Speaker Placement Calculator
Work out where to put your speakers and where to sit. Enter the room and the layout and the speaker placement calculator gives the stereo triangle and the toe-in, the bass dip each wall, the floor and the ceiling cause at your listening position, the first reflection points where an acoustic panel does the most, and which of the room's modes are weak or strong at your seat. Everything is worked from geometry, in meters or feet.
Measure to the drivers: distances run from the walls to the woofer's face and to your ears, the points the sound actually leaves and arrives at.
Your room and speakers
The layout
First reflection points: the nearer pair from each speaker's own side wall, the further pair from the opposite wall.
- Each speaker to your ears
- 2.54 m
- Angle between the speakers
- 60.0°
- Toe-in to aim at your ears
- 30.0°
- Each speaker to its side wall
- 0.63 m
- Your ears to the back wall
- 1.90 m
- Your seat along the room
- 62%
The two speakers sit 60.0° apart from your seat, inside the 60° ± 5° of EBU Tech 3276's stereo layout.
Boundary bounces and bass dips
Each wall, the floor and the ceiling send a copy of the woofer's sound to your ears a little later than the direct sound. Where the copy arrives half a wavelength late it cancels part of the bass: the first dip below. The bass test's sweep makes a deep dip easy to hear as a note that drops away.
| Bounce off | Arrives later by | Quieter by | First dip |
|---|---|---|---|
| Front wall, behind the speaker | 4.8 ms | 4.3 dB | 104 Hz |
| Near side wall | 2.4 ms | 2.4 dB | 213 Hz |
| Far side wall | 8.7 ms | 6.7 dB | 58 Hz |
| Back wall, behind you | 10.4 ms | 7.6 dB | 48 Hz |
| Floor | 2.0 ms | 2.1 dB | 245 Hz |
| Ceiling | 3.9 ms | 3.6 dB | 129 Hz |
The near side wall's dip (213 Hz) and the floor's (245 Hz) fall within a third of an octave of each other, so they deepen the same notes. Move the speaker so those two distances differ more.
The front wall's dip (104 Hz) and the ceiling's (129 Hz) fall within a third of an octave of each other, so they deepen the same notes. Move the speaker so those two distances differ more.
The front wall's dip at 104 Hz moves up as the woofer moves closer to that wall and down as it moves away from it.
First reflection points
The points where the tweeter's sound bounces off a side wall or the ceiling on its way to your ears. Sit in the seat while someone slides a mirror along the wall: where you see the tweeter in it is the point. An absorber there clears up the stereo image; the acoustic panel calculator says how much a given panel absorbs.
| Surface | Reflection point | Arrives later by | Quieter by | To be 10 dB down |
|---|---|---|---|---|
| Near side wall | 1.45 m from the front wall, 1.09 m up | 2.4 ms | 2.4 dB | Absorbing 83% or more |
| Far side wall | 2.28 m from the front wall, 1.14 m up | 8.7 ms | 6.7 dB | Absorbing 53% or more |
| Ceiling | 2.06 m from the front wall, 1.30 m from the near side wall | 3.5 ms | 3.4 dB | Absorbing 78% or more |
Off a bare wall, the near side wall's reflection is only 2.4 dB quieter than the direct sound and arrives 2.4 ms later. EBU Tech 3276 asks for reflections in the first 15 ms to be at least 10 dB down from 1 to 8 kHz, so the spot needs a panel taking 7.6 dB more off, one absorbing about 83% of the sound. The right speaker's points mirror these on the other side of the room.
Room modes at your seat
The room's own resonances along its length, width and height, and how strong each is where you sit. The room mode calculator draws the full set and their pressure across the floor.
| Mode | Frequency | At your seat, from its peak | Reading |
|---|---|---|---|
| Length 1 | 34 Hz | -8.7 dB | In between |
| Width 1 | 45 Hz | Null | Null: weak at your seat |
| Length 2 | 69 Hz | -2.7 dB | In between |
| Height 1 | 69 Hz | -24.0 dB | Null: weak at your seat |
| Width 2 | 90 Hz | 0.0 dB | Peak: full strength at your seat |
| Length 3 | 103 Hz | -0.9 dB | Peak: full strength at your seat |
| Width 3 | 135 Hz | Null | Null: weak at your seat |
| Height 2 | 137 Hz | -0.1 dB | Peak: full strength at your seat |
| Height 3 | 206 Hz | -14.5 dB | Null: weak at your seat |
4 modes have a null at your seat (45 Hz, 69 Hz, 135 Hz, 206 Hz): those notes sound weak there however loud the speakers play. A seat on the room's center line sits on the null of every odd width mode, which no position along the room changes.
How to place speakers, step by step
- Center the layout across the room. Put both speakers the same distance from their side walls and the seat on the room's center line, so the two channels meet the same room.
