Actually, I would expect far fewer problems mixing a SBD + AUD where the AUD is M-S, Blumlein or X-Y. In all of these situations, the mics are truly coincident which gives excellent mono compatibility. Near coincident arrangements like ORTF, NOS, DIN, Dina, or any other non-coincident setups like A-B or any random combination of spacing and angle will have limited mono compatibility. In my experience, the former mix with a SBD much better and produce far fewer phase anomolies, and result in a better sounding mix.
YMMV.
- Jason