Box. External dimensions: 18" x 18" x 24"
Subwoofer 2
My brother wanted a more robust subwoofer for his home theater system. Together we knocked this out in about 12 hours.
Woofer: Adire Tempest 15"
Amp: Parts Express plate amp with remote (300-793)
Enclosure: 85L (3 cu ft) sealed; 3/4" MDF with Douglas Fir bracing.
Stuffing: Ripped most of the Polyfill from an averaged sized pillow.
Veneer: 10mil paper backed Cherry.
Box. External dimensions: 18" x 18" x 24"
Fir bracing.
My brother Frank posing next to the new subwoofer and an old mini 'fridge.
I keep threatening mount the 'fridge handle on the subwoofer.
Nothing like veneering in December. In order to make the solvent based
contact cement work properly we had to shut the doors and windows to keep things
warm. I wore a respirator.
The new sub with some feet and a coat of Danish Oil. We'll shoot some
lacquer on this spring.
Even though the whole subwoofer weighs close to 100 lbs. we were able to make it
dance across a tile floor with enough power and the right sine wave.
"Curry", a professional woofer, approves of the new project.
Impedance. Since this sub is to be used in a home theater system, I
thought that a Qtc of .80 would be ideal. My brother wanted a Qtc. of
.70. The measured Qtc came out to be .75.
We set the mic about 1m above the floor and about 3m from the woofer and ran
some in-room sweeps with an external amp and the plate amp. By changing a
few resistors the Parts Express 300-793 is capable of up to 6dB of bass
boost. The spec sheet claims that the amp is shipped with no bass boost
added in. However the plots above and below clearly show a fair amount of
bass boost right out of the package. (It is possible we did not get the
woofer back into the same room position for both tests - possibly causing the
dip at 170Hz.)
Nearfield. The mic was placed on the floor at the edge of the
enclosure. The sub will be used only from 100Hz down so we are not really
concerned with what might be causing the differences above 100 Hz. Below
100Hz, it is quite clear that the default amount of bass boost from the plate
amp is just right.
Results: Very Good. Mild incontinence for anyone within 30ft. Excellent price to performance ratio.