 0.717S + 0.291jD 1.23 M + j 0.4991 S Y' = 0.583D S W' X' Y' are feeds to the Speaker Matrix at HF after Shelf filtering as noted in the 1977 Integrex article. I also show this normalised to Y' = S for comparison with the Minim. NO FURTHER SCALING REQUIRED. W = 0.65S - 0.27jD(a /180) 0.8667M - j 0.36 S Super Stereo KEATING X = 0.98S + 0.40jD(a /180) 1.307M - j 0.5333 S Y = 0.75D(a /180) S where: S = Left + Right D = Left - Right a = Width control, varying between 0 and 180° j = 90° phase shift Yes probably from "The generation of virtual acoustic environments for blind people" by D A Keating at the University of Reading. I took this straight off RKRs web page so don't know if it's "Strict" or HF. Probably "Strict". I presented these 3 cos they were different and seemed to represent Michael's thinking over time, 1977 Integrex, Superstereo Keating?, then 1980s Minim. Geoff Barton 1982 W = 0.6098637*S - 0.6896511*j*w*D 0.36253 M - j 0.40996 S w X = 0.8624776*S + 0.7626955*j*w*D 0.51270 M + j 0.45338 S w Y = 1.6822415*w*D - 0.2156194*j*S S w - j 0.12817 M where 'w' is a width setting, the optimal (in some senses) value of which is about 0.593, S & D are as defined above. NB, in MAG's notation W'' etc is the signal after the shelf filter, W before. "Strict" B-format. For w = 1, this is very similar to the "Minim", except for the j 0.12817 M term which is a bit of Forward Preference. But adding this means it doesn't drop to strict mono when w = 0. You could consider the "Minim" a simplified version of 1982. Applying w = 0.593, moves it nearly towards the Keating and 1977 Integrex decoders. Correct value for w, a, width etc. depends on what angle you think a stereo stage should extend. Opinions directly to Robert Greene please. Can anyone report on listening tests for any of these? eg like Steve Thompson. I played a bit 20+ yrs ago but seem to remember the 1977 Integrex was as good as anything fancier. Work really well on Blumlein. Show spaced omnis as crap. Richard L PS I've taken the liberty of editing the above to use W X Y ONLY for strict B-format. PPS The above encodes (except for the Integrex) are suitable ONLY if the decoder uses full Shelf Filters. If not, you need to use "Energy" playback. see "SHELF FILTERS for Ambisonic Decoders" from ambisonicbootlegs.com _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
