those almost every time. I have the 90 enclosures in my Z with 6.5" Infinity Reference speakers. While they do sound very good, the rubber surround on the cones actually touches the underside of the interior trim (or whatever you want to call it). This means that when the bass notes are to loud, the cone binds on one side and the voice coil is knocked out of square to the magnet structure. Thus killing the efficiency of the speaker and possibly (on some speakers) damaging the voice coil. I've since gone with the adapter plates from ebay since they drop the speaker down about 3/8 of an inch which allows for proper cone travel.
Some speakers won't be bothered by this, most will. Just my experience.
