Room Modes in an 8x23 ft Room with a 9 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 24.5 Hz, set by the 23 ft length.
• Your 23 ft length is almost exactly three times your 8 ft width, so their modes fall close together without quite stacking.
• Your 23 ft length and 9 ft ceiling height both resonate near 122.3 Hz, so bass at that note will be much louder than its neighbours.
• Between 24.5 Hz and 48.9 Hz there are no modes at all, so notes in that 24.4 Hz gap will sound thinner than the bass around them.
• Mode density drops in the 31.5 Hz third-octave band (0 modes against 1 in the band below), so bass will sound uneven from note to note.
• The proportions (1 : 0.89 : 2.56) fall outside the Bolt area because the room is long and narrow for its height, so modes bunch up along the length.
• Below about 185 Hz (the Schroeder frequency) individual modes shape the sound; above it, reflections and reverb matter more.

Because your 23 ft length and 9 ft ceiling are close in size, their modes stack near 122.3 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 1 : 0.89 : 2.56, this room sits outside the Bolt area because the room is long and narrow for its height, which bunches modes up along the length. Expect to lean on bass traps and seat position a bit more than in a room with friendlier proportions.

How to fix it, in order

1. Put your first traps in the four vertical corners where floor meets ceiling; that is where every mode in this room reaches its loudest point, ceiling height included.
2. At 122.3 Hz the quarter wavelength is about 2.3 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.
3. Avoid the exact middle of the 23 ft length for your seat or mix position; try around 8.7 ft from the front wall (38% of the length) as a starting point, then nudge from there by ear.
4. Test more than one subwoofer position. Corner placement drives the most output but also the least even bass; moving it along a wall or using two subs at different spots tends to average out this room’s peaks.
5. Confirm the fix with an REW measurement at the listening position, paying closest attention below 185 Hz; above that, general room reverb matters more than any single mode.

Every mode below 200 Hz

This room has 63 modes below 200 Hz, 13 axial, 31 tangential and 19 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 8x23 rooms

Will an 8x23 room work for a home theater?

This size suits a bedroom theater or dedicated music room, though the 50/100 modal score signals some work ahead, mainly because two of its dimensions reinforce the same note near 122.3 Hz.

Where should I put bass traps in an 8x23 room?

Start in the four floor-to-ceiling corners; every mode in this room peaks there. The 122.3 Hz mode itself would need about 2.3 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 122.3 Hz.

What subwoofer size is right for an 8 by 23 ft room?

There is no fixed sub size tied to 184 sq ft; that number mostly sets this room's mode frequencies (63 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 8x23 room have one loud bass note?

The short answer for this room: two of its dimensions reinforce the same note near 122.3 Hz. 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 8x23 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 122.3 Hz, since that note's own quarter wavelength (about 2.3 ft) is too deep for any panel. From there, move your seat to about 8.7 ft from the front wall, then measure with REW below 185 Hz to see what still needs work.

Similar room sizes

• 9x23 ft, 9 ft ceiling
• 8x22 ft, 9 ft ceiling
• 8x24 ft, 9 ft ceiling
• 8x23 ft, 8 ft ceiling