So, I do have questions. So, even if we assume that software can recreate a 100% accurate reinterpretation of a speaker system, that itself is a massive undertaking with many possible confounds, but I accept that it likely can be done to a very acceptable level of accuracy. Saying that, you still need to account for the fact that every headphone still has mechanical properties that will change how things sound. So I am trying to get my head around (pun intended) how something as complex as software trying to collapse complex physics into a created interpretation can then interact with a very different and new physical environment (the headphone) and craft something that is true to the source (the room and speaker system it is emulating). It seems to me that the software would also have to analyze everything about the headphone, interpret the many possible interaction effects, make adjustments and then output a signal.
Correct.
Measurement of the actual room listening environment is encapuslated into the PRIR. Normally produced by putting calibrated microphones into both ears which are themselves connected by wire to the A16 so that their responses can be digested. Sweep signals for a full frequency range are emitted by the A16 itself, played individually through each speaker in the environment and "heard" by the microphones in your ears, with the "sound" (as heard by the microphones, affected by everything in the listening environment from electronics, speakers, floor/wall/ceiling baffle treatments, your location, etc.) relayed to the A16 for analysis. Normally three repeats of the entire process (sweep signals sent to each speaker) are performed, first with your looking "straight ahead", and then "look left" (i.e. -30 degrees), and then "look right" (i.e. +30 degrees). The A16 analyzes the audio results (as heard by the microphones in your ears) from the three "rotational listening perspectives" in order to derive a complete "picture" of how the listening environment sounds to your own ears, virtually placing each of the speakers horizontally around you in a virtual mapping. Eventually this same process will be extended vertically as well, for capture of how speakers above and below you sound to your ears when sweep signals are sent to them individually by the A16.
That's the PRIR. It reflects only how the sound of the room is "heard", to your ears.
For the second part of the process, as you have observed, there must be a second measurement of the particular headphone equipment you will be using to listen to source content played (and processed via the PRIR used "in reverse") through the A16. This separate measurement of a paricular headphone/amp/DAC is named HPEQ, and it too is a digital file that is produced by the A16 through a calibration process. Totally unrelated to the room in which you are sitting when you produce the HPEQ, you have the same two calibrated microphones inserted in your ears. And then you place the headphones you want to measure over your ears, meaning also over the microphones inserted into your ears.
The A16 then emits another set of sweep signals to the headphones, with the microphones inserted in your ears measuring how things "sound". This takes into account your own body and how sound is affected by your ear canal, skull, body mass, etc., not to mention the audio characteristics of the heaphones, amp and DAC. What the microphones pick up, from whatever cause, is conveyed to the A16 during the process of producing the HPEQ... which is unique for a specific person's biophysical hearing system, and also for a specific headphone/amp/DAC being listened through.
That's the HPEQ. It reflects only how the specific headphone/amp/DAC sound to your ears.
At playback time, when you listen to any new source multi-channel content fed through the A16, you select a particular PRIR and HPEQ together, to define the "listening environment" you want to virtually recreate. Obviously the HPEQ you select must correspond to whatever particular headphone/amp/DAC you are now using to listen through. You would not use any different HPEQ for a different headphone/amp/DAC, other than the specific one you previously measured into a specific HPEQ for that specific listening equipment you are currently using. If you have a second headphon/amp/DAC and have separately measured it with its own HPEQ, you can use that equipment if you'd like and also select its HPEQ.
But regardless of HPEQ selected (which obviously must match the specific headphone/amp/DAC you're now using to listen to this new content through) you can in fact pick ANY PRIR you want to listen through to as if you were once again there, since that reflects how a particular "room" sounded to your ears, when you took the measurement in that room and produced the corresponding PRIR. Using any PRIR and playing any new content through it will "duplicate" how that same content would actually have sounded to your ears if you were once again sitting in that room and this new content was being played through the speakers in that room. The accuracy of that simulation is provided through the HPEQ selected which implies the audio characeristics of the headphone/amp/DAC you are now using to listen through.
So at playback time it is the combination of previously calibrated microphone-derived and A16 processing which measured things and produced the corresponding HPEQ (associated with the headphone/ampDAC you are now listening through) and the particular PRIR you are now using, which allows the virtual simulation of ANY CONTENT to be heard now listening through headphones as it would have been heard by you and your own ears, if you were now once again truly physically sitting in that room excactly where you were when the original PRIR measurement was made, and now listing to this new arbitrary content played through the room's speakers.
At playback time you pick:
(a) specific HPEQ, which the A16 uses to know how sound in general is reproduced by your headphone/amp/DAC and is heard by your ears, and
(b) specific PRIR, which the A16 uses to recreate what it is like for you and your own ears to hear anything in that specific room's listening environment, whatever physical or electronic it was that made up that room's auditory signature as heard by your particular ears
The result "dupllcates" how anything sounds to your own ears in that listening environment characterized by the PRIR, when using the current headphone/amp/DAC equipment characterized by the HPEQ.
