Don't think so, Fred. The adjustment goes down to 32 ohms. Of course, you've got to be sure that, on the other side, you don't go below the minimum combined resistance, but, other than that, you don't hurt anything. I can actually run one in line with 2 8 ohm cabinets at 8 ohms on a system that will run comfortably at a minimum of 2.
You can sure blow up a power amp if the load is less than the specs. The ohm dial is pretty handy and a way to protect the system if set right. Many times, I line out of the main PA into a Carvin keyboard amp and use the Hot Spot out of the extension speaker kack. then, I don't need to fool with the Ohm dial, just the main power on the Carvin. When I use the Carvin as a fill amp, i may need to raise the volume on the Carvin and increase the resistance via the ohm dial to get the monitor volume where I need it. Been using one on small jobs since the mid-80's. they last until the outside heat and sun deteriorates the plastic frame. I toss it and get another one.
[This message has been edited by captain Russ (edited 06-14-2008).]