"Bed layer" is basically "everything but overheads" so all of the speakers in a 5.1 or 7.1 or 9.1 setup if you ignored the overhead Atmos...

The term Bed Layer is also applicable to DTS:X and Auro 3D speaker layouts, and in those configurations is again anything in a traditional surround setup without any "height layer" or "overhead" speakers.

Nice progress by the way.

Farewell - June 4, 2020