Product Review - Dolby Surround
Pro Logic II - The Technology and the Sound - March, 2001
Brian Florian and Stacey Spears
THE TECHNOLOGY (by Brian Florian)
While for decades the term "Stereo" has implied
two-channel/two-speaker audio systems, this is not really accurate. "Stereo", in
the strictest sense, implies any reproduction system with two or more channels. The dawn
of commercial stereophonic sound was achieved not in the music recording industry, but in
the movie theater. The 1940 release of Fantasia ushered in a then new audio
experience for the audience: 4 channels of audio through a system named
the 50s, movies had become big business with larger and wider film formats in development
to thrill audiences. In addition to having a better picture, the larger films had more room for
audio. The 1953 film "The Robe" is recorded as the first CinemaScope release with 4
channels of magnetic sound right on the film strip, the technology being virtually
identical to today's cassette or open reel tape, with 2 channels going in each
direction. This landmark was quickly followed with "Oklahoma"
whose 70mm ToddAO release featured 6 channels of magnetic sound. These events formed the
catalyst for the development of 6 track magnetic sound on 70mm film, a practice that would
endure for decades.
But by the 1970s,
the grand 6-track soundtracks of the 50s and 60s were all but doomed: 70mm prints were too
expensive, the magnetic sound (literally) wore off after repeated runs, and there was not
enough room on 35mm prints to do much of anything. By the 70s, movie sound was back to
dull mono. But in 1975, Dolby introduce the sound format Dolby Stereo. On the
ubiquitous 35mm release prints, it is possible to squeeze in two optical soundtracks, call
them Left and Right. The Dolby Stereo system also records, in those two channels, sound
for a center channel and a surround
channel (see technical explanation below), thereby delivering 4 channels via a 2 channel
carrier. The system was simple in its implementation, it fit on inexpensive 35mm prints, and
was compatible with mono playback systems. Surround sound had come to the masses, and to
this day, there is hardly a movie released which does not, as a minimum, have a Dolby Stereo
One could almost say that this wonderful hobby we all enjoy was born
of a coincidence. LaserDisc, Stereo VHS (analog and Hi-Fi), and even stereo TV broadcasts,
all featured sound delivery with two channels. When a movie was transcribed to one of
these mediums, the Dolby Stereo soundtrack, itself being carried by two channels, came
along for the ride. The center and surround channel were just waiting to be separated back
out, and the full dimensionality of the theatrical soundtrack realized.
In 1982, Dolby licensed a consumer decoding system for Dolby Stereo
soundtracks named Dolby Surround, and home theater was born. Later in 1987, Dolby
licensed a much more advanced system for decoding the soundtracks named Dolby
Surround Pro Logic (or Pro Logic for short). Originally a very expensive technology found
only in the most up-scale consumer hardware, it was not long before all of its complex
functions could be implemented on an integrated circuit (IC), bringing home theater to the
But how does a Dolby Stereo soundtrack place additional channels in
the left and right tracks, and how does the decoder know which sounds belong to which
channel? To understand how Dolby Stereo is decoded, we must first understand how it is
The Dolby Stereo Soundtrack
In Dolby Stereo there are 4 channels: Left, Center, and Right (across
the front), and a single surround channel (produced by speakers all around the audience in
a theater or two speakers to the sides of the listener in the home). We start our
explanation from these 4 'stems'.
The Left and Right channels are the carriers of the other two. That
is, nothing special is done to these two input stems. They are the basis for what we will
call LeftTotal and RightTotal, once the center and surround information have been added to
them. This system is called a Matrix.
The Center channel stem is added equally to the Left and Right, but
reduced by 3 dB so as to maintain constant total power when being carried by two channels
as it is.
The surround channel is also input equally to both the Left and Right channels, but each
half gets a 900 phase shift opposite from each other. The surround channel information
that is in Left and Right therefore ends up being 1800 to each other. In other words,
they are totally out of phase. Before getting added to the soundtrack, it gets a
-3 dB reduction (for
the same reason as the center), is then filtered to the frequency range of 100
Hz to 7 kHz, and
undergoes a form of Dolby B-Type noise reduction.
