 Adventures
in Surround Sound, from 7.2 to Quad
(personal
and historical notes, basics, and acoustic realities often
forgotten)
= P
a r t 2 =
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Digression
III -- Other Surround Options
"Depth"
Quad -- a good old idea
No
sooner had stereo been introduced to the masses in 1958,
there were fools like me thinking about the next steps. The
late, great Bert Whyte (who recorded some of the finest
stereo masters for Everest records, remastered now on CD)
wrote a monthly column (in Radio/TV News) that praised three
channel stereo. He had campaigned in 1956 for a home medium
with three tracks, especially after Wilma Cozart and Bob
Fine had thoughtfully arranged a secret demo for him of
three-track orchestra recordings they were making for
Mercury Records. Those first mentions on stereo in Bert's
"Certified Record Review" had electrified me, and began my
path that led to my first Switched-On recordings. But
four-track equipment came about more easily than three (just
double up two quarter-tracks as I did on my little custom
Viking deck). The question arose: "where do you put the
extra channels?
Above is one rather
fascinating idea I read about and tried with that Viking
recorder pictured way above. The microphones are positioned
in front of the sound sources in a
similar diamond shaped pattern.
The left and right channels are moved wider apart than you'd
use with 2-tk stereo, and the center is filled not once but
TWICE!. There's a mike that's really up close to the
musicians (assume this is a music session), and another
further away than the left and right pair. For playback you
duplicate the positionings as you see here. If a person were
to walk about while speaking, in and around the microphones,
there would be an uncanny ability to judge exactly where
s/he was at any moment if you listened with this "Depth"
Quad arrangement. It may not work over a very wide angle,
it's certainly not as "surrounding" as some of the other
schemes here. But it is a charming way to duplicate a
soundfield in startlingly realistic ways. Those of you who
can try it out will be happily surprised at the
reproduction.
Note: the close speaker
would be best if mounted rather low, so the center distant
track will not be blocked. The mikes don't need the same
finesse. It's effective to deepen the positions even more if
you have the room. I first tried it with a deeper than wide
arrangement, and that was pretty cool. The mikes are just as
important as the speakers, and we have another
page devoted to this side of the
equation. Clearly
this is not the place for the way most of us work today:
panning and repositioning a multitrack source in the mix.
Depth Quad works best with one mike per speaker. You can try
more than four channels, but of course, dovetailing the
additional channels to either side of this one. How about
four more, in pairs, to either side of these here, one
close, one distant, total of eight -- gotta hear THAT
someday!
"Diamond
Surround Quad" -- a poor old idea
Here's
another "diamond" arrangement for four channels: Left-Side,
Center, Right-Side and Rear (similar to what's called:
LCRS).
Offshoots of this one have been widely popular, as it is the
basis for the Dolby Stereo matrix that we've all enjoyed
many times (Dolby carefully moves the sides up front).
Electro-Voice was an early advocate of the above, but this
was before "logic steering" circuits simulated full stereo
separation. Sansui used a similar plan at the core of their
decent QS quadraphonic system's "Regular Matrix." But they
finally adopted the much worse "obvious quad" layout scheme,
in a rush back to the corners, feh. Most of the ill-fated
quadra-phonies made the same mistake, although they added
logic circuits to help enhance the limited separation
(nothing filled in the big "holes"). CBS/Sony had a worse
scheme called "SQ", which needs a bit more space to speak
about, so we'll put that tale on a related matrix-wars
page HERE.
There's additional tech background on matrix
surround systems HERE.
Not many four channel
systems stayed with this "diamond" plan. There were
problems. The angle between adjacent speakers is a rather
unrealistic 90 degrees. Ever hear stereo with the speakers
that far apart? Yep, no "fusion" between them, a hard to
ignore "hole-in-the-middle", as it's usually called. With
the "Diamond Quad" scheme you get four of those black holes,
four large sectors in which no sound source seems to be
located. One might place "filling in" speakers with fancy
logic circuits that derive the best-guess signals that would
be expected when the actual channels are outputting a
particular pattern. Klipsch did this with his Heresy
speakers to fill the large gap in the stereophony that two
corner speakers caused. We spoke about that earlier, and,
yes, my center speaker is one of those Model-H for heresy
designs: meant only for along-the-wall placement, and not
the bass response of the bigger monsters.
