Surround Sound Explained * Part 9

YOU ARE SURROUNDED
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Sound On Sound
YOU ARE SURROUNDED : April 2002
Surround Sound Explained
Part: 1 2 3 4 5 6 7 8 9
Surround FAQs
Friday 22nd August 2003
YOU ARE SURROUNDED
Surround Sound Explained - Part 9
Technique : Recording/Mixing
Published in SOS April 2002
Surround
Sound
Explained *
Part 9
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Compiled by Matt Bell
Over the past few months,
we've seen how it's
possible to use analogue
or digital mixers designed for stereo mixing to mix 5.1-compatible audio
instead, and spoken to various producers about how they've achieved it.
However, in most cases, it is of course easier to tackle surround mixing in some
kind of software-based mixing environment, as this can be customised to suit
the number of channels you're working with far more easily than hardware. This
month, for the final part of this series, we look at how the major project studiooriented MIDI + Audio sequencers handle surround. Nearly all of these
packages have proper, purpose-built surround support -- only Cubase VST
does not, and even then it's possible to fudge a way of making it work, though
with less flexibility than the competition.
Steinberg Cubase VST & Nuendo
It's certainly possible to create a limited surround mix using Cubase, but since
Steinberg want to differentiate it from Nuendo, there are no built-in features to
help you. It's important not to be misled by the various third-party 3D panning
plug-ins for Cubase, such as SpinAudio's 3D Panner (www.spinaudio.com),
Zeep's LocaliserDSP (www.zeep.com),
and Pixelsonic's Surrounder (www.pixelsonic.com). These all provide an insert
effect that can receive stereo audio, pan it anywhere between left, right, centre,
and surround outputs, but they then use various surround-encoding processes
such as HRTF (Head Related Transfer Function) for use with headphon
es, or Dolby Pro Logic for speakers,
to reduce the output to a stereo
signal. While genuinely useful for
these applications, they don't let
you route sounds to more than two
output channels, and are therefore
unsuitable for Dolby 5.1 surround
mixing.
Nevertheless, we have come up
with a scheme that will let you
position each channel in any static
position in a surround environment
(see screen shot top right). With the default stereo output pair of your soundcard
allocated to the Master Channel for front left/right duties, you first need to click
the Active buttons for two additional stereo busses in the Master Mixer, and
name these 'Rear' and 'Cntr/LFE' in the Master Mixer.
Next, rename an unwanted Group channel as 'unused', pull its faders right
down, and then route the output of each and every channel required for
surround work to this 'unused' Group. Having dispensed with the normal stereo
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routing, we can now utilise six of the eight available aux sends as individual
level controls to the six surround busses. To do this, click their On buttons, and
select Master L, Master R, Rear L, Rear R, Cntr/LFE L, and Cntr/LFE R in their
Send Routing pop-up windows.
You can now position any channel anywhere you wish within the surround
environment, as well as sending low-frequency special effect material to the
Sub channel. Since the aux sends are being used post-fader, the channel
faders still provide overall level control for each sound, and channel level
automation will still work well, although the channel pan controls are
redundant. Of course, you'll have to have access to an external multi-channel
recorder capable of receiving at least six inputs simultaneously on which to
record your surround mixes.
This approach is perfectly useable (if somewhat fiddly) for setting up static
surround mixes, and it's even possible to implement surround panning if you're
prepared to record multiple automation passes of the aux send controls.
Thankfully, although the full price of Nuendo is £799, Cubase users can
upgrade for a much lower £579 if they want to throw in the towel and adopt a
more elegant approach!
In contrast to Cubase VST, Steinberg's Nuendo incorporated a particularly
flexible implementation of surround sound right from version 1.0 (see
screenshot below. You can define any number of output channels from two to
eight in its VST Master Setup window, and then define their azimuth (angle)
and radius (distance) settings.
Presets are provided for stereo,
quadraphonic, Standard 3/2
(similar to Dolby 5.1, but without the
Sub channel), Dolby 5.1, 6.1, 7.1,
and LRCS (Left/Right/Centre/
Surround), and a graphic window
shows how the surround channels
are positioned.
Once defined, the appropriate
number of output meters appear in
the mixer Master channel, along with a single master fader. Each channel in the
mixer can then be routed either to any stereo output buss, any of the defined
surround channels, or to surround pan. Selecting the latter replaces the normal
panpot graphic with a surround pan plug-in whose pointer can either be moved
with your mouse, or by any cheap PC analogue games joystick. For more
precise control, double-clicking launches a much larger Panner window with
further options, such as position or angle mode display.
