I think holler's original question was regarding two rotors and stators with the same port ratio, and whether it is better to have both rotors driven by the same motor or separate motors. In terms of achieving the highest acoustic efficiency, both rotors need to be synchronized (phase-locked), other...

Just to clarify according to the above question, I'm talking about any siren that rotates its beam of sound, whether the rotation mechanism is driven by the siren motor or a separate motor.

Here's an interesting question that came to me while watching test videos: what was the earliest model of siren to be sold that used a rotating beam of sound instead of omnidirectional propagation? Would it be the Mobil-Directo?

Thanks!

Arrested for what exactly? I wonder what the charge would be? if someone has a bug up their bum, I suppose they could hit you with something like disturbing the peace or disorderly conduct. Though I think in most locations that would be at worst a civil infraction (ticket) and not something that'd ...

I don't think you could overload a Thunderbolt without something like a very large (industrial) screw compressor. The first thing to happen would be acoustically overloading the throat of the horn with air turbulence. As the pressure increases, supposing there is unlimited flow available, eventually...

XRMTM9eOGLw I haven't seen this posted here yet, but here is Nashville's new siren ambience with the Federal Signal 508 and Eclipse-8 sirens. It's a great sound, and I'll bet these sirens are kept around in Nashville for a long time. This isn't my video, but I don't think the contributor posts here.

The best siren system design (though not necessarily cheapest) will include both rotating and omnidirectional sirens. Omnidirectional sirens have the benefit of acoustic summation between siren sites, so they can be used in town centers where it's important to deliver consistently high sound levels ...

Lol at the one comment on that video.

I suppose everybody wanted to be able to hear the sirens inside their houses.

If the amplifiers are the Class-D type, using a switch-mode output stage, they contain an output filter to remove the PWM carrier frequency (which would otherwise overheat the drivers with the superimposed but inaudible carrier frequency) and 'reconstruct' the output waveform from the modulated sign...