About CarsFM

What CarsFM Covers — and What It Doesn’t

CarsFM is a car-audio reference site built around six calculators, a set of guides, and a history museum. It covers the math that comes up when you’re planning or troubleshooting a car-stereo install: subwoofer enclosure volume and port tuning, amplifier power and speaker impedance, wire gauge and fusing, estimated loudness, and passive crossover components. It does not cover head-unit firmware, navigation apps, car insurance, or general automotive repair, and it is not a shop — we don’t sell speakers, amplifiers, installs, or anything else.

The site is independently run and pays for itself through display advertising, not subscriptions or gear sales. We are not affiliated with any speaker, amplifier, subwoofer, or head-unit brand referenced in a guide or calculator, and no brand sponsors a result. Every calculator produces an estimate built from established car-audio formulas and published driver or enclosure specifications — not a certified measurement — and your actual result depends on your specific gear, vehicle, and workmanship. None of this is professional installation or electrical advice: work touching amplifier fusing, grounding, or an amp’s minimum stable impedance carries real fire and equipment risk, so treat every number here as a starting point and have a qualified installer check anything safety-critical before you wire it in.

The Six Tools

Each calculator is built around one recurring install question:

• Subwoofer Box Calculator— net internal volume for a sealed or ported enclosure holding one or more subs, the port length that tunes a ported box to your target frequency, and outer cabinet dimensions once you set a panel thickness.
• Amplifier Power (RMS) Calculator— a recommended RMS range for the speakers you have, an under/matched/over verdict for an amp you’re considering, and how available power changes as impedance drops.
• Speaker Impedance Calculator— total load for speakers or voice coils wired in series, parallel, or series-parallel, including dual-voice-coil subs, with a warning when the result drops below what a typical amp can safely drive.
• Amplifier Wire Gauge Calculator— power and ground wire gauge (AWG) from an amp’s RMS output or fuse rating and the run length, with an estimated current draw and a suggested inline fuse.
• SPL (Loudness) Calculator— an estimated sound pressure level from a speaker’s sensitivity, power, and your listening distance, using +3 dB per doubling of power and free-field distance loss.
• Crossover Calculator— component values for a passive first- or second-order crossover, the tweeter’s high-pass capacitor and the woofer’s low-pass inductor, from your chosen frequency and driver impedance.

The guides go through the reasoning behind those numbers, and the blog covers car-audio topics in more depth.

The Museum

The Museum of Car Audio & Soundis a separate, browsable history of in-car listening — from the earliest car radios to the modern head unit, the anatomy of a system, the speakers and enclosures that shape how it sounds, and the electronics behind the signal. Its entries, images, and facts are drawn from Wikipedia and Wikimedia Commons; the museum is not affiliated with either project, and it’s meant for background reading, not as a source of new claims about specific gear.

If Something’s Off

If a calculator gives you a result that doesn’t look right, or a guide is missing a step you needed, the contact page is the place to say so.