- Pick the seat first. Try 38% of the room's length from the front or the back wall, away from the middle of the room, where the first length mode has its null. Then check the modes table for this room.
- Make a triangle. Set the speakers as far apart as each is from your ears, so they sit 60° apart, the layout EBU Tech 3276 uses for stereo listening, and turn each in to point at you.
- Choose the distance from the front wall. Watch the front-wall dip move as you change it, and keep it apart from the side wall's and the floor's dips so they do not stack.
- Treat the first reflection points. Put absorption where the mirror shows the tweeters on both side walls, and on the ceiling if it is low.
- Listen and adjust. Play the speaker test's channel and phase checks, then move the speakers a few centimeters at a time and listen again: the dips in the tables above move with every change.
What speaker placement can and cannot fix
Moving a speaker changes three things at once. It changes the stereo geometry, the angle the two speakers make at your seat and how far away they are, which decides how wide and how focused the image is. It changes the reflections, every wall's copy of the sound arriving a little after the direct sound. And it changes how the speaker drives the room's own resonances, as moving your seat changes how you hear them.
The reflections matter at both ends of the range. In the bass, a reflection off a nearby wall or the floor arrives late enough to cancel part of the direct sound at one frequency, which is the dip each boundary causes. In the treble, the first reflections off the side walls and the ceiling blur the stereo image, which is why they are the places an absorber does the most.
All of it is geometry, so it can be worked out before anything is moved: a mirror image of the speaker behind each surface gives the extra path, and the extra path gives the delay, the level and the frequency it cancels.
The ideas behind the controls
- Listening triangle
- The two speakers and the seat at the corners of an equilateral triangle, so the speakers sit 60 degrees apart as seen from the seat.
- Toe-in
- How far each speaker turns toward the seat. Pointed straight at the ears, it puts the listener on the axis the speaker's frequency response is measured on.
- Boundary dip
- A cancellation in the bass where a wall's or the floor's reflection arrives half a wavelength behind the direct sound.
- First reflection point
- The spot on a wall or the ceiling where the sound bounces once into the seat: where you see the speaker in a mirror laid flat on that surface.
- Room mode
- A resonance of the room between two parallel surfaces. It peaks at the walls and has nulls in between, so the same note is loud in one seat and weak in another.
Speaker placement FAQ
How far should speakers be from the wall?
There is no single distance: every distance puts a bass dip somewhere. The wall behind a speaker sends back a copy of its bass that cancels the direct sound where the extra path is half a wavelength, so with the woofer 0.5 m from the wall the dip lands near 170 Hz and at 1 m near 86 Hz. The calculator works the dip out for your room and seat, and the useful rule is to keep the distances to the front wall, the side wall and the floor different, so their dips land on different notes.
How far apart should speakers be?
About as far apart as each one is from your ears, so the two speakers and your seat make an equilateral triangle and the speakers sit 60 degrees apart. That is the stereo layout EBU Tech 3276 specifies for listening rooms, with 2 to 4 m between the speakers. The Equilateral spacing button sets it for your seat.
What is the 38% rule for speaker placement?
A starting point for the listening seat: 38% of the room's length from the front or the back wall. It keeps the seat away from the middle of the room, where the first length mode has its null and its bass goes missing, and away from the back wall, where every length mode peaks. It is a rule of thumb for a rectangular room, so the calculator shows how strong each of your room's modes is at the seat you choose.
Should speakers be toed in?
Turning each speaker in to point at your ears puts you on the axis its frequency response is measured on, and the calculator gives the angle for your layout. Treat that angle as the starting point: listen with it pointed straight at you and turned a few degrees outward, using the channel test of the speaker test, and keep the one where the center is sharpest.
Where should acoustic panels go?
At the first reflection points: the spots on the side walls and the ceiling where the tweeter's sound bounces into your seat. Sit in the seat while someone slides a mirror along the wall; where you see the tweeter is the point, and the calculator gives the same points from the room's measurements. EBU Tech 3276 asks for those early reflections to be at least 10 dB below the direct sound, and the calculator says how much absorption each point needs to get there.
What is speaker boundary interference (SBIR)?
The dips in the bass caused by a speaker's own reflections off the nearest walls and the floor. Each reflection arrives a few milliseconds late and cancels the direct sound where it is half a wavelength behind, so each boundary carves a dip at a frequency set by its distance. The bounce table lists them, and it warns when two land within a third of an octave and deepen the same notes.
Why does the bass sound weak at my listening position?
Two things the calculator shows separately. A boundary dip is a cancellation between the speaker and a nearby wall, which moves when the speaker moves. A room-mode null is a place where one of the room's resonances has no pressure, which moves when you move: a seat in the middle of the room sits on the null of the first length mode and of every odd width mode. The bass test's sweep makes either one easy to hear as a note that fades away.