Whelen the manufacturer has also done very expensive testing and they would not engineer a bracket to mount it there if it was much of an issue. Theirs is also a 100w driver and most departments do not use a push bumper.
Whelen didnt have anything to do with that location, the engineers on the Police program decided it would go there.
Primary to them was crash and body integrity, ease of install by Chicago Mod Center, sound output was secondary.
The engineers said their threshold was meeting (not exceeding) California Title 13 Siren regulations. Which many use as a bench mark.
That's just a standard, not the best mounting location.
I stood there when this discussion was going on, this isnt hearsay.
Dual speakers on the forward pushbar are noticeably louder there is no comparison.
Make sure the siren unit is capable of pushing 200W, so 100W to each driver, then you will see the difference. Also a common mistake is wire the two 100W siren speakers in parallel. You need positive and a negative to each siren speaker from the siren amp. That's 100W per speaker. Some siren amps are only 100W rated.
We cut the wire off and run 4 new wires out to the pushbar where we have dual 100W Federal Signal AS124 speakers.