Capacitors tested in a real world enviroment

Often times when people experience headlight flashing on big bass hits, they'll be told by their local audio shop or friends to install a capacitor. The capacitor is a bandaid to the real problem, the cars electrical system is being taxed beyond what the factory wiring can handle! Dont believe me, read on for real world testing of power capacitors in a car audio system..


The Test System:


JBL W15GTi subwoofer

JBL A1201GTi 1200WRMS Monoblock

2x 900CCA batteries

0g wiring harness

Lightening Audio Competition Series 1.0 Farad Cap


Test Equipment:

Digital Multimeter

Goldline DSP-30 RTA


Test Method:

Amp hooked up to  CRO, gains adjusted @ 60 Hz until clipping, and then backed off. LP Xovers set to 80 Hz using CRO & DMM.

Engine idling @ 800RPM. Tests run with voltage on amp terminals showing @ 14.1V idle. 15 minutes cool down between runs.


Run some tones, find the "mad note" @ 51 Hz and commence testing.



No Rear Battery, No Capacitor.

Voltage on Burp: 12.8V (1.3V Drop)

Output: 140.7dB, 140.7dB, 140.6dB


No Rear Battery, 1 Capacitor.

Voltage on Burp: 12.6V (1.5V Drop)

Output: 140.5dB, 140.4dB, 140.3dB


Both Batteries, No Capacitor.

Voltage on Burp: 13.8V (0.3V Drop)

Output: 141.0dB, 141.0dB, 140.9dB


Both Batteries, 1 Capacitor.

Voltage on Burp: 13.2V (1.2V Drop)

Output: 141.0dB, 141.0dB, 140.9dB



The installation of a capacitor in a weak audio system leads to a LOSS of SPL. This is due to the capacitors nature of draining very quickly then increasing the electrical load on the system as it attempts to recharge. Hopefully these results will inspire you to avoid a capacitor and spend the money on a proper battery & large gauge cabling system