I have one KM750, with a 4ohm sub connected to it in bridged mode. I just know the voice coil gets hot, as evidenced by the cap feeling really warm. If I don’t drive it hard, it’s normal. Wife is at the beach, so I’ve been rocking out. On a whim, I touched the woofer dust cap, and was concerned by how hot it was. I don’t want to cook my beloved subwoofer. The new Royal Blood album is a subwoofer workout.