Audio Cable Loss, Resistance & Capacitance Calculator
Calculate electrical wire resistance, insertion loss in decibels (dB), high-frequency capacitance rolloff, and amplifier damping factor degradation across speaker, line-level XLR, and guitar instrument cables.
1. Cable Type & Conductor Gauge
2. Signal Loss & Frequency Rolloff
Understanding Cable Resistance, Capacitance & Damping Factor
Every audio cable exhibits physical electrical properties that interact with source and load impedances:
- Speaker Cables (Series Resistance & Damping Factor): In high-current passive speaker lines, cable resistance acts as a voltage divider against the speaker impedance. Excessive resistance reduces bass tightness because the amplifier loses the ability to electro-mechanically brake the speaker cone (damping factor degradation). Keep speaker wire resistance under 5% of the speaker load.
- Guitar & Instrument Cables (Capacitance Rolloff): High-impedance passive guitar pickups (5kΩ to 15kΩ) combined with high cable capacitance form a low-pass RC filter that rolls off treble frequencies above 5 kHz. Using cables longer than 20 feet without a buffer pedal audibly dulls guitar sparkle.
- Balanced Microphone Cables: Low-impedance microphone outputs (150Ω) can easily drive 300+ feet of balanced cable without treble loss or audible signal degradation.
Worked examples: what gauge and run length cost you
Four of the six gauges the calculator offers (12 to 18 AWG), driving an 8 Ω speaker, at three common run lengths. Loss is the voltage divider between cable resistance and the load. Damping factor is what the amplifier can still do to control cone movement once the cable is in the way, and below about 20 the bass stops sounding controlled.
| Gauge | Run | Round-trip R | Capacitance | Loss | Damping factor | Bass control |
|---|---|---|---|---|---|---|
| 12 AWG | 25 ft | 0.080 Ω | 750 pF | -0.09 dB | 66.7 | tight |
| 12 AWG | 50 ft | 0.160 Ω | 1,500 pF | -0.17 dB | 40.0 | tight |
| 12 AWG | 100 ft | 0.320 Ω | 3,000 pF | -0.34 dB | 22.2 | tight |
| 14 AWG | 25 ft | 0.125 Ω | 800 pF | -0.13 dB | 48.5 | tight |
| 14 AWG | 50 ft | 0.250 Ω | 1,600 pF | -0.27 dB | 27.6 | tight |
| 14 AWG | 100 ft | 0.500 Ω | 3,200 pF | -0.53 dB | 14.8 | soft bass |
| 16 AWG | 25 ft | 0.200 Ω | 875 pF | -0.21 dB | 33.3 | tight |
| 16 AWG | 50 ft | 0.400 Ω | 1,750 pF | -0.42 dB | 18.2 | soft bass |
| 16 AWG | 100 ft | 0.800 Ω | 3,500 pF | -0.83 dB | 9.5 | soft bass |
| 18 AWG | 25 ft | 0.320 Ω | 950 pF | -0.34 dB | 22.2 | tight |
| 18 AWG | 50 ft | 0.640 Ω | 1,900 pF | -0.67 dB | 11.8 | soft bass |
| 18 AWG | 100 ft | 1.280 Ω | 3,800 pF | -1.29 dB | 6.1 | soft bass |
The pattern worth taking away: signal loss stays under a decibel almost everywhere, so the number that actually decides your cable is damping factor. 16 AWG at 100 feet loses only 0.83 dB but drops damping to 9.5, which is audible as loose, slow bass long before anyone notices the level. Doubling the copper is cheaper than any other fix.
Capacitance barely matters at speaker level and matters enormously at instrument level. That is why the same 100 foot run is unremarkable between an amplifier and a cabinet, and unusable between a guitar and a pedalboard.
Working Vocabulary
Key audio electrical engineering terms:
- AWG (American Wire Gauge). The standardized wire gauge system where smaller numbers indicate thicker conductors with lower electrical resistance.
- Damping Factor. The ratio of speaker load impedance to the amplifier's internal output impedance plus cable resistance, determining speaker cone control.
- Capacitance (pF/ft). The electrical charge stored between two conductors per foot of cable length, creating high-frequency filtering in high-impedance circuits.
- Insertion Loss. The reduction in signal power level (measured in dB) resulting from the insertion of a cable or component into an audio transmission chain.