A Short Discourse on (Home Theater) Surround
Here are home theater setup suggestions
and a mini-history from the original THX to "now", and towards
the future. If you're thinking about going from stereo to surround, or from
5 channel surround to 6 or 7 channel surround, read on...
Since everyone in HOME situations don't
always build or install rooms using an acoustics consultant (or even a protractor)
the results will vary and nothing is cast in stone. There are always personal
preferences, decor objectives, etc. which override everything else. And
while this is all my opinion gleaned from 55+ years in audio, your mileage
Everyone is entitled to operate their
sound system as they see fit. If you enjoy it and it's right for you; great.
But I like to assist people by getting all the wrong things out of the way
first (speakers in the ceiling is always good for starters) so that you
don't wind up with a room full of equipment which annoys you and you feel
you're not getting the bang for the buck you feel you deserve.
I can't tell you whether to prefer red
wine or white wine - that's up to you - but the careful convergence of setup
ideas for the room acoustics, speakers, electronics, AC power, and wire
hookup all play a part in the sum total of your overall enjoyment.
Whatever you do, enjoy experimenting. You could discover
And don't forget that a sound (and video)
system is definitely a weakest-link phenomena. ONE loose and crackling wire,
in an otherwise pristine system, will cause the owner of the system to remark
that the whole thing sounds like junk, or worse. I would suggest that the
utmost care and attention be paid to what you might initially think is the
smallest detail - such as contact cleaning and enhancing chemicals... and
even labelling wires! You'll thank yourself later.
Perhaps because of genetic, physical,
or chemical attributes, some people are "Bass Freaks" or "Treble
Freaks", etc. Some people will listen to a song and not even notice
the bass is present, while some won't pay any attention to the singer but
know every bass line. The point is people are different. You may like something
completely different than what any artist, record producer, or engineer
ever intended! There is, therefore a very wide range of what you might personally
consider "loud enough" or "enough bass" or "too
loud", etc. Fortunately the engineers at THX studied this very carefully
and came up with a technical set of parameters designed to minimize the
The whole concept of surround sound
is a complex psychoacoustic phenomena which if set up well is convincing,
and if set up poorly is annoying at best, and becomes frightening to some,
because people are not used to, nor prepared for, sounds coming from behind
them without turning around to see what the sound is; and in the case of
a movie this becomes a momentary distraction instead of an emotional concentration
toward the screen.
Many people put surrounds too high or
behind them -and then turn them up too loud and the result is not pleasant.
Placing the surround speakers at the most desirable angles and getting the
most desirable room coverage / splay will do wonders to smooth out the desired
immersiveness of the experience.
My suggestion is to START with everything
set at a calibrated, neutral position (and that includes the correct geometric
placement of the speakers as I will explain) and then work outward from
there, continually fine tuning your system mechanically and electrically
until you feel it sounds right to you. This is not a trivial issue. Expect
to spend a few weeks at this.
There are methods of setup which are
DESIGNED and SUGGESTED if you want to experience the seat-of-your-pants,
this-is-how-they-hear-it-in-Hollywood type of setup. There are suggested
setups for those who might like classical music and like the feeling of
being, for example, in the 5th or 15th row center. This also brings up a
whole series of questions such as, "How was the piece mixed? From whose
vantage point? From the guitar player's perspective? From the conductor's
perspective? From the 5th row center concert seat? Nowadays, DVD's with
movies on them intended for home release are specifically mixed with the
intent of being played back in a home setup, where the speakers are essentially
near to mid-field, at perhaps 4 to 15 feet from the listeners' ears. The
soundtracks for the Theatrical release of the same film is usually different:
it is intended for playback in a much larger space, with the speakers much
further away to begin with, and therefore the spatial characteristics that
are an integral part of the mix are different between these two different
One way to approach this entire setup
phenomena is to get the stereo image correct first, before concentrating
on the overall home theater experience (meaning 'surround sound' ) as a
whole. Some people concentrate only on the picture and the visual phenomena,
and then stick some speakers up wherever they can. That result is often
disappointing. If, after the system is completely set up, you find yourself
"leaning in" to the sound, subconsciously trying to get "closer"
or "more immersed" in it then I would suggest repositioning your
seating so you are somewhat closer to the picture, then reorganize the speakers.
