The "Oscillating" design of the Whelen rotators allows the loudspeaker array to be hardwired to the amplifiers at the base of the pole. Brushes and collector rings such as those used by the Federal EOWS sