Cable Loss Estimator

ext, enter information about your amplifier. These specifications should be printed in the user manual or on a data sheet. Make certain you enter the correct output power and load impedance (Output rated into…). These two values are always specified in pairs. Then enter the amplifier damping factor. Next, enter the nominal impedance of your loudspeaker. Finally, select your wire gauge from the pull-down selector, enter the length of the cable between the amplifier and loudspeaker, and enter the capacitance per unit length in picofarads. You should be able to find the characteristic capacitance of the cable from the manufacturer’s literature.

The single most important piece of information on the right side of the calculator is the net power loss in the cable. This is a measure of how much of the amplifier power is dissipated in the cable, before it ever gets to the loudspeaker. The lower the power loss, the more power actually goes into making sound. For an 8-ohm loudspeaker connected to 40 feet of 18-gauge zip cord, the power loss is about ½ dB, which is neither audible nor significant, especially for an amplifier with high power output. So, from the standpoint of power transmission, 18-gauge wire is suitable for many home applications. But for longer cable runs, the losses can be greater and you should consider changing to a larger diameter cable.