You might also want test by removing the driver to see if the leads on the driver are too long. If so this will cause the cone to make contact with leads, thus making that "popping" sound.

Good Luck!

Tom

M80's VP150 QS8's Earthquake SuperNova MKV-15
Integra DTR-7.4 Outlaw 755 Outlaw M200's Outlaw ICBM