But without four more
speakers to try to fill in the holes (eight in all!) this
idea doesn't work too well. Another problem is that when you
face forward it's difficult to tell what's coming from
exactly in front of you versus exactly behind you.
(The
most reliable way is swing yourself around sideways, then
the other two channels become ambiguous -- and so
forth.) You can conduct
the blindfold tests I used to amuse
(bore?)
guests with. You need a tiny noisemaker, like the toy metal
"crickets" or "clickers" that novelty shops sell. Blindfold
the guest, and move the cricket all around, making the sharp
click sounds from every direction you can think of. A weaker
chirp right in front and below is nearly never heard as
coming from there. And behind is often confused with in
front. Even with discrete channels, you'll really only
detect three of them at a time if you adopt the plan above,
a poor old idea we can dismiss, at least in this form. (It
will return with Dolby Stereo, a different story, covered
below.)
Dolby
Stereo -- Making the "diamond" work
With
several modifications from the above "diamond", we obtain a
much more effective plan, one that's at the heart of most
motion picture stereophony, from Fantasia's
Fantasound,
through the early 50's CinemaScope
films, and ending up with Dolby
Stereo™.
The Left and Right channels have been moved back to the
front. In this case they're rather closer together than
you'd choose for music, keeping in scale with the widest
screen a motion picture would be projected on in a room of
these proportions. That constraint produces screen-left and
screen right as the widest positions. Everything else not on
the screen is suggested by a monophonic "Surround" channel,
played on as many speakers as you can manage. There are
designs that avoid some of the "comb-filter effect" that
playback of the same signal on multi speakers will
introduce, and other ways to diffuse the signal so that it
becomes omniphonic, hard to locate, just a vague impression
of sound from the sides and rear, without any accurate
positional clues.
Dolby Stereo is not
really multi-tracked. All the mix ends up on a standard
stereo pair, usually called: Lt
and
Rt. What is to be
heard from the C channel will eventually end up as an
identical signal at the same phase in both Lt and Rt (the
so-called "sum" signal). What is to be heard from the
surround channel is mixed into Lt and Rt at the same level,
but 180 degrees out of phase (the so-called "difference"
signal). As long as only one or two sounds are to be located
simultaneously at any given moment, a special circuit called
"logic" steers what signal goes where, and reduces the
crosstalk inherent in all "matrix" methods. More than two
sounds at once, and you get a vague blur of sound all
around. For the particular purposes of film sound,
especially when the engineers have monitored through the
matrix and can judge the final results, it can do a
reasonable job of suggesting a real four track experience.
For music it's a tradeoff, often a major one.
But the monitoring
setup shown here is not designed just for listening to
pseudo-surround sound. It works splendidly for discrete four
channel presentations. Since the surround speakers are
usually smaller and less wide-range than those in front, you
must bear that in mind when recording music and sounds for
playback with most systems. Usually a single subwoofer is
added, and this ought improve the overall results and
visceral "impact." That's why most of the setups we'll be
discussing employ at last a single subwoofer. The standard
philosophy is to position it anywhere practical in the room,
as low bass is not too directional. Some engineers like to
play pink noise over a subwoofer that's placed in the
listener's position, then walk around and find a place where
you hear the low rumblings best for that room. And that's
where you put the subwoofer. There's more to be said about
this, but let's first move over to surround schemes better
suited for music.
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5.1
Surround Sound for Music
Typical
Surround Monitoring Setup -- 5.1
Channels
Now
this is the monitoring arrangement I hope each of you has or
will have, to check out your surround mixes. Note that this
time we have a single subwoofer (position not critical), as
most setups are arranged that way. You lose only a little
compared with stereo subwoofs, since most low bass is
omnidirectional (but not all -- hard attack bass sounds do
establish small directional clues...). This is a variation
of our initial plan. The LF and RF speakers have been
rotated slightly for less "toe-in." That's because you'll
probably want to allow several people in the room to hear
what's going on, and many listeners don't like to have their
stereo speakers too angled in these cases. There are good
arguments that suggest that more toe-in has notable
benefits, but this is a topic for another discussion.
Similarly, the center speaker is moved slightly closer to
the listener, as it will be so in most movie theaters, home
theaters, and professional studios. (Often LF, C and RF will
be placed along a straight wall, hmm...)
(I
should note that with very short, sharp transient sounds
there is a detectable change with as little a variation from
equidistant spacing as six inches. But this is usually
not easy to hear with normal music program, up to 2-3
feet, perhaps. Be aware that the theoretical optimum is
best, but also realize that you can bend the rules slightly
with little harm, most of the time.)
