People spend thousands on converters and cables chasing bass that a wall took away for free. A speaker near a boundary sends sound to your ears twice: once directly, and once a fraction of a millisecond later off the wall, the desk or the floor. Where those two arrivals disagree, the bass cancels — and no amount of gear fixes geometry.
Enter your measurements and this works out which frequencies are being cancelled, by which surface, and how far you would have to move things to stop it.
The chart stops at 2 kHz on purpose. Above roughly that point a speaker beams rather than radiating in all directions, so far less energy reaches the walls — and this model, which treats sound like light travelling in every direction equally, would draw a dense comb that does not exist in the room.
Every reflecting surface is replaced by a mirror image of the speaker behind it. The sound that reaches you off the wall has travelled exactly as far as a straight line from that imaginary speaker, so the extra distance it covers is the whole story. Call that extra distance Δ. The two arrivals cancel wherever Δ equals half a wavelength, and reinforce wherever it equals a whole one:
first cancellation = c / (2Δ), then every odd multiple of it — where c is the speed of sound, 343 m/s.
For a wall directly behind the speaker at distance d, Δ works out to roughly 2d, which gives the familiar c / (4d). A speaker 30 cm from the wall therefore has its first cancellation near 285 Hz; at 80 cm it drops to about 107 Hz, right in the middle of where bass guitars and kick drums live. This is what people are hearing when they say a room “eats the bass”.
Now the caveat, and it is a real one. This ray-tracing model assumes sound behaves like light. Below the room's Schroeder frequency it does not — the room stops supporting free waves and starts resonating in discrete modes instead. In a typical domestic room that crossover sits somewhere between 100 and 200 Hz, which is exactly where the worst cancellations land. Treat the first null as a solid prediction and everything below the marked line on the chart as an indication of where trouble lives, not a measurement. A calculator that pretends otherwise is selling you certainty it does not have.
Two more limits worth stating. Real speakers are directional at high frequencies, so reflections above roughly 1 kHz are weaker than this model assumes. And the depth of each cancellation depends on how absorbent the surface is, which is why that dropdown exists — it changes the answer a lot, and nobody knows their own number precisely.