Topic: Improved PAS technique - better imaging with good clarity

[al w.]

Just popping in to say I love Improved PAS! I've been using it for a while now and just made one of my fave tapes yet with it

hypers, 70°, 29cm

https://archive.org/details/eggy2024-05-04.alw?webamp=default

Thanks Gutbucket

[robeti]

Interesting topic! Checking in:)

[Gutbucket]

Thanks for the feedback and good to hear the Improved PAS technique has been working well for those employing it! 

Attached is the latest Improved PAS write up. 

To make it as easy as possible to use, the angle/spacing is now presented as a list of setup diagrams arranged by PAS angle, rather than a table of angles and spacings. The other change is that in addition to standard 2-microphone Improved PAS, the technique has been extended to 3-position PAS, which uses 3 or 4 microphones. Using 3 microphones, one is placed in the center between the other two.  Better is 4 microphones, with two of them sharing the central 3rd position in a coincident X/Y or Mid/Side arrangement. Tapers who are only interested in 2-mic PAS can just ignore the 3-position stuff.  I considered starting a new thread to discuss 3-position PAS separately, but since it's really just a further extension of the PAS technique from a single stereo pair to a mic array of 3 or 4 channels, I decided it would be best to keep everything together in this thread.

The 2-mic PAS portion of the new diagram-based PDF is based on the same data as the older table version, which was originally derived from the Sengiepelaudio.com on-line calculator tool.  That means you'll get the same answer if referring to the older Improved PAS table, the new 2-mic PAS diagrams, or the online Sengiepel tool.  The new 3-position PAS diagrams are based on data from the online Schoeps Image Assistant tool, which is capable of handling both 2 and 3 mic-position configurations. The 2-channel PAS solutions provided by Image Assistant are very close to those provided by the Sengiepel tool, but are based on a somewhat more extended data set. In comparison, Image Assistant provides additional information and control options (some of which are a bit hard to find, burred in the menu), yet tends to be less straightforward for most folks to use in comparison to the Sengiepel tool.  Additionally, I used a slightly different way of determining the appropriate offset between the PAS and SRA angles, some details of which are mentioned in the PDF write up.  Happy to discuss that and any other questions about Improved PAS in more detail if anyone is interested.

To skip the introduction and description of what is going and go directly to the diagrams, proceed to page 3 of the PDF for 2-mic Improved PAS, and page 5 for 3-position Improved PAS.

[Gutbucket]

Taking a step back to view the big picture- 

The extension of Improved PAS to 3-microphone positions illustrates the natural progression from 2-channel Improved PAS toward multichannel OMT microphone arrays using higher channel counts.  3-position Improved PAS setups using 3 or 4 microphones are the most recommended OMT3 and OMT4 setups.   

Four mics arguably represents the point of diminishing returns, and is as complex as many tapers choose go with a multiple-microphone array.  In simplified terms, OMT arrangements greater than OMT4 further extend this progression with the addition of a wide-spaced omni pair (when a spaced directional mic pair is already in use), a spaced directional pair (when wide-spaced omnis are already in use), and/or rear-facing microphones.  Each of those further additions are useful, yet how valuable when weighed against the increased complexity is the practical determination that each taper interested in exploring such multichannel techniques needs to make.  Four mics tends to be the right answer for most tapers looking to move beyond a straight stereo pair.