I am running a 2ohm 15" Kicker L7 with a RF800.2 and recently blew the sub. A friend of mine told me it's because I don't have a sub-sonic filter? What should I do to prevent from blowing another sub with my setup?

 

The only alternative to the filter is to run a sealed box.

 

kicker requires a subsonic filter on the ported boxes. it is stated in the manual.

 

where can I get one or what do you recommend?

 

some amps have them built in or you can buy a crossover unit that has one.