Where should I place 30 foam panels to improve acoustics in my 4m music room?

A room keeps two kinds of sound: the one it makes back to you, and the one it lets go. Thirty squares of two-centimetre foam will reshape the first and barely touch the second — so aim them at the path between players and ears, not at the walls in general. Stand where the drums sit. Sound leaves a kit in a long low fan; foam at that height won't carry the kick, but it will soften the snare crack and the cymbals that reach your own head. So put the squares where you actually stand — behind the kit, at the bass player's shoulder, in the corner behind the amps — in clusters of two or three, off-centre, never mirrored evenly around the room. Symmetry looks tidy on paper and sounds hollow in practice. Then leave the walls alone for a week and let your ears tune it across different weather, different heat. Fibro and tile talk back more when the air is dry. Add the next cluster where you still hear the ring, not where a diagram says. The aim isn't a stuffed room. It's a room that answers you quickly.

Those thirty thin foam squares will help a little with high-frequency reflections and flutter echo in the corners of your voice range, but with drums, bass, and electric guitars in a fibro and tile room, they will not soundproof the space or stop low frequencies from escaping. Bass and drums carry massive energy that passes right through lightweight walls and thin foam. If you want to tackle the acoustics rather than true soundproofing, focus your panels at head height on the walls where sound first bounces from your instruments, particularly opposite your guitar amps and around the drum kit. Leave gaps between them rather than clustering them all together, as scattering absorption works better than deadening one small patch. For drums and bass, you will need much denser traps in the corners to catch low-end build-up, and you might need to decouple your amp and drum riser from the floor so the vibrations do not travel straight through the fibro structure into the rest of the house.

Two-centimetre foam is best used sparingly to reduce harshness, not as the main treatment. With 30 squares, arrange them as five groups of six rather than covering the room evenly: - Put two groups on the side walls at the first-reflection points: sit where the guitars are heard, have someone move a mirror along each wall, and mark where you can see the speakers or players. Mount the foam there. - Put one group on the wall behind the drummer, and one behind the main listening or recording position. - Use the final group as a loose ceiling “cloud” above the centre of the room, leaving an air gap if possible. Keep the corners clear for proper bass traps made from thick mineral wool or fibreglass; foam will do almost nothing for kick drum, bass guitar, or sound escaping through the fibro walls and tiled roof. For actual soundproofing, the effective work is structural: seal gaps, improve doors and windows, and add isolated, heavy wall/ceiling layers. Avoid fixing foam over every wall, since that can leave the room unnaturally dull while low-end remains uncontrolled.