I am running a kenwood dx512 and DB571 they say the range is 52mhz-whatever
I am assuming if I use the preouts on my HU my high pass filter on the dx512 will no be used? So do I need to set the amp to HPF and turn the setting to like 60mhz or should I set it more like 80mhz?

Thanks just not sure how low the DB571's will take it.

 

The preouts on your headunit are all pass. Your radio will send out all frequencies played through it. Setting your door speakers to a high-pass system is dependent on how you like your sound. If you listen to your music loud, you may want to set it to high-pass. Play around with it at nominal volumes, you'll hear a difference. The higher you set your high-pass filter, the less bass you will hear out of your door speakers. Personally, I have my low-pass and high-pass on my headunit set to 80hz. That's just how I like it. Other people will tell you differently, others may tell you the same. Just play with it. Your Polks can take quite a beating!