Surround Sound Whitepapers
Audio Products
Buy Videos
Film / Video Production
About Filmaker
Is it just our techno-crazed culture? Given that we have only two ears, must we now have 5.1 channels of sound instead of two? If it’s time for you to invest in a DVD player and surround speakers for your home, turns out you could also enjoy new “DTS music CDs.”
Why digital surround? If you were around when all sound reproduction involved just one channel (monaural, monophonic, or mono for short), you remember how astonished you were upon first hearing stereo. With mono hi-fi, it sounded as though you were listening through a hole in a wall to an orchestra in the next room. With stereo, the orchestra came into the room and filled the whole wall. With “matrix” surround sound (derived from two channels, the best being Pro Logic), a sense of “spaciousness” filled the entire room.
Today, discrete 5.1 channel surround is enjoyed by nearly every movie-goer, with speakers not just left and right, but center, left-surround, right surround, plus optional Low Frequency Effects (LFE, the .1 channel). With digital surround, you leave the room and are “transported” to another acoustic space – the concert hall – with the sound of it all around you.
Now, digital surround is coming to a “home theater” near you.
Why 5.1 channels instead of two? Because it’s more fun, more emotionally involving, and for movies more enhancing to storytelling than stereo or legacy matrix surround. Now beyond movies, new music-only releases are an added reason for having 5.1. Here we’ll explore the basic benefits of digital surround and how to have it at home. For comments on music and movie titles and for more about acoustics, THX, help setting up a digital surround home theater system, if you need a subwoofer, and generally getting the best sound for your money, see supplemental articles.
We
begin demystifying digital surround with a fact many find startling: In
our Information Age, sound is just data!
The bits are etched on a CD (compact disc), or a DVD (Digital Versatile
Disc), where surround sound accompanies motion pictures for the home theater
just like in the movie theater.
So a leading provider of movie theater surround systems, DTS (Digital
Theater Systems) felt, since it sounds so good, why not adapt digital
surround for reproduction of music alone? To
date in more than 160 music albums released, DTS fits six channels of
audio data on a CD-ROM using technology that delivers to the consumer
a mirror of the production master, just as it does for theater films.
If you have the requisite DVD player, DTS decoding receiver, and
five speakers with or without subwoofer for the LFE, you can enjoy music
in digital surround for no additional investment other than new DTS-encoded
music CDs.
In
practice, as with stereo or for that matter the gramophone that started
it all, reproduced music sounds only as good as the musicians performing
it, the acoustics it’s performed in, and the audio engineer who recorded
it. Examples ranging from
superb and mediocre can be purchased online in the form of so-called “DTS
music CDs” that are not to Red Book audio CD standards, but that a DVD
player consents to play. Another
format intended for newer players, DVD-Audio is unavailable at this writing,
delayed to market by politics in the process of standards-setting.
What can you enjoy today in
digital surround that won’t cost a bundle or be obsolete tomorrow?
- DVD movies with
Dolby Digital (DD) or DTS digital surround can be rented in video stores
or purchased online and require a DVD player with digital output, audio
receiver with digital input and five amplifier outputs, and five speakers
(subwoofer is optional).
- DTS encoded music
CDs can be purchased from several sources online and can be played on
the same equipment as the movies above.
For
hardware, DTS music “CDs” can be played on a DVD player, using it as you
would a CD player. The data connection is either coaxial
or a more expensive (but no better) optical cable. Do not play a DTS “CD” in your analog-only
CD player because, if data itself reaches your speakers, it could damage
them – the reason Dolby doesn’t offer non-standard music CDs.
You
won’t have to choose between DD and DTS if the receiver you choose decodes
both. While you can purchase players with a digital to analog converter,
or DAC, in each for use with older, discrete (five or six) power amplifiers
via five or six analog audio cables, the trend is one DAC in the receiver,
which selects from various audio sources, whether digital or analog. Good
receivers that decode DTS as well as DD start about $500 and are the control
center for selecting video to send to and from your VCR and TV/monitor
as well. You can upgrade
a stereo system for about $1,000 and up for a DVD player, digital surround
receiver, and a “three-pack” of additional speakers, although complete
low-cost systems such as Sony’s DAV-300 are available for $600.
