Closed back in a midrange usually pushes fs too high for them to be useful, IMO... I'm thinking of e.g. the Visaton M10 (4") or MR130 (5") midranges, which realistically aren't good for much below 1 kHz.
Have fun designing a crossover for this one.
This one also comes with a resonance within the passband free of charge, yay.
Now you know why these "cups" are a thing. It's not like you need a huge amount of volume for a midrange (if memory serves I've had some good results with <0.5 l in Boxsim) but you definitely want
some. A midrange should be capable of crossing over at 500-600 Hz without too much hassle.