Speaker help? stereo guru's

[jabartram]

I have the exact same speakers in my rear deck and my front doors, over this weekend my brother and i were doing some sound adjusting, pulling all the bass of the interior speakers. worked with the fronts, and am able to crank full volume, 35 on the volume scale they do get garbled, but i will adjust that out later, then we started working with the rear speakers, and at 32 they quit? until i shut off the system and turn it back on, so i swapped channels to make sure it wasn't the amp, it is the rear speakers, is it besause they are basically running free air? being in the rear deck? when they quit all i hear is a little crackling. they won't come back on when i lower the volume, i have to shut it off. i'm getting ready to purchase 2 sets of polk db6500's do i need to create an enclosure for them like the doors have? any advice?