[P-90]

Let me bore you with a little math to clarify what I meant.

I'll start by defining an acoustical watt; this is the amount of sound your speaker would make with 1 watt of input, if it were 100% efficient. A typical guitar speaker is between 2-3% efficiency, so expect it to take 30-50 watts of amp power to make one acoustical watt.

For a 12" speaker to make one acoustical watt at 1000 Hz, the cone has to be able to move forwards and backwards about 1/200th of an inch. Does this sound challenging? Not at all. To produce one acoustical watt at 80 Hz, it has to be able to move forward and backwards by over half an inch. This is not just challenging, it is impossible without breaking the speaker; to take a look at the Eminence Tonker (12", 150 watts, 300 watts peak), for example, its maximum cone excursion ("Xmax") is 0.8 millimeters, or about 1/32 of an inch. So it would be physically impossible for that speaker to produce over 1/16 of an acoustical watt at 80 Hz without bottoming out or breaking.

At 3% efficiency, 250 watts would translate to 7.5 acoustical watts per speaker. To produce that level at 80 Hz, the cones would need to be moving forwards and backwards by almost 4 inches!

So that's the problem, you see. It may be a 400 watt speaker at 1 KHz, but at the fundamental frequency of low E, no 12" guitar speaker can handle much more than 10 or 15 watts. The cones just can't move that far.