How many resonance panels does a room need, and where do they go?

Where they go is answerable now: in the corners, flat against the wall, in the corners belonging to the axis that is out of line. How many is a design output, not a number this page can give you: it depends on the room's volume, its proportions, which axis is misbehaving and by how much.

That is not a deflection, and here is the test of it. If a page could tell you the quantity from a room size alone, the quantity would be wrong for every room whose proportions differ, and proportions are precisely what decides which frequencies the room reinforces. A number that ignores the thing causing the problem is a guess with a decimal point on it.

Where they go, in detail

Floor-to-ceiling in the vertical corners, and along the wall–ceiling junctions where the height axis is the problem. Flat against the wall in the corner, not wrapped around it and not spread out along the walls away from it. The corner is the whole mechanism; a panel that has drifted a metre down the wall is a much weaker device.

Which corners depends on which axis is boomy, and this is the part most people have never been told. A room has three axes and they misbehave independently. The ceiling corners, where the ceiling meets the walls, are the lever on the floor-to-ceiling axis. The vertical corners work the other two. So resonance treatment is not a general low-frequency measure applied wherever there is space: it goes where the axis that is wrong lives.

And the quantity is tuned rather than maximised

Enough to bring the offending axis into its window, and no more. Over-damping an axis is a real failure: a room can be made dead at the bottom as easily as boomy, and the treatment that did it has already been bought and fitted. Do not dump it all in one place either: the panels are working the axis, not the wall.

What to read next

Whether this replaces the bass traps you were about to buy: the honest answer is not simply yes. Or the design service.