Some subwoofer notes
I have a nice pair of large three-way speakers which are making
glorious sounds in a smallish suburban living room. Why am I
starting to think about building subwoofers?
One lump or two?
Two subwoofers are better than one.
Certainly not because you or I can hear much of a stereo image below
There are several advantages, however, to having two widely spaced
subwoofers in your system.
Closed, ported, passive radiator or coupled cavity?
The choice of low-end loading for the driver determines
the roll-off rate for the speaker and also the response and
power handling at the lowest frequencies.
The closed box
has, for any given driver, the highest -3dB frequency, but the
shallowest rolloff below it, namely 12dB per octave. This gives the
most output at very low frequencies, but not much power handling.
The ported enclosure
by contrast has a lower f3 and a steeper rolloff (24dB
The passive radiator
is similar, but does not suffer from the uncontrolled cone excursions
of the ported box below resonance.
is again similar, but with higher efficiency and power handling,
and the disadvantage of complexity in design.
What needs to be counted against increased output at low
frequencies is the effect of room loading, which increases the
efficiency and hence the response of a speaker at frequencies
where the wavelength is longer than the size of the room.
The flattest frequency response will be from a sealed box whose
f3 is chosen to match the corresponding increase in
Because of this, and strongly motivated by the additional
advantages of simplicity and ease of design for a simple driver
in a box, I'm inclined towards sealed boxes.
At this point my plans are still inchoate, but I do have plenty of
ideas and a pair of Maplin's 150W
MOSFET amplifier circuits waiting for a home.
My intention is to build a pair of closed boxes, probably using the
10" Scan-speak driver linked to below (which I notice ProAc are
now using in their new
Some subwoofer drivers
Some recommended subwoofer-related links
Some subwoofer projects
Back to DIY page.