Does A16 allow multiple virtual speakers to be connected to the same channel?
Not specifically. But when the LEFT channel input is fed to the car's audio system however that sounds (via all the speakers of the car) to the microphones in my ears is what gets measured as the LEFT channel in the resulting PRIR. Same with feeding RIGHT channel input, as played through all the speakers of the car, ending up being the RIGHT channel in the resulting PRIR. A 2.0 PRIR only has two channels, so that's it.
The total set of speakers in a listening environment constitute what gets measured. If the room only has front L/R speakers and that's all that gets energized when LEFT channel input is fed to the electronics, then it's only the front L speaker which is reflected in the PRIR, etc. But if multiple speakers are energized together when the LEFT channel input is fed to the electronics (e.g. 5-channel STEREO or 7-channel STEREO in Yamaha AVR's, which feed the single input channel source to all of the "left front/side/rear speakers", etc.), then that's what the PRIR reflects.
So in the car whatever multiple speakers are energized for LEFT channel input, that's the LEFT channel of the PRIR. Same for right.
Now... to report the results of today's goal of producing a PRIR from my car, I sadly report that the project was 100% unsuccessful. Not because the concept or objective was flawed, but because for some reason there was a major buzz induced when connecting the L/R outputs of the A8 to the AUX input of the car's audio system. This wasn't a 60-Hz ground loop hum, but a buzz.
We were in the parking garage of a building, and using a 3-prong power outlet on the wall. I had brought a "lifter" with me (that eliminates the ground prong) so we tried that, although the buzz was not really a ground loop hum sound. As expected it had no effect in eliminating the buzz. We also tried using jumper cables to ground the car, connecting the car to some pipes that were hanging on a nearby wall, but again there was no effect and the buzz persisted.
We then hypothesized that maybe it was caused by connecting the 120v AC Realiser to the DC AUX input. Perhaps using the car's 12V DC system to power the Realiser might help, so off we ran to Fry's Electronics to buy an "inverter" (to generate 120v AC from the car's 12V cigarette lighter). In passing I comment that the once mighty Fry's (whose flagship store in San Jose has 32 cash registers) is now a "carcass" of a store (thanks to online shopping). On this Saturday before Christmas there were six cars parked in the huge parking lot. Inside the store there were five customers, and seemingly two employees, in what seemed like acres of store interior space. 90% of the pegboard pegs (to hold items for sale) were empty, and there was hardly any stock. Couldn't find any adapters, connectors, or extension cords for 3.5mm/RCA plugs which I wanted. Amazingly, they actually DID have a number of "inverters", so I bought one.
Unfortunately the inverter also accomplished nothing as far as eliminating the buzz. Of course just because an inverter is the source of the AC power, the Realiser is still an AC device and is still feeding a DC AUX input, if that is the cause of the buzz.
We did test the "solo" output of the A8 using the headphone outputs (both the phono plug on the front, as well as the RCA outputs on the rear), and there was no buzz. The buzz was definitely caused by connecting the L/R main RCA outputs on the rear to the 3.5mm AUX input of the car. And we tried both Darin's A8 as well as my A8, with both producing the buzz.
In theory, if we had enough cables and adapters we perhaps could have tried going from RCA to balanced, and then balanced back to RCA, as a way of perhaps eliminating the buzz. Unfortunately we didn't have the necessary converters to try this. But really we were at a loss to fully explain what was happening, other than to face the reality that unless the buzz could be eliminated there was no way to run a calibration.
Anybody have an idea what might have induced this buzz, and how to eliminate it?
However, I am not sure if you will be able to really achieve that by just measuring 8 PRIRs which means you are essentially simulating only 4 speakers while your HK system likely has (much?) more (e.g. HK system in BMW 3 series has 16 speakers with 8 channels). You may have to measure PRIRs of all individual speakers rather than channels although it may not be feasible without touching the wiring....
