No sense whatsoever. At the end they come together in one signal where they cause the same problems.
You can NOT get a single speaker to play mono, and mono is more complex than just tying (via adapter or cables) together two sides of a stereo signal.
You can get smaller LDs (8″ and 10″) which of course are a lot lower in price than the 12″. And they still sound good. Again, small footprint, especially handy in a small condo, but a full system nonetheless.
There are more brands that sell those units. Some have been featured in reviews over on the blog/website. It’s quickly becoming THE way to solve small space sound requirements while still providing gear with plenty of power and sound quality for those smaller spaces like condos and living rooms.
As for bluetooth, I thought that was standard in the 615, so not sure what adapter you are referring too. Assuming your phone like any other has BT, you should be able to just stream your playlist to the speaker?