They are usually read as 6db and 12db per octave. Every time a signal frequency (or music note) is doubled, it goes up by an octave. So going from 100Hz to 200Hz, you are increasing by an octave..going from 100Hz to 50 Hz, you are going down by an octave.

6db/octave low pass crossover will reduce the signal amplitude(peak) by half (or power by -6db), for every octave above the cut off frequency. So if your crossover is 'crossed' at 40Hz, an 80Hz note will be reduced to half of the amplitude of the 40Hz note.

12db/octave filter will simply double the rate of attenuation.

Simpler crossover such as a single cap and resistor will provide 6db roll off. For 12db or higher roll off, you need more complex crossovers.

This might help but the other replies are dead on the money. The link does not explain much but helps one build a crossover.

http://www.carstereo.com/help/Articles.cfm?id=55


Hope this helps.


HT-EXT