For DVD movies, check the package to verify which if any surround it contains. Then to play, select DD or DTS 5.1 from language/audio/caption setup menu. DTS music CDs play automatically if your receiver has been configured to decode DTS connected to its digital input.
How
does DTS encoded music sound? Although
theater and home systems differ, you already have an idea if you’ve seen
one of more than 1,000 DTS movie titles in one of more than 18,000 DTS
theaters. With picture, digital surround, either
Dolby Digital or DTS, is the highest achievement in cinema sound. All five 1999 Oscar nominees for sound
were in DTS, with the best picture of the year, Saving Private Ryan,
winning the Oscar for sound as well.
Imagine that quality at home.
And while Dolby Digital™ is elegant technology that sounds very
good, DTS sounds superb because it uses gentler compression with samples
up to 20 or 24 bits instead of 16 used by normal music CDs. Less compression (data reduction) means
imperceptible artifacts from lost samples; four to eight more bits means
a potential dynamic range of 117 to 141dB, equal to the range of loudest
to softest sounds perceived in human hearing.
Even if they take it for granted in theaters, digital surround heard at my home astounds people – in part because they don’t expect a theater-size experience. At home hearing DD and DTS side by side, DTS is just discernibly better - more dynamic (from subtle to chest-pounding), and intricate details are crystaline, especially with classical and acoustic jazz. And it’s the availability of digital surround music that today gives DTS an advantage. Happy listening.
Robin Miller is an entertainment technologist and member of AES (Audio Engineering Society) and SMPTE (Society of Motion Picture & Television Engineers). Mr. Miller is a filmmaker recognized nationally by 52 awards and specializes in surround recording.
DTS is a trademark of Digital Theater Systems, THX and THX Surround EX are trademarks of Lucasfilm, Dolby Digital, Dolby Pro-logic and Dolby Surround are trademarks of Dolby Laboratories Licensing Corporation.
1. The Workings of Digital Surround for the Home Theater
Several technologies compete in delivering to the consumer a “mirror of the production master” - really a “perceptually precise image” of the movie or music producer’s sound mix. It’s not an exact copy, because the compression (data reduction) is “lossy” – and missing data produces artifacts, even if we can’t perceive them (some people can some of the time). Compression artifacts is the price paid for 5.1 discrete channels of sound instead of stereo’s or matrix surround’s two. And the perception of being enveloped in multi-directional sound, delivered within the limited bit budget of DVD, DTV, or DTS-CDs, is what digital surround is all about.
In theory, digital surround works because your ears can “tell” a lot more than just left from right. Once your brain interprets their signals, you can also tell front from back and even up from down. It is recreating the illusion of “where” that makes stereo more lifelike than mono, and surround more lifelike than stereo.
In a movie, the story is more compelling when sound from all around adds “images” outside the frame of the picture, such as the roar of the jet after it has flown off the side of the screen and around back. Immersing you in a believable stereotype of the sound-field that existed in the original firefight, or horse-and carriage you’ve just seen pass by, or baseball crowd. For music such as distributed on DTS “CDs,” transporting you to the opera house or the unplugged club can be a no-cost benefit – added reason why people want digital surround for their next entertainment purchase or system upgrade.
2. Digital surround Movies and DTS CDs and how they sound
Compressing
a feature movie’s picture plus several sound formats including digital
surround on a 5 inch optical DVD the size of a CD is a remarkable achievement
of technology. Similarly remarkable is putting 74 minutes of 5.1
channels of surround music on a CD as DTS does. But how does digital
surround sound?
Hearing
a DTS music CD was not the first time I felt like I’d never heard such
good sound before. I have learned that with every jump in
reproduction quality, the bar is raised.
