Room Modes in a 19x20 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 28.1 Hz, set by the 20 ft length.
• Between 40.8 Hz and 56.3 Hz there are no modes at all, so notes in that 15.5 Hz gap will sound thinner than the bass around them.
• Mode density drops in the 40, 50 and 80 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 : 2.11 : 2.22) fall outside the Bolt area because the floor is close to square, which concentrates bass problems on fewer notes.
• Below about 129 Hz (the Schroeder frequency) individual modes shape the sound; above it, reflections and reverb matter more.

No mode falls between 40.8 Hz and 56.3 Hz, a gap of 15.5 Hz. That is a spot where bass naturally loses energy instead of gaining it.

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 gap. 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 : 2.11 : 2.22, this room sits outside the Bolt area because the floor is close to square, which piles bass problems onto fewer notes instead of spreading them out. 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. Treat the four floor-to-ceiling corners first; they are common to every mode this room produces.
2. Full absorption at 40.0 Hz would take about 7 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. Move your listening position off-center along the 20 ft length; roughly 7.6 ft from the front wall (38% back) is a common starting spot before fine-tuning.
4. Walk the subwoofer around the front of the room while playing a bass-heavy track and listen from your seat: corner placement is loudest but least even, and a second sub or an off-corner spot often fills in this room’s weak points.
5. Once traps are in, measure with REW from the listening position. Focus on frequencies below 129 Hz (this room's Schroeder frequency); that is where individual modes, not general reverb, are running the show.

Every mode below 200 Hz

This room has 122 modes below 200 Hz, 16 axial, 57 tangential and 49 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 19x20 rooms

Will a 19x20 room work for a home theater?

This size suits a dedicated home theater or media room, though the 66/100 modal score signals some work ahead, mainly because there is a gap of 15.5 Hz between 40.8 Hz and 56.3 Hz with no mode in between.

Where should I put bass traps in a 19x20 room?

The four vertical corners first. Full absorption at 40.0 Hz would take roughly 7 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 subwoofer size is right for a 19 by 20 ft room?

There is no fixed sub size tied to 380 sq ft; that number mostly sets this room's mode frequencies (122 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 19x20 room have weak bass notes?

The short answer for this room: there is a gap of 15.5 Hz between 40.8 Hz and 56.3 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 a 19x20 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 7.6 ft from the front wall, then measure with REW below 129 Hz to see what still needs work.

Similar room sizes

• 18x20 ft, 9 ft ceiling
• 20x20 ft, 9 ft ceiling
• 19x19 ft, 9 ft ceiling
• 19x20 ft, 8 ft ceiling