Hi theboch,
a good question, it would be interesting for other user.
Leveling - the point of view comes to the fore:
Realiser shows input levels only in SVS Mode - note that the total level of the SVS output is the
addition of up to eight non-linear HRTF signals.
A good SVS recording with 8 ch has an overall level between -3 to -6 dB FS
For comparison: input -20 dB FS Pink Noise, 8 x 20 dB = 29 dB incoherent signals, LFE +/- 10dB = 28,5 - 32,3 dB), Realiser output at 0 dB.
Realiser LED Phones Clip (PRIR hekeli siba 7.1 90 deg):
White Noise at 0 dB FS (HDMI input), output scaled to -18 dB
White Noise at -18 dB FS (HDMI input), output scaled to 0 dB
Both measurements Realiser output SPDIF resampled at 96 kHz, RME Digicheck - 2dB FS
No Clipping at input level + 6dB (HDMI), but I don't know anything about signal chain inside the Realiser. Manual: 2,8 V RMS at -10 dB, means app. +19 dB headroom.
Manual says, that the Realiser has a max. output level of 1,4 V RMS (1-6, 1 V = 0 dB scale), approximately +2,9 dB headroom (at consumer level -10 dB app. +12 dB)
That's not a lot (Standard GER is 1,55V = +6 dB, USA 1,23 V = +4dB, studio reference value 0,7746 V), but enough headroom for superposition or heavy spikes in the main speakers.
In Mix Mode the dowmmix levels affects the master level of the Realiser output.
I use in Mix Mode only L+R at a level of +10 dB, because of SVS simulation monitoring, the SVS output is set to 0 dB, so I must deal with the input signals (Overall gain - 3 dB FS is a good value having 24Bit). The reflection, to improve signal-to-noise ratio with higher input levels is beside the point because of max. SNR of the PRIRs (82 to 85 dB).
Keep in mind that there is a difference between dB FS and dB VU - the A8 manual details shows RMS values, this means attack times from 10 ms to 300 ms, real digital FULL SCALE levels are mearsured with an interval of 1 ms. Input meter of Realiser shows dB FS, catch it if you can ...
At 48 kHz 1 ms means 480 samples - only a true peak meter with oversampling (like RME DigiCheck) can show clipping in this tiny interval.
If someone is hungry for leveling knowledge (hard stuff):
http://www.sengpielaudio.com/calculator-db-volt.htm