Hi Fred,
Sorry for the delay; busy with the newsletter. If we're speaking of movie soundtrack mixes and TV 5.1 mixes, the bass is mixed to the ".1" subwoofer channel, or at least encoded in that channel, and that includes the soundtracks for live opera broadcasts from the Metropolitan Opera as well as DVD/Blu-ray mixes of music concerts. During a live mix, or a live-to-digital storage mix, the mix guys at the board usually don't have a subwoofer in a mobile van or control room, but the bass will be encoded in the sub channel, which is only for bass below 100 Hz.
Cheers,
Alan
