Room Modes in a 20x28 ft Room with a 10 ft Ceiling

Mode spectrum

Each line is one standing wave. Axial modes, the strongest kind, stand tallest; tight bunches and wide empty stretches are where the bass will sound uneven.

Axial modes by dimension

What this means for your room

• The lowest room mode is 20.1 Hz, set by the 28 ft length.
• Your 28 ft length and 20 ft width both resonate at 140.7 Hz, so bass at that note will be much louder than its neighbours.
• Your 20 ft width is exactly twice your 10 ft ceiling height, so their modes stack at 56.3, 112.5 and 168.8 Hz and bass at those notes will be much louder than its neighbours.
• Mode density drops in the 25 and 40 Hz third-octave bands, where fewer modes fall than in the band below, so bass will sound uneven from note to note.
• The proportions (1 : 2.00 : 2.80) fall inside the Bolt area, the range of room ratios that spreads modes most evenly.
• Below about 100 Hz (the Schroeder frequency) individual modes shape the sound; above it, reflections and reverb matter more.

Because your 20 ft width and 10 ft ceiling are close in size, their modes stack near 56.3 Hz. Expect that one note to sound louder, and ring longer, than the rest of the bass in this room.

In a home theater, this shows up as one bass note in an action scene sounding far louder than the rest of the mix, usually a kick drum hit or an LFE cue landing right on that stacked note. In a music room, the same thing means certain bass notes on a track jump out while others next to them feel buried.

At a ratio of 1 : 2.00 : 2.80, this room sits inside the Bolt area, the zone where modes tend to spread out rather than pile up. Shape is doing you a favor here.

How to fix it, in order

1. Start with bass traps in the four floor-to-ceiling corners; every mode in this room peaks there, including the ones set by your ceiling height.
2. Full absorption at 56.3 Hz would take about 5 ft of trap depth, well past what any room can fit. Fill the corners as deep as you reasonably can (6 to 12 in, with an air gap behind), then lean on a membrane trap tuned near that frequency, your seat position and a second subwoofer with EQ to tame the note itself.
3. Do not sit dead-center on the 28 ft length. Start near 10.6 ft from the front wall, about 38% of the way back, and adjust from there.
4. For the subwoofer, try a few spots before settling: a front corner usually gives the most output but also the most uneven bass, while pulling it off the wall or adding a second sub often smooths out peaks like the ones this room has.
5. After treating, run an REW sweep from the seat. Everything below 100 Hz is where these modes live, so that is the range worth checking before you call the room done.

Every mode below 200 Hz

This room has 190 modes below 200 Hz, 19 axial, 84 tangential and 87 oblique. Read the axial rows as the ones you will hear most clearly. Tangential and oblique modes add texture but usually only become audible when they land close to an axial mode.

Questions about 20x28 rooms

Is a 20 by 28 ft room good for a music room or home theater?

This size is workable for a dedicated home theater or media room, but its modal score of 45/100 is low, driven by the fact that two of its dimensions reinforce the same note near 56.3 Hz. Go in expecting a serious treatment plan.

What is the best corner for bass traps in a 20x28 room?

The four vertical corners first. Full absorption at 56.3 Hz would take roughly 5 ft of trap depth, so treat that note with a tuned membrane or pressure trap instead, and use thick porous corner traps (6 to 12 in) for everything above it.

What size subwoofer does a 20x28 room need?

Subwoofer size is less about this room's 560 sq ft and more about the output headroom you want; room size mainly changes where the 190 modes below 200 Hz fall. A room this size needs more sub output to reach the same level as a smaller one, and running two subs at different spots evens out the response between seats.

Why is bass boomy in one spot in a 20 by 28 ft room?

Here it comes down to this: two of its dimensions reinforce the same note near 56.3 Hz. That is a property of the room's shape, not your equipment, so treatment, not a better sub, is the fix.

What is the fastest fix for bass in a 20x28 room?

Corner bass traps come first, as thick as you can fit (6 to 12 in) plus a membrane trap tuned near 56.3 Hz, since that note's own quarter wavelength (about 5 ft) is too deep for any panel. After that, reposition your seat near 10.6 ft from the front wall and verify with REW below 100 Hz.

Similar room sizes

• 19x28 ft, 10 ft ceiling
• 20x27 ft, 10 ft ceiling
• 20x28 ft, 8 ft ceiling
• 20x28 ft, 9 ft ceiling