Sometimes a good way to determine speaker placement is to set up ladders
with boards between them and keep moving things around until you are convinced
things are the way you like them. Another method might be to hire an acoustics
consultant/studio designer to get it right the first time!
BRINGING THE MOVIE THEATER HOME
Besides the simple psychoacoustic effect
of the stereo image, there is an even larger psychological effect when the
sound is coupled to picture. The HIGHER and WIDER the placement of the L
and R speakers are the more "Hollywood" the effect. The closer
together and lower the L and R are (to a certain extent) the more "intimate"
The Center Channel is mostly for dialog,
and the L and R are mostly for M&E (Music and Effects).
Historically, music engineers/mixers have only had a stereo pair
to work with, and all the LR placement and panning heard by you the listener
was based on the psychoacoustic phenomena of the phantom center channel.
But movie engineers and mixers
have had a REAL center channel to work with, and so operationally
we now have the following sub categories:
Music mixed in stereo
Music mixed in surround (5 channels)
Film mixed in surround for the theatrical release.
Film mixed in surround for the home DVD release.
Different film mixers and rock n roll mixers have rather
varying operational philosophies about all of this. Do not expect to play
a movie DVD and then switch to a rock n roll CD and then switch to a classical
CD and not expect to have to adjust things. This brings up a serious point:
Just because you think your system is calibrated, there is such a wide range
of program material differences that you essentially MUST adjust each and
every disc -- perhaps each and every song, if you want to lean towards being
an audio perfectionist.
For the movie, the real C channel
is essentially for dialog, and therefore should be placed as close to the
spot on the screen where the actors mouths are! Unfortunately this means
right in front of the picture, which of course we typically cannot do...
so in the case of a projection screen, it MAY be advantageous to place the
speaker behind a perforated screen; in the case of a tube, Plasma, or LCD
picture it should be placed below the picture if possible. The L
and R can go somewhere near the centerline of the picture, or a little
higher. The L, C and R tweeters do NOT necessarily
have to be lined up as long as they are not too far (many feet) away from
being in a line. In other words, if the C is below the picture, the
LR might be on a line 2 or 3 feet above where the C is. When
figuring out these angles and setups, it is a good idea to make the subtended
angle of the L and R speakers 60 to 75 degrees, with 60 degrees
being the preferred number. More about this will be shown in the diagrams
Placing all 3 front speakers too high
up such as in a row above the picture near the ceiling is generally not
a good idea and is to be avoided whenever possible. Among other acoustic
anomalies, this often causes the audience to "lean in" to the
sound, tightening the occipital muscles as opposed to relaxing them, and
the result is an experience which leaves the viewers tense, not relaxed.
However there is an interesting phenomena
with a moderate room and the subwoofer in the front somewhere: when the
younger 'kids' are sitting on the floor as they often do, they love the
bass. So they are sitting nearer the sub and the higher frequencies are
splaying sort of over their heads. The more mature and elderly, who usually
do not like bass so much, are more in the direct field of the higher frequency
drivers, and also get somewhat less bass. So now, rather than attempt to
get the sound "the same" everywhere in the room, (the concept
of making the room "flat") we have used the natural acoustic phenomena
and anomalies of the room to accomodate the auditory desires (real or imagined)
of the listening audience. Do not underestimate this phenomena! I would
suggest getting the sound "right" for your main "sweet spot"
seating area, and allowing the natural sound patterns in the room to then
be used to their full advantage --- even to the point of intentionally UN-balancing
the room somewhat. Use the anomalies of the room to your advantage! Have
a mother-in-law who hates bass? put her in the null. Now everyone is happy.
Once the speakers and the sound system
is adjusted properly, it should essentially disappear into a continuum of
surround sound, where the localization appears real and smooth; which is
to say if some dialog appears as if its coming from over your head then
it isn't set up correctly!
