Hi there "jrm1", and welcome. Please read the
forum rules for posting (click here). You seem to be missing a couple of things!
The type of bass trap you are describing is often referred to as a "suberchunk" trap, dating back to an old thread on the Studiotips website, ir I recall correctly. As Dan said, your plan will work: that's a good way of making superchunks, and there are other materials that could be used instead of mineral wool.
Regarding your room testing and tuning: Yes, it's always a good idea to run tests on your room, starting with an initial "baseline" test with the room empty of everything, except the speakers and a desk to put your DAW on. Here's how to run those tests:
How to calibrate and use REW to test and tune your room acoustics
Should I use some kind of room tuning software to home in on room modes?
This might seem to conflict with what I just said, but no, it is NOT a good idea to use room tuning (a.k.a. "room correction") software or hardware to tune your room at this stage. Not even to identify some of the issues. What the manufacturers of those products conveniently neglect to tell you, is that you can only use those products in a TREATED room! You can't use them in an untreated room, because the major problems in such a room are relate to resonance and reflections, and "room correction" hardware or software can do absolutely zero to "correct" such problems in a room. Those are basically just glorified parametric equalizers, and as you probably already know, you can't use equalization to fix resonance, nor can you use it to fix reflections. EQ can only fix frequency related problems, but those are acoustic issues. They are related to the time domain, and the phase domain, not the frequency domain. EQ can only adjust frequencies, not time or phase. Think of it this way: after the sound wave leaves the speaker, it bounces around the room in various ways, interacting with the walls, floor, ceiling, furniture, etc., and carries on doing that for several hundred milliseconds, before it eventually dies away. If you think about it logically, there is NOTHING that an equalizer can do to fix problems that occur AFTER the sound has already left the speaker! It can only fix problems that cause frequency changes up to the point where the sound is leaving the speaker.... And you won't even be able to find out what THOSE problems are (up to the speaker), until you have already treated the room, because the basic room issues are so much larger than they are, and overwhelm them in the acoustic testing: you won't even be able to see what they are until you first treat the room.
Here's an example of a room that was initially designed, properly, then treated properly, then finally tuned digitally in the end.
thread about Studio Three Productions' studio
Here's another case that is currently under construction, where the room has NOT yet been tuned, but HAS been treated:
thread about Steve's high-end control room in New Orleans We are about to start on the digital tuning in that room in a few days, so check back on that one regularly, to see the results.
So: first, test your room with REW, then treat it as well as you possibly can... and only then, at the end, can you use software and hardware for the final tuning.
Digital tuning is the "icing on the cake", so to speak: you can't ice the cake until you first mix it, and bake it!
- Stuart -