There is equipment that can correct for such differing
distances by adding a 1-4 ms. delay to the too-close
speaker(s). Your preference still ought be for as close to
equidistant from the listener (for all channels) as you can
manage. But even without delay circuits the modest change
you see above will not have a major damaging effect. Since
it is also quite popular, we present here it for your
consideration, along with the caveats. Next let's look at a
more equivocal modification...
Maximum
Side/Rear Separation Setup -- 5.2
Channels
Here
you see a fairly common variation that many studios are
happy with. The front speakers are as they appeared in the
previous layout, less toe-in, center speaker more inline
with the LF and RF speakers. I've also shown the room with
stereo subwoofers, as my room has them, in the original
views. But here we've made a slightly larger tradeoff. The
two side speakers, LS and RS, have been moved rearwards. In
this case we've not gone very far, they are both a mere 5
degrees rearwards of the position above. If you try this for
yourselves I think you'll discover not much change. The side
channels still sound reasonably to the sides (you're losing
a little of the ability to position sounds to the exact
sides -- a compromise). But you'll find that the effects
that you want to locate rearwards remain rearwards a little
better if you shift your head about while working. Once you
stop moving either setup is fine, but when you move your
chair back from the console in this new setup the side/rear
sounds will stay more rearward than before, at the price of
extreme side positionings.
We're splitting hairs
here, I admit it. Still, you don't want to go too far with
this variation. More than 10-12 degrees rearward bias on LS
and RS, and you create the same old problems, losing more
than you gain, don't fool yourself. Try it out in several
rooms using different program material with lots of side and
rear activity. (You'll
also get into trouble enlarging those two 65 degree sectors
any further, see the next section.)
There are convincing arguments to be made that this might be
a pretty decent compromise to make in many studios, and in
many theaters and homes. You can be fooled by the visual
impression, thinking that the first variation has only front
and side loci, the second adding a little rear. Um, sorry
not true. The first setup can create a completely convincing
wrap-around effect, which will only vanish if someone is
moving greatly, or decides to sit at a steep angle to the
room, sidesaddle. Then the sound will remain confined to the
one hemisphere. People sit sideways all the time with the
foolish four corner positionings described above. Watch them
squirm and twist about, trying to figure out: "speaker,
speaker, who's got the sound?" With an arc of sound they
don't do that nearly as much. And you won't want to,
either.
Once you hear
well-mixed music on either of these systems, you'll see why
surround is as much better than stereo as stereo is better
than mono (nuts,
I've revealed the final conclusion on page five, you can go
home now... ;^). By
avoiding "wasted" channels that satisfy visual impressions,
you work with
the way our hearing apparatus is designed, not oblivious to
it! When it comes time to fill in the room with more sounds
which even a moving side-facing listener can hear as
surround, it's time to take the next step, to 7.1 or 7.2
channels. Or you might add the two channels halfway in
between the LS-LF pair, and the RS-RF pair. This particular
expansion will stabilize the soundfield, better than any
five channel system, if you must move side to side. Suddenly
we're slipping along an infinite regress, because once you
have seven main channels, you might want another five to
produce the perfectly cylindrical field of 12 channels (but
whichever way you now face, a third or more of those
channels will be "wasted"). How about 12 close up channels,
with 12 more further away to gain the special dimensions of
"Depth" Quad, described above? And there are always ceiling
speakers like Ussachevsky
investigated in McMillin/Miller,
and IMAX provides in their theaters. It never ends! Let's
try to be happy with what we've just gained, and save the
next step for the future...
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5.1
Surround Sound for Films
Filmsound:
Reduced Front, Wide Rear -- 5.2 Channels
Right,
for music we want a wider front image, as the 30 degree
separation between LF and C and RF produces. For film work
that's usually not the ideal way to go. It's just a small
modification, though, to move in the LF and RF channels as
shown here. This is a 25 degree version. Some theaters with
smaller screens might require only 20 degrees or less.
Whatever value represents the most likely way your
particular audience will hear your results ought determine
the way you'll want to setup your monitoring space. Right
here we have an excellent compromise for both music and film
mixing and monitoring, but one that favors the film
soundtrack to purely musical use. It will also be practical
in larger home installations, where the rear wall behind the
viewing chair or sofa prevents any rear speakers anyway.
