Re: [LAU] ssr and alternatives

On 2/26/21 7:26 AM, Brandon Hale wrote: ... Hi Brandon, You will need two things: - a way to design a decoder - a way to run that decoder For designing Ambisonics decoders I use ADT (the Ambisonics Decoder Toolkit, by Aaron Heller): https://bitbucket.org/ambidecodertoolbox/adt/src/master/ You will probably want to read through the references there to learn about the different design methods available, the respective tradeoffs and tricks. It is not extremely difficult but like everything else you have to learn stuff. This is definitely not a "single button, press here for decoder" solution. ADT will generate a proper Ambisonics decoder, dual band with phase matched filters, near field compensation filters for the speakers and (optional) level and delay compensation for your array. It can output ambdec configuration files (but limited to 3rd order, of course) and also Faust source code for the full decoder (which is what I currently use). Faust can be compiled to any number of plugin and whatnot formats. I have used standalone QT/Jack apps in linux and supercollider plugins - I think it can easily generate pd as well. For very irregular arrays and "weird speaker locations" there is, sorry, no magic. In some cases you might conclude that Ambisonics is not the correct solution (for very irregular arrays). I have successfully used ADT to create decoders for our concert systems (up to 32.8) and for our Stage small concert hall with a 56.8 system and Listening Room (full 3D 22.8). A LOT of work to get properly calibrated arrays but the result sounds pretty darn good (if I may say). My experience with fairly regular "dome" speaker arrays is that ALLRAD works best (Slepian decoders have the appeal of using the "right" harmonic functions but in my experience they are not good with highly irregular arrays). If your speaker coverage has "holes" then it is all about tradeoffs. You can optimize for even energy (loudness) but then you will have directional errors and/or mismatches of perceptual cues at low and high frequencies, if you minimize directional errors you will have uneven loudness. If you want Ambisonics you need decent speaker coverage for best results. You can look at the plots of meaningful parameters when designing your decoder with ADT and see what you get for different configurations. This is all with the caveat that there are limits to your perception, so what looks like an error on paper might not be significant in practical listening conditions, and as Fons rightly points out, going above order 7 does not make much sense. Some data from a composer's point of view here (Natasha Barrett): https://www.natashabarrett.org/Barrett_IRCAM_Report_v2.pdf In the paper she explores the limits of what was for her significant in terms of max ambisonics orders. My current compositional work uses mixed 5th/2nd order Ambisonics and I am quite happy with the results (in a 56.8 system that can potentially decode 6th order[*]). Hope this helps, -- Fernando [*] https://lac.linuxaudio.org/2019/doc/lopez.pdf