Wayne Parham Messages: 18832 Registered: January 2001
Illuminati (33rd Degree)
The compression driver mounts onto the horn with a couple of 1/4-20 bolts that are spaced 3" apart. Each mounting bolt is 1-1/2" from the center. Some call this the "standard two-hole mounting pattern."
In the case of the B&C DE-250, you could use 1/4-20 bolts but they include a couple of studs and nuts with that compression driver so I personally always use 'em.