Voice coil 39.0mm (28.0mm, 2+2Ω, 4layers)

Copper has better electrical conductivity but is significantly heavier, which can increase the overall weight of the voice coil.

Aluminum wire is much lighter than copper, which reduces the coil's weight, but it has lower conductivity compared to others (to achieve the same resistance as copper coils, a thicker wire is required, which increases the outer diameter).

Copper-clad aluminum is lighter than copper, retaining aluminum's weight reduction benefits, and the copper coating improves conductivity compared to pure aluminum.