It is important to know the distance between your receiver or amplifier and speakers; longer distances can cause significant power loss, and thus require thicker cable. The distance of your run is how you will decide what gauge speaker wire you will require. For multi-room installs, it may be beneficial to buy two different gauges. A thicker gauge for the longer runs and a thinner gauge wire for your shorter runs. If you are using an installer, he/she should be able to assist you in this calculation. Otherwise use a string from your receiver location to each of the intended locations of your speakers. Carefully pull the string along and doorframes, corners, or other obstructions in the intended wire path. Allow plenty of slack for the wire to take gradual turns, since sharp bends can impair performance and allow for a margin of error.
Gauge is determined by the thickness of a wire’s conductive copper bundle as standardized by the American Wire Gauge or AWG number. The lower the gauge the thicker the wire (or more copper) and the better capacity to pass the amplified audio signal. While clear jacket cable is suitable for most in-room speaker installations, if you are running wire behind the a wall or in a ceiling, you need to use UL rated Class 2 or 3 rated cable (CL2, CL3) to be in compliance with most building codes. Class 3 cables will not degrade in extreme temperatures because it uses an extra plenim sheath to protect the cable.
Now that you have determined the distance use the chart below to determine the gauge speaker wire you need.
Distance from speaker to amplifier________Gauge
Less than 40 feet__________________________16
40 to 120 feet_____________________________14
More than 120 feet_________________________12
CL3 UL rated speaker wire can be affordable, however I have seen the price vary by $500.00 for a 500 foot roll of 14 gauge wire. One of the most cost effective ways to keep your price down for a low voltage installation is to purchase your own speaker wire and speakers. Remember, installers are essentially resellers of goods and installers, so if they can make additional money from an install by selling you the speakers and the wire, they will. Its good business, however as an educated consumer, you will save money by being honest and straight forward upon the initial bid, that you have the speaker wire and speakers, you are strictly seeking an installation only bid.
I urge you to compare pricing.