DTS is the one to beat now, the current state of the art. With my eyes closed and moistening with
the music’s beauty and power, Holst The Planets (London Symphony)
moved me as never before outside a live concert.
To my ear, this surround release has been “derived” from a stereo
(possibly binaural “dummy head” microphone). While the impression is that of a concert
hall stage in front with you in an expensive seat, side reflections exhibit
“spectral splitting” – a psychoacoustic limitation of 5.1 that causes
successive notes on the scale seem to snap back and forth from left to
left surround and right to right surround.
Remastered
in DTS 5.1, Lyle Lovett’s excellent Joshua, Judges, Ruth album
was more intimate and fun – with the choir and B3 in Church singing
from the balcony behind me.
Other samples are novelties, gee whiz at first, but doomed by decreasing attention spans and time to market. As with most popular music recordings, so-called stereo is really “panned-monaural,” assigning dozens of mics shoved into every horn and down every throat, effectively eliminating any acoustical blending, for either listener or performers (who record wearing headphones), and creating bigger-than-life ambiences electronically. Boyz II Men in Boyz II Men -II sends each singer to their corners, one per speaker – with you in the middle, where you can really hear how good they are.
Diano Krall singing Gershwin’s They Can’t Take That Away From Me (Love Scenes) is more distantly mic’d (except for the bass) and therefore more natural-sounding. But the new medium is somewhat wasted, using the surrounds for only reverb and vocal reproduced mostly as a fragile phantom between left and right speakers, reducing the center speaker’s value as an “anchor.”
Similarly, Trisha Yearwood (Where Your Road Leads) is a phantom vocal with instrumentalists panned to their respective corners, plus reverb and guitars behind you. You’re left in the middle – a new and very different experience than being in the audience with musicians on stage in front of you that might be more a novelty.
Tapestry’s spiritual Canticum Canticorum overcomes the “panned mono” by unifying effect of dripping reverb.
Brian Wilson’s Your Imagination is a novelty where both Brian and the drum kit are as wide as your left and right speakers – impossible in reality but fun nonetheless.
With
picture, it’s the highest achievement in cinema sound – with all five
of 1998’s Oscar nominations for sound in DTS and the picture of the year,
Saving Private Ryan (DreamWorks), winning the Oscar for sound as
well. This movie sounds incredible with ricochets
that make you duck in your lazyboy. Similarly, in Dances With Wolves
(Image Entertainment), approaching musket balls whiz past and behind. Yet in Story of Us, the new medium
seems wasted by pedestrian placement of music in simple stereo left and
right, dialogue center, and reverb in stereo in back. A very scary pre-release of The Haunting
rattles the subwoofer with what must be 5 Hertz!
Sheryl
Crow Rockin’ the Globe (Image) and Eagles Hell Freezes Over
(Image) concert video DVDs with DTS 5.1 surround seem to take you to the
concert, not just bring the concert to your den.
Roy Orbison B&W Nights (Image Entertainment) is much
too loud due to good ol’ pop music compression (volume, not data reduction). Digital surround’s dynamic capability
means such compression isn’t needed except when car 5.1 debuts this fall
(available from Pioneer, Blaupunkt).
All
this talk of DTS surround technology isn’t to say that Dolby Digital (DD)
isn’t great, both in the theater and at home on DVD – The Spy Who Shagged
Me and Mask of Zorro among the best I’ve experienced.
If you want to compare DD with DTS, try listening to chapter seven
of Bowfinger both ways back-to-back and notice how, when all channels
get busy, “bit starvation” in the more compressed DD datastream sounds
a bit muffled, where DTS maintains full frequency response. Some versions of Saving Private Ryan
also squeeze both DD 5.1 and half-rate DTS 5.1, which still sounds excellent.
3. Setting up a Digital Surround Home Theater
Even
with escalating feature sets, electronic technology is available at ever
lower costs to manufacture. But not so electro-mechanical components,
so an investment in digital surround gear will pay mostly for speakers.
