The ATLSQ12D4, however, ditches the ATL12D2’s circular frame in favor of a square frame. In addition, the ATLSQ12D4 utilizes a 3” voice coil with a glass fiber former and aluminum cone neck reinforcement that supports 4 ohms versus 2. The ATLSQ12D4 also features a 1” tall rubber surround for larger excursion, a 140 Oz magnet, and a ported nickel plated back support.