The one weakness here
is the two angles of 70 degrees, LS to LF, and RS to RF.
Those are about the maximum separation between any two
speakers if you expect imagery from in between each pair to
"fuse", and not create "holes" in the soundfield (90 degrees
is certainly too wide). That's one of the reasons to prefer
about 60 degrees between each channel, except the fronts,
where it probably ought be somewhat smaller (remember, our
most acute directional hearing is up front). It's surprising
you never hear suggestions to divide the whole semicircle by
five channels equally, placing the LF and RF even further
apart, or about 40 to 50 degrees between each channel (no
"holes" at all) as
was described earlier.
It would certainly work for music, whereas you'd need a 90
degree wide screen (curved?) to cover that LF-C-RF
distribution! For home theaters the single subwoof version
shown next may be an ideal starting place.
It need not be pointed
out that we're not following any engraved set of "rules"
here. You won't break any laws of any country or religion if
you prefer to mix your music tracks using a narrowed front
soundfield, or monitor your film mix with a front field so
wide no screen this side of Cinerama and Omnimax will be
capable of covering it. Some engineers have reported that
they find they can hear with more accuracy when the speakers
are wider than the screen, more like the suggestion above.
Panned dialog and effects might not match exactly, but as
these nuances have been forgotten about (dammit) for over
two decades, you can ignore it, too. When mixing for films
it's not often you'll encounter two subwoofer channels. The
so-called "Baby-Boom" of six track (70 mm) roadshow prints
of only a very few major films since the late 70's have used
a pair of subwoofers. These were the former midway screen
channels, LC and RC that mixers had stopped using when Dolby
Stereo became the major soundtrack method. Since 70 mm had
the extra tracks these often were chosen for low
frequencies, only. Or the extra two channels would be used
for Surround Left and Surround Right, and were then called
"Split Surrounds". Most theaters, though went with the next
plan.
Most
Popular Surround Setup -- 5.1 Channels
Now
we have again a single subwoofer, as the very name for the
newest digital sound systems describe it: 5.1 channels, the
.1 being taken for that channel that only covers about a
tenth of the usual audio spectrum. Logically many of us have
gotten used to calling the stereo subwoofer/effects channels
"another .1, for a total of .2", in other words, according
to the convention you've been reading on this page: 5.2.
Most older theaters have not yet doubled their subwoofers,
and so you'll probably want to check your mixes with the
plan just above. There's still one small problem, if your
goal is film mixes more than music. With music you'll often
want to be able to place a few instruments into the side
channels, LS and RS. Solos work very well once the speakers
are not behind you. It just feels like you're up close to
the stage, near the band or orchestra, a very common way to
hear music.
For that reason the
music monitoring setups above are best served with single
side channel speakers. Since now we're discussing film
soundtracks, the goal changes. And to best provide the most
dramatic sound locations and movements in a movie theater
you might want to do a mild version of what LCRS soundtracks
did for the single "S" channel -- multiple speakers. We can
add several on either side, to the rear of the main LS and
RS speakers, so that we obtain this next pleasing
arrangement (again, note the 70 degree weak-links, something
common to most soundtrack setups):
Full
Film Mix Surround Setup -- 5.1 Channels
Note
that the LS signal is being fed also to the two or more LR
Surrounds, ditto for the RS signal to the right. If you
won't be playing full range, wide dynamic sounds over the LS
and RS channels, all these can be smaller surround speakers
as has become typical in theaters since the 70's, well, even
back 20 years before that. Then you can replace the large LS
and RS speakers as shown above with something that matches
the other rear speakers. Your choice, and also depending on
what equipment will be used in the final theaters, a best
guess. Since many modern theaters have sufficiently wide
range auditorium speakers to play nearly as wide ranged
(dynamics and frequency response) as the screen speakers,
perhaps the setup shown above will be the most useful way to
hedge your bets, and not compromise what you do in the
mix.
For those of you who
are only going to be listening, perhaps at home, this is
still a very practical "target" plan. You'll probably only
have a single pair of the LR/RR speakers, these might be
dipole designs, and they will get the same signal as your
side speakers, perhaps at a somewhat reduced level. It's
once again a matter of "trust your ears". Take an approach
and try it out. You can't beat the practical lessons gleaned
from experimenting with several alternatives before you
decide the leave things more or less permanently in
place.
