Room Modes in an 11x17 ft Room with an 8 ft Ceiling
At 11 by 17 ft with an 8 ft ceiling, this room works well as a bedroom theater or dedicated music room. Its first room mode, the lowest note the walls naturally reinforce, falls at 33.1 Hz, set by the 17 ft length.
That puts its modal score at 79 out of 100, a decent score, typical for a room this shape. The main thing to plan around: there is a gap of 18.1 Hz between 33.1 Hz and 51.2 Hz with no mode in between.
Mode spectrum
8 dense clusters (≤5 Hz apart) — overlapping resonances are harder to treat evenly.
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
| Dimension | 1st | 2nd | 3rd | 4th |
|---|---|---|---|---|
| Length (17 ft) | 33.1 Hz | 66.2 Hz | 99.3 Hz | 132.4 Hz |
| Width (11 ft) | 51.2 Hz | 102.3 Hz | 153.5 Hz | 204.6 Hz |
| Ceiling height (8 ft) | 70.3 Hz | 140.7 Hz | 211 Hz | 281.3 Hz |
What this means for your room
- The lowest room mode is 33.1 Hz, set by the 17 ft length.
- Between 33.1 Hz and 51.2 Hz there are no modes at all, so notes in that 18.1 Hz gap will sound thinner than the bass around them.
- Mode density drops in the 40 Hz third-octave band (0 modes against 1 in the band below), so bass will sound uneven from note to note.
- The proportions (1 : 1.38 : 2.13) fall inside the Bolt area, the range of room ratios that spreads modes most evenly.
- Below about 194 Hz (the Schroeder frequency) individual modes shape the sound; above it, reflections and reverb matter more.
Between 33.1 Hz and 51.2 Hz there is no mode to reinforce anything, a gap of 18.1 Hz. Notes that fall in that gap sound thinner and quieter than notes just above or below it.
If you use this room for movies, that gap tends to show up as boom on specific low-frequency effects rather than an even rumble. If it is a music or mixing room, that same spot makes some bass notes read louder on playback than they actually are on the recording, which makes mixing bass by ear risky here.
Height, width and length work out to 1 : 1.38 : 2.13, which lands inside the Bolt area. Rooms with that proportion usually need less correction than a room shaped like a cube or a hallway.
How to fix it, in order
- Start with bass traps in the four floor-to-ceiling corners; every mode in this room peaks there.
- At 40.0 Hz the quarter wavelength is about 7 ft, deeper than any practical panel, so a porous trap alone will not fully absorb that note. Build corner traps as thick as you can fit (6 to 12 in, straddling the corner with an air gap behind) to take the edge off, then handle the note itself with a membrane or pressure trap tuned near it, careful seat position, and more than one subwoofer with EQ.
- Do not sit dead-center on the 17 ft length. Start near 6.5 ft from the front wall, about 38% of the way back, and adjust from there.
- 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.
- After treating, run an REW sweep from the seat. Everything below 194 Hz is where these modes live, so that is the range worth checking before you call the room done.
These numbers assume an empty rectangular 11x17 room with hard walls. Draw your real room, add furniture and speakers, and simulate the bass at your seat.
Every mode below 200 Hz
This room has 56 modes below 200 Hz, 11 axial, 27 tangential and 18 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.
