I was thinking of building a new cabinet with all 8 Bose drivers facing forward and use a tweeter, subwoofer and crossover I have on the shelf from a previous projects. Basically, just using the Bose drivers to build a new speaker with a crossover at ~200hz to the sub and ~2000hrz to the tweeter. I did set up and measure the frequency response using REW and without the equalizer, it looked pretty bad. Correction....very bad.
Comment?
My short answer is DON'T!
Using a single Bose driver as a small mid-woofer, combined with a dome tweeter
might work. But I doubt if using 8 of them at the same time would be good. Have you given any thought to how you would wire 8 mid-woofers? In parallel, in series? Their responses and impedance will be quite different depending on how you wire them. Any cabinet you made for this would be unusually bulky and awkward.
Throwing in a crossover that you happen to have sitting around is almost certain to not work. All crossovers are essentially custom made for the drivers they're intended to work with. To do that, you must know what the mechanical and electrical properties of the drivers you intend to use. These properties are called Thiel/Small parameters, often abbreviated as T/S parameters. It is highly unlikely that the unused crossover you have lying around will be a good match for what you have in mind.
If you buy a tweeter, the manufacturer will supply its T/S parameters, but similar info for your 4" (?) Bose drivers are probably not available. You'll have to measure those yourself. In addition, you'll also need to measure their response vs. frequency as well as their impedance vs. frequency across the audio range intended for their use. And you'll have to do that while they're mounted in a cabinet that you intend to use. All that data is required to design a properly working crossover.
Software like REW will not work for crossover design. It's a good tool for measuring how a loudspeaker performs when combined with wall, ceiling & floor reflections from a room. But it's a poor tool for designing loudspeakers and their crossovers.
I'm guessing that you've never tried designing your own loudspeakers and crossovers before. Your general idea of using one or several of those Bose 4" drivers may or may not be a bad one, but your ideas of how to go about it need work.