The cab tuning for the mod is optimized for a Basslite S2010 driver. Other drivers will 'work', but may not work at their best. The S2010 has significant power handling, so I added a terminal cup allowing the cab to be used as a light weight (17 lbs) 110. To minimize port noise (chuffing) I used both ports. You could get by with a single port if you plan on only using the internal 40w amplifier. The port length would be 1 1/16 inches. And you'll need to tightly close the other port. Of course, you can always experiment. However, given the low cost of port material, why not just use both?
I have tried the Rumble 40 cab with several other drivers. To my ears, none of the others have out performed the S2010. You can always try other drivers - those similar to the S2010 (particularly Qts, Vas and Fs) will likely perform like the S2010... in the bass. However, the overall tone will probably be different. If you try other drivers, you will almost certainly need to retune the cab, because the stock driver and tuning are somewhat unusual.
