Richard is correct. To supplement, attached are two pictures.
One shows an AC application, and I've pointed out the holes for a non AC application.
Also I included a non AC horn.
Note the different angle of the bracket. The AC app comes out of the horn at the 12 o'clock position, and the non AC app is roughly 2 o'clock. In both cases the horn "discharge" points down at 6 0'clock.