I'm using an external speaker cabinet with a combo amp.The 1/4" plug in the back says use a min of 4 ohms because the internal speaker is parralled at 4 ohms. The cabinet I have is 16 ohms. Is this ok, or would it be best to change the ohms of my cabinet to 4? And if so, how do I change the ohms. The cab is a 4x10