A Visaton WG300 (cheap) can be adapted to an RS28F/RST28F with a simple 3D printed adapter plate. It integrates with a 6.5in woofer nicely.
Basically invariant within 60deg included angle.
STL file for adapter and more info here:
Simple Passive Harsch XO Using PTT6.5 and RS28F in a Waveguide
Basically invariant within 60deg included angle.
STL file for adapter and more info here:
Simple Passive Harsch XO Using PTT6.5 and RS28F in a Waveguide