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Surround Sound
M1 ACTIVE REFERENCE MANUAL 31
Mixing for discrete six channel
reproduction: matched vs. specialized
speakers
While most speaker systems for monitoring music in surround use the same speaker
cabinet in all positions, both front and rear, keep in mind that most consumer video
surround installations use a different speaker in the rear channels. These rear
speakers typically do not have the same directionality or wide frequency response of
the M1 Actives. When mixing for film, speakers with a broad ambient, non-
directional response are used to mimic the multi-speaker situation in most movie
theatres. Keep this in mind when making music mixes with full-range high-power
speakers like the M1 Actives as the surround speakers.
The difference between music surround and video surround playback has a long
history:
• Dolby Pro Logic, which works best with dipole (i.e., speakers splayed in different
directions out of phase) surround speakers, has been the standard for surround
sound in the home for 10 years.
• The most accepted home playback medium, VHS videotape, can only play back
(mono) surround in Dolby Pro Logic. VHS will not support Dolby Digital or
DTS.
• There are only two playback mediums, laser disc and DVD, that support Dolby
Digital (discrete) and DTS (discrete). After 20 years in existence, laser disc has
only a 2% market share. Some digital satellite broadcasters have started
broadcasting in Dolby Digital, but these discrete broadcasts will be reserved for
blockbuster movies initially.
• Discrete Dolby Digital, DTS and Sony’s SDDS are most commonly mixed for
theatrical release using surround, not monopolar (direct) monitors.
• Among the recording engineers who have recorded audio-only, the consensus
seems to be that the role of the surround speaker is to give the listener a sense of
immersion in the musical event. This is done by reserving the rear channels for
audience sounds, in the case of a live recording, or perhaps by reproducing the
reverberant acoustics of the recording environment itself. Other
engineer/producers prefer using five identical full-range speakers and mixing
primary instruments and vocals into the surround channels.
So, our basic recommendation for mixing an audio-only six channel recording is to
intentionally limit the frequency response of the rear speakers using a graphic
equalizer or high-pass (100 Hz rolloff)/low pass (12 kHz rolloff) filter on your mixer.
This will help you get a rough idea of what a home system playback will sound like.
This arrangement will also allow your mix to sound best over a well set up car audio
system. This is because professional installers have learned that a mobile system
performs best when they concentrate on producing a soundstage across the front of
the vehicle. They do this by placing high quality drivers in the front of the vehicle
which produce frequencies from the mid bass (about 80Hz) on up. In the rear go the
subwoofers and sometimes, small full range drivers which provide “fill”. So, in
essence, today’s best car audio systems are designed to produce an enveloping
environment very similar to that of a home theater.