The Subwoofer Design

The subwoofer is a standard 15-cu. ft. ported enclosure tuned to 19 Hz with two 4-inch ports. Yes, the enclosure is 2 ft x 2ft x 4ft! I used WinISD to design the enclosure. The picture shows the cabinet as the front wall was being constructed. Click the image to see it full-size. Note the 4-Ft drywall square I placed there to show the correct scale. The driver is a dual 4-ohm voice-coil Rockford-Fosgate 18-inch speaker with a free-air resonance of 22 Hz. Each voice coil is rated at 600 watts. The Xmax (voice-coil excursion) is 19 mm or 0.74 inch. A large rubber surround makes this possible. This monster can put out a 16-Hz signal that is only 3 dB down from an 80 -Hz signal. It is driven by a 2-channel amp capable of 250 RMS watts/ch or 500 watts/ch peak. It is crossed-over from the main speakers at 80 Hz. I use a Behringer sub-harmonic synthesizer in order to take maximum advantage of the capability of this sub - that's the secret to getting a 16-Hz signal. All of these speakers radiate from the single plane of the front wall. The sub is in the left corner, and I have found that it works extremely well - it's source can not be pinpointed - it just fills the room with awesome bass. (Actually, the whole house shakes!)