Subwoofer 101 Needed...

I have just picked up a used custom made 15" subwoofer to supplement my existing speakers. It came with an extensive array of variable control parameters. (Please see included photos.)

Sub 1

Being a Newby to the world of subwoofers, I would like to ask for a bit of guidance in their use. What would I expect to hear/measure (using REW) using them? (For example: varying Q?)

I am not interested in thunderous AV, but rather an unobtrusive refined extension to the bottom end for listening to classical, jazz, world and occasional pop music.

I look forward to your thoughts and appreciate any assistance. Thank you!