Gear & setup

Treating your room: what actually works

7 min read

Every untreated room colours what you record and misleads what you hear back. You cannot buy your way out of that — but you can fix most of it with materials that cost very little and a weekend.

Here is what the problems actually are, and what fixes them.

The three problems

Reflections. Sound bounces off hard surfaces and arrives back at the microphone or your ears a few milliseconds later, added on top of the direct sound. This smears detail and makes your recording sound like it is in a bathroom. Short, dense reflections are the problem, not the loudness of them.

Modes. At certain frequencies, the room's dimensions reinforce sound between two parallel surfaces, producing boomy low frequencies that come and go depending on where you stand. These are the "bass everywhere" problems.

Reverb. The overall decay of sound in the room. This is what makes a recording feel like a recording in a space rather than up close to the source.

What fixes what

The pattern is simple: mass and air gap. What works is heavy, porous material with a gap between it and the wall. What does not work is thin, dense, or decorative material.

Broadband panels: the workhorse

A broadband panel is a rigid, airtight frame holding a porous absorber, mounted with an air gap from the wall.

The frame: 18 mm plywood or MDF, sealed and painted. It has to be airtight — a panel that leaks air leaks sound, and a leaky panel absorbs almost nothing.

The filling: mineral wool (Rockwool or Owens Corning is what people usually mean), 50 to 100 mm thick, around 30 to 70 kg/m³ density. Ordinary fibreglass insulation works but degrades over time and it is unpleasant to work with. Do not use foam, and do not use polyester wadding — both are too thin or too dense to do the job.

The depth: 100 mm is the sensible choice for most home rooms. 50 mm will handle high frequencies but not much else.

The air gap: 50 to 100 mm between the back of the panel and the wall. This matters as much as the panel itself. A panel flush against the wall behaves completely differently from one with a gap.

The facing: breathable acoustic fabric stretched and stapled to the front. It must be porous — a solid, painted or vinyl surface reflects the sound instead of letting it into the absorber. Heavy cloth, hessian or a purpose-made acoustic fabric all work.

A working size

Two panels of 60 × 120 cm will change a small room noticeably. Build four if you can. The most useful placement is the first reflection point on each side of your recording position — sit at the microphone, clap, and note where the echo comes from; that is where the panel goes.

Bass traps: where the money really goes

Bass traps are broadband absorbers, but tall, thick and positioned in the corners, where all the room modes converge.

The simplest and most effective version is a corner bass trap: a triangular prism of mineral wool, 50 cm on each side, running floor to ceiling. It works because it fills the corner where the walls and ceiling meet — the place where pressure accumulates at low frequencies and where no amount of flat wall panel will help.

Practical notes:

• They must reach the floor. A trap that starts 30 cm above the floor does much less.
• Stack them and brace them if you are building a box, because a tall panel of dense wool is heavy and will lean.
• If you cannot build, a tall stack of absorbers in the corner is better than a thin panel.

If you only do one thing to your room, make bass traps. Every other treatment is a refinement of that decision.

Cheap treatments that genuinely work

• Heavy curtains on a window — proper lined curtains, not net curtains. They absorb high frequencies and some midrange. They do nothing for bass.
• A rug and a thick carpet on the floor — helps high frequencies and footstep noise. Almost nothing for bass.
• Bookcases full of books act as broadband absorbers, and they cost nothing if you were going to have books anyway.
• A wardrobe or a mattress stood against a wall — surprisingly effective, and free.
• Soft furniture — a sofa and cushions absorb midrange and high frequencies.
• Heavy blackout blinds — better than thin ones, and they help with heat as well.

What does not work, and why

• Foam. Acoustic foam is thin, has a narrow absorption range in the midrange, and does essentially nothing below about 500 Hz. It is decorative. It is also the single most over-marketed product in audio.
• Acoustic paint and thin panels. Very little mass, very little absorption.
• A rug on its own. Carpet does not stop bass modes, and those are what make a small room sound bad.
• Bass traps sold as "plug-in" foam corner pieces. Same problem as the foam: too small, too thin, wrong frequency range.
• Egg cartons. They do essentially nothing.
• Moving your speakers to a different corner. It changes the interference pattern at one seat. It does not change the room.

A practical plan on a real budget

Around $150 to $300

• Two DIY broadband panels at the first reflection points.
• One corner bass trap.
• Heavy curtains on any window.
• A rug in front of the desk.

This is where most of the available improvement is, and it will be obvious.

Around $300 to $800

• Four to six panels.
• Two corner bass traps.
• Thick rug and heavier curtains.
• Isolation pads for desk monitors, and a decent closed-back headphone pair.

Over $800

• Professional measurement and treatment design, usually with a consultant.
• Replacement or additional monitors, after the room is right.

Note the order: the professional route is worth it only once the cheap stuff is done.

Measuring the room

You do not need expensive software to find the problems. A free room analysis tool — Room EQ Wizard is the well-known one — can show you the response curve and the decay times, and it will tell you which frequencies are problematic. Even so:

• Measure from your listening position, at ear height.
• Do not trust a measurement taken in the middle of the room.
• Measurements guide the treatment; they do not replace listening.

Listening is the point

Treatments are a means, not an end. After each change, listen to the same material — a familiar track you know well, and ideally the same spoken word recording — and ask whether the change helped. Keep what helps.

Do not treat a room because a chart told you to. Treat it because you can hear the problem and the treatment fixed it.

A safe order of work

1. Measure and listen to the untreated room.
2. Fix the obvious — heavy curtains, a rug, a bookcase, moving the desk away from a bare wall.
3. Build or buy two broadband panels and place them at the first reflection points.
4. Build a corner bass trap.
5. Listen again, from your normal position, with the same material.
6. Only then consider monitors, and only then a professional.