SCREEN 6: USING BLAUBOX (Cont'd)
STYLE
Many box styles can be used to make bass,
each.
but, pro’s and con’s exist for
The following list is terribly short but encompass 90% of the
styles used today in the car or home.
2.
3.
4.
5.
A sealed box is simple to build, will take lots of power due to the
box
“air spring”, and sounds reasonably good in most installations.
But, the -3db frequency is much higher than a vented box for example.
This is the best design for “inexperienced” box builders because of its
tolerance to sloppy construction.
A vented box will provide a lower response than a sealed box but the
woofer can become unloaded and begin to move excessively below its
frequency due to the loss of an air load on the back side of the
-3db
driver.
The single vented
box is probably the best design for the car
because it offers the low frequency response of the simple vented box
but also an interior sealed chamber provides an “air spring” cushion&g
the back side of the woofer.
Unfortunately, it is more complicated to
build than the simple sealed or vented boxes above but the performance
results certainly justify the extra expense
The single vented
box with series coil operates the same as
the regular box but adds an inductor in series with the woofer.
This
sometimes adds a small bump in the frequency response below the normal
cutoff frequency for the box thus giving 1-2 db of extra gain at the
very low frequencies for that extra “punch” in the low end.
It will
also reduce a lot of the high harmonics from an amplifier being
overdriven.
The double vented
box offers even lower frequency response and
higher efficiency than the above boxes
it is very‘sensitive to
lousy construction techniques. Like simple vented boxes, it will
become unloaded below the -3db frequency, but with higher distortion
and more devastating results when the woofer fails.
FABRICATION
(of the
final box)
FABRICATION is a short discussion of the various box designs and their
final fabrication.
1.
2.
3.
4.
5.
First, measure the trunk volume that is available (measure and multiply
length x width x height to get cubic inches). Use “BOX MATH” to
convert from cubic inches to cubic feet for the “ENCLOSURE PERFORMANCE
CALCULATIONS”.
Use this volume in cubic feet now in all of your
BLAUBOX calculations.
The rectangular box design is the simplest box to build and is
recommended for most installations.
The tubular design is becoming
quite popular due to the cosmetics and general ease of construction.
The wedge shape maximizes the volume in most trunks but becomes more
complex to build with the various angled cuts.
All of the above designs can be modified using the MODIFY DIMENSIONS
command under screen 2.
The dimensions can be changed until a box
fitting the exact trunk area is designed.
By working through BLAUBOX
backwards (forcing box volumes in Screen 2 and reviewing the frequency
response plots in Screen
you can then determine the final frequency
response once the box volume is conclusive.
The PORT command under screen 2 allows for changing the port tube
length for a given port diameter tube that is conveniently available
in-house.
Most importantly, using DRAW BOX, you are able to’print out a drawing
of the box.
make sure
Verify all dimensions before you start building the box to
the box will simply fit the speaker.
(A 15” woofer with 12”
side walls is going to require substantial creativity to make it fit
inside!
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