Get a DSP, there are some very economical ones out there. My thoughts are if you are going to spend 700.00 on a pair of Beyma coax spend the extra and tune them correctly.

 

I fairly recently installed some PRV 6.5 NDY/MMat DTX26T speakers in the fairing of my 2009 FLHT. I ran them in parallel off my BT4180 amp. The sound wasn't bad and they play loud/clear going down the road. That said, I also looked at some small DSP's and passive Xovers. I ended up going cheap and bought a pair of passive XO's on Amazon prime for $20, knowing if they didn't work out I could easily return them. After install and buttoning up the fairing after everything was working, I am happily content. Now, I only have about $250 invested in my set up, but I achieved my goal of hearing tunes clearly when rolling down the road at 70+mph. Maybe some day I'll hear a finely tuned DSP set up and realize the difference. For now, I'm happy.