I've done a search on this already, and did get a good deal of information, but still have a couple of q's. I am going to be using an eminence Kilomax 18 as a sub, and have used multiple box design programs to come up with a basic design(kind of an average of all of the results from different programs, besides any that produce wildly strange numbers compared to the others). The eminence site recommends a maximum box size of 12.5ft3, but my best curves regarding power handling, max SPL and tuning suggest a 17ft3 box tuned to 30 hz. Is there any disadvantage to this larger size than portability? Most of the design programs when auto-calculating the ideal size for that driver seemed to like 22ft3, so I can't see that it would be that much too large. Also, the average number I came up with for port size at that box volume without port noise would be 4x5" ports at around 7"L each. Does this sound right compared to these specs?..... Resonant Frequency (fs) * 33hz Impedance (Re) * 5.84 ohms Coil Inductance (Le) * 2.38mh Electromagnetic Q (Qes) * .58 Mechanical Q (Qms) * 14.24 Total Q (Qts) * .56 Compliance Equivalent Volume (Vas) * 8.47ft3 Peak Diaphragm Displacement Volume (Vd) * 1141cc Mechanical Compliance of Suspension * .13mm/N BL Product (BL) * 19.7 T-M Diaphragm Mass inc. Airload (Mms) * 186 grams Equiv. Resistance of Mechanical Suspension Loss (Rms) * 2.69Nsec/M Efficiency Bandwidth Product (EBP) * 57 Voice Coil Overhang (Xmax) * 9.8 Surface Area of Cone (Sd) * 1159cm2 Impedance at Resonance (Zmax) * 150 ohms Maximum Mechanical Limit (Xmech) * 38.1mm Also, I am figuring when this is finished, I will get one of my cheeseball car audio test CD's and use the 30hz test tone to tune the box by eye according to cone movement as I trim the ports(I am going to cut them a bit long). Any thing wrong with this? Many thanks for any help.