Why your room has a bass peak at 60 Hz

Sound travels at about 343 metres per second. A room resonates when half a wavelength fits exactly between two opposite surfaces, so each pair of surfaces has a fundamental resonance at 343 divided by twice the distance between them.

• A 2.86 m distance resonates at 60 Hz. So a 2.86 m ceiling height, or a 2.86 m room width, will give you a 60 Hz peak.
• The same pair of surfaces also resonates at every multiple: 120 Hz, 180 Hz, 240 Hz.
• In feet: 1130 divided by twice the distance. A 9 ft 5 in dimension lands on 60 Hz.

Run that arithmetic for your length, your width and your height, and the three numbers you get plus their multiples will account for most of what your measurement does below 200 Hz. If a peak does not match any of them, the room is probably not a plain rectangle: an alcove, an open doorway or a stairwell couples in its own resonances.

A mode is a standing wave, so it has places where the air pressure swings hardest and places where it barely moves at all. Pressure is always at a maximum against a wall and at a minimum somewhere in the middle.

That is why the same room measures a huge peak at one seat and a hole at another, at the same frequency. It is also why sitting with your head against the back wall gives you the boomiest bass in the room: every mode has a pressure maximum there.

1. 1.Move your seat. Free. A modal peak is a property of where you are sitting as much as of the room, and 40 cm is often enough to change it by several decibels.
2. 2.Move the speakers or the subwoofer. Free. A source standing at a mode's node cannot excite that mode at all, which is a genuinely useful lever for a subwoofer since it does not need to stay symmetric.
3. 3.Cut it with a parametric filter. Cheap or free. This is the one case where EQ is a real fix rather than cosmetic: cutting the drive to a resonance shortens its ringing as well as lowering its level.
4. 4.Corner bass traps. A few hundred in materials. These shorten the decay across the whole bass region rather than fixing one frequency, and they improve every seat rather than the one you measured at.
5. 5.A second subwoofer. The most expensive and the most effective for evenness, because two sources in different positions excite the modes differently and fill in each other's nulls.