Can you put a 6x9 and a sub in the same bag.
And how well will it work.

 

You would need to completely Isolate the sub from the 6x9, subs make their sound by moving air, you really don't hear base as much as you feel it. so if both speakers are sharing the same air space the more powerful speaker will defeat the other.

Take a look in the audio section of this forum there are some high tech guys over there.
https://www.hdforums.com/forum/audio-systems-153/