And referring to the second question you answered, it seems that ACA/ASC took inspiration from a few Whelen sirens, the Quadren a specific example with its brackets and cell shape. The cells are just fatter; if you slimmed them down they would look like a Whelen
The Quadren has absolutely nothing
in common with a Whelen omni. Each quarter of a cell has 4 100-Watt drivers with a horn above and below the cell (meaning every other cell is a dummy). The intent was for the Quadren to be placed in sections, as seen in the ads posted on this site. The circular shape is a natural extension of creating a 360 degree horn. The Quadren shares absolutely no design similarities, besides an unavoidable passing visual similarity, with Whelen.