5.1.2 Atmos · 20 × 24 ft
5.1 plus two overhead (height) speakers. Positions below assume the screen on the 20 ft wall, a main seat 14.9 ft from it, and an 8 ft ceiling.
Speakers
7
+ 1 sub
Main seat
14.9 ft
from the screen wall
Front spread
50°
between L and R
Front distance
15.3 ft
ears to each front
Computed for a 20 by 24 foot room with an 8 ft ceiling and the main seat 14.9 ft from the screen wall.
Watch: One dimension is a whole multiple of another
length and height are close to a 3:1 ratio: every mode of the shorter dimension lands on a mode of the longer one. That doubles up modes at the same frequencies instead of spreading them out, which is the same problem a square room has in a milder form. Corner bass traps and careful subwoofer placement will earn their keep.
Watch: 71 Hz gets reinforced twice
The height and length modes both land near 71 Hz, so that note will be noticeably louder than its neighbours at most seats. This is the frequency to look for if the bass ever sounds like it has one favourite note.
Good: Front stage lands at 25°, inside the target
With the seat 14.9 ft from the screen wall, the front left and right fall inside Dolby's 22 to 30° window, giving a 50° spread between them. This is the one angle worth getting exactly right, and this room gives it to you without compromise.
Good: Height speakers reach 71° above ear level
That is inside Dolby's 65 to 100° window, so the overhead layer will sit properly above you rather than sounding like it is coming from the walls. Aim in-ceiling drivers at the main seat if they have pivoting tweeters.
Note: 3800 cubic feet needs real output
A room this size is past what one small sealed subwoofer can pressurise. Plan on two subwoofers or one large ported one, and pick speakers rated for the space rather than the cheapest that fit. Reference level in a room this big asks roughly four times the amplifier power of a 1,500 cubic foot room.
From the left wall (X), the front wall (Y), and floor to tweeter (Z). Mark these with painter's tape before mounting anything.
| Speaker | From left wall | From front wall | Height | Angle from seat | Dolby target |
|---|---|---|---|---|---|
| Front Left | 3.5 ft | 1 ft | 3.3 ft | 25° | 22–30° |
| Front Right | 16.5 ft | 1 ft | 3.3 ft | 25° | 22–30° |
| CenterDirectly below or above the screen, angled toward ear height. | 10 ft | 1 ft | 2.8 ft | 0° | 0° |
| Surround Left | 1 ft | 17.3 ft | 4.8 ft | 105° | 90–110° |
| Surround Right | 19 ft | 17.3 ft | 4.8 ft | 105° | 90–110° |
| Top Middle LeftTop Middle: nearly directly above, slightly in front of the seats. | 8.6 ft | 14.2 ft | 8 ft | 63° / 71° up | 65–100° up |
| Top Middle RightTop Middle: nearly directly above, slightly in front of the seats. | 11.4 ft | 14.2 ft | 8 ft | 63° / 71° up | 65–100° up |
| SubwooferStart in the front corner for maximum output, then run the subwoofer crawl to fine-tune. | 1.5 ft | 1.5 ft | 0.8 ft | n/a | n/a |
How we got these numbers
Surround formats are mixed for speakers at specific angles around the listener, so placement starts from the seat, not the walls. In a 20 by 24 foot room we place the main seat 14.9 ft from the screen wall (62% of the length), which keeps it out of the worst bass null at the room's centre and off the back wall.
From that seat, the front left and right are placed at 25° against Dolby's 22 to 30° range, side surrounds at 105° against 90 to 110°. Every speaker in this layout reaches its target angle without being pushed into a wall, which is not true of every room this size.
This room's first length mode is 24 Hz and its first width mode is 28 Hz, with a Schroeder frequency around 121 Hz below which the room behaves modally rather than statistically. Two of those modes coincide within 5%, so expect a pronounced peak rather than an even response. Start the subwoofer in a front corner and run the subwoofer crawl to smooth those modes at the seat.
Common questions
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Surrounds or a small-room stereo pair on a budget
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Front left/right in medium to large rooms
A three-way tower that measured within roughly plus or minus 2 dB on-axis at Erin's Audio Corner with real bass extension to about 40 Hz, so it can play full range in a medium room. It shares drivers with Polk's flagship Legend series at a fraction of the price.
Center channel paired with Reserve R700 or R600 towers
The large center in the same Reserve series as the R700, using the same tweeter and Turbine Cone woofers so voices match the towers across the front stage. Sound & Vision found the Reserve system dynamic and immersive for its price.
Small rooms and music-focused systems
A compact 13-inch sealed cube that Audioholics found goes well beyond entry-level performance, with app control, parametric EQ, and clean 20 Hz extension. The natural pick for small rooms, music-first systems, or a pair on a budget.