# DIY Audio & Video

## L-Pad (Driver Attenuation Circuit) Designer / Calculator Help

L-Pads (Loss Pads) are used to decrease the output level of a driver. This is useful in a multiple driver system where the drivers do not have the same sensitivity. A L-Pad, or driver attenuation circuit, can be used to decrease the output levels of the louder driver to match, or attenuate, the sensitivity of the less sensitive driver. Note that when this is done you are decreasing the power that the entire system will deliver.

An L-Pad is simply 2 resistors, one in series (R1), and one in parallel (R2) with the driver.

Z = Total Driver Impedance in Ohms

A = Required Attenuation in -db

Example: Say you have a two way system with a 8 Ohm horn tweeter with a sensitivity of 97 db and 100 Watt power handling and a mid with a sensitivity of 91 db. You need to lower the output of the horn by 97 - 91 = 6 db. Using the above formulas where Z = 8 Ohms and A = -6 db you get results of R1 = 3.99 Ohms and R2 = 8.04 Ohms.

Important: Please read the end of the Basic Electronics page for information on required wattage ratings of resistors. Be sure the resistors you purchase meet the power handling (Watt) requirements of circuit.