Subwoofer Placement Calculator
Enter your room, seat and one to four subs. See your room modes, how each reaches your seat, the predicted bass at your seat, and layouts to try.
5.5 by 7.5 by 2.8 m room: the lowest modes are 22.9 Hz along the length, 31.2 Hz across the width and 61.3 Hz floor to ceiling. With one sub (front-left corner), 3 of the 15 modes below 80 Hz reach your seat strongly and 10 hardly at all.
One seat in a rectangular room with floor subs. Sub models, gain, delay, polarity, more seats and other room shapes are in Cinema Designer. Damping is an assumption, not measured room decay.
Light: the mode is loud there. Dark: a null.
Response at your seat
Calculating for your numbers…
Rigid rectangular room, uniform damping assumed, ideal subs, relative level, not calibrated SPL. Ticks along the top are the room's axial modes: W width, L length, H height.
Arrangements for one sub
Moving a sub changes which modes it drives: a mode cannot reach your seat from a sub sitting in its null. The layouts are not ranked; keep a curve and compare.
Room modes
| Frequency | Mode | Kind | At your seat | From the subs | Reaches your seat |
|---|---|---|---|---|---|
| Length 10,1,0 | axial | 0.06 weak | 0.99 strong | weak 0.06 | |
| Width 11,0,0 | axial | 0.00 weak | 0.99 strong | weak 0.00 | |
| Width 1, length 11,1,0 | tangential | 0.00 weak | 0.98 strong | weak 0.00 | |
| Length 20,2,0 | axial | 0.99 strong | 0.98 strong | strong 0.97 | |
| Width 1, length 21,2,0 | tangential | 0.00 weak | 0.97 strong | weak 0.00 | |
| Height 10,0,1 | axial | 0.33 partial | 1.00 strong | partial 0.33 | |
| Width 22,0,0 | axial | 1.00 strong | 0.96 strong | strong 0.96 | |
| Length 1, height 10,1,1 | tangential | 0.02 weak | 0.99 strong | weak 0.02 | |
| Width 2, length 12,1,0 | tangential | 0.06 weak | 0.95 strong | weak 0.06 | |
| Length 30,3,0 | axial | 0.19 weak | 0.95 strong | weak 0.18 | |
| Width 1, height 11,0,1 | tangential | 0.00 weak | 0.99 strong | weak 0.00 | |
| Width 1, length 1, height 11,1,1 | oblique | 0.00 weak | 0.98 strong | weak 0.00 | |
| Width 1, length 31,3,0 | tangential | 0.00 weak | 0.94 strong | weak 0.00 | |
| Length 2, height 10,2,1 | tangential | 0.33 partial | 0.98 strong | partial 0.32 | |
| Width 2, length 22,2,0 | tangential | 0.99 strong | 0.94 strong | strong 0.93 | |
| Width 1, length 2, height 11,2,1 | oblique | 0.00 weak | 0.97 strong | weak 0.00 | |
| Width 2, height 12,0,1 | tangential | 0.33 partial | 0.96 strong | partial 0.32 | |
| Width 2, length 1, height 12,1,1 | oblique | 0.02 weak | 0.95 strong | weak 0.02 | |
| Length 40,4,0 | axial | 0.97 strong | 0.91 strong | strong 0.88 | |
| Length 3, height 10,3,1 | tangential | 0.06 weak | 0.95 strong | weak 0.06 | |
| Width 2, length 32,3,0 | tangential | 0.19 weak | 0.91 strong | weak 0.17 | |
| Width 33,0,0 | axial | 0.00 weak | 0.91 strong | weak 0.00 | |
| Width 3, length 13,1,0 | tangential | 0.00 weak | 0.90 strong | weak 0.00 | |
| Width 1, length 41,4,0 | tangential | 0.00 weak | 0.90 strong | weak 0.00 | |
| Width 1, length 3, height 11,3,1 | oblique | 0.00 weak | 0.94 strong | weak 0.00 | |
| Width 2, length 2, height 12,2,1 | oblique | 0.33 partial | 0.94 strong | partial 0.31 | |
| Width 3, length 23,2,0 | tangential | 0.00 weak | 0.89 strong | weak 0.00 | |
| Length 4, height 10,4,1 | tangential | 0.32 partial | 0.91 strong | partial 0.29 | |
| Width 2, length 42,4,0 | tangential | 0.97 strong | 0.88 strong | strong 0.85 | |
| Width 2, length 3, height 12,3,1 | oblique | 0.06 weak | 0.91 strong | weak 0.06 | |
