I put 3500 down towards my home studio treatments in a 30x15 room. I used eq wizard when I was finished and saw +/- 5db across the spectrum which is pretty great considering most professional studios are at +/- 3db. I have to tweak a couple things and I’ll be closer to that gold standard.

I used 17 bags of Safe n sound insulation (12 Batts per bag),33x 4x8 MDF board, and fabric from Joanne’s…but this wasn’t a listening area, it was for a studio with a drum kit lol. You’ll want some clouds over the listening area, bass traps in the corners, and some panels behind and to the side of the speakers. If it were me, I’d try to turn the listening area into a rectangle somehow, which would mean adding some sort of false wall…or not, probably not necessary. The main thing is to keep it as dead as possible around you’re listening area but I’d highly recommend using eq wizard before and after.

“How can I remove value from my home?”

How about the family room? If you can get approval for using it, it has better dimension ratio than the garage

I put a wall across my garage, parallel to the overhead door. I left about 6 feet on the exterior side, and used that for easily accessible storage. On the other side, the main space, I did my theatre. That has worked very well, in several ways. I did put a man door in there so I could reach the storage from the theatre room, and I put a fridge in the storage side.

Damn you’re lucky. I’ll offer layout advice here. I see some great opportunities. First, create a small utility closet for the mechanical systems (I assume that is a water heater and maybe a space heater? Hard to tell.) Then I would consider a wall across the front, parallel to the garage doors, to create a storage area accessible from the driveway. Make it like 7 or 8 feet deep and the full 30 feet wide. Perfect for yard equipment, car related stuff or whatever else. This would leave you with a music room at around 23 x 26 with direct access from your laundry room vestibule. That new wall would serve as a buffer from the garage doors which would be nice, offering the opportunity to have an insulated wall there for thermal benefits (and for sound containment if that is an issue for neighbors.) Going further, you might put in a storage closet to help refine the room dimensions a bit more, getting a more rectangular space. That could be for gear/accessories/media storage and a record cleaning setup, or whatever you want. Drywall ceiling for sure. Lots of power outlets by the equipment of course.

I suggest you use workout mats or horse mats on the floor, they will still be sturdy enough to drive a car or do some kind of winter maintenance on a vehicle in a jiffy if you’re a handy dude and they absorb low and high fairly decently especially the textured ones with the million ridges in them. On the garage door I suggest you implement the double layer method to insulating the door. (It’s like a poor man’s insulation method that actually far outpaces normal insulation methods I think a channel called garage door man or something has a video on it) anyways itl help with noise coming from the outside in as well as help with reverb and other unwanted acoustic noises for a fairly cheap solution.

Lastly I suggest if the roof of the garage isn’t finished. Which It probably is since your floor plan looks like there’s a room above it I’d finish it and use mineral based insulation as much as you can as fiberglass isn’t great for sound. You really just need to stack porous mass as much as you can and try and fix the squareness of the space. A great way to do it tastefully is to put corner shelving that acts as obviously a shelf but secondly to avoid those nasty reflections. You’ll want something on the flat surfaces as well. I recommend building those acoustic sound dispersing wall art things out of blocks of wood glued to a frame. If you stain and paint it with a gradient they look beautiful and would fit the garage asthetic but this is all just my opinion. Just be blessed you have a wife that recognizes you want your own space as some of us unfortunately don’t have that

I put a wall across my garage, parallel to the overhead door. I left about 6 feet on the exterior side, and used that for easily accessible storage. On the other side, the main space, I did my theatre. That has worked very well, in several ways. I did put a man door in there so I could reach the storage from the theatre room, and I put a fridge in the storage side.

I have to ask, what’s with the 8x11 room inside your primary room… there’s no other door to it. Is it a secret room for secret things you do away from the kids? 🤔

My dream for this would be lots and lots of rockwool filled panels on the walls, at least 4" thick, with a sound transparent false wall in front - could be as simple as some wood framing with fabric stretched over it. And as others have said, drywall off the garage door area to make a rectangular space on both sides, one for the room, the other for storage.

And some suspended absorbers from the ceiling (since you said it’s already finished) to tame reflections. Again some simple wooden frames filled with rockwool would work and be cheap.

Possibly some bass traps in the corners but they don’t do much below 100Hz unless they are either enormous or active (eg expensive). If I could afford it for subs, I’d have an active echo cancellation setup, eg a load of subs at the front, and a load at the back, DSPd so the rear ones completely absorb the incoming sound and eliminate standing waves. It’s been done in the pro audio space, there’s a video on Youtube somewhere - but they did use about 24 subs in total!

Room within a room, large airgap in between the inner and outer wall, with fabric covered wool in between. Ceiling should be the same, and the the whole room should be on posts/lifted up to minimize contact with the floor.

First place to start is the figure out the best dimensions and shape of the room. Everything else is secondary.

Typically a square room is terrible because any standing waves will be doubled. Perhaps add a secondary “room” parallel to the existing garage door that would serve as a storage area for lawn equipment, bikes, etc. and would also change the listening room dimensions to something conducive to good sound. You will also need to probably adjust the ceiling height or modify it to have a slope or varying heights.

By the way, I am totally jealous.

To get a rectangle and retain space for storage, tools or whatever else, why not bisect it with framing/drywall and make a smaller, rectangular room. You can then apply the great suggestions everyone else is making to a smaller space and get more bang for your buck speaker and amplifier wise. Just an idea and no idea if that’s more of an intervention than you were planning!

When/if you do the walls/ceiling, try to make it so none of them are 100% perpendicular with another surface.