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Optimum
Quadraphony
Typical
Quadraphonic Setup -- 4.2 Channels
Ah,
the glorious days of Quad! A time of breakthroughs in audio,
enveloping sound all around you, a band performing right in
your own living room, audio that has not been matched since!
That's not quite the way it was. Unfortunately there were
two major dilutions which quickly dissuaded most listeners
from taking that expensive step of doubling up on speakers
and amplifiers. The advertising promised what the reality
wasn't able to deliver. One of the problems was that most of
the recordings released in albums marked "Quadraphonic" were
actually only stereo. They relied on one of a handful of
"Matrix Quad" bootstraps to turn the actual stereo two track
recordings into four separate signals for your quad amps and
speakers. In truth, they were out to get something for
nothing. Pure corporate greed and larceny, nothing new here.
We'll cover the matrix story elsewhere. Just keep in mind
that in limited cases, like the use Dolby put it to for film
soundtracks, such a scheme can be useful, especially when
constraints prevent a real discrete method from gaining
widespread use.
But for most music
applications the truth is not far from what your brain is
telling you: it won't work. Well, it still can create some
nice, pleasant musical effects. And with certain kinds of
music the very best "logic decoders" can do somewhat better
than that. Let's ignore the question since there now are
several fine systems available to present excellent
multichannel surround to the home listener, the newest being
the DVD-Audio format.
The second major
dilution that crippled the early quad systems is the faulty
plan of distributing this doubled information in a way we
can readily hear and appreciate. The folly of "Obvious Quad"
has already been covered up above, in Digression I. That
provided the second of the "one-two punches" that spelled
the end of quad. Until now. This time we've started by
basing the music surround systems on the well-proven film
surround designs. We're not as likely to fall into either
trap, as we will have truly discrete channels of very high
fidelity indeed, and will distribute these channels around
the room in an extension of good filmtrack practice. For
musical purposes there's still a lot to be said for four
track versions, or Quad. Most home systems don't have
particularly good center speakers, often making do with the
"phantom center" that any ordinary stereo can do. And many
musicians seem less interested in plopping the vocalist
automatically in a center channel, and don't even have much
need for that channel.
Above is a really
effective way to monitor and listen to Quadraphonic
recordings. Had this been the way it was done in the 70's,
and had the manufacturers avoided their phoney early matrix
systems, quad might have had a real chance to survive. Think
of what a wonderful backlog of masters we'd have now to
place on our new DVD-A's!
Minimum
Basic Quadraphonic Setup -- 4.0 Channels
There
are two changes in the next plan. Many homes and studios
don't have subwoofers, so we've left them out. Won't change
the directionality one whit, a matter of wide fidelity
rather than stereophony. Also we've placed the side speakers
back to the theoretical optimum, directly opposite one
another on both sides. For music this is certainly the
preferred choice, and the original quad was nearly always a
music, not film sound, method of reproduction. Since we've
covered the LCRS four channel systems like Dolby Stereo
above, now we're looking at home music systems, and the
studio setups for making and monitoring such recordings. The
other change you may consider to favor music reproduction is
to restore an equal 60 degrees between each pair of
channels, back to where we started above.
Narrower
Basic Quadraphonic Setup -- 4 Channels
But
wait a minute, before doing that, let's consider if your
listening space is rather narrow for either of the plans
above. What should you do, reduce all the speaker spacings
all around, or just narrow in the width of LS and RS? We've
taken the second approach here, as the change is not a large
one. Certainly a smaller scale of any of these plans will
work well. You could enlarge one up to the sizes of an
auditorium, much like the Theater on Columbia University's
campus, described
at the beginning of this essay.
In our plan above, however, we've narrowed our room
somewhat, about 15% from the above variations. And we're
going to leave those front two speakers at a 50 degree
spacing, since now we'll be moving the LS and RS speakers
inwards. So all the speakers have effectively been scaled in
sideways from the original 60/60/60 spacings so ideal for
music.
Yes, it's true that the
side channels now are several inches closer to the listener
than either front channel. For this modest difference, no
harm is done. You can add a millisecond or two of delay to
the LS and RS channels, much as we mentioned above regarding
a too-close C channel (remember, at the average speed of
sound of 1100 f/s, you'll need about 1 ms. delay roughly for
each foot of "inwards" correction). But that may be overkill
when the change is so small. You listen to stereo often when
the distance to the left and right speakers have a foot or
more difference, and yet you still hear stereo. I discovered
while trying this out, moving the big Cornwalls in different
spots before the final choice was made, that side speakers a
bit in can be rather cool when listening to plain old stereo
over all channels. If you put the left track on both LS and
LF, LS down a couple of dB from LF, and do the same with the
right track on RS and RF, something really effective
happens, a kind of "ultra-stereo."