Meeting increasing demands for quality in the face of unwavering
laws of physics is why. Also the fact that we now need five or
six. It’s only wise to skimp
on small, inexpensive speakers if you plan to upgrade them in the future,
or if your apartment just doesn’t have the space – or need the acoustic
power to sound loud enough without the speakers distorting. For a starter system, audition the Sony
DAV-300 for $600 complete.
On
the other hand, if you’re upgrading a good stereo, at minimum you’ll need
a DVD player capable of both DTS digital output (it then must have DD
and CD play capabilities), a digital receiver capable of both DD and DTS conversion from a digital
input, and three speakers to add to the two existing ones. For lasting enjoyment, shop in the $1,000+
range to upgrade. If your
old speakers are good ones, let them continue to be your new left and
right – just buy a “three-pack” consisting of center and two surrounds,
all of which can have small woofers (5 inches or less diameter) and more
limited bass and therefore lower cost.
On the other hand if you wish to upgrade your system beyond the
quality of your older speakers (for example if they have woofers smaller
than 6.5 inches diameter), move them around back and buy three better
quality speakers for left, right and center.
Physics
note: Many speakers have dual woofers that roughly compare on the basis
of equivalent area, which mathematically varies with the square of the
radius. For example, two
5 inch diameter woofers about equal one 7 inch, and two 7 inch would equal
one 10 inch, etc. In practice,
a single larger driver is preferable because it’s lower free-air resonance
determines the system’s actual low frequency cutoff and mid frequencies
won’t comb-filter (sharp acoustical “EQ” that changes coloration with
your listening position), as happens with two separated speakers play
the same sound. Using satellite-size speakers with their
largest driver 6.5 inches or less in diameter for the five main channels,
consider a common-bass subwoofer to extend your surround system’s range
from their practical limit of about 100 Hertz to the lowest limits of
human hearing, about 20 Hertz.
In addition to its DAC, full-featured digital receivers have a DSP (digital signal processor) that allows mixing and matching speakers with different low frequency capabilities and for properly directing the low sounds in the absence of an LFE subwoofer for LFE, called “bass management.” In rooms between 1,000 and 2,000 cu ft, receiver power of 70 watts per channel (times five) will with reasonably efficient speakers be able to achieve without speaker-damaging “clipping” (overload) the typical “home theater standard” of 83dB SPL (sound pressure level). The DSP also allows one-time setup of proper delay for surround speakers closer to the listener than front speakers and sequencing filtered pink noise for adjusting them for equal level. Advice: Do all these DSP setup adjustments or the surround illusion just won’t be working. For lifelike reproduction of movie dialogue and acoustic music, distortion less than 0.1% is desirable (where it will be inaudible because it’s 60dB quieter than the sound that caused it - and in any case masked by much greater speaker distortion on the order of 1~10%).
If
you’re not upgrading a good stereo, you’re starting from scratch – give
the old stereo to the kids (if they’ll accept it) or relegate it to the
rec room. Starting from scratch
raises the low end of the cost range above by two additional speakers,
CD player, tape or MD deck, etc.
Completing the video side of a home theater requires a large, clear
monitor/TV, hi-fi VCR, etc.
4. What’s next?
Just as stereo improved upon monaural, surround improves upon stereo. But researchers have determined that a totally realistic soundfield would need 30 speakers, if not a million. 10.2 has already been demonstrated – and would fit in a DVD-Audio. Back to 5.1, nearly everyone I’ve demonstrated it to not only heard the difference, but wanted it for themselves. Look for car surround this fall, already introduced by Pioneer and Blaupunkt. Not far behind, look for a portable player that plays CDs, DTS music, DVD, & MP3 CDR, with a DSP that “encodes” ear and head-related cues to deliver the surround illusion using any headphones that costs under a grand (Oh, and could it record them too?). Spurred by the unquenchable thirst of humans for entertainment and of marketing, technology, and artists to provide it, the evolution in sound reproduction continues.
5. Links
http://www.smr-home-theatre.org/