Can a fixed and variable LPF be used at the same time?

[GuyPanico]

The amp i'm looking to get has a 12db variable xover on it. To get a sharper rolloff could I also use a 80hz 12db LPF? I only ask because I have one laying around from parts express. Would there be adverse effects? Or would they simply work together as I suspect? Thanks guys!!

An externally hosted image should be here but it was not working when we last tested it.

 

[BassAwdyO]

I dont think a passive sub filter is really your best option be it variable or not! High slope is required and the losses in a passive crossover become high.

 

[simon5]

The signal will be attenuated first by the variable x-over so I guess he won't lose too much in power and heat.

If you use the variable x-over below 80 Hz or at 80 Hz, I'm quite sure you can use both. Check if the x-over can take some power and heat.