If you set a crossover does the drop off start at the frequency you chose or the next octave? For example you set a lpf with a 12db slope at 80 hz for your sub will it be minus 12 db at 81 hz? Or will it start dropping off at the next octave which is 160 hz?
At the frequency you choose for the crossover, assuming we're discussing active crossovers, the level is attenuated 0 dB. One octave higher the level is attenuated the amount of the slope. In your example the output is 12 dB lower at 160 Hz. This is why 12 dB slopes are not desirable for subwoofers, because it will be playing audibly well into the midbass region.
I thought a crossover can be any slope? Well I guess what Im trying to ask is when does the crossover start cutting your speakers output? Is it the next octave or does it start right at the crossover point?