THE STUDIO vs THE HOME
In a studio, the front speakers are
usually placed in an arc because we're really dealing with panned mono signals,
and the easiest way to help to ensure that all the levels are the same,
and in true electrical phase with each other, is to place the speakers the
same distance from your head, in an arc. But at home, many people simply
put the speakers on a straight line and adjust the levels [to be the same]
The EARLY DAYS of HOME THEATER - ENTER THX
Once we get past the phenomena of stereo,
we arrive at the next historical stop: the suggested THX setup with DIPOLES
placed at 90 degrees. The listener is sitting in the null of the out-of-polarity
(often somewhat incorrectly stated as 'phase' - they are actually "180
degrees out of phase") surround dipoles, and the dipoles are splaying
the Ls Rs outward along the walls of the room. This decorrelated
[side] splay gives the listener the sense they are in a large(r) theater.
Fig (1) - one of the original THX SETUPS
Notice in the above diagram there's
NOTHING behind you. (Of course many people place the surrounds "anywhere"
because that's the only place they'll 'fit' or 'go'.) Some people put the
"surrounds" in the back, or incorrectly stated, in the "rear".
This is psychoacoustically and psychologically wrong. Tom Holman (and others,
including myself) found, after much experimentation, that sounds from directly
behind frighten the young and the elderly, and in fact detract from the
theatrical experience, and cause people to turn their attention away from
the screen toward the offending sound.
The THX phenomena did and continues
to do a lot for the industry by not only specifying minimums, and by continually
exceeding these minimums and raising the bar so that manufacturers are always
striving to build a better product. If you were to do nothing else than
buy all THX approved products, and blindly hook them up, and set the switches
to the THX position, you would at least be assured of a minimum theatrical
experience which is quite respectable and satisfying, even if you were not
an audio, nor video, nor home theater expert. Often, this is the best and
certainly easiest choice.This makes the entire setup painless and almost
Even following the THX guidelines, you
can expand and extrapolate on their good foundation by making things "bigger";
specifying for instance a higher powered version of all the equipment so
that the overall experience is maintained at a high level but there's MORE
of it still.
Of course all the great equipment of
the world cannot sound good if it is hooked up wrong, adjusted wrong, or
set up in a space which is an acoustic nightmare. You would not want to
listen to the best speaker in the world if it were placed in a glass shower
stall with continuous reverberation which builds up to complete distortion.
Therefore there has to be at least some attention paid to the room acoustics
and its acoustic surroundings, which become part of the overall audio (and
There were some speakers intended for
"surround use" which were dipoles, as originally suggested by
the THX setup, and as shown in FIG. 1. There were also some speakers which
were just like the speakers at the front of the room, i.e. "front-firing",
(out of the front of the cabinet) and these were placed at the Ls Rs
Then Ken Kreisel at M&K invented
the Tripole, people in studios put the Ls Rs at 110 degrees of arc from
the "C", the ITU and the AES published their suggestions,
and that gives us the world "standard" 5 channel surround sound
setup. This is typically how things are set up, monitored, and mixed in
Fig (2) - Typical 5.1 suggested setup.
This is the STANDARD SUGGESTION for "SURROUND SOUND".
This diagram does not presuppose you
put speakers in a circle - although that would be best. The supposition
is you extend the angular lines outward until they intersect a wall and
you put the speakers on that wall. IF front-firing speakers are used, (at
the Ls Rs positions) you aim them as shown. If TRIPOLES are used,
you place them flat on the wall, so that the correct ratios come out of
the [sides of the] box and splay on the walls.
6.1, 7.1 and MORE
Many receivers have a combination of
proprietary "surround " modes which support a 6th or a 7th additional
speaker. To make a very long issue short these surround modes are usually
digitally synthesized and additionally processed and reverberated from the
original 5 channels. I suggest to most people that the better path is to
set up a "better" 5.1 system (which is how things are mixed) than
a more diluted 6 or 7.1 system. Merely adding sound sources to a room does
NOT enhance intelligibility in any way --- to the contrary, often you are
adding 2 more sources but have not changed the relative levels of the rest
of the speakers therefore the relative level of the all-important Center
dialog channel is now lower!
The setup below shows a typical setup
using a moderate to high-end home theater receiver or control center such
as a Denon, Marantz, Pioneer, Harman, some Yamahas, etc. They typically
have a pair of Lb Rb outputs which for the most part ARE NOT DISCRETE!
