I inetend to changeout the factory horns, and replace with Hella's, but are the horns on my 2007 A4 Q???

 

They are located behind the bumper skin, you have to take it off.
Its pretty easy, remove the belly pan, remove the front wheels and pull the fender liners back and remove the nuts holding it on (2-3) on each side, then pull out the lower grilles and you should see a large allan bolt going straight upwards through the bumper beam, pull those out and it should come right off.
The horns will be right behind it.

 

Thank you - but that doesn't sound so easy! I've done lots of work on cars, but I don't have a lift.

Perhaps I'll pay an AUDI tech to do it for me.

Thanks again.