18"
Sd = 0.108 m^2
Cms = 106.6 um/N
Vas = 174 liters
Re = 6.2 ohms
Mms = 305 g See Below
Fo = 28.2 Hz
BL = 23.3 t*m See Below
Qe = 0.62
Qm = 8.90
Qt = 0.58
SPL = 90.5 See Below

15"
Sd = 0.068 m^2
Cms = 159 um/N
Vas = 103 liters
Re = 6.2 Ohms
Mms = 267.0 g See Below
Fo = 24.4 Hz
BL = 23.3 t*m See Below
Qe = 0.469
Qm = 6.05
Qt = 0.44
SPL = 89.0 See Below

The data above is derived from the impedance curves.  Note that the Mms values above includes ALL of the acoustic mass as well, which is substantial in subwoofers.  In addition, the actual BL values for these drivers is about 8% higher than the parameters above.  As a result of both of these measurement artifacts, the calculated SPL 1W/1m dB's are lower than actual SPL's by 0.5 to 1.5dB.  We have provided the actual SPL's in the data above.