Quick side bar: Already one can see the genius of the Matrix system: All sounds are
present in the LeftTotal/RightTotal carriers. When played back over a conventional 2
channel system, the center channel will be reproduced as a phantom image between left and
right for persons seated in the center (the audiophile 'sweet-spot'). The surround channel
will take on a diffuse character thanks to its out-of-phase nature.
The simplest way to decode a matrixed soundtrack such as Dolby
Stereo is a simple passive system, as was implemented with Dolby Surround. In it,
LeftTotal and RightTotal are passed unchanged to the Left and Right outputs. With no
center channel output, the system relies instead on a phantom image between the left and
right speakers. To extract the surround, LeftT and RightT inputs are passed through a
differential stage ('subtracted' from one another).
While simple at the core, any matrix system is challenged by leakage from one channel to
another. On the surface, one can see that there is near perfect separation between left
and right channel information as they are on separate carriers. The separation between
center and surround is likewise near perfect, as surround information will by nature be phase-inverted
1800 and cancel itself out from the front left/right speakers. Likewise the center component going through the surround
stage will get shifted 1800 and cancel itself out. But between any two adjacent
channels, the perceived separation will be at best 3 dB. The surround channel fortunately
is predominantly an ambiance channel, its sounds being omnipresent in nature. But to
improve the perceived separation, the Dolby Surround decoder performs some processing of
the surround channel, namely 7 kHz low pass, delay, and noise reduction.
The 7 kHz low pass at input is of course applied in anticipation of
the 7 kHz low pass in the decoding process. It exists in the decoding stage because phase
shift anomalies in the 2-channel delivery systems become more severe with
frequency. In other words, there is greater chance for decoding errors in the higher
frequencies. Dialogue sibilance is a terrific example of high-frequency leakage from front
to surround which would be particularly distracting. The band limiting of the surround
channel is far from objectionable from a fidelity point of view since the channel is intended
to deliver a diffuse surround sound effect, not a localizable point source.
The delay circuit capitalizes on the Precedence or Haas Effect
whereby if an identical sound comes from two sources, but one begins at least
(milliseconds) sooner than the other, our brain will accept the sound as only coming from the first
source. Leakage of front information to the surrounds is greatly minimized by this
If we were to simply and passively play back the center channel by
summing LeftT and RightT, the result would not be ideal. Consider the most classic example
of a front soundstage dilemma: We have dialogue from the center and music from the left
and right. Because the center channel is the sum of the left and right, the music will
also be output from the center channel. Likewise, because the center channel is in leftT
and rightT, it will also be output there. A passive center signal will therefore tend to
narrow the perceived stereo effect considerably.
What to do, what to do?
The Pro Logic decoder, a direct descendant
of the cinema Dolby Stereo decoder, is best thought of as a passive decoder
followed by an active matrix which provides directional enhancement though a constant
Gain Riding was used in many early matrix systems including some ill fated music systems of
the 60s and 70s. In such a system, the decoder detects which signal is dominant (in our
example, the dialogue) and reduces the gain of the other channels accordingly. Of course,
we hope that the dominance of the dialogue masks the fact that the music has been reduced.
If left to itself, gain riding fails miserably in a dynamic environment where dialogue is
starting and stopping: The gain of the left and right channels are bouncing up and down in
response, producing a distracting "pumping" of the sound.
More successful is the concept of signal canceling. In the case of
our center being dominant (the dialogue), the decoder takes the Left signal, phase inverts
it 1800, and adds it to the Right output. The inverted center channel component from the
left cancels out the center channel component in the right, eliminating the center channel
component in the right output. The reciprocal is performed on the Left output. But we
still have music from both Left and Right in the center, not to mention the left and right
now carrying a copy of each other. But unlike gain riding, the overall level of the
soundtrack can be maintained.
At the heart of Pro Logic then is Signal Dominance
As a single channel becomes dominant, the remaining sounds are redistributed via signal
masking as described above, keeping the overall level of the soundtrack constant, but
providing appropriate directional enhancement where and when it is needed. The Pro Logic
decoder then has two modes of operation, passive and active, based on the presence of a
dominant signal. It is passive until a dominant signal is detected, at which time it
goes active, applying directional enhancement. Pro Logic's active matrix looks at
the relative level and phase of its input, and sends the information to VCAs (Voltage
Control Amplifiers) to control the level of antiphase signals (the "inverted
copies") applied to each channel. This system has come to be known as "feed
forward" in that the enhancements are applied looking forward down the decode line.
