Acoustic advice re: building a room (in wall or on wall) treatments

In between studs carbon technology for acoustics.

See article below:

Mike

https://www.acousticfields.com/carbon-absorber-wall/

Look into the wall construction products made by ASC. I have heard a room constructed with them, and the structure of the room---especially the walls---was the least resonant I have ever heard, by a considerable margin. Rapped with one’s knuckles, the sound produced was a mere "click", not the normal resonant "tonnnk". The walls were like rock!

The ASC system begins by isolating the first layer of sheet rock from the studs it is normally secured to. A layer of WallDamp is then applied to that layer of sheet rock, and another layer of sr is then put in place. The WallDamp material is a constrained layer adhesive, and put between two resonant surfaces like 4’ x 8’ pieces of sheet rock (which left undamped vibrate/resonate like a drumhead) it creates a remarkably non-resonant structure. It can also be used in the construction of double-layer shelves for equipment racks, and in double-walled loudspeaker enclosures.

Having solid, sound proof walls is great. 

In terms of controlling the resonant character of a room though, I think that for most of us panels are a great way to go thanks to the flexibility and ability to grow over time.

I've been in the Magico demo room, and it's great, but it was built by expert acousticians. Unless I had that ability of no-hold-barred acoustic design I'd probably go with a mix of double wall construction as @bdp24 mentions, as well as after build panels.

Also, don't forget the ceiling, especially between the listener and the speakers.