I don't think this is gonna be a major problem, since I left an air gap between the pipes connecting the smoker and the speaker...
I never saw any smoke escaping throught that gap; which leds me to beleive that the speaker isn't sucking much smoke...
In any case, the speaker is mounted on its side , facing the rear; and it will be easy to make a drain in the bottom of the enclosure; using a small pipe and a wick...
Here's a few pics of the lay-out....