I'm looking to replace all 4 speakers in my Ampeg v2 cab. It's a 412 that's center ported. Id like to put something suitable for bass, bass vi, and synth. I'm running it with a V4 into an 810 as well.
I'd guess he's looking for 4 ohms given that he wants to run it in parallel with the 810 using a V4. That said, you'd need either 4 or 16 ohm speakers. The eminence delta line has some that might work out impedance wise, haven't done the calculations to know if they'll work well with the internal volume/porting. The delta 12B is 16 ohms, the delta 12LFC is 4 ohms with better xmax and flatter response. Going only on those specs I'd probably go for the LCF, but again, haven't done the calculations to know if they'd work properly.