A:Answer400W RMS or 400W Peak? 400W RMS would be more for a subwoofer and you should run 12AWG wire for those. 400W Peak which will be about 100-150W RMS (continuous and what really matters, peak is an advertising gimmick and means absolutely nothing), you’ll be perfectly fine with 16AWG copper wire. Make SURE you are getting COPPER wire because there is a PLETHORA of cheap CCA (Copper Clad Aluminum) wire on the market today and there are no disclaimers or warnings on the packages. CCA can only flow about 20% of what copper can for the same gauge! Also be careful of the terminology “AWG” and “Gauge” or “Ga”. AWG is what you want. Gauge/Ga is a junk Chinese standard. This wire is AWG even though the packaging states “Gauge” but that’s because quality companies haven’t caught up with the fact that cheap companies are cheating with sub-par standards!
A:AnswerIf this were 100% oxygen free copper it'd be well over $100 for 25ft of wire. They say "copper material" for legal reasons due to the fact that it's insulated, and how the manufacturing of copper materials works. What's deemed "pure copper" rarely (if ever) is and is commonly mixed with a small amount of a compatible metallurgic material depending on application. This is what's known as "copper grading" or UNS.
You can read more about it here if you'd like and are the inquiring mind that's eager to learn.
Copper doesn't have to be "100% pure copper" to be oxygen free. OFC alloys do exist.
https://www.totalmateria.com/page.aspx?ID=CopperGrades
