Does Time alignment and Phase coherency make for a better loudspeaker?

Eric - yes and as you no doubt aware, there are lots of other fundamental design principles at work; pistonic drivers, matching of drivers to within .25 db, testing the assembly in aneochic chamber against the reference, cabinet within a cabinat, high pass filtered midbass and up, same transfer function for main amp as sub amp, 11 bands of EQ below 120 hz for best image placement vs eliminate bass issues and live w image....the list goes on, since 1977

Not for everyone 

This is what some DIYers are saying  might affect my new dual FR design speakers,, that running a  pair of FR, one FR might be slightly nearer my listening field and thus reaches my ear BEFORE the other FR,, this a  bunch of muddled fq's. 

I say not so.

I've experiemented with this Duo design and had no issues with time/p incoherency.

 

Its all a  myth. 

Sure if you have 1 driver 1 foot behind the other,, the its possible, but all drivers at same distance, there is no such thing as 1 driver faster than the other due to one milli second slower/faster vs the other driver.... thus distortion,, its all baloney.

, matching of drivers to within .25 db ~~~~~~~~~~~~~~~~~~~~~~~~ All my drivers are completely dif sensitivity. 87, 91, 95 and about to add a 93. Sounds wonderful.

I'm afraid that while much is made of it ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Yep,

Jason excellent point which is why i don't use or advocate modern multi track recordings as a reference. Cat will chase own tail using those......

2 or 3 microphones please....