L-pad calculator

What an L-pad does

Tweeters are often several decibels more sensitive than the woofer they're paired with. An L-pad is a two-resistor voltage divider — a series resistor (R1) before the driver and a shunt resistor (R2) across it — that attenuates the driver to level-match it while presenting an approximately constant impedance to the crossover, so the filter tuning is preserved.

This calculator solves the standard L-pad relations for the target attenuation and load. To model the full crossover the L-pad sits in, use the crossover designer.

Sizing the resistors

Use non-inductive (wirewound or metal-oxide) resistors close to the calculated values. The series resistor dissipates real power, so give it headroom: enter the branch power above to get a conservative minimum wattage (≥2× the worst-case dissipation).