i recently bought a used ampeg svt 15 cab to use as a practice cab with my svt classic head. the thought was to eliminate having to drag the 8x10 around just for rehearsals. will it harm my amp to play through this 8 ohm cab with my head at 4 ohms? we're not talking major volume here, rehearsal volume is usually set around 2 to 3 on the head. thanks in advance for any replies.