In the quest to achieve the perfect soundstage for a sound quality
system, there are many variables that make or break the final result. Simply buying a set of $800 fine European
components will get you nowhere. Proper
placement and angles is something we have control over during the designing of
the system. One of the most important
things to understand is how speakers disperse sound in order to properly
install a component set. In this
article, we are going to address acoustic centers and how to get the best image
and stage possible in a vehicle.
99% of the time when you see a set of components in a car, the midbass
driver is in the lower front corner of the door and the tweeter is directly
above it, at the top of the door, or in the corner off the corner of the glass
on the trim panel that covers the side mirror mounts. In the last decade, installing components in
the kickpanels has become fairly popular.
If you’ve read the “How to Stereo Image and Soundstage” article, you
understand that the farther the speakers are away from you, the more equal the
distant between the right and left sides are.
This is critical in having a stage that is not perceived as “too loud on
one side” and for getting the soundstage as centered as possible.
BUT, WHAT ABOUT HEIGTH? It is not
too tough to get a good center stage.
Getting it high (above the dash” with speakers mounted in the kickpanel
can be a nightmare if you do not know what you’re doing… So what do you
do? Let’s look at some options…
I had a friend who built a great car.
It was well designed and had a great center stage. But at Sound Quality competitions, judges
always docked him points for his stage being too low. I told him to use keep his system as it is,
but to also add a set of 3.5” coaxial drivers in the top corner of the dash in
the oem locations. These were in
addition to his expensive components in the kickpanels. I had him wire them out of phase to better
couple to the components due to pathlength differences. I also had him buy some potentiometers (gain
knobs) to be able to have them considerably lower in amplitude than his
components. The result was additional
speakers that were impossible to hear.
It sounded like they weren’t even there, but they lifted the entire
sound stage, not just the upper frequencies.
It sounded like his midbass and tweeter drivers were all mounted on top
of the dash. He went on to become the
rookie of the years in IASCA.
Assuming that you haven’t built anything yet and we have a blank canvas
to paint on, let’s do what we can to get our acoustic center to provide the
best stage possible.
With any cone or dome driver, the high frequencies roll off the edge of
the cone while the higher frequencies come off of the center of the dome or
dustcap. Read this again… With crossovers separating frequencies to
midbass and tweeter drivers, it becomes imperative that we understand what
exactly is happening to sound radiating off of each driver. The picture below shows a side view of
components mounted in a door with the midbass at the bottom front corner and
the tweeter mounted directly above it.
The red line represent where the crossover frequency comes off of each
driver – lowest frequency off the outside edge of the tweeter and highest
frequency off the center of the dust cap of the midbass. The blue line represents the acoustic center
and where the sound stage will be projected.
Obviously, the sound will be projected to the center of the car on the
floor. Now, maybe you’re weirder than I
am, but I never enjoy listen to my music with my head between my seats! Yet this is how many components are
installed.
Let’s see what happens if the tweeter is mounted higher as we mentioned
above…
As you can see, while the acoustic center is still aiming slightly down,
it is not nearly as bad as before. So,
our problem is lessened but not fixed AND we just inherited another
problem. The closer a speaker gets to
your ears, the louder it will be perceived.
By having the tweeter higher, the tweeter is now considerably louder and
overpowering the midbass. Crossovers are
designed with the drivers as close to each other as possible. In essence, we just created a mess. Joe Blow who doesn’t know poop about high end
audio would never notice the difference, but if you’re still reading this
article, you obviously care and what the most impressive system possible. Some of you may have already asked the
question to yourself, “What in the heck am I supposed to do then – put my
tweeter under my midbass to make the stage go upwards?!?!” Well, Mr./Mrs. Brainiac, let’s see what would
happen…
Well, I’ll be darned! It
worked! NOT!! Yes, the stage may be aiming in the right
direction, but again, we introduced another problem. Now that our tweeter got further away, it
will be inherently less loud. And, as
frequencies get higher, they become more and more directional. Having the tweeter partially hidden under a midbass
is a bad idea as well. But at least we
understand the concept right?
Now, if we try to lessen the pathlength difference by putting our
components in the kickpanels, we will find some great new changes. Aside from sounding more like you’re in the
center of the car, we can put our tweeter almost anywhere around the midbass
without any obstruction to the sound.
Just as in the drawings above, we will find that having our tweeter
below the midbass will help drastically to lift the stage up.
So, is it safe to say that wherever the tweeter is, that sound will go
the opposite direction? Pretty much,
yeah. So what happens is the kickpanel
baffle (what the speakers mount to) is not vertical? Well, this just opens another whole can of
worms, doesn’t it? There are several
home audio companies that have angled baffles.
Not only does this reduce reflection cancellation by standing waves
inside the box, but is also does this…
It accounts for the acoustic center and places is level and directly in your face. Home audio doesn’t have to deal with dimensional issues, so it is fairly easy to get a great soundstage. In car audio, we have many dimensional issues. We have doors to limit the width of our sound stage. We have a windshield to limit the depth and we always have our speakers lower than our heads which limits height. Taking what you just learned, you can now install speakers in appropriate locations, with the proper orientation of drivers to each other, and with the baffles angled to suit your needs. Such a simple concept that is never properly explained and is based of true physics and acoustic theory. Now that you’re an acoustic genius, go build that awesome system and send us pics of your vehicle, self & trophies! ;^)
by: Grizz Archer
Note: I got this article from the web some time ago and saved it in my local drive. I will try to look for the original source to link it to.
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