You can export an audio file in 'Multi-channel Split' and 'Multi-channel
Interleaved' formats, as well as mono and stereo modes, but Nuendo also
includes Matrix Encoder and Decoder plug-ins for converting to and from LRCS
format, and for Pro Logic-compatible encoding. Provisions are built in to let you
apply effects plug-ins to various combinations of channels when mixing in any
surround mode.
The optional Nuendo Surround Plug-in Pack will let you apply global effects
such as compression, loudness maximising, seven-band parametric EQ, and
reverb across up to eight channels simultaneously, to provide precise control
over the final 3D mix, while its LFE Splitter lets you create a subwoofer channel
from an existing mix. The LFE Combiner, on the other hand, integrates a
separate subwoofer channel back into the other surround channels. TC Works
have also released the impressive Surroundverb for Nuendo which uses
technology based on their System 6000 hardware surround processor. Martin
Walker
Emagic Logic
Logic handles surround in a very straightforward and intuitive way, the only
requirement being a soundcard or audio interface with at least six output
channels. From Logic's Audio menu, the Surround page provides the means to
select any of the currently standard surround formats from stereo and quad (up
to 7.1), with or without centre speaker, though the most common format is 5.1.
This window shows which outputs carry which surround channels and also
shows the file name extensions that will be given to any bounced or mixer
surround files (see screenshot, below).
The next task is to set up a surround mixer in the Environment, which at its
simplest means a number of channels with surround panners plus six outputs (I
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used two stereo and two mono) to carry the six components of the surround mix
(the Centre and LFE outputs were fed through the mono outputs). The LFE or
Sub channel would normally be
low-pass filtered at 120Hz for film
work, and in Logic, this is achieved
by inserting a suitable low-pass
filter plug-in into the LFE Output
insert point (an 18dB-per-octave or
third-order filter is good for this).
Your monitor system is fed from
your soundcard's outputs, so if
these are also feeding a mastering
recorder, some kind of signalsplitting and level control system
may be required.
Your individual mixer channels are first set to surround mode as shown in the
screenshot above, then, by double-clicking on the surround pan control, a
larger pan window opens (visible above the Mid and LFE faders) where a pulldown menu allows the user to pick the required surround format for the channel
(I used 5.1 for all channels, but with the no-centre option selected for channel 7
and 8 -- I'll tell you why in just a moment). By moving the virtual surround pan
control (much like a joystick), the signal is distributed between the five surround
channels, while an LFE control at the bottom of the surround panner window
sends a proportion of the channel signal to the LFE/Sub output (6). If you need
more control over what signals appears (or not) in the centre channel, you can
set up the individual channels for no centre speaker, then configure a post-fade
Aux to send any desired amount of the channel signal directly to the Centre
output (5) via a Buss. This would allow the contribution of the centre speaker to
be adjusted manually for each channel, independently of the surround pan
control setting. In my screenshot, the last couple of channels have been set up
in this way, the centre signal being routed to Output 5 via Buss 1. Note that as
Buss outputs are stereo, the pan control is used to steer the signal to Output 5
only.
While controlling and mixing surround within Logic is easy, there's always the
question of how to deal with external sources, such as MIDI controlled
hardware instruments. The best solution is to record these sources as audio
back into Logic. Once recorded into Logic, they may be treated as any other
audio tracks and positioned within the surround environment accordingly.
Similarly, virtual instruments behave in exactly the same way as audio tracks as
far as surround is concerned.
Once a surround mix has been set up (and automated if required), it can be
bounced to a new set of mixed files, which in the case of surround means six
discrete audio files labelled as in the first Logic screenshot bottom left. These
may then be reloaded into Logic for playback or imported into a suitable
surround editing/authoring package ready
Surround-compatible I/O
for transfer to surround media such as
For The PC
DVD-A or DTS. It avoids complications if
the sample rate of the original recording
matches that of the intended delivery
medium and that the recording bit-depth is
equal to or greater than that of the final
format. Paul White
MOTU Digital Performer
When MOTU set about adding surround
mixing to Digital Performer they weren't
messing around. The implementation
in DP3 is superb -- easy to set up and
highly flexible. What's more, DP's Mix
Mode facilities make converting stereo
mixes to surround (and vice versa)
straightforward.
