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How to maintain an accurate stereo
image and soundstage
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While
earth-shattering 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.
Overall sound
quality: how naturally a car stereo
recreates the sound of an original
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.
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
picture 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 appear to
move with frequency variation.
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 through centre to
right.
Obtaining
accurate imaging is a matter of
understanding not only the
components themselves, but also how
they interact with your vehicle and
the people sitting in it. Properly
tweaked, your car 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
When you listen to tracks at
home, you probably don't make a habit of sitting
straight 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.
To get proper imaging, you need
equal path distances between left and right speakers
and your ears - or as far as is possible. These
paths should also be unobstructed. With your left
door speaker about four feet from your left ear and
your right door speaker at about half that distance,
this is clearly not the case. Playing with the
receiver's balance control can help the driver's
listening experience; but destroys it for the
passenger.
There are a number of
disadvantages to this "side-biased"
listening. The music on your right reaches you
before the music on your left. Within certain
bandwidths, this may seem to alter your system's
response, emphasizing some frequencies over others.
The sounds on your right may also seem louder, which
will distort the soundstage.
Equalizing path lengths
A good way to overcome this
problem is to install component speakers mounted in
a set of kick panels in your car. While this is not
possible with all cars, if it is then it can offer
the best solution. With the separates installed in
the pods by your feet, you can approach the equal
path lengths vital to good imaging, and your music's
detail, dynamic balance and natural soundstage are
restored.
There are some listeners,
however, who believe that speakers at their feet
create a soundstage that is lower than it should be.
It has been suggested that this can be helped by
mounting additional tweeters and midranges up higher
on each side of the listener. This arrangement is
called a horizontal array.
Other mounting options
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However, not all
cars site their speakers in a
kick-panel position. If your speaker
components are mounted with the
woofers in mid-door and perhaps
tweeters higher on the dashboard, it
is wise to keep the woofer and
tweeter as close together as
possible so that the two drivers
will act together as a single source
point.
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
dramatically improves the level of
detail and the quality of your
stereo image. Most Kenwood matched
component sets let you adjust the
firing angle of the tweeters to
further optimize imaging. (Keep this
feature in mind when selecting your
add-on tweeters.). |
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High notes are very directional. Try
to select tweeters that have an
adjustable firing angle
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Adjusting for rear fill
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 that 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.
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.
If you're running a subwoofer in
your boot, 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.
Testing your system
When you have all your components
in place, test your system to see that it's imaging
properly. We recommend using the material on a test
CD. The test disc should 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.
As you tweak your system to
perfection, spend some time listening to other
people's setups. Rather than attempting to precisely
duplicate the systems you like, try to pick up
general ideas and techniques, keeping in mind that
every vehicle differs acoustically. What sounds
great in someone else's VW Golf may sound muffled in
your Vectra. Besides, some of us like very precise
imaging, while others prefer sound that is a little
more spacious and open.
In the final analysis the stereo
image that suits your tastes is the one that's right
for you.
Trust your ears! |