Dolby Surround Pro Logic II : The next level.
Introduced last year, Dolby Pro Logic II is an improved, more
intelligent matrix decoder. So improved is its decoding, that it succeeds where Pro
Logic performed poorly, i.e., playback of non-encoded material such as conventional
2-channel music. That's not to say it is a music-only application, but it certainly
makes for a new and wide appeal. Conventional Pro Logic decoding lends itself perfectly to
motion picture soundtracks. The surround channel is predominantly diffuse ambiance,
and the bulk of the soundtrack is focused to coincide with the visual front and
center. It is this "center heaviness" that many music enthusiasts find
objectionable with 2 channel music through Pro Logic.
In Pro Logic II, the most significant technical difference from Pro
Logic is that it incorporates a "feed back" design, in that the directional
enhancements are applied back to the input of the active matrix.
To illustrate how Pro Logic II improves upon Pro Logic, consider a
sound placed by the artist to image at 'half right', between the center speaker and the
right speaker. This results in the sound being greater in RightT than LeftT. Because of
this inequality, the passive decoder will not remove all of this front signal from the
To achieve full cancellation of this signal not wanted in the
surround output, Pro Logic II servos (negative feedback) the inputs to make them equal. VCAs on each input to
the surround decoding stage share a common control signal to maintain equal input to the
surround stage. In our example of the "half right" sound, the RightT signal
going to the surround decoder will be lowered a little while the LeftT will be raised a
little so that they perfectly cancel each other out at the surround decode stage.
These same "balanced" signals are also used to feed the center decode stage, but
are added rather than subtracted from each other to yield the center signal.
Because it is controlling the Left and Right feeds, this servo is known as the Left-Right
axis. There is a similar servo which operates independently on the Center-Surround
axis. The net result is that Pro Logic II responds faster and is more accurate than
Where a Pro Logic decoder sends a single surround signal to two
speakers (in other words, mono), Pro Logic II decodes independent left and right surround
outputs (in other words, stereo). Again,
back to detecting signal dominance, the Pro Logic decoder has four cardinal vectors along
which it is equipped to detect signal dominance: Left, Right, Center, and Surround.
Pro Logic II simply includes two additional cardinal directions to detect signal
dominance on, and derives its two surround outputs from these.
In addition to improved technology at the decode level, Pro Logic II
incorporates additional features over Pro Logic:
Bass management, made ubiquitous by the proliferation of Dolby
Digital, is now a required part of the package.
While Pro Logic II offers a "Pro Logic" mode which includes
the band-limiting of the surrounds, in its native mode, the surrounds are full range and
are independent Left/Right outputs.
An optional "Width" control may be incorporated by the
manufacturer (the receiver or processor manufacturer).
An optional "Dimension" control may be incorporated by
An optional "Panorama" control may be incorporated by
While Pro Logic II is the first system
to incorporate the feedback design outlined above, there have been several
other matrix decoding systems floating around, such as Circle Surround, Logic
7, and more recently DTS:Neo 6.1. Each of these have their
own little twist on the passive decode scheme, though the basic principles are
all the same.
Brian Florian -
IN PRACTICE (by Stacey Spears)
So, how does it sound?
Now that we all have Dolby Digital, DTS, and maybe even
DVD-A or multi-channel SACD, which give us full range discrete sound in 5.1
channels, what are we supposed to do with our hundreds of millions of old
two-channel CDs? And what about our VHS movie collections, FM radio, and TV?
Dolby has the answer, with Pro Logic II, giving full range stereophonic sound
even in the rear, and Meridian, being a world leader in consumer electronics,
is the first to deliver. The result? WOW!!! . . . What a sound!
