Test was done in my parking lot.
The dB meter was 45' from the speaker in a straight line in front of it and at the same height.
The siren that drove the speakers is a new Federal PA300. 100W rating. Powered at 14.2V by an Astron.
Speaker#1- Federal Dynamax: 113dB at 45'
Speaker#2- Whelen SA314P : 118dB at 45'
Winner: Whelen.
The Whelen produces a "clearer" and more true sound than the Dynamax. To my ear, it's louder (which is why I even did this test to begin with). It's lighter and cheaper. It's also harder to mount with it's rear-mount design. They need side holes like the Dynamax.
I know- they is all kind of meter weighing and other technical aspects of dB measurement, but this was just to see which one used the driver power more efficiently.
Whelen SA314P vs. Dynamax
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Sorry, hang on. I just had to defib myself. Jim, I was expecting something ranting about the poor engineering and quality of a Whelen product. I'm shocked, literally!!!! 
Anyway, so how much of a difference is 113 vs 118 db? I've never had them side-by-side before.
I do like the plastic vs the metal. As far as mounting, I've found that any speaker has it's quirks depending on the vehicle. I'm sure there plenty of applications where the Whelen mount would be a lot easier than the federal and vis-versa
"I'll eat you like a plate of bacon and eggs in the morning. "
- Some loser on rr.com
eBay at it's finest:
Me: "What exactly is a 900Mhz UHF CB?"
Them: "A very nice CB at 900Mhz speed!"
- Some loser on rr.com
eBay at it's finest:
Me: "What exactly is a 900Mhz UHF CB?"
Them: "A very nice CB at 900Mhz speed!"
Mmmmm dB math... 
In dB:
+3dB = Double the electrical power
+6dB = Double the electrical voltage or four times the electrical power
+10dB = Approxiamtely double the perceived loudness or ten times the electrical power
The dB is simply a logarithmic expression of the relationship between two values. It is meaningless without an indication of the value and measurement units being used as a reference for comparison.
In the case of acoustical ouput, values are expressed in dB SPL (Sound Pressure Level), where 0dB SPL is assumed to be absolute silence, and 1dB SPL is assumed to be the smallest change in level that the human ear can differentiate.
Since there are very few sets of calibrated ears out there, the whole thing is a little bit arbitrary. Then there's the whole issue of wieghting and scaling...
I just hope I never have to run into that high school math teacher who I told that I didn't see why we were learning something as useless as logarithims.
In dB:
+3dB = Double the electrical power
+6dB = Double the electrical voltage or four times the electrical power
+10dB = Approxiamtely double the perceived loudness or ten times the electrical power
The dB is simply a logarithmic expression of the relationship between two values. It is meaningless without an indication of the value and measurement units being used as a reference for comparison.
In the case of acoustical ouput, values are expressed in dB SPL (Sound Pressure Level), where 0dB SPL is assumed to be absolute silence, and 1dB SPL is assumed to be the smallest change in level that the human ear can differentiate.
Since there are very few sets of calibrated ears out there, the whole thing is a little bit arbitrary. Then there's the whole issue of wieghting and scaling...
I just hope I never have to run into that high school math teacher who I told that I didn't see why we were learning something as useless as logarithims.