That depends, as I was looking to ask above.. but if this is only to manage the baffle step then this is not actually a bipole, and can be treated like any other speaker.
That said, it is perfectly reasonable to put one driver on the rear, and it might be called a 2.5 way.
That said, it is perfectly reasonable to put one driver on the rear, and it might be called a 2.5 way.

Over time people seem to prefer the castle version of these bipoles:

https://www.diyaudio.com/community/threads/microtower-bipolar-ml-tl-for-chr-70-or-el70.148901/
dave
In a normal context I might agree, but we've just tabled the question of whether this is even a bipole. What if it is only working below the baffle step?will always
What if it is only working below the baffle step?
An x.5 system. Althou that usually means the helper woofer comes in at or a bit below (√2/2) the Fbs(-3) but to not be a bipole the XO should be below the bipole dip.
If the XO is at or below the quarter wavelength of the distance between them then it matters not what direction it fires.
dave
Bipolar & Dipolar speakers will always remain very room & position dependent.
Hmm actually I've heard bipolars be surprisingly less position dependent. One thing that can happen is they have too much bass unless the rolloff works in your favor. There's no baffle step loss but there is room gain.