Each box/driver design on our website has accompanying graphs of the system's
performance. Knowing how to "read" the graphs will help guide you to the
right system. And impress your friends!
Out of Car Response
This graph shows the frequency response of a woofer and enclosure
outside of the vehicle in a "Free-Air" or open space condition. This response
graph is pretty close to the measured performance in a showroom.
|
In Car Response
This graph shows the frequency response of the woofer and
the enclosure inside a typical vehicle. The reason for the increase in
bass performance is due to "Room Gain" (sometimes called Transfer Function).
The woofer, enclosure, and the vehicle's interior interact to produce
the bass response you will actually hear. The Room Gain is different from
car to car so we can only show you an approximation of the response in
an average vehicle interior. Most vehicles will increase bass frequencies
3db at 50 Hz and rising up to 12 dB at 20 hertz. This is why the subwoofer
will sound better inside the vehicle than in a store showroom.
We have reproduced three examples of in-car response
graphs to help you understand the relationship between the graphs and
the kind of sound you will hear.
|
|
Example 1 is of a bandpass enclosure. The slight peak at 48Hz will give you good
"gut punch." The extended deep bass response makes this a good design
for "Bass-CD's" and hip-hop. This is not a great choice for people looking
for "tight" and "accurate" bass.
|
This
graph is an example of a ported enclosure. The large peak at 40Hz makes
this very "punchy" sounding, perfect for Hard Rock lovers. The quick roll-off
after the peak means this system will not be great for "Extreme Bass"
CDs.
|
This
graph is an example of a sealed enclosure system. Notice that the response
curve is very flat and accurate with excellent deep bass extension. For
some listeners, that is a good thing, but many car stereo listeners are
not looking for accurate bass but "dramatic" bass.
|
|
Cone Displacement
This
graph shows how far the woofer cone moves (measured in millimeters) at
various frequencies at the woofer's continuous power rating. Woofers with
high cone displacement at low bass frequencies are not recommended for
ultra high volume use. The woofer's suspension and voice coil may be damaged.
The example below is a 10-inch driver in a bandpass enclosure. This driver
has a maximum linear excursion (X-max Linear) of 9mm so this box design
keeps the driver within its limits. Driver/enclosure systems that allow
excursions higher than the "X-max Linear" rating of the driver will have
limited power handling and will be prone to making bad noises or breaking
when played loud.
|
|
Vent Air Velocity
This
graph shows how fast the air inside the port or vent is moving at various
frequencies, measured in "Meters Per Second". The lower the number, the
less turbulence and noise generated by the port. Figures that exceed 18
to 20 can be noisy at higher listening levels. Obviously, this is not
a concern on sealed enclosures. Above 20 can be audible at high levels
|
