You should play with the sub volume up or down so that when you run the calibration, the aVr sets the level within +/- 3 DB; being, 0DB the ideal. If you pio is setting it up at -8db, lower the sub volume. I usually start at 10 o'clock in the sub dial. (manual says to put in in the middle, 12 o'clock, but that is too high). Make sure crossover setting in the sub is all the way up, so you make the adjustments at the avr.
Yamaha RX-V673 | HSU HC-1 MK2 | HSU HB-1 MK2 - LR | Pioneer SP-BS22-SLR | BIC RtR-V44-2 (Presence)