| How
To Stereo Image and Soundstage |
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While humongous-sounding bass may
let people know you're coming, true
car audiophiles know that what really
keeps people listening to a system
is more than a matter of volume
and unbelievable bottom end. |
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Overall sound quality,
how naturally a car
stereo recreates the
sound of a master recording,
is a key concern of
everyone who really
appreciates music in
an automotive environment
- from the casual enthusiast
to the serious competitor.
And a big part of the
overall sonic impression
your system makes has
to do with the quality
of your stereo image.
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When we use the words
image
or imaging,
we're talking about
a speaker system's ability
to create sound in such
a way that you can close
your eyes and envision
where all the musicians
were standing when the
recording was made.
The position of the
voices and instruments
should be easily identifiable
and shouldn't seem to
change with frequency
variation. |
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The speakers themselves
should seem to disappear,
replaced instead by
this spatial arrangement
of music sources, or
soundstage.
Although the soundstage
is created by both front
and rear speakers, it
should seem to come
from in front of you,
filling the space from
left to center to right.
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Getting great imaging
is a matter of understanding
not only your components
themselves, but also
how they interact with
your vehicle and the
people sitting in it.
Properly tweaked, your
car or truck can be
a dynamic "listening
capsule" - a fantastic
place to listen to music.
But in order to get
your vehicle to provide
that type of environment,
you need to compensate
for some of its natural
limitations. |
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| "Side-biased"
listening |
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When you listen to tunes at home,
you probably don't make a habit
of planting yourself smack dab in
front of your left speaker. If you
did, you'd be missing out on the
detail the right channel has to
offer, as well as the spaciousness
of a complete stereo image. Yet
when you listen to music in the
driver's seat of your car, and you
have conventional speakers in your
doors or dash, you probably get
the same type of imbalanced listening
experience. |
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To get proper imaging, you need
as close as possible to equal path
lengths between your speakers and
your ears. These paths should be
unobstructed as well. With your
left door speaker about 2-1/2" feet
from your left ear and your right
door speaker about five feet from
your right ear, this is clearly
not the case. Playing with the receiver's
balance control can help the driver's
listening experience, but it throws
the image out of whack for the person
in the passenger seat. |
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There are a number of disadvantages
to this "side-biased" listening.
The music on your left reaches you
before the music on your right.
Within certain bandwidths, this
may seem to alter your system's
response, emphasizing some frequencies
over others. The sounds on your
left may also seem louder, which
will distort the soundstage. |
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| Other
Mounting Options |
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Despite the growing popularity of
products like Q-Forms, many of us,
for reasons of taste or budget,
still choose to improve our imaging
with a more traditional use of matched
components, mounting the mid-woofers
in factory locations and tweeters
up high on the dash or door. It's
wise to keep the mid-woofer and
tweeter as close together as possible
so that the two drivers will act
together as a single point source.
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While a conventional component speaker
set-up does leave path lengths unequal,
there usually is a direct line from
the tweeters to your ears, and this
lack of obstruction alone really
steps up the level of detail and
the quality of your stereo image.
Many matched component sets let
you adjust the firing angle of the
tweeters to further optimize imaging.
(Keep this feature in mind when
shopping for add-on tweeters.) In
fact, a number of forward thinking
speaker manufacturers now offer
this feature on several of their
coaxial speakers. |
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| Adjusting
For Rear Fill |
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Once you have your front speakers
set up the way you want them, you'll
want to make sure that your rear
speakers are doing their part to
create an ideal soundstage. While
personal taste plays a role here,
most experts agree that the correct
volume for rear speakers is where
you're just barely conscious of
their presence. |
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While your front speakers should
give you the best high frequencies
possible, your rear speakers can
be conventional coaxials or low
frequency drivers. Their purpose
is to add ambience and depth to
your forward soundstage and if they
reveal too much high frequency information,
they'll "pull" the stereo image
to the rear of your vehicle, away
from where you want it. |
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If you're running a subwoofer in
your trunk, you want to avoid the
sensation that all the bass is coming
from the rear of the car. To keep
the soundstage up front, set your
crossover to feed your front speakers
the lowest frequencies they can
safely handle and set your subwoofer
crossover between 80 and 100 Hz
if your system allows. This setup
allows some bass to come from your
front speakers and restricts your
sub to low bass which is very difficult
to localize. |
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| Testing
Your System |
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When you have all your components
in place, test your system to see
that it's imaging properly. We recommend
using the material on. The discs
in this series provide several tracks
to evaluate your system's imaging
and to help you determine exactly
where corrections are needed. They
also provide a broad group of tests
along with several music tracks
that are great for overall system
appraisal. |
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As you tweak your system to perfection,
spend some time listening to other
people's set-ups, informally or
at sound-off competitions. Rather
than attempting to precisely duplicate
the systems you like, try to pick
up general concepts and techniques,
keeping in mind that every vehicle
differs acoustically. What sounds
great in a trophy-winning Camaro
may muddy up the sound of your BMW.
Besides, some of us like very precise
imaging, while others among us prefer
sound that is a little more spacious
and open. |
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In the final analysis the stereo
image that suits your tastes is
the one that's right for you. So,
trust your ears. |