The key to DP3's surround flexibility is the
Audio Bundles window, which at first
glance doesn't appear to have an awful lot
to do with surround. But it's here, under the
Output tab, that you can select and
configure output 'bundles' ranging from
mono and stereo, through LCRS, Quad
and 5.1, right up to 10.2 format (!). Once
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A degree of confusion
surrounds the issue (pun
not intended) of suitable I/
O hardware for PC users
keen to try surround work,
but suitable products do
exist. Although Creative
Labs' SB Live! has built-in
DSP algorithms with
surround capability, and
does provide separate
front and
rear outputs, it doesn't let
you access these
separately from within a
music application, so you
can't use it for surround
mixing -- only for listening
to specially encoded
surround effects in games,
for instance.
However, Creative's new
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these bundles are set up (and this can be
done on a project-specific or global basis)
they're available as output assignments in
normal mono and stereo tracks.
The type of bundle you select for an
individual track determines what panner is
assigned to it in the Mixing Board. Select a
mono bundle and you get no panner at all;
stereo, and you get a conventional pan
pot. If you select any bundle greater than
stereo, though, a surround panner
appears, with a representation of speaker
placement, and an indicator running
around the outside showing spread
between the speakers. This Mixing Board
panner is just the tip of the iceberg, though.
Click the little button next to it and you
open one of four 'specialist' panners that
allow much more accurate imaging control.
You can switch between these at any time,
and every track can have its own type of
panner.
Audigy soundcard does
provide individual access
to its Front L/R, Rear L/R,
and Centre/LFE outputs
when using its ASIO
drivers, so you can use
these to create a Dolby
5.1 audio mix. The card
also has a built-in decoder
to listen to existing Dolby
5.1 mixes. Terratec's DMX
6Fire soundcard (reviewed
elsewhere in this issue)
also helps the budding
surround-sound musician,
since its Control Panel
utility provides a handy
global fader controlling its
Front L/R, Rear L/R, and
Centre/LFE outputs.
Creamware's Luna II is yet
another soundcard that
provides special surround
features -- this time a 16channel surround mixer -but you have to mix all
your songs within its
environment, rather than
using your main sequencer
application. Martin Walker
Arc Panner (pictured below left) is like a
magnified version of the Mixing Board
panner and additionally provides an image
focus control. n-Panner is effectively two
pan pots combined -- one each for left/right
and front/rear -- and again it has a focus
control. TriPan is similar except that it
offers a 'three knob' mode which allows
signals to be very easily panned in straight
lines around the surround field. It also offers full control over divergence -- the
extent to which signals panned to one speaker 'bleed' into the others. Amongst
other things, this lets you exclude the Centre channel from general imaging
duties, freeing it up for use by other tracks. All these panners offer flexible
stereo placement modes along with configurable low- and high-pass filters
which help to manage the frequency content of the LFE channel.
The remaining panner, Auralizer, is a little different. Basically it combines
surround panning with a fine-sounding reverb, and adds doppler effects and
psychoacoustic processing for good measure. Used well, it's a
jaw-dropper, and can create
wonderfully believable cathedralsize simulations as well as
unnerving 'fly buzzing around your
head' effects!
DP3 has some plug-ins dedicated
solely to surround mixing, such
as Calibration, which invites you to
feed it the output of an omnidirectional mic placed at your
listening position before proceeding to play a range of tones that are used to
automatically balance the output levels of your monitor speakers. Then
there's Bass Manager, which is dedicated to keeping the LFE channel under
control and can help to prepare mixes for home theatre systems which lack
dedicated subwoofers. There are also surround versions of many of the
standard MAS plug-ins, including the superb Delay (shown bottom right), which
offers separate delay and feedback parameters for each channel, and eVerb,
which can handle any number of input and output channels that you want to
throw at it.
Finally, DP3 makes provision for surround tracks, so you could, for example,
bounce down your 5.1 mix to a single six-channel track on which you've placed
the surround edition of the MasterWorks Limiter plug-in. Additionally, multichannel tracks really facilitate editing, archiving and distribution of final
surround mixes. Robin Bigwood
Digidesign Pro Tools
Purpose-built surround mixing came to Pro Tools Mix systems with the release
of software version 5.1 -- a happy concidence in the numbering scheme! Prior
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to this, many Pro Tools mix engineers involved in film and DVD production
used the standard kludges for using a stereo mixer as detailed earlier in this
series, and owners of systems that pre-date Pro Tools Mix still have to employ
these (more on this in a moment). Two significant things set Pro Tools Mix and
the new HD systems apart and make them fully-fledged surround mixing
environments: the ability to set up multi-channel busses, and surround panners.
