speaker cables are manufactured with the highest grade materials in the industry. The copper wire is rated in AWG spec which stands for "American Wire Gauge". The AWG rating was developed by the USA as a result of some wire manufacturers stating their wire was a certain spec when it really wasn't. You'll notice most imported wire and cable manufacturers will rate their wire in "G" or Gauge (not AWG). The "G" rating can be used for any wire size.
For example: A 12G rated cable may only be equivalent to a 18AWG cable (or worse). There are no regulations or specifications on "G" rated cables. How can you determine if a "G" rated cable is the same spec as an AWG cable? Unfortunately, you can't unless you test the power loss per foot. Sometimes the weight may be an indicator.
For example: 50ft 12AWG cables weigh about 4lbs whereas most of our competitors weigh about 2.5 lbs. This may be a result of the copper wire gauge not being true AWG.