I received an e-mail around Christmas, 2000, from Bob Stuart (Meridian's
President) asking me if I would like
to get an early listen to Pro Logic II (PL II). Of course, I jumped at the
opportunity. In fact, I have been enjoying PL II since Santa Claus took his
It has been a long time since I have listened to a matrix encoded
format. I have been spoiled by Dolby Digital (DD), just like you. One of the
characteristics I noticed right away in PL II was the amount of information in the
surround channels. At first I found the levels to be louder than I was
accustomed to. In fact, on music, I thought it was too loud.
My surround speakers are full range floor-standing speakers. I have them
directly to the side of my listening chair. They are sitting on top of cement
cinder blocks to raise them slightly above ear level. I have a fireplace,
which is not used, located 2’ behind my listening chair. I have three full
range speakers up front, and I am currently not using any subwoofers.
I spoke with Roger Dressler, from Dolby, about the surround levels. He asked
me how I had set the levels, what type of speakers I had, and their height.
Apparently, the way I had been calibrating my surround levels was not quite correct.
So, I thought I would take the time to pass along this
I have always sat in my primary listening chair, held my arm straight out in
front of me with the SPL meter pointing straight up. It turns out that when
the levels are calibrated this way, the surround level ends up being 1-2 dB
higher than it should. The correct way to set the level, according to Roger,
is to have the meter in the same location your head will be. Of course you
need to keep your body out of the way. This is a little difficult to do with
the Radio Shack meter, though it is possible. Instead, I broke out my dusty
Audio Control Spectrum Analyzer. It has a much more sensitive SPL meter
built-in. I put its microphone on a stand and placed that on my chair. I then got far
enough away and re-setup all of my levels. This made a noticeable difference,
as the surrounds were not nearly as loud. The diagrams below show the correct
and incorrect way to hold the SPL meter when calibrating sound levels of your
Of course there is more to the surround than just the level. In the discrete
multi-channel world, the only information coming from those surround speakers
is what the film makers intended. In the matrix world, you often get some
leakage from other channels. This made me think back to the days when DD was first introduced,
especially around the time "Forrest Gump" came out on Laserdisc. Many people
were upset with Forrest because there was little to no surround information on
the DD soundtrack . . . that and the fact that there are no chapter breaks on the disc.
The PCM track had lots of ambient noise in the surround channels. Well, the
filmmakers did not want the audience to be distracted by the surround channels.
They wanted your attention focused on screen. They did not have a tight control
on the matrix encoding found on the PCM track.
The point I am getting at is that we are now used to discrete sounds in all
channels, and when
you go back to matrix with PL II, using a 2-channel source (such as a CD), you will find the surrounds to be a bit more active.
If you switch
between PL, PL II, and DD, you may find that there is a change in volume. This
is a complex subject that we will cover in a later article.
Pro Logic II options
PL II offers two different decoding modes: Music and Movie. With PL II Music,
there are 3 optional parameters: Dimension, Panorama, and Width. The range of adjustments mentioned
below are based on the Meridian 861 and may be different for surround
processors and receivers from other manufacturers.
Dimension is used to adjust the front-to-rear balance in
the room. The adjustment has 7 possible positions. The default position is 0
which has the balance equal. A setting of +3 puts the balance toward the front
of the room and a setting of -3 puts the balance to the back of the room. I
played around a bit with this setting. Roger suggested pushing the balance
more towards the front if I did not like the amount of surround information.
After extensive playing, I settled on the default value of 0.
Panorama is used to wrap the sound field around you. You
have two options, On or Off. The default is Off. It took me a long time to
actually detect this in action. If the surrounds are busy, you don’t always
notice the change when you turn Panorama on. I have since found several good examples, and while
I do get some interesting side wall imaging, I prefer the Off position. This is one parameter where the location and type of side
speakers will play a big role in the overall appreciation of it.
I found the best examples where there was an
instrument on one side of the room or the other, and the surround activity was
minimal. The opening and closing of Minority, which is Track 11 on the Greenday
CD “Warning”, is a good demo of the Panorama effect. The track begins
and ends with Billie Joe playing a guitar solo in the right front speaker. If
I turn on Panorama, he moves from the right front of the room to the side of
my room. Another good example of this is with the old Wild Cherry song, "Play
the Funky Music."
Width is a center spread adjustment. The default value
is 3. A setting of 0 sends most of the information to the center channel, and a
setting of 7 is full left and right only. This provides a phantom center
image. I usually found either 3 or 4 to be the best setting. This was with a
center channel speaker that is identical to the left and right.