It's just the
serendipity of the situation, almost something for nothing,
which I'd never have guessed "ad hoc", without stumbling on
it first. You obtain something rather better than the usual
stereo, approaching, but certainly not reaching, the
subtleties of true quadraphonic surround sound. It's nice to
learn we won't have to discard our stereo-CD's after
becoming surround-ready. You can take my word for it on
this, although, once again, I'd much prefer to have you work
it out for yourself, do some experimentation. And it may
inspire you discover an even better
way to go!
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Quadraphonic
Folly
Tetrahedral
Surround Plan A -- 4 Channels
Now
and again the suggestion of "Tetrahedral" channel placement
arises, Phoenix like, from the ashes. It usually goes like
this: "Say, if we've got FOUR separate channels, why not
create a 3-D solid of sound, using a FOUR-sided tetrahedron!
We can place one channel in each of the four corners of the
'hedron, use a microphone with four directional elements
aiming in each of the four directions, mount the speakers
the same way. Then we can have sounds come from any
direction at all!" Great! Certainly is a lovely notion on
paper. Except there's something worrying here: a speaker in
every corner. Haven't we already seen that no matter how
obvious an approach this is, it comes up as an argument with
"holes" in it, to turn a phrase?
If four independent
channels are insufficient to cover a flat 360 degree plane,
certainly there's little hope they can cover MORE than that,
like a spherical 360 sound space. Good grief (you're right),
there's no hope at all (they don't), it sounds lousy. A
favored configuration is the above "Plan A" (from Outer
Space...? ;^). Note how the LF speaker is located down on
the floor, then the next channel, RF is mounted up high in
its corner, and around we go, down, up. Neat, huh? Compare
the result with the folly of "Obvious Quad" in
Digression
I above. Only now
the angle between each speaker is more than 110 degrees. You
liked the big holes in the middle with 90 degree spacing,
you're gonna LOVE it -- nearly 120 degrees of pure
emptiness! We've destroyed what little "fusion" there
existed before in front, as the pair along any wall must
span the full diagonal length of that wall. No surprise to
find black holes all over the place.
Evenso, there are some
benefits to record
with such four-element microphones, like the famous Calrec.
By matrix manipulations of the sum and difference type we
can "extract" the equivalent of a directional mike aimed in
any spherical direction. You can capture an event with many
recording channels, four per soundfield mike, and then later
trim and fine-tune the mike aiming points. No, you can't
effectively reposition the mikes, but it still is a most
flexible scheme of event capture. If you have enough
channels of monitoring, perhaps eight or more (Octophonic
Sound, anyone?), and place these into a more modest
configuration, you might be able to come up with a workable
soundspace of environmental sound.
Tetrahedral
Surround Plan B -- 4 Channels
But
if you're stuck with only four channels for reproduction,
there's not much more you can do about the up-down, or
"third axis". Here's another scheme, Plan B, above which
tries to square the circle, trisect the angle, invent
perpetual motion, and on down to oblivion. Is it just me, or
isn't this one kinda nervous making? I mean, would you mind
having a large loudspeaker suspended right over your head,
aiming down at you? Great for "the voice of God" effects! Of
course one of the six channels in IMAX theaters does exactly
this. At least they have five other tracks, so the main
expanse of the screen is better handled that the above plan,
with only three channels left to define 360 degrees. Yes,
that's gonna lead to more of those blackholes, who says we
haven't discovered "all the missing dark matter" in the
Universe?
In any case, I've put the
cart in front of the horse here. Our hearing apparatus is
very weak at detecting up-down movement and locations. I
could have added another experiment to try in
Digression
II above. It's easy
enough to do. With your two channel stereo turn your head
over to the side by 90 degrees, one ear aiming down, one up.
Now listen to the two speakers, one effectively "above" your
head, the other "below". What's wrong with this picture? Do
you hear much separation? Close your eyes and listen
carefully. Play some "ping-pong" stereo material, or have a
friend rotate the balance or level controls so the sound
definitely moves back and forth between the speakers. How's
it sound? Straighten up and compare. Unless you do have an
extra ear on top of your head, I suspect you'll come away
from this a little less excited by the prospects of 3-D
spherical surround sound. I was. The test here works better
outdoors, where there are no clues from reflections on walls
or ceiling. More honest test that way, unless you have an
anechoic chamber handy.
