Cables and connections
OFC vs CCA
Oxygen-free copper is solid copper wire; copper-clad aluminum is aluminum with a thin copper skin that has about 60 percent more resistance.
OFC, oxygen-free copper, is high-purity copper and the standard for speaker cable. CCA, copper-clad aluminum, uses an aluminum core with a thin copper plating. It is lighter and cheaper, but the aluminum carries the current, and aluminum has about 1.6 times the resistivity of copper.
The gauge printed on a CCA cable therefore overstates its performance: 16 AWG CCA behaves roughly like 18 AWG copper, so length limits from the 5 percent rule shrink accordingly. CCA is also more brittle, corrodes at terminals, and crimps less reliably.
Buy OFC, or go up one gauge if you are stuck with CCA. Real OFC weighs noticeably more than the same spool in CCA, and reputable cable states the conductor material; unlabeled 'copper' at a suspiciously low price is usually CCA.