FYI/FWIW, Hornresp calcs Mmd = 343.14 g, yet your Mms is lower, not somewhat higher as it should be, so something's amiss. 🙁
I previously built a multidriver subwoofer TL with sonotube and it worked very well. It was four 12" drivers in a box manifold, then 12" sonotube extending from that. Output was tremendous.
Because of GM's comment about the Mms of the driver that I tested, I ran the test again. This time I ran a 20 hz sine wave, at about 10 watts, through the driver for 1.5 hours before doing 2 tests with the DATS. Results:
Re = 3.649 , 3.62 ohms
Fs = 31.73 , 31.9
Qts = .7335 , .7264
Qes = .9969 , .9921
Qms = 2.776 , 2.711
Le = .3876 , .3859
Vas = 2.235 , 2.236 cubic feet
Mms = 350.1 , 346.2 grams
Most of the results are close enough to the original tests to seem reliable. The original Mms value may have been the result of user error. I used the added mass method of determining Vas and Mms. Maybe the weight that I added for the test wasn't stuck firmly enough to the cone of the woofer?
Re = 3.649 , 3.62 ohms
Fs = 31.73 , 31.9
Qts = .7335 , .7264
Qes = .9969 , .9921
Qms = 2.776 , 2.711
Le = .3876 , .3859
Vas = 2.235 , 2.236 cubic feet
Mms = 350.1 , 346.2 grams
Most of the results are close enough to the original tests to seem reliable. The original Mms value may have been the result of user error. I used the added mass method of determining Vas and Mms. Maybe the weight that I added for the test wasn't stuck firmly enough to the cone of the woofer?
The factory specs show around 8 ohms impedance at 20 Hz, 8.94 volts would be about 10 watts.
My guess is that wouldn't make the cone move very far.
The suspension won't be "broken in" until reaching (or exceeding) Xmax, about 38mm (1.5inches) peak to peak, and the suspension would still need to be warm, a cold basement may cool it down, stiffening it back up.
Any length of time at low excursion still won't stretch the suspension, so will result in too high Fs, too small VAS, etc.
Using a lower frequency will apply more power and make less noise doing it. You can also exercise the cone in and out by hand to Xmech without needing to apply any power, but that won't warm the suspension.
The tests need to use enough drive level to get the cone moving a bit.
If the suspension was not broken in, more mass would be required to drop the free air resonance by around 25%.
If the Fs has not dropped that far, more mass needs to be added.
The mass weight of near the Mms should be distributed symmetrically around the cone near the center.
The driver should be rigidly supported vertically (like clamped in a vise) away from surfaces, if the weights weren't stuck firmly enough to the cone, they probably would have fallen off 🙂 .
Art