They are resynthesized from the 5 channels that already exist, and the signal(s)
sent to the back contain either a simple delay and/or artificial reverb
and digital processing to MAKE THEM SOUND AS IF THEY WOULD IF THERE WERE
REAL CHANNELS BACK THERE. Certain decoding methods, such as DTS have one
(6.1) or more (7.1) channels and those 'extra' back channels are synthesized
and then encoded AT THE TIME OF ENCODING, therefore they are already on
Certain other companies, such as Yamaha
and Lexicon, have their own proprietary surround resynthesis schemes which
sometimes suggest that speakers be placed in locations that can only be
described as "unconventional". Even so, some of the schemes, although
considered odd by the engineers and producers who set up and mix the original
music, are nonetheless very interesting, proving that the art of audiophile
experimentation is not dead!
To take this even one step further,
Tom Holman has demonstrated a 10.1 channel sound system, (and more...) and
as the software upgrades for the various receivers and decoders matures,
we may expect to see all sorts of unusual and proprietary processing tricks
In some rooms which have a ratio of
very long to wide; or are acoustically 'dead' or dampened, the addition
of these channels 6 and 7 MAY be somewhat beneficiary. The overall suggestion
is to not go to a 7.1 setup if it is going to compromise the "correct"
5.1 setup in ANY way.
FIG (3) - 7.1 Channel setup for the home theater
If you feel you MUST set up 7 channels,
do it this way. The angles of the Lb Rb speakers becomes part of a psychoacoustic
balance: if you think there's sound that DOESN'T BELONG behind you, it will
be frightening. If it properly blends into the scenario of the film and
the rest of the acoustic phenomena happening in the room, it will feel "correct".
It would seem that firing a speaker right into the back of your head cannot
be correct. My suggestion is to make the back pair about half the subtended
angle of the front pair, therefore about 30 degrees a part. See below for
some other alternative surround setups (either 5.1 or 7.1).
But here's a catch: we don't actually
need Lb Rb; (the back channel resynthesis) we can make this 2nd pair
of surrounds ALSO be Ls Rs, just like in a movie theater, where there
are almost always multiple sets of Ls Rs. In fact we can have multiple
rows of listeners, and multiple rows of Ls Rs; all we need are (usually)
dedicated channels of amplification to drive each "pair, like this
Fig (4) - Multiple Surrounds, such as in a larger
home theater presentation room,
with multiple rows of seating.
You will notice that the surrounds are
placed so that each row of listeners gets hit by a surround pair at about
110 degrees of arc from the C spaker. So Surround sets 1 and 2 can
be Ls Rs, and surround set 3 can be EITHER Ls Rs -OR- Lb
Rb, depending upon if the receiver in question supports it. There is
absolutely nothing wrong with using multiple sets of surrounds. Some receivers
have the option to adjust the delay timing to these multiple sets, so that
the additional few milliseconds of delay to these "rows" makes
the room seem larger.
In some instances, notably if the room
is reflective, close to square, or the entire listening area is quite small,
the addition of a Lb Rb pair may muddy up the whole thing and may
detract from the intelligibility of the C channel dialog, because
you're adding 2 more uncorrelated sources, with different delay timing into
the equation, and this muddys up the entire soundfield. This may cause the
C dialog channel to be less intelligible because now the Center dialog
channel represents LESS of the overall averaged sound level.
In a room which is very rectangular,
(and it depends where you are sitting in this room) very dead (plush carpets,
wall hangings, soft furniture, acoustic trapping) the Lb Rb surrounds
may be VERY beneficial.
A "REAL" CENTER CHANNEL vs A "PHANTOM"
What's the future? The industry, now
that real multiple panning output plug-ins are available for DAW's, may
be moving in the direction of "Panning Pairs" that is, where every
pair of adjacent speakers has ITS OWN PHANTOM CENTER IMAGE, just like a
stereo L R has its own phantom center.
The film industry has ALWAYS had a center
channel speaker for dialog, and places M&E (Music & Effects) in
the L and R.
The MUSIC industry, (i.e. rock n roll,
classical) has NEVER had a discrete Center channel; they have always used
a PHANTOM center image formed between the L R. This has formed a
remarkable dichotomy in the world of mixing which is continually unresolved.
