Hi Martin, A few things...
1. You should use a first-order decoder to play first-order sources. That's not the same as playing a first-order file into the first-order inputs of a third-order decoder. 2. 1st-order periphonic (3D) ambisonics on a full 3D loudspeaker array gets the energy correct, and hence the sense of envelopment; localization is not that precise. The magnitude of the energy localization vector, rE, in this situation is only sqrt(3)/3, which Gerzon noted is “perilously close to being unsatisfactory." [1] 3. The decoders in the AmbiX plugins are single-band rE_max decoders, a dual-band decoder will improve localization for central listeners a bit. Both Ambdec and the FAUST decoders produced by the ADT (the ".dsp" files) support 2-band decoding. 4. If you really want more precise localization, consider parametric decoding using Harpex or the Harpex-based upmixer plugin from Blue Ripple Sound. In my experience, it works very well with panned sources and acoustic recordings in dry environments (outdoors, dry hall). For recordings in very reverberant halls (like my recordings), the improvement is not that great. Aaron (hel...@ai.sri.com) Menlo Park, CA US [1] Michael A. Gerzon. Practical Periphony: The Reproduction of Full-Sphere Sound. Preprint 1571 from the 65th Audio Engineering Society Convention, London, February 1980. AES E-lib http://www.aes.org/e-lib/browse.cfm?elib=3794. 1. On Wed, Jul 5, 2017 at 3:10 PM, Martin Dupras <martindup...@gmail.com> wrote: > I've deployed a 21-speaker near spherical array a few days ago, which > I think is working ok, but I'm having difficulty with playing back > some first order A-format recordings on it. They sound really very > diffuse and not very localised at all. I figured that some of you good > people on here might have some idea of where I might be going wrong or > what is not right. > > At the moment I'm using Reaper, and for decoding I'm using Matthias > Kronlachner's Ambix decoder plug-in, with a configuration that I've > calculated with Aaron Heller's Ambisonics Decoder Toolbox. I think the > decoder configuration is right. I've calculated it with ambix ordering > and scaling, and third order in H and V. The speaker array has six > speakers at floor level (-22 degrees elevation), eight at ear level at > 1m70 (0 degrees elevation), six at 45 degrees elevation and one at the > apex. > > Now: if I pan monophonic sources using a panner (e.g. o3a panner, 3rd > order), the localisation is pretty good. I've tested that with several > people by panning to random places and asking to blindly point out to > where they hear the source. Generally, they're in about the right > place (say within 45 degrees on average.) > > On the other hand, if I play 1st order A-format recordings (mostly > that I've made using our Core TetraMic), the localisation of sources > is pretty poor. I also tried with the "xyz.wav" example file from Core > (https://www.vvaudio.com/downloads) with the same results. To convert > from A-format to B-format, I've tried using Core's VVtetraVST plugin > with the calibration files for the mic (followed by the o3a FuMa to > Ambix converter), and the Senneheiser Ambeo plugin (which does the > same job, but in Ambix form already.) > > So what am I doing wrong? I've spent the last couple of days checking > everything thoroughly. I've calibrated all the speakers to within 1dB > SPL for the same signal received with an omni mic at the centre of the > sphere. I've triple-checked that the encoder is in the right channel > numbering: > > //------- decoder information ------- > // decoder file = > ../decoders/BSU_Array_6861_RAE1_3h3v_allrad_5200_rE_max_2_band.config > // speaker array name = BSU_Array_6861_RAE1 > // horizontal order = 3 > // vertical order = 3 > // coefficient order = acn > // coefficient scale = SN3D > // input scale = SN3D > // mixed-order scheme = HV > // input channel order: W Y Z X V T R S U Q O M K L N P > // output speaker order: S01 S02 S03 S04 S05 S06 S07 S08 S09 S10 S11 > S12 S13 S14 S15 S16 S17 S18 S19 S20 S21 > > I'll welcome any suggestion or advice! > > Thanks, > > - martin > _______________________________________________ > 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. > -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20170705/4e0f65b6/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.
