If your TC Sounds 15" is anything like the Audiopulse 15", you could have gone with a much smaller box. At 4.8 cf ft net internal volume, it will be kind of like a 22Hz SPL box. I'm showing 120.5 dB @ 22Hz free air response. That'd be more like 133 dB in-room. A smaller box would have evened out the huge peak at around 22Hz. You can toy with weights to move it around, but the peak is going to be there, even worse as you remove weight. The peak rides down to 118 dB @ 35 Hz free air response, not a horrible peak, but it would be gone with a smaller box, and, well you would have a smaller box. I probably would have gone with 2.5 cu ft net internal volume with that driver.
BTW, you linked to a 10" rather than a 12" at Parts Express.