Do tweeters with open rear chamber need enclosure?

If it doesn't have a sealed back,I would worry about the woofers back pressure causing damage to it.Also, I think the constant pressure changes would move the driver in the tweeter,causing distortion or some sort bad sound results.

Even with the open design of the Alon,it is not sharing the same enclosure as the woofer.Open back designs have been around for decades,but I can't think of any that share the same enclosure as the woofer.The Dahlquist DQ10 was an open back design,but both tweeters may have been sealed.The builder of the tweeter,and the midranges would be the one to recommend whether they need an enclosure,or not.I still doubt they would want an open back driver in a shared air(volume) enclosure with the woofer.