I tried posting this on the WGS forum but I think they may be having issues because it doesn't go through and they have had no new posts since 9/30. Sorry for the long post below but I'm trying to get all the info out there.
I have a 30 watt WGS Reaper paired with a 65 watt WGS ET-65 in a 2x12. They are both 8 ohm speakers wired in series for a total impedance of 16 ohms. This combo should give me a watt rating of 60 watts by multiplying the lowest speaker rating by the number of speakers, in this case 2x30 =60.
I've used this cab with 50 watt heads and my Class 5 without issue. I recently picked up a MOSFET 3210 with the matching 1966 cabinet. The amp works flawlessly through the 150 watt, 8 ohm cab. The MOSFET manual states that at 16 ohms the head will deliver 50 watts to the load (it is rated 100 watts into 4 ohms). My 2x12 is rated at 60 and is connected 16 ohm so I should be safe. It doesn't appear so. I hooked up the head and on the boost channel with the gain at about 7-8 and the master around 3, (loud but not house rattling)I started smelling something cooking. I shut down immediately and let things cool down. I did not detect the burn smell in the head so i assume it came from the cabinet. I hooked the 3210 to the 1966 and it worked fine. Then I hooked up my C5 to the WGS cab and both speakers are still working.
I've spoken with WGS and they think that the MOSFET might be delivering really high peak current and that is what caused the overload. I also emailed Marshall and they confirmed the output of the 3210 as 50w rms at 16 ohms. I really like the WGS combo with this amp but I'm afraid to connect back up to it. From the specs everything should be safe. Does anyone know of some checks I can do on the speakers? Am I missing something in my calcs? Any suggestions are appreciated.