Theater Calculators

TV mounting & DIY

Subwoofer Quarter/Eighth Space Placement Estimator

Each nearby large boundary can add about 6 dB. Floor only is half space (+6). Floor+wall is quarter (+12). A corner is eighth (+18). How smooth the response is at the seat is not included.

Inputs

Units

0 free, 1 floor, 2 floor+wall, 3 corner.

dB

Free-space level. Ground-plane review data already include the floor: count one boundary fewer.

Results

Boundary gain
12dB
Corrected SPL
102.0dB

The Result is indicative and educational. It does not constitute a design, a technical opinion or medical advice and does not replace calculations or verification by a person with the appropriate qualifications and authorisations. Before purchase, installation or use in practice – in particular in electrical installations – the Result should be verified by a qualified specialist. Details: Terms of Service, point 4.

Example products

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Calculation method

Gain = 6 dB × number of boundaries (0–3). Add to an anechoic SPL.

Exact formula

G = 6N, N ∈ {0,1,2,3}. Limits: infinite rigid planes, the driver well inside a quarter wavelength of each (about 1 m at 80 Hz), no room modes, no destructive interference at the seat.

Frequently asked questions

Is +18 dB real?

In a textbook eighth-space, toward 18 dB. In a leaky living room, less, and lumpy.

Dual subs?

Two locations beat one louder corner. This tool is one sub.

Raise it off the floor?

A short stand keeps most of the +6 dB, because bass wavelengths are metres long. Lift it a metre or more and the floor stops helping above about 343 / (4 × height) Hz, with a dip after that.

Add the room-gain result on top?

No. That estimator already adds its own, milder 3 dB per boundary. Use one model or the other.

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