| Frequency | Type | Mode (length, width, height) |
|---|---|---|
| 33.1 Hz | axial | (1,0,0) |
| 51.2 Hz | axial | (0,1,0) |
| 60.9 Hz | tangential | (1,1,0) |
| 66.2 Hz | axial | (2,0,0) |
| 70.3 Hz | axial | (0,0,1) |
| 77.7 Hz | tangential | (1,0,1) |
| 83.7 Hz | tangential | (2,1,0) |
| 87 Hz | tangential | (0,1,1) |
| 93.1 Hz | oblique | (1,1,1) |
| 96.6 Hz | tangential | (2,0,1) |
| 99.3 Hz | axial | (3,0,0) |
| 102.3 Hz | axial | (0,2,0) |
| 107.5 Hz | tangential | (1,2,0) |
| 109.3 Hz | oblique | (2,1,1) |
| 111.7 Hz | tangential | (3,1,0) |
| 121.7 Hz | tangential | (3,0,1) |
| 121.9 Hz | tangential | (2,2,0) |
| 124.1 Hz | tangential | (0,2,1) |
| 128.5 Hz | oblique | (1,2,1) |
| 132 Hz | oblique | (3,1,1) |
| 132.4 Hz | axial | (4,0,0) |
| 140.7 Hz | axial | (0,0,2) |
| 140.7 Hz | oblique | (2,2,1) |
| 141.9 Hz | tangential | (4,1,0) |
| 142.6 Hz | tangential | (3,2,0) |
| 144.5 Hz | tangential | (1,0,2) |
| 149.7 Hz | tangential | (0,1,2) |
| 149.9 Hz | tangential | (4,0,1) |
| 153.3 Hz | oblique | (1,1,2) |
| 153.5 Hz | axial | (0,3,0) |
| 155.5 Hz | tangential | (2,0,2) |
| 157 Hz | tangential | (1,3,0) |
| 158.4 Hz | oblique | (4,1,1) |
| 159 Hz | oblique | (3,2,1) |
| 163.7 Hz | oblique | (2,1,2) |
| 165.5 Hz | axial | (5,0,0) |
| 167.1 Hz | tangential | (2,3,0) |
| 167.3 Hz | tangential | (4,2,0) |
| 168.8 Hz | tangential | (0,3,1) |
| 172 Hz | oblique | (1,3,1) |
| 172.2 Hz | tangential | (3,0,2) |
| 173.2 Hz | tangential | (5,1,0) |
| 173.9 Hz | tangential | (0,2,2) |
| 177.1 Hz | oblique | (1,2,2) |
| 179.6 Hz | oblique | (3,1,2) |
| 179.8 Hz | tangential | (5,0,1) |
| 181.3 Hz | oblique | (2,3,1) |
| 181.5 Hz | oblique | (4,2,1) |
| 182.8 Hz | tangential | (3,3,0) |
| 186.1 Hz | oblique | (2,2,2) |
| 186.9 Hz | oblique | (5,1,1) |
| 193.2 Hz | tangential | (4,0,2) |
| 194.6 Hz | tangential | (5,2,0) |
| 195.8 Hz | oblique | (3,3,1) |
| 198.6 Hz | axial | (6,0,0) |
| 199.8 Hz | oblique | (4,1,2) |
Questions about 11x17 rooms
- Will an 11x17 room work for a home theater?
- This size fits a bedroom theater or dedicated music room well. At 79/100, the modal score is good, so treatment here is mostly fine-tuning rather than fixing real problems.
- Where should I put bass traps in an 11x17 room?
- Start in the four floor-to-ceiling corners; every mode in this room peaks there. The 40.0 Hz mode itself would need about 7 ft of depth to fully absorb, more than any panel can give, so build corner traps as thick as you can fit (6 to 12 in) and pair them with a membrane trap tuned near 40.0 Hz.
- What subwoofer size is right for an 11 by 17 ft room?
- There is no fixed sub size tied to 187 sq ft; that number mostly sets this room's mode frequencies (56 of them under 200 Hz). At this size you will want more headroom than a small room needs, and two subwoofers usually beat one at keeping bass even from seat to seat.
- Why does my 11x17 room have weak bass notes?
- The short answer for this room: there is a gap of 18.1 Hz between 33.1 Hz and 51.2 Hz with no mode in between. Bass unevenness like that is built into the shape of the room and shows up regardless of what speakers or sub you use.
- How do I fix bass problems in an 11x17 room?
- Put bass traps in the four floor-to-ceiling corners first, as thick as you can fit (6 to 12 in) plus a membrane trap tuned near 40.0 Hz, since that note's own quarter wavelength (about 7 ft) is too deep for any panel. From there, move your seat to about 6.5 ft from the front wall, then measure with REW below 194 Hz to see what still needs work.
Similar room sizes
How these numbers are calculated
Modes use the rectangular-room equation f = (c/2)·√((nx/L)² + (ny/W)² + (nz/H)²) with c = 343 m/s, for an empty room with rigid walls. The Schroeder frequency is fs = 2000 x sqrt(RT60 / V), assuming RT60 = 0.4 s. The modal score starts at 100 and subtracts penalties for stacked modes, density dips, gaps, proportions outside the Bolt area and dimension multiples. Doors, openings and furniture shift real rooms away from these values, which is what the room mode calculator and the 3D editor are for.