I'm recently retired & I'm spending even more time listening to my home theater system with my wife. We use my system for movies & TV 60% of the time & music 40%. I bought most of my current speakers 13 years ago. I have Polk Monitor 70s up front - Monitor 50s as surrounds - I recently upgraded my center channel to a Polk CSiA6 (from a CSiA3) - I added 2 height speakers - Polk RTiA1s - last summer. The only subwoofer I've ever owned is the Polk PSW12 - a "powerhouse" 12" ported sub with 100W.
My house was struck by lightening last summer & blew up all of my electronics. I had a surge protector, but it had gotten too old to save my system. The good news is I was able to replace my TV with a 65" TCL 4K TV - replaced my AVR with a Sony STR-DN1080 - a Sony UBP-X700 4K Blu-Ray player replaced my Blu-Ray player - and an Apple TV 4K replaced my old Apple TV. I moved into the 4K/DolbyVision/HDR/DolbyAtmos world suddenly. The new receiver improved the sound of my main speakers dramatically (this is my 3rd AVR in 13 years). Unfortunately, it has also exposed my subwoofer as being woefully under-performing.
I have a tough room to work with in some ways. It's 16' x 17 with a ceiling that starts at 9' on one side of the room & reaches 14' on the other side. One wall has a double doorway leading to a small home office - another wall has a double doorway leading to the kitchen/dining-room & it also includes a pass-through window that's 60" x 32" - another wall has a stairway leading to upstairs & a hallway to 2 bedrooms. One wall is solid, but it has a large window on it. So... I'm forced to use a corner placement for my TV & my couch is diagonal in the room - parallel with the TV. I'll add some pics to this before I post it. Given the awkwardness of my room, my speakers are positioned fairly symmetrically for my listening position. Everything looks & sounds better than it ever has, except for...
We are both retired, so an unlimited budget isn't in the cards. My wife enjoys movies & music on my system, but she doesn't appreciate what we're NOT hearing on the low end. She hears "better subwoofer" only as "even louder music & explosions". I have a slight uphill battle for this project, so keeping it as "stealth" as possible is important - I'm thinking down-firing or dual-opposed end-table or coffee table. I probably need to keep total driver cost around $400-$500, but I'm open to suggestion. I believe DIY is my best option & I'd love a flat pack. But I have a friend who makes cabinets for a living, so a custom design is doable. However, I'm lost as to whether I'd be better served by two 12" or 15" drivers as opposed to one 18" driver. Or, I'm torn between ported & sealed, of course. I lean toward sealed, but I appreciate what a well-designed ported sub can do. I don't feel compelled to get below 20Hz. Getting down to 20Hz would be wonderful.
I'm further handicapped by the fact that I only own a MacBook Pro, so most of the common subwoofer design programs are apparently unavailable to me.
I need you to put your best thinking caps on. My problems are slightly different than the ones Ricci faces ("As usual with me it's not about the most I can get out of a single driver or for the least amount of cash but what can I get out of X amount of cubic volume for application X using whatever means necessary. Can't help it it's just what I find interesting anymore."). I need to spend as little as possible, but receive the most performance possible. Everything's easier when that pesky "cost" constraint is removed.