Devialet phantom gold

[ragwo]

I am using Spotify but it might be the layout of my room causing the problem.
It’s a 12m*4m room and I’m placing my phantom about 3 m from left wall and 9m from right wall

Where's your listening position? How close to the wall behind the speakers are the speakers located?

The phantom is located just in front of the wall maybe 5 cm from the wall and I am on the other side of the room at the back maybe 4.5m away. There is a little side wall so the phantom basically has even distance from both side walls but the room is open in a rectangular shape . Maybe I need 2 phantoms to pressurise the room properly

I believe you're right, a single Phantom will not be able to fill such a large room with bone shaking bass. To get the best sound quality you should use a proper stand and place it as a normal speaker. 5 cm from the wall isn't optimal.