"Where do we put the voice? In the C only, with a little reverb
in the LR?" (that's the film mixer talking) vs "Where do
we put the voice, in the LR with some in the Center to make it "feel
" correct? and if we have the voice in all three, then what happens
when it's downmixed to stereo? We're not used to this available Center channel
--- help!!!" (that's the music mixing engineer speaking...) There are
always issues and workarounds.
So now if we put every pair of
speakers 60 degrees apart, that gives us this: (6 x 60 degrees = 360 degrees;
while the 7th speaker [the Center] is ALWAYS separate and distinct). That
setup then looks like this:
Fig (5) - 60 degree splay setup - part of what the
future may hold...
Now there's a phantom center image between
each pair, (between L and R; between L and Ls;
between Ls and Lb and so on, around the room) and yet the
speakers are "placed" in the room in such a fashion as to be approved
by spouses (of any gender) and interior "designers" and "decorators".
The setup becomes "easy".
This gives fabulous spatial localization
even with systems which have less than ideal phase linearity (important)
or frequency linearity (somewhat less important); or where, say, one set
of speakers on one side of the room is higher than on the opposite side
of the room, because that's the only place you could "stick" them.
But guess what? !!!!! The Ls Rs
are at 90 degrees to the 'main' listener again, just like in the original
THX setup, except that the original THX setup called for DIPOLES at the
sides and these later diagrams call for front-firing speakers all around.
One very desirable solution is to set
everything up so you can, in fact, hear everything how the producers, directors
and engineers intended, and this holds true for both the visual, the audible,
and the sum total of the theatrical emotional experience.
Once you understand that entire philosophy,
then you are able to modify it, if you so choose, to fit in with your lifestyle,
room decor, budget, and technical adjustibility, so that the end result
is most pleasing to you.
MONITOR or PLAYBACK?
You could also strive to make your room
seem like a pro studio, setting up the room with the speakers not necessarily
against the walls, but in a much tighter circle as shown in the diagrams,
perhaps, say, in an 8 or 9 foot diameter circle. What that does is tend
to focus you in this tight sound [near]field, where you hear every nuance
of what is in the mix, and LESS from the room; kind of the opposite of the
philosophy of widely splaying tripoles (or dipoles). You are in the nearfield,
and you do NOT really hear the first order reflections, because you are
so tight in the circle. By the time the sound hits the walls and comes back
to the inside of the circle, the Haas or precedence effect has long since
taken over, and the room splay now becomes a much smaller percentage of
the overall sound.
For an even added tightness, and the
MOST up close and personal mix possible, treat the room acoustically to
help make it flat, neutral, and have little or no first reflection and THEN
sit inside the 'small' circle. The widely splaying effect is great for relatives,
friends, neighbors, lookers-on, and so on, but there is nothing so personal
as being in your own self-contained, focused, field of the mix; sort of
flying in the cockpit as it were as opposed to "looking out the side
windows" as an uninvolved passenger...
One last word about this 'small circle'
setup: this becomes the most effective way in a smaller apartment where
you would want to bother the neighbors the "least" --- since you
are sitting 6 to 10 dB CLOSER to all the speakers than might otherwise be
the case, you have all the added benefits of the initmacy and a wider dynamic
range, because you're "starting" with the speakers turned down
6 dB. Therefore you just gained a "free" 6 dB additional headroom
and dynamic range.
If you have the time, patience, and
room, experiment with this circle starting as small as possible and then
extending the so-called circle out to the room's boundaries. You just may
find the magic combination FOR THAT ROOM where the direct, nearfield sound
properly balances out the room's own refelectivity, and this then makes
the entire system disappear, and the surround field, even with a 5 channel
system, seem quite seamless.
For some interesting reading on room
acoustics and how to preserve the acoustic balance and purity in a Home
Theater room check out Art Noxon's articles at the ASC / Tube Trap site:
Click on the Volume I, II, III etc links, not the PDF versions. The link
to each of their next page is WAY, WAY down at the bottom of each page.
For a very interesting and somewhat differing view on
subwoofer placement, read Floyd Toole's article here:
PDF file, 815k