Q. What does the “.1” stand for in Dolby Digital and dts multichannel surround sound?
A. The “.1” channel—and it is a separate, discreet sixth channel—handles only the lowest frequencies present in movie soundtracks or multichannel music recordings. Technically, it’s “bandwidth-limited,” which means it carries bass frequencies of 100 Hz and lower, hence the “.1” designation. The remaining five channels of Dolby Digital or dts are full-bandwidth channels, carrying the full frequency range from 20 Hz to 20 kHz if no subwoofer is used. When you set the speaker designations in your A/V receiver’s setup menu to “Small,” the receiver’s bass management system (a crossover) routes the frequencies below 100 Hz to the subwoofer (LFE) output jack. Most receivers let you choose the crossover frequency for the deep bass.