In addition to the optional items above,
Music Mode has the following characteristics:
There is no delay added to the surround channels by
default. You can adjust the delay from 0ms to 15ms.
Autobalance mode is off by default. Autobalance tends to steer
vocals toward the center channel. This is not always desired in music
because a vocalist can be placed off center on purpose.
The only option available in Movie Mode is a Pro Logic Retro option. The default value is
Off. When this option is turned on, the surrounds
are once again mono and they are bandwidth limited to 7 kHz. They include this
mode for backwards compatibility. (This will allow PL II decoder makers not to
need a separate PL mode.)
In addition to the optional item above,
Movie Mode has the following characteristics:
There is a 10ms delay added to the surround channel.
You can adjust the delay from 10ms to 25ms. (The original Pro Logic has a
default delay of 15ms.)
Autobalance mode is on by default.
Meridian has chosen to keep their original Pro Logic mode,
and they also offer the Retro mode in PL II. The original Pro Logic mode
offered by Meridian has the ability to provide mono rears or Meridian’s
propriety steered rears.
Meridian has also implemented a third mode, PL II THX.
This is the movie mode with THX processing added, and it includes the THX
RE-EQ and Timbre Matching features.
Pro Logic II in action
PL II Music is something that grows on you. Or at least
this is what happened to me, because at first, I was not impressed. To put
things into perspective, I have been using Meridian’s Trifield DSP mode for a
long time. Trifield is a passive matrix decoder, and there is very little
information in the surround channels. The surrounds really just add ambiance
to the room, which is extracted from the recording. PL II, in contrast, has
aggressive surround channels that envelope you. However, the more I listened to
PL II, the more I began to enjoy it.
The best way to describe PL II Music is fun. You are
immersed in this larger-than-life sound field that manages to wrap itself
around you. The soundstage upfront is vast. It goes from one end of the room
to the other, and it stretches from the floor up to the ceiling. (I have a
vaulted ceiling and I perceive this huge sense of space.) If you are a serious
2-channel aficionado, you may not like the effects of PL II. There are times
when instruments or vocals end up in the surrounds. PL II will be a matter of
taste. Of course, with processors and receivers that have it, you just turn
the effect off when you don't like it, and listen in standard 2-channel mode.
While there were
some songs that I think sounded strange in PL II, like Sweet Caroline,
I found many others that were greatly enhanced by PL II. There were several
tracks on the Destiny's Child CD "The Writings on the Wall", which include
Bug A Boo, Jumpin, Jumpin, and Say My Name. Each of of these
songs is high energy, and you really feel involved with the music as it wraps
around you. Nelly's CD "Country Grammar" has two songs that I like, and also
really work well with PL II. These are the title track Country Grammar
and E.I. If you are not into RAP, then you may not care for these, but
if you like this genre, you have never heard them like this! One last CD that I have to
mention is "Hotshot" from Shaggy. Every song on this CD is great, but my
current favorite is Angel. The previous CDs wrap around you, but this
one keeps most of the action up front and just provides nice ambiance in the
For those who may not know, PL II was created by Jim
Fosgate. Jim is the same person responsible for the famous 6-Axis matrix
decoder that was exclusive to the Citation line of A/V products, which included
the Citation 7.0 and 5.0 surround decoders. My first experience with Jim’s
products was the famed Fosgate Model 3A. (I actually had the Model 3 and later
upgraded it to the 3A.) Unlike Jim’s previous work, which had a limited market
do to specialty products, he wanted more people to be able to enjoy the fruits
of his labor. What better way than to join forces with Dolby? Dolby is
handling all licensing for PL II. This means that you can expect it to show up
in products at all price points. I expect it will be a tremendous product for
Personally, I am really excited about Jim letting Dolby
handle the license for PL II. The one thing that I have always felt that was
missing from the Meridian surround processors was a killer matrix decoder for
movies. Music was never a concern previously because they had always offered Trifield.
PL II Movie is an improvement not only over Pro Logic
but all other matrix decoding formats I have heard, and this includes 6-Axis,
Logic 7, Circle Surround 5.1, and DTS Neo:6.