| Width 3, height 13,0,1 | tangential | 0.00 weak | 0.91 strong | weak 0.00 | |
| Width 3, length 1, height 13,1,1 | oblique | 0.00 weak | 0.90 strong | weak 0.00 | |
| Length 50,5,0 | axial | 0.31 partial | 0.87 strong | partial 0.27 | |
| Width 1, length 4, height 11,4,1 | oblique | 0.00 weak | 0.90 strong | weak 0.00 | |
| Width 3, length 33,3,0 | tangential | 0.00 weak | 0.87 strong | weak 0.00 | |
| Width 1, length 51,5,0 | tangential | 0.00 weak | 0.86 strong | weak 0.00 |
Showing 36 of 144 modes, 20 to 120 Hz.
Why subwoofer placement matters
This subwoofer placement calculator answers one question: where should the sub go in your home theater or home cinema room, and what do the room’s modes do at your seat? Below roughly 80 Hz the room dominates. A room mode is a standing wave that is loud in some places and almost silent in others, so the same sub can boom at one seat and vanish at the next. Where you put the sub decides which modes it excites, and where you sit decides which you hear.
The table lists every mode from 20 to 200 Hz. For each it gives how loud the mode is at your seat, how strongly your subs drive it, and whether it reaches you. The chart shows the predicted response at your seat for the layout you choose, from the same solver the Cinema Designer uses.
One sub: corner, quarter-points and the centre
A single sub in the front corner couples to three boundaries and makes the most output, and it drives every mode, peaks and dips alike. In the default 5.5 by 7.5 by 2.8 m room it excites 3 of the 15 modes below 80 Hz strongly at the seat. A sub on the front wall at a quarter-point skips the modes that have a null there, and one at the centre of the front wall skips the odd width modes. The classic advice to walk the sub around the room, the sub crawl, is a way of finding which position drives the modes you want.
Two, three and four subs
More subs help by cancelling modes rather than adding level. Welti and Devantier (2006, JAES 54(5)) compared layouts for several seats. Two subs at the front quarter-points cancel the first width mode, two at the front and back wall centres cancel the first length mode, and four at the quarter-points of the front and back walls cancel both. The four mid-wall layout is among the smoothest. Pick a count, then try each layout and keep a curve to compare.
Where you sit matters as much
The same modes are heard differently at each seat. A seat at the middle of the room length sits in a null of the first length mode, and the centre line is a null of every odd width mode. In the default room the first length mode reads 0.06 at the centre seat and the first width mode 0.00. Move the seat a metre and the table changes. A layout that looks smooth at one seat can be worse at another, so set the seat to where you sit most.
What this calculator assumes
The room is a closed rectangle with rigid walls and the subs are ideal point sources on the floor, equally driven. Damping is the designer’s assumption of 10, 20 or 40 per second, not measured room decay, so the curve is relative and not calibrated SPL. The tool does not model sub models, gain, delay, polarity, EQ or more than one seat, and a room larger than the engine’s browser budget shows the modes without a response.
When to go further
The Cinema Designer takes the same room, seat and subs and adds sub models, gain, delay and polarity, every seat in the room, and RP22 bass headroom. Continue there with this layout already in place, then confirm the result with a measurement. For the room’s modes on their own, see the room mode calculator.