Monoprice 38177 Audio Control Device

This Impedance Matching Outdoor Volume Control allows you to connect multiple speaker pairs to a single power amplifier or receiver. It increases (or decreases) the impedance of the connected speaker pair to ensure that the overall impedance level presented to the amplifier is high enough to prevent damage to the amplifier. It can support amplifiers with up to 100 watts of output power and has a waterproof enclosure, allowing it to be used in outdoor applications.