With all due respect, and for sake of friendly discussion, i believe the view of the screws on those 604E's is obfuscated by lighting and camera angle.

I know of no other way to secure a 604C and beyond horn than those 2 bolts/screws that secure the horn to the pole piece of the woofer motor.

I suppose there's room for the screws to be on a flange external of the horn throat and hidden by the dustguard, but i cannot recall seeing that in a factory C, E, G horn.

With the later style Urei horns, you cannot see the screw from the front as they are covered by foam.

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