great videos. thanks for sharing.The carpet you want is automotive carpet, you can buy that at any autoparts store, just ask for it. Its the same stuff they use for lining trunks and what not.
Check these videos: http://www.metacafe.com/watch/yt-Qb_hhu6nTX0/car_audio_tutorial_how_to_build_a_speaker_box/
http://www.icixsound.com/iv/view_video.php?viewkey=5a2e075a1a4a6e1b9770