The other suggestion
for a test, with a tiny noisemaker, a "cricket "or "clicker"
should be repeated here. Have the sounds be moved from below
to above at the same left-right angle. See what differences
can be heard. Try it outdoors. Compare with front rear
motion or arbitrary jumps, and near to far motion and jumps.
We have to be sure about what we can easily detect and what
we can't. Our eyes will deceive us, both ways: we can hear
"phantom center" sounds between two speakers equidistant
from us, our eyes tell us the space is empty. Our eyes see
speakers above and below, but our ears are not so sure it's
mostly guesswork. It's by coming up with concepts that look
good to the eye we blunder both ways. We come up with plans
that can't be heard well, and never consider the plans our
ears will really enjoy. It's another case of how easily we
can fool ourselves, especially if we've invested a lot of
time and money in an idea resting on acoustic folly. Please
trust your ears as you navigate these rocky narrows. Do
everything "double-blind", with verification by others who
seem to have excellent hearing. Find out what works for you,
in any case, even when the lights are out, and it's every
ear for itself...
There
are other very important issues for good surround recordings
that we've not been able to cover here. Many of the
techniques and philosophy that go into fine (2-track)
stereophony will carry over directly into the newest
wrap-around systems. If any of the better available setups,
like some of those above, is adopted as the basis for our
favored system, instruments can be placed in many more
apparent positions than ever possible before with two
tracks. Attending a live concert in a superb venue like
Carnegie Hall, and sitting fairly closely, you'll hear a
wide arc or "curtain of sound," and many acoustic
reflections and reverberation coming at you from all
directions. Your ears will pick up the original sound
placements up in front easily, and will certainly hear a
large part, but not all, of the ambient information. Such
clues of size of the room and shape are the ones to try to
capture on a recording. Don't worry about some theoretical
ideals of "completely reconstructing the listening space."
You can't. Not even with 7.2 channels, you can't.
So don't fret about
what will be lost, don't assume you can recreate such
effects unambiguously "a posteriori," using a multitrack
master and a fine surround mixing studio. Go back to the
basics. Get the overall balances between the sounds right,
that's not going to change. Set the equalization and wet-dry
mods where they sound best, the same as usual. Let the
reverb come mostly from the side channels, along with at
least some of the instruments (don't waste LS & RS just
on reverb/echo). Some reverb or ambience ought be heard from
the front, too, and probably it should use shorter delays
and decays, and a bit less level. You can use neat toys like
Psi-Networks (for 90 degree constant phase shifting) without
worries of incompatibility and corruption as existed with
all the pseudo quad matrix schemes: SQ, QS, RM, etcetera
(I'll have more on matrix networks and early quad systems
and my trial by fire with SQ in a related page here soon).
You can use the widening of "sound-shuffling" processing to
great effect on 5.1 channels, it's nothing to be tossed
aside just because we're working with more than two
channels. The transition to full surround is simply a move
to a superset of everything else we already know, from
creating, engineering and producing, to the "all-enveloping"
new playback systems at home. We don't have to begin all
over again. This is NOT rocket science!
I've been mixing most
of my music in surround sound since the early 60's, and have
saved all the master tapes in good condition. Now that DVD-A
has been standardized, I expect to have a LOT of fun making
these available to you. Yeay!! I love the liberating feeling
to compose FOR surround, actually conceive it as a part of
the creative process, not something slapped on later like a
coat of paint. 5.1 or .2 is going to be WONderful for the
recording arts and sciences. Much much more important than
96k/192k sampling idiocy at a hype-y 24 bits.
(Did
you hear that?
Did I hear what? You
know, the tighter ambience, contoured timbral nuance and
extended silky imaging?
Oh, right, of course, I was just about to mention it: a
SPLENDID
new suit of clothes, your Majesty!)
Spend that extra DVD bandwidth wisely: give
us multichannels!
Ahem. That's something
everyone can hear as an improvement. Let's not "blow it"
this time, people, defending some theoretical folly or
visual chauvinism, as was done in the 70's. Let's get it
together this time.
Pep talk is over. Hope
you tend to agree. Be back again with more soon. And thanx
for reading all of this!
--Wendy
Carlos
©
Copyright 2001 Wendy Carlos -- All Rights Reserved.
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