Car Audio
Subs, amps, wiring & SPL
Subwoofer Box Designer
Sealed, ported, T-line, or bandpass — pick your geometry and get net volume, port length, and tuning.
Open →Ohm’s Law
Solve any two of V, I, R, P for the other two.
Open →Speaker Wiring & Impedance
Compute the final amp-facing load for multi-driver setups.
Open →SVC Wiring (Multi-Amp)
Detailed Single Voice Coil wiring for multi-amp arrays. Shows every valid configuration.
Open →DVC Wiring (Multi-Amp)
Detailed Dual Voice Coil wiring — every valid coils × subs configuration with final impedance.
Open →QVC Wiring (Multi-Amp)
Detailed Quad Voice Coil wiring (4 coils per sub) — every valid configuration with final impedance.
Open →Amplifier Power
Output voltage, current draw, wire gauge, and fuse size.
Open →Port / Vent Length
Given a target tuning and box volume, returns the port length needed.
Open →SPL / dB
Estimate SPL from speaker sensitivity, power, and distance.
Open →Wire Gauge & Current
Pick the right AWG from total watts, voltage, and run length.
Open →Capacitor Sizing
Recommended farads — and when a battery upgrade is the better fix.
Open →Why these numbers matter
Are these accurate enough to build from?
They use the same formulas the trade does — Thiele/Small for enclosures, voltage-drop tables for wire, load math for charging. Treat the output as a starting spec, then sanity-check against your gear’s manual before you cut wood or crimp lugs.
Do I need an account?
No. Every calculator is free and works without signing in. A free account saves your results so you don’t re-enter numbers at the next show — and gets you partner discount codes.
Why does the alternator calculator recommend so much output?
Alternators make their rated amps at cruising RPM, not idle — output can drop 30–50% sitting still. Since that’s exactly when you’re demoing in a parking lot, the math sizes for idle reality.
A capacitor is cheaper than a battery — why does it say otherwise?
Caps handle millisecond transients; sustained bass draw is a reserve problem. That’s stored energy, which means a battery. The capacitor calculator says so out loud rather than selling you the wrong part.
Want the reasoning behind the math? Read the guides — or find a show to go put the build to work.