All curent car audio HLCD's are designed to be mounted off axis (under the dash, parallel with the floor, firing at your shins). As Dukk mentioned, the horn couples with the bottom of the dash, and actually becomes an extension of the lense. It is quite important that both sides are symetrical, because all the sound travels up the dash, on to the listeners ears.
Now, some competitors have bent the rules a little (IE- Mark Elderidge, Larry Chijner, Jerry Ziegler, Patrick Gates, Jim Adams) and either mounted the horn in the top of dash firing up at the windshield, or on top of the dash firing right at the listener. In all casses the horns had very expensive compression drivers mounted to the lense, and very extensive mods/tuning. Mark E will be the first to tell you that mounting the horns on top of the dash is very challenging, and not for the faint at heart...
Anyway, here is a pic of the Veritas HLCD mounted in the traditional way under the dash in my car.
[ May 08, 2004, 10:51 AM: Message edited by: Kilowatt ]