When calibrating speakers using the SPL meter you use tests signals for main channels at -30dB and calibrate to 75dB. With the LFE you use a -40dB signal and calibrate to 75dB. The upshot of this is that the LFE speakers are now 10dB louder than the main speakers and any signal passed to them is played 10dB louder...

Mark

My Music : My Cinema