Smallest Speaker - Wearable Project

Yes and a very lot of work went into that to make it sound that good. Most if it involved computer modelling of the acoustic properties of the case and emitter. You can ensure that it is as good as it can get.

I find that very surprising

I would try and seal the back of the speaker inside the shell. Make this as airtight as you can. This sort of thing is known an an infinite baffle.