eps = 0.01;
infty = 100;

wall = 1;

slot_off_x = 8;
slot_off_y = 8;

slot_l = 30;
slot_depth_front = 6;
slot_depth_rear = 2;

hole_h = 20;
hole_d = 1.5;
hole_step = 1.8*hole_d;
n_holes = 3;

base_angle = 5;

hole_side = 2*wall;

module horn() {
	difference() {
	hull() {
		// base
		rotate([0, 0, base_angle]) {
			translate([slot_off_x, slot_depth_front-eps, 0])
				cube([eps, eps, wall]);
			translate([slot_off_x + slot_l - eps, slot_depth_rear-eps, 0])
				cube([eps, eps, wall]);
		}

			for (y = [1:n_holes]) {
				translate([0, hole_h -(y-1)*hole_step, 0])
					cylinder(r = hole_d/2 + hole_side,
						h = wall, $fn = 6);
			}
		}

		for (y = [1:n_holes]) {
			translate([0, hole_h -(y-1)*hole_step, -eps])
				cylinder(r = hole_d/2, h = wall + 2*eps, $fn = 6);
		}
	}

	// slot
	rotate([0, 0, base_angle]) hull() {
		translate([slot_off_x, 0, 0])
			cube([eps, slot_depth_front, wall]);
		translate([slot_off_x + slot_l - eps, 0, 0])
			cube([eps, slot_depth_rear, wall]);
	}
}

horn();