Most home multichannel systems contain a set of electronics called Bass Management or Bass Redirection. These systems extract the bass below the cutoff frequency of the 5 channels and send the sum to a sub-woofer, along with the content in the LFE or 0.1 channel. Most "full-range" studio monitors in fact cut off at 40-50 Hz. Since "full-range" is defined as extending downwards to the lowest frequencies audible (20 Hz), many monitors miss at least a whole octave or more of sound, from 20-40 or 50 Hz. The consequence is that a professional in a studio setting not equipped with bass management will not hear low frequency rumble because his monitors cut off at 50 Hz. The listener at home, on the other hand may hear the rumble. His home 5-channel satellite loudspeakers cut off at 80 Hz, but his bass management system is sending the low-frequency content to a subwoofer that extends the frequency of all channels down to 20 Hz. If bass management is not used to monitor the program during production, electrical summation of the channels may result in phase cancellation when played back on a bass managed system at home. This phase cancellation would not be noticed under the original monitor conditions, even if five true full-range monitors are used during the production process. This is because acoustic summation in the studio and electrical summation at home may well yield different results, since electrical summation is sensitive to phase effects in a different way than acoustic summation. So... always use a subwoofer when mixing surround.