You guys are making me curious, need to go to garage now to check! This is like CSI business you manage and I couldn't even spot the 2 (vanished or what) tweeters of my H/K system at the rear (there are only 2 speakers in my car at the back, should be 4) and after a basically fruitless Forum thread and a tiresome internet search, an audio shop technician told me listening some music in the car that "there are definitely tweeters inside those speakers at the rear parcel shelf" which I took it as it is and now I am counting them 8 visible and 2 not-visible, total of 10 speakers as it should be