Other Matrix decoders
I thought it would be fun to see just how PL II compares
with the other matrix decoders on the market. I managed to acquire several
surround processors to make my comparison. What better way to tell you how PL
II works on films than by telling you what it does different than the others?
I used the following processors to perform the
Meridian 861: Pro Logic II Music; Pro Logic II
Theta Casablanca II: Circle Surround Cinema;
Circle Surround Non-Encoded
Lexicon DC-2: Logic 7; Music Logic
Denon AVR-3801: DTS Neo:6 Cinema; DTS Neo:6
My 861 is equipped with an IA40 multi-channel input
card. This card has two pairs of 6-channel inputs. This allowed me the ability
to connect two external processors to the 861 so that I could switch between
them and PL II. I was only listening for matrix
decoding artifacts, nothing more, so I was judging only the
matrix enhancements each
I configured the Lexicon DC-2 with 5 full range speakers and
no subwoofer. All speaker delays were set to 3’ (three feet). This was the lowest value
you could use. But since they are all the same delay setting, this was not a
problem. The DC-2 has several options that allow you to customize to your
liking. I left all of the settings in their default position. Some interesting
ones to note are Soundstage and the Surround Roll-Off. Soundstage will
actually attenuate the surround level based on source material.
Soundstage is set to Rear, which has 0 dB attenuation
of the surrounds.
Surround Roll-Off is set to 6.9 kHz. This is similar
to the 7 kHz filter in Pro Logic. Remember, PL II has no filter. While I
could have made the surrounds in Logic 7 full range, I chose to leave it in
the default position. This is how Lexicon ships the product.
Soundstage is set to neutral, which has 3 dB of
attenuation to the surrounds.
Surround Roll-Off is set to 4 kHz.
I configured the Denon AVR-3801 with 5 full range speakers
and no subwoofer. All speaker delays were set to 0.
I configured the Theta Casablanca II with 5 full range
speakers and no subwoofer. The front three speakers had their delay set to
10ms, and the surrounds had they delay set to 15ms. The fronts allow a delay
setting of 0ms to 10ms, while the surrounds allow a delay setting of 15ms to
31ms. I had no choice here, so I kept a note to myself should I experience any
strange delays that the other three did not have. None were found.
I calibrated each processor to match the levels of the
861 using the DD tones on the Avia DVD. After this, I still had to adjust the
volume so all of the processors where at the same volume. There seems to be a
volume difference between matrix decoders, because all play DD at the same
level. The Lexicon ended up being very close if not a tad higher than PL II.
The Denon was actually a lot lower in volume, but easy to fix. The Theta was
close. In the end I was able to match the volumes.
Best of Chesky Classics & Jazz and Audiophile Test
Disk Volume 3 (They spelled disc incorrectly, not me.): Track 28, natural
Surround Test CD from Finlandia Records: Track 19,
Noise panning (L-R-L 20Hz to 20kHz); Track 21, Stepped Noise Panning (20Hz
Tarzan DVD (Walt Disney): Chapter 8 (17:25 to 17:35)
Star Trek First Contact DVD (Paramount): Chapter 2;
Chapter 3 (6:01 – 6:09)
Elizabeth DVD (Polygram): Chapter 2.
Beautiful Girls Soundtrack: Track 14, Neil Diamond
The decoders really could be grouped into two pairs.
First, PL II and Logic 7/Music Logic had similar behavior, and both provided an
The other pair was Circle Surround and Neo:6. Both of
these matrix decoders did several things that I found distracting. They really
broke the cardinal rule of decoding, namely that they brought attention to
themselves. They tried really hard to let you know that the surrounds are
discrete. I use the term discrete and not stereo because that is how I perceived
them to be. I did prefer CS over Neo:6 in all cases.
