OK, if your amp doesn't have a LP setting then you can't do it. The XD amps are not as flexible as I thought. Then your calibration procedure would be:
- Set Ch1&2 filter to "off" (so the underseats get all frequencies between 20 and 200Hz)
- Disconnect sub (so it doesn't interfere with calibration)
- Correctly set the volume
- Run sweeps
- After calibration, make sure you have good tonality, stage width and midbass
- If not, change amp gain and recalibrate
- Set Ch1&2 filter to "HP" (keep at 80Hz)
- Reconnect sub (set Ch3 filter to "24dB" at 80Hz and adjust gain to your liking)
Make sure your sweep volumes are all roughly the same level. Best to do this through the "secret menu", playing pink noise through each channel, and measuring with an iPhone app. Since you cannot use the LP trick to chop off frequencies above 200Hz from the underseats (MS-8 "design" flaw), you have to artificially lower the output of the underseats by around 4-6dB compared to the other channels. The reason for this is a bit complicated to explain but if you want to know, read this thread:
http://www.e90post.com/forums/showthread.php?t=724447