What do two crossovers add up to?

[chillin 10+ year member]

Kinda of a weird question, but im curious what happens when an amp crossover and a HU crossover is used in conjunction. Say your amp crossover has a 12db slope and your HU has a 12db slope and they are both set to 80hz. Do you end up with a 24 db/octave or is there some mathematical equation makes it higher or lower.

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[Rich B 5,000+ posts]

In theory two 12db crossovers would result in a 24db crossover, but its not a good idea mainly because theres no way to make both effect the exact same crossover frequency, so it ends up smearing the sound.

 

[RAM_Designs 5,000+ posts]

A lot of sq people use a dual crossover setup with their subs. Say, a 12db slope at 63hz on their HU, then set the amp crossover at around 120hz to kill the stuff higher than that(frequencies and slopes will vary with install, but you get the idea). This is mainly done to still have the smooth rolloff of a 12db slope, yet be able to decide where to steepen it and avoid whatever area you do not want any volume coming from. I need to tinker around with that idea, as I'm only using a 12db slope at 63hz right now.

 

[chillin 10+ year member]

I dont use both, it was more of a theoretical question. But curious as to why it would smear the sound.