I wanted a second opinion on Neo:6 because of my lukewarm
impressions. so I enlisted the help of my roommate
Aaron. Aaron is not an audiophile, but he does enjoy music and movies. He is
an EE by trade. I first placed Aaron next to the left surround channel. I had
him put his ear up to the speaker. I played the first 20 seconds of Sweet
Caroline in PL II Music. After that I started the song over but switched to
Neo:6 Music. Four seconds into the song, he asked my why it was clipping. I said,
“Exactly!” He, being an engineer, said, "Well I can hear it with my ear to the
speaker, but will I really notice it from the listening chair?" So Aaron then
took a seat in the sweet spot. I repeated the track with PL II Music and he
made no comments. I then started, yet again, in Neo:6 Music. About six seconds
into the song, he looked at me and shook his head, like what were they
thinking. This clipping sound did not happen on every CD I tried, but I would say
it happened on over half of them.
The tracks I used on this CD are designed to check the
phase and image uniformity across the three front speakers in a multi-channel
system. However, they proved useful for testing a matrix decoder’s ability to
properly place the sound. This is the same problem that happens on "Tarzan" with
the Elephants' voices.
I tried both tracks in music and film mode on each
Let's start with PL II, because it performed as advertised. On
track 19, the sound panned back and forth from left to right at a constant
level and speed. On track 21, I got the same expected results. The bursts
appeared in the correct locations: Left, left-center, center, right-center, and
right. The phantom images between the center and side speakers were well
defined and were placed precisely between the speakers.
Logic 7 was a bit different. Track 19 also panned, but
the sound appeared to arrive at the center a bit early. While it was at the
left-center position, I could hear the center already on, but at a lower
volume. As it passed from the center on to the right-center location, again
the center took a little longer to go away. Track 21 had the bursts in the
same location as PL II, where they belong.
Circle Surround was where things started to go south.
Track 19 performed as expected with the exception of a perceived level
increase as the pan swept across the center channel. The volume would bump up,
then down again as it passed. Track 21 was also not as precise as the previous
two. The left-center and right center bursts were pulled more towards the
right and left speakers instead of imaging in between.
DTS Neo:6 followed in the same fashion as Circle
Surround but the errors were more pronounced. Track 19's pan had the level
anomaly as it swept across the center channel, but it was more abrupt. In
the sound went up and then down. In Neo:6, it
went up and down too, but it happened very fast. Track 21 was also
worse than CS. The left-center and right-center bursts were almost in the
same location as the left and right bursts. Neo:6 could not present the phantom
center image between the speakers.
The scene in "Tarzan" is a real world example of the
"Finlandia" tests. Since this disc is a DD disc, I first listened to the scene
in DD to know what it should sound like before I proceeded to listen to the
matrix version. There was not a separate 2-channel mix on this DVD, so the DVD
player down-mixed the 5-channel into 2-channels. Tarzan is a 5.0, not a 5.1
Before I move on, I need to describe my theater layout. I
am using an 87” wide (100” diagonal) 16x9 screen. The front left and right speakers
are located 6 inches from each side of the screen. I mention this because the
artifact has less effect in my situation. I also used the mini-theater (family
room system), which has a 27” diagonal 4:3 TV. The surrounds in this setup
are 3’ from each side of the screen.
In both PL II and Logic 7, the dialog of the elephants
is properly placed. The left elephant dialogue is left-center, and the right
elephant dialog is right-center. Both are more towards the center, but you get
the idea. This places the dialogue in the same position as the onscreen
Circle Surround appeared to be halfway correct. The images were
pulled a little further to the left and right.
Neo:6 was just plain wrong! The left elephant was in the
far left speaker and the right elephant was in the far right. With the 87”
screen, this was not as bad because I have such a wide screen. In the case of
the 27” TV, it just destroyed the illusion. I took my eyes off the TV to
follow the sound.
This is another fun CD. It has many examples of real
spaces vs. created spaces. I chose track 28, which is their natural stereo
imaging track. It has David Chesky walking around a micrphone, beating a tom-tom
drum. The pan goes center to left, to back left, to back right, to front, and it
repeats once more.
First up was PL II. In the music mode I got a sense of
David walking across the front of the room, then completely around me and back
to the front. The front to back went rather quickly. In PL II movie mode, there
was better sidewall imaging on the left, but the back did not seem as real as
PL II music.
Logic 7 and Music Logic were less impressive here.
While David managed to walk across the front of the room, I never got the
feeling he walked behind me. It felt like he walked around in front of me.
