A Short Discourse on (Home Theater)
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,
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 may vary.
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 something great!
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 confusion.
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 releases.
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 effect.
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] accordingly.
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)
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 plug-and-play!
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 theatrical) experience.
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 surround
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 studios.
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 the disc.
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 emerge.
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
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" CENTER
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
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