1. Fed Sig CP100 (hands down)
2. Fed Sig AS124
3. Any speaker with a big cone.
4. Feniex Triton
5. Whelen SA315P
The old adage "bigger is better" is SO TRUE when it comes to siren speaker cones. Just think of the big cones used to project a person's voice at cheer rallies before amplifiers were made...... a person could simply talk and be heard across the gym. It's the same principle... the longer and larger the cone, the better it will project sound. Period.
Think about it.... the sirens on fire trucks and ambulances in the old days were only 58 or 100 watts.... yet they were LOUD. Why? Speakers. Speakers could be mounted outside on the bumpers with no obstructions (still my preferred method and they way my patrol car is), and had large cones. Current manufacturing has overcome some of the shortcomings of having a reduced bell, but nothing can fully make up for smaller cones. Due simply to room restrictions, I run dual Tritons behind the honeycomb area on my '15 4Runner and they do fine... not spectacular, but acceptable (also running a Touchmaster Delta on one and a Powercall on the other).
You just cannot make up for cone (i.e. projection) loss. If ever I put a grille/brush guard on my 4Runner (which I do see happening in the future), I will go back to "long cone" speakers on the outside of the grille.
Over the last couple of weeks, I have done some very informal testing, and have compared the AS124, Whelen SA315P, the Feniex Triton, and the Feniex Typhoon..... all on the same siren (Touchmaster Delta), and all at a distance of about 175 yards..... the AS124 was the loudest, then the Triton/Whelen (some argue these and the #2/#3 placing), and the Typhoon came in last; with sound loudness between each speaker being considerable. This was the consistent result of numerous tests involving numerous different people.