Basically what I did in my car was keep my speakers very close together on each side and I chose my crossover points and slopes based on the diameter of the speakers and their proximity. My 6.5" drivers play up to 1 kHz, well before they start beaming, the 2" drivers play up to 6 kHz, just up to the edge of beaming, and the 1" tweeters play the rest. By intentionally preventing beaming(technically, the tweeters will beam but let's ignore that) I'm not so concerned about how far off axis my ears are from any of the speakers, and the same applies to my passenger.
Small town service, family owned and operated for over 50 years. Our mobile friendly online store: store.513electronics.com
Home to CDT Audio's Systems Design Specialist
Perfect Fit Speaker Kits
Our CDT Audio dealer store, Clarion,_JBL,_Pioneer,_DB Drive,_Metra,_T-Spec,_NAV-TV,_Crùx
My system: rebuild in progress, temp system is Clarion_VX404, Clarion_XC6610, Infinity Kappa One, CDT HD-6/ES-04/HD-1A/BL bi-amped 3-way, Audiomobile Elite 2212 1.3 cu ft @ 33 Hz