I suspect electronic.
Lower frequencies travel farther.
An electronic siren at it's lowest frequency (bottom of it's wail sweep)
is still putting out full volume.
An electromechanical at low frequency is not pulling in as much air and therefore it's volume is decreased.
Also, in electronic, most sound energy is projected forward.
Electromechanical sound is dispersing in most directions.
CP-100 speakers seem best at projecting lower frequencies.
Followed by TS-100 with shorter exponential pathway, then the compact speakers.
Though the Whelen wide flat speaker has a remarkably long exponential path, 3+? feet!!!, it seemed to be least efficient at projecting sound.
Any thoughts?