Subwoofer Array Spacing Calculator (Cardioid, Endfire)
Quick answer: Pick array type, enter center frequency, and number of subs. Get spacing, delay, and rear rejection.
Calculate spacing and inter-sub delays for cardioid, endfire, or broadside subwoofer arrays. Tells you how far apart to place subs, how much to delay them, and the expected rear-rejection in dB. Built for live audio engineers and PA system designers.
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Last reviewed: April 2026Report an error
Typical 60-80 Hz.
Spacing
1.36 m / 4.47 ft
Endfire: subs spaced 1.36m apart, each progressively delayed. Aims energy forward. Wavelength: 5.44m. Inter-sub delay: 3.97ms. Estimated rear rejection: 20 dB.
Spacing
1.36 m
Spacing (ft)
4.47 ft
Inter-sub Delay
3.97 ms
Rear Rejection
20 dB
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The Formula
λ = c / f ; endfire_spacing = λ/4 ; cardioid_spacing = λ/2
- λ = Wavelength at the center frequency (meters)
- c = Speed of sound (343 m/s)
- f = Center frequency to tune for (Hz)
- delay = Inter-sub delay (ms) = spacing / c × 1000
How to Use This Sub Array Calculator
- 1Pick array type: endfire, cardioid, or broadside.
- 2Enter the center frequency to tune for (typically 60-80 Hz for live sub arrays).
- 3Enter the number of subs in the array.
- 4Read spacing, inter-sub delay, and estimated rear rejection.
Frequently Asked Questions
- Endfire: subs in a row, all firing forward, each progressively delayed. Creates strong forward beam. Cardioid: pairs of subs (one forward, one rear-firing), rear delayed and inverted polarity. Strong rear rejection (~12 dB) but requires more subs.
- Most live PA arrays tune to 60-80 Hz — the kick and bass guitar fundamental range where directional control matters most. Below 50 Hz, subs are essentially omnidirectional regardless of array type.
- Math works for all subs. But results vary by sub type: front-loaded cabinets work best for endfire; horn-loaded subs are harder to predict. Always measure and tweak with software like Smaart.
- Endfire with 4 subs: ~16 dB at the design frequency. Cardioid: ~12 dB consistently across 50-100 Hz. Broadside: 0 dB rear rejection (broader pattern, no directionality).
- Stops bass from bleeding onto stage (fewer feedback issues, happier mix engineers), reduces neighborhood complaints (less low-end leaking outside venue), and improves clarity for audience members on the sides.
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