12db or 24db octave?

what it means is that the slope of the crossover is steep than the 12 db. For each consecutive octave up or down depending on if it is set on high or low pass you will lose 12 db or 24 db depending on which one you buy. The 12 db is less abrupt than the 24db. Frequencies after (low pass) the crossover setting will be a little louder with the 12 db than with the 24. I hope this helps a bit.   

 There is usually a couple of differences in these amps, one is warranty for us in Canada, 1yr. vs. 2 yr. The second difference is the power supplies, the Power series amp has a larger power supply to handle difficult loads with more precision and capabilities. A 24db slope on the crossover is usually referred to as a brick wall filter, nothing gets by it that is not supposed to. Sound does not end magically at the crossover point, it is rolled of gradually, either at 12db per octave in this case or 24 db per octave. Imagine that you are doing stopping tests in a car. Car one takes 200 feet to stop from 100mph. Car two takes 150 feet to stop from 100 mph. Both cars do the same speed, both cars are identical, the only difference is the braking system, one can stop quicker than the other from the same point in which the brakes are applied. In this case the brakes are the crossover and as the sound is rolled off above or below the crossover point, which is the stopping line from 100mph. One of the guys, probably Dyohn will post up the tech side of it, but I'll let you get the basic understandings from this. I personally use 24db slopes on all of my systems designed for sq.Top Secret, I can tell you but then my wife will kill me.

Hey Rob.  Here's my technical input on this one;  You said it!    No need for anything else.

so go with the 24db then?

That would be a good move!Top Secret, I can tell you but then my wife will kill me.

A 12 db slope will let more upper bass content pass through.  A sub that fires directly into the listening environment is most likely to benefit from a 24 db/octave slope.