Amp wattage with 1x12 question

[nigelpkay]

I just picked up an ISP G112 ported 1x12 cabinet. It’s really great so far, light to carry and can get as quiet or loud as I need. It has an 8-ohm G12T-75 speaker that sounds great in this enclosure.

I bought it primarily to use with my ISP Theta preamps and Stealth Pro poweramp.
However, my Marshall 2203X sounds great through it too, so my questions are:

1) How much wattage is a 2203 putting out at low home volume (nothing above 2). I know the G12T-75 is considered hard as nails, I just want to know how far I can go without getting scared of damaging it.

2) Now the real stupid noob question... I like to run my preamp pedals into the FX return of the 2203X. When you do this, it bypasses the internal preamp and all the knobs on the Marshall don’t do anything except the presence knob.
Is my preamp pedal volume level now the “master volume” and at low volume I’m still at low wattage kicking out, or is the master on the Marshall now considered “wide open” (cuz it gets super loud real quick if you are not careful where your preamp level is when you turn it on, ask me how I know ) The amp isn’t kicking out full 100 watts to the speaker in this case right? The wattage/volume is still being controlled by my preamp level I’m feeding it?

 

[cardinal]

At low volumes you're good all around. It would need to be pretty darn loud to push 75 watts of actual output.

And I suspect the power amp alway is "wide open." The master volume probably just limits the preamp signal that goes to the power amp; same as with your pedals into the loop.

 

[Markedman]

Two things I've done that make a speaker stop. Heat from being too loud for too long and a sudden excursion (asshole drummer using the mic as a drum stick!) A sudden microphone stuffed into the monitors or super loud feedback through a guitar to the point the speaker melts should be experienced at least once in life. You'll remember the speaker crying right before it stopped emitting sound. The guy from scumback speakers knows this sound well in my imagination.

It's a fine line between the speaker doing it's thing and blowing up. I've blown more EVM12L & M's than 1960's green backs. That's when the EVM's were 5X the price and green, cream and black back's were frowned on for metal, well I guess they still are.

I'm jealous of you guitar players who can walk into a bar and not have the owner tell you to turn it down before I've even played a single note.