Check out the attached pdf. I want to install two biaxial waveguides in my dashboard. Would something like this cover 300 - 20k?horn box.PDF

THERE IS A GRADUAL AND SLIGHT EXPANSION IN CROSS-SECTIONAL AREA
(AN ATTEMPT TO MINIMISE COMPRESSION EFFECTS)FROM THE CONE DRIVERS
TO THE BEGINNING OF THE TRACTRIX PROFILE. CROSS-
SECTION ROTATED 90 TO MAKE USE OF AMBIOPHONIC
BARRIER FORMULA: L =x*(h+t)/d. "D" IS SIGNIFICANTLY REDUCED,
MAXIMISING "L". WHERE X= 24, H= 6, T=.25, D=2; L=75 INCHES.
INTENDED PLACEMENT IS REPLACEMENT OF INSTRUMENT CLUSTER AND
ABOVE GLOVE BOX, BETWEEN VENTS.

The speakers used will be SS 10f- 8ohm. For midbass, ~80-500hz, I plan on using 4 SB Acoustics 8" drivers in an opsodis arrangement (180 deg to listener). If you are familiar with my install(s), I am partial to dual-stage setups.