Low resonant frequency:
Drivers with a lower resonant frequency ( Fs less than
40 Hz) will make better subwoofer drivers in most instances.
Size Does Matter!
The lower the frequency, the more air the driver's cone has to move. Consider this - for
every octave that you go down in the audio spectrum, your speaker has to move 4 times as
much to provide the same output level! As a consequence of this, your subwoofer is
probably going to end up being the largest speaker in your living room.
The following can be used as a rough guide to determine the minimum size
required for your subwoofer, based on the size of the woofers in your main speakers, and
typical excursion specifications for subwoofer drivers.
Mains |
Subwoofer |
| Type, |
Driver size |
Typical Vd |
Target Vd |
Minimum Size |
| 2-way |
11.5 cm (4.5") |
40 |
160 |
20.3 cm (8") |
| 2-way |
13.3 cm (5.25" |
54 |
215 |
25.4 cm (10") |
| MTM |
11.5 cm (4.5") |
80 |
319 |
25.4 cm (10") |
| 2-way |
16.5 cm (6.5") |
82 |
329 |
25.4 cm (10") |
| MTM |
13.3 cm (5.25") |
107 |
429 |
30.5 cm (12") |
| 2-way |
20.3 cm (8") |
125 |
498 |
30.5 cm (12") |
| 3-way |
25.4 cm (10") |
259 |
1038 |
45.7 cm (18") |
Some popular subwoofer drivers are:
Sturdy construction:
Flimsy cones and driver baskets
are likely to produce distortion, resulting in a less than perfect subwoofer design. To
test the cone of a driver, push down one side of the cone near the surround. If the cone visibly distorts or doesn't move
straight down into the basket, choose another driver.
Impedance:
If you're planning to build a passive subwoofer (i.e. one that's driven by your
main amplifier), then its impedance has to be the same or greater than the amplifier's
minimum impedance rating. If you plan to build a powered subwoofer, then impedance
is less of a concern (most subwoofer amplifiers can easily handle 4 ohm impedances).
Please note that there is NO requirement for the impedance of your subwoofer to
match the impedance of your main speakers.
Car Audio Drivers:
Typically, car audio drivers will not do well as drivers for a home subwoofer
system, as they are usually designed to produce a good response when a car's cabin gain is
taken into consideration. However, there are a few for which the T/S
parameters suggest that they can produce good results in the home. IOW, if you're
planning to use a car audio driver in your design, treat it as a home audio driver and
design a system based on its T/S parameters to get the best results.