I have 2 Alpine type R 12's. I installed them in a box. I lightly tapped the plastic part of the cone near the surround with my finger. (your asking why and I can't tell you) In doing so, as I moved around the speaker at one spot the deep thud sound became a clearer, more plastic higher pitch sound. The other speaker sounded fine all around. When I fired them up I could not hear any distortion, but a lot of things were buzzing one these bad boys staarted up. My thought was that the plastic was separated form another ply of paper on the back sid eof the cone at that spot and was defective. Any thoughts on what it is and what to do. I bought these on ebay, NEW.
do a close visual exam of the speakers side by side. front and back look for any deformities or issues in construction. while the subs are in the box, push teh cones in evenly (not with pressure at jsut one side. that's a bad idea) and see if the cones come back out equally, at the same speed, and without any scraping sounds or freezing up. also try using a DM to test DC resistance at each pair of coils to make sure the subs don't have a damaged coil somewhere.
GlassWolf as always, good advice. I did try placing light even pressure on the speaker and noticed no scraping. When I fired them up for the first time I had the box outside of the car to hear them with no distortion from the trunk vibration. they sounded fine. My concern is that there is a slight delamination between the two cone materials in one spot that may increase with time long after the warrantee expires. Of course, if you were to visually inpect the speaker or listen to it it looks and sounds fine. That's today. Do I have a leg to stand on if i inform either Alpine or the person i bought them from of a possible problem now and giving them the option of replacing it?