If,
for some strange reason, you've been kept under a rock,
and don't know what a subwoofer is, then I strongly
recommend www.dictionary.com.
For
everyone else, you will identify a subwoofer as a big,
bad-ass bass speaker that makes your car shudder and
rattles your floorboards. For those who are into music
with a bit of 'doof doof', a subwoofer is much more
a necessity than it is a mere luxury. |
A
typical subwoofer driver - in this case a 'Lanzar Vector'
unit
|
Appropriately named 'Earthquake' driver |
I
decided I was 'bad-ass' enough to own a large subwoofer
unit. The first step was to find the central component
- a driver.
After
drooling over some $200 'Lightning' brand drivers,
I settled for an 12 inch 'Earthquake' brand driver
from the USA for $50. This particular unit was capable
of 200W RMS power.
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Of course,
for any loudspeaker to work, one needs an amplifier.
In the case of a subwoofer, an additional piece of circuitry
to filter out the high frequencies is required so that
only low frequencies are fed into the driver.
If this is
not done, serious damage to the driver is easily possible
because the mechanism is simply not designed for high
frequency vibration.
The low pass
filter I decided to use was directly from a kit sourced
from Dick Smith Electronics, and afforded the extra
ability to change the cut-off frequency, adjust the
roll-off curve etc.
|
Low pass filter/processor
unit |
40W RMS dual channel amplifier
unit |
I
realised that if I was to put the subwoofer in my room,
200W was going to be complete overkill (probably knock
over the walls). Thus I decided on an amplifier with
an output of about 40W RMS. This was again purchased
in kit form - it just saves all the trouble of circuitry
design, particularly difficult for power amplifiers. |
This is
a picture of an extremely messy installation inside
the sub box... this picture was taken during a repair
operation in 2006 when it mysteriously failed. Upon
opening the box and seeing how ruthless I was in mounting
everything made me wonder I ever expected this to work
for more than a few months.
Anyway it
turns out the repair operation was successful - the
problems due to loose connections (hardly a surprise). |
|
Completed subwoofer unit!
|
All
loudspeakers need some sort of box to enhance the
desired frequencies. Generally speaking, the lower
the frequency output, the larger the required enclosure.
There
are online calculators which assist the layman in
working out the required dimensions of a box based
on the sound output requirements and the driver attributes.
Of course, if you like to get technical there is always
the odd sound engineering textbook around!
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After
a while I decided that the wood I had used for the
enclosure looked slightly tacky at the very least.
As
a result, a rejuvenated subwoofer was born, with a
coat of glossy silver paint and aesthetic adjustments
to the equalizer panel.
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Rejuvenated subwoofer unit
(coke can for scale)
|
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Here
is a view of the driver behind black acoustic screening
- the final touch added to provide a bit of dust/insect
protection.
Notice
the two vent holes in the bottom. As this was an open-box
design, these vent holes were required to stop the
box from exploding when the sound pressure is too
high.
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