f = c ÷ 4d · 60° triangle
Speaker placement calculator
How far your monitors sit from the walls decides which bass notes the room cancels. Check the dips, then set up the stereo triangle.
Cancellation dips
- Front wall dip
- 143 Hz0.60 m (1.97 ft) away · D3 −45¢
- Side wall dip
- 78 Hz1.10 m (3.61 ft) away · D#2 +5¢
- Floor dip
- 86 Hz1.00 m (3.28 ft) away · F2 −30¢
f = c ÷ 4d with sound at 343.3 m/s, 20 °C (68 °F)
Where the dips fall, 20 Hz to 1 kHz
Cancellation frequencies
| Boundary | Distance | First dip | Next dips to 1 kHz, Hz |
|---|---|---|---|
| Front wall | 0.60 m (1.97 ft) | 143 Hz | 429, 715 |
| Side wall | 1.10 m (3.61 ft) | 78 Hz | 234, 390, 546, 702, 858 |
| Floor | 1.00 m (3.28 ft) | 86 Hz | 257, 429, 601, 772, 944 |
- Ears from each speaker
- 1.20 m3.94 ft, tweeter to ear
- Ears from the speaker line
- 1.04 m3.41 ft, straight back from between the speakers
- Toe-in
- 30 °each speaker turned in to point at your head
- Ears from the front wall
- 1.64 m5.38 ft, 39% of the room length
Why the wall behind matters
Bass spreads out from a speaker in every direction, so some of it heads back to the wall, bounces and rejoins the sound coming forward. That trip is twice the distance d to the wall. When it equals half a wavelength, the bounce arrives upside down and cancels the direct sound:
f = c ÷ (4 · d)
A speaker 0.6 m from the wall dips near 143 Hz at 20 °C; at 1 m the dip falls to about 86 Hz. Further dips follow at three, five and seven times that frequency. The side wall, floor and ceiling each add their own set, which the chart lines up so you can see where they pile together.
Boosting the dip with EQ boosts the bounce by the same amount, so the cancellation stays. Moving the speaker shifts it, which is why the distance is worth trying out here first.
For the triangle, put the speakers’ tweeters at ear height and sit at the point of the triangle, with each speaker turned in to point at your head.
Sources
- Cancellation frequency f = c / 4d for the distance from the front of the speaker to the wall behind it: Genelec support, I am not getting enough bass, do I have a backwall cancellation?, which also gives the 430 Hz figure for a speaker under 20 cm from the wall. The effect of nearby boundaries on a speaker’s low-frequency output: R. F. Allison, The Influence of Room Boundaries on Loudspeaker Power Output, J. Audio Eng. Soc. 22, 314–320 (1974).
- Speed of sound in dry air, c = √(γRT/M): R. Nave, Speed of Sound, HyperPhysics, Georgia State University.
- Stereo arrangement: listening angle of 60° with the listening distance equal to the speaker spacing (§8.5.3), speakers at ear height with their axes through the listening position (§8.5.1.1): Recommendation ITU-R BS.1116-3 (02/2015). For another angle θ, each speaker is (spacing ÷ 2) ÷ sin(θ/2) from your head, by plain trigonometry.
- Feet and °F: NIST Special Publication 811.
Questions
Should the speaker go closer to the wall or further away?
Either moves the dip. Close to the wall pushes it up: Genelec’s note says that under about 20 cm the dips sit at 430 Hz or above, and the extra bass the wall then adds can be trimmed with the speaker’s room-compensation settings. Further out pulls the dip down into the bass. Try a few distances here, then measure at your chair.
Why measure to the woofer for the side wall and floor?
The low frequencies these dips affect come from the woofer, so its centre is the point the bounce starts from. Genelec’s note measures the wall behind from the front of the speaker.
Does the triangle have to be equilateral?
60° is the reference that ITU-R BS.1116-3 uses for critical listening. You can enter another angle to see the distance and toe-in it gives; a narrower angle puts you further back.