Speakers stop working

Probably blew up the speakers. Take an ohm meter (or multi-meter that measures resistance or go to your local RadioShack) and place the positive to the red wire and the negative to the black wire on the speaker. On the back of the speaker it will tell you how many ohms it is rated for (A number and then an Omega symbol) -- If the resistance is lower than the number on the speaker (typically 4 or 8 ohm) then you blew the speakers.

Let me know if they check out okay.

If they are indeed blown, make sure you install high-pass filters on the wires to prevent your bass from blowing up your new set.