Single vs dual resonator?

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I'm trying to figure out what the extra resonator does vs the single one I had on my rusted out one.

 

Make it sound less raspy? My macro camera has to charge but in the chamber it all has baffles inside in both chambers.

 

http://img.photobucket.com/albums/v77/SubaruWRX/Photos/IMAG0110.jpg

 

The 2nd cat was for my 95 Legacy as seen in my avatar but I totaled that car year before last so it's sat in the box unused (well I kinda made it into a HFC) I'm going to throw it on just to see how it is.. It's a Bosal and the center pipe is a walker, funny the Stock subaru gasket on the 2nd cat did not really fit at all.. I had to get a little creative with it.