Neo:6 did well here. In Music mode, there was excellent
sidewall imaging on the left side of the room. It sounded like David clearly
walked across the left side of my room. The back pan went rather quickly, and
there was no real right sidewall imaging. In Cinema mode, I had not only less
left sidewall imaging but also less rear wall imaging.
I played two different tracks here. First was
chapter 2 where you see Jean-Luc Picard being assimilated by the Borg. The
other was in chapter 3, from 6:03 to 6:06. Here it has the USS Enterprise
panning from the rear to the front. There is a whirling sound as the blue
portions of the Enterprise come on screen. Sorry, not being a Trekke, I am not
familiar with the proper names of the ships' parts. I first listened to these
scenes in DD 5.1, and then I switched back to the 2-channel version on the
In PL II, the opening of chapter 2 sounded very much
like the 5.1 mix. It was very enveloping, and then the run down the hallway had
voices all around. PL II did an impressive job. The chapter 3 scene with the
pan was not exactly like the 5.1. In the 5.1, you hear the whirling come from
the right and then left rear and a pan up to the front channels. With PL II,
appears to come from the front the entire time. Not at all distracting, just
Logic 7 was much like PL II, but perhaps there was a bit
more surround info in the right rear channel. Not distracting, but I only noticed
it because I played this same scene numerous times.
Neo:6 called attention to itself during the Borg scene
in chapter 2. Instead of the stereophonic sound field, it felt like two
different sound fields. I had the left half of my room and the right half of
my room; it was as if Moses himself parted the sound field. During the pan in
chapter 3, all of the whirling noise came from the right surround speaker. It
completely called attention to itself. I actually took my eyes from the screen
and looked over my right shoulder. I don’t think the filmmaker would want
Circle Surround was similar to Neo:6, though not as pervasive. In the
Borg scene, I got a better sense of a cohesive sound field. The pan did wander
to the right surround a bit more, but not enough to pull my eyes away from the
screen. I did notice a bit of dialogue leaking into the surrounds.
I got a real surprise when I switched to the original
Pro Logic, using Meridian’s steered rears. It actually sounded like the real
5.1 mix in this mode. There was little frontal action, so I only paid attention
to what the surrounds were doing.
Chapter 2 begins with a scene in a large cathedral. It
actually opens with a roar from the previous scene where bodies were being
burned. This sound quickly fades to the rear, and you hear the echo of the
footsteps in the background. I used the 5.1 soundtrack as a reference, but
then I used the 2.0 mix for the matrix decoders.
PL II again does well. This is the first piece where I
noticed rear wall imaging. I actually had the sense of a large space behind me, even
though in reality, my fireplace is just two feet back.
Logic 7 performs much like PL II. The roar fades, and
then you are left with this wonderful rear wall imaging.
Circle Surround loses it here. The roar decides to take a trip to
the right side of the room, and I get no sense of rear wall imaging.
Neo:6, like Circle Surround, loses it once again. There is absolutely
no sense of rear wall imaging. I can detect discrete sounds coming from
the left and right surround, but they never come together to form a cohesive
stereophonic image. The roar actually dies off and goes to the left surround.
Above, I gave a few examples of how each matrix
decoder performed on a variety of material. While there were small nuances between
PL II and Logic 7, both seem to be going in the right direction. I should note
that I was running 4.0 software on the DC-2. I have listened to Logic 7 in the
past with older software and had noticed the front sound field pump, but I did
not notice any of that in this test.
Circle Surround and Neo:6 appear to be going the wrong
direction. By that I mean they appear to be designed to call attention to
themselves. As I said previously, I did not find Circle Surround to be as obnoxious as
There were times when both would let dialogue leak into the surround, while PL II
and Logic 7 kept the dialogue up front. There was one other characteristic I
noticed with Neo:6, namely that the soundstage was unstable. It had a
tendency to shift back and forth at times, as if it did not have an anchor.
I believe that PL II is one of most promising audio developments
to occur in the last few years. THX Surround EX and other similar products are
getting a lot of attention, but the fact remains they will have a limited
market for a while, because we are all tired of adding speakers after the
arduous conversion to 5.1. PL II works with your existing speakers, will add a
new dimension to all those old CDs, and everyone can enjoy it right away!