Confused, which woofer?

Download this file for the T212D4.  This sub, wired in parallel, will yield 2 ohms which will work with most mono amps.  (Note:  the TS parameters of this sub are given with the coils wired in series.  Wiring in parallel will change the total Q just slightly lower but not enough to make a difference in box design.)

This subwoofer wants a lot of power.  I used 1000 watts as the power applied.  Unibox is the software tool that I used for this workup:

cb_response_rockford_t212d4.gif

vb_response_rockford_t212d4.gif

You can get a nice SQ sub out of this with the sealed box at 25 liters net volume.  The second graph is a ported box tuned to 50 Hz., 48.3 liters net volume, slotted port 100 centimeters (1 meter) of opening area and 49.27 centimeters in length.  You'll note a much higher SPL with the vented enclosure.  The equivalent round port design would be an 18 cm diameter.  Those are the best designs I came up with.

Note with those graphs:  they'll load up small, but an icon will appear in the lower right corner that will enable expansion.

Also note that if you are going to be using an amp capable of a 1 ohm impedance load for an output of 1000 watts, you can use the T212D2 instead and use these same box and port volumes.