As on the other MIDI + Audio sequencers mentioned in this article, the variety of
playback formats now available (from mono to 7.1) demands that the
fundamental architecture of the mixer be flexible. In order to achieve this,
Digidesign created the I/O Setup page. While most hardware mixers are hardwired to provide mono and stereo input channels, and stereo mix busses (such
as control room, group, and aux mix busses), I/O Setup allows you to configure
your routing options from scratch. This can include a variety of inputs, inserts,
output busses, and internal busses, which are anything up to eight channels
'wide'. It's easier to understand how this works by looking at something more
familiar, so the screenshot (top left) shows the template for a normal stereo
output structure in a Pro Tools system with eight audio interface channels. A
graphical grid system maps the stereo mix busse
s on the left (which Pro Tools calls
'Paths') to the available physical
outputs along the top. The paths
declared in I/O Setup appear as
destinations in the mixer, available
to any track's output or aux send
sections. In addition to these four
stereo paths, we could also set up
mono paths, linked to single
outputs. With a routing template like
this (probably the most common in
use), if you wanted to route a mono
track to, say, output 1, you could
either set its output directly to 'A1', or set the output to 'A1-2' and set the stereo
panner fully to the left.
The new Surround routing capabilities are just an extension of these ideas. The
screenshot top right shows a well-specified output set up for use in the 5.1
format. There are two main paths: a six-channel path (5.1) mapped to outputs
1-6, and a stereo path using up the two remaining outputs. There are also a
number of sub-paths, mapped to various relevant output groupings, such as
Left/Right only. If you wanted to place a track in the Centre speaker, you could
just set its output to Centre, but what if you need to place it in between the Left
and Centre, or have it spread out across the whole front wall? This is where
surround panners come in, and the track would be given one automatically if
you set its output to Full 5.1. The final screenshot, below right, shows a 5.1
panner. The green dot represents the position of the sound in the mix, while the
blue square indicates its 'width' or 'spread'. Additional controls serve to feed the
Sub, and attenuate the Centre channel.
As mentioned earlier, people with Pro Tools 24 and host-based systems built
on Pro Tools LE as don't have access to these nice new surround facilities, but
there are plenty of workarounds, such as that described by Martin Walker
earlier in this article for Cubase. Space precludes me going into too much detail
here, but my Pro Tools Notes column in SOS November 2001
(see www.sound-on-sound.com/sos/Nov01/articles/pronotes1101.asp) tackles
the subject in full. In summary, as in Cubase as described earlier, a
combination of a track's main output and aux sends must be used for surround
placement. For example, a vocal track might have its main output going to the
centre, with a send feeding the Left and Right speakers to widen it. This works
fine, although it's not as convenient as a surround panner, and it's difficult to
achieve moving pan effects. Pro Tools 24 systems have a considerable
advantage over host-based systems running Pro Tools LE, in that the former
can run two third-party plug-ins which solve the problem. Smart Pan Pro, from
Kind Of Loud, and the Dolby Surround plug-ins use clever behind-the-scenes
trickery to provide surround panners. They both take a signal and distribute it to
more than one of the existing stereo busses, achieving the same effect as the
built-in panners in Mix or HD systems. Simon Price
Final Words
And that brings us to the end of SOS's series on surround, although we'll be
returning to the topic at some point in the future for some practical advice
articles. At the time of writing, although it seems clear that some form of
surround is here to stay, the most important format for audio production remains
stereo, and most recording gear is still designed with that in mind. Whether this
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balance will shift over the coming couple of years, or whether surround sound
will merely continue to exist alongside stereo production as a specialist format
is far from certain, even now. Arguments continue to rage over the best format
for presenting surround, from the optimum number of speakers to the best
playback medium, which makes choosing 'future-proof' surround gear a risky
business at present. Nevertheless, one of the aims of this series was to show
that if you are interested in working in surround, it's possible to attempt it without
throwing away your entire studio and re-equipping from scratch, and hopefully,
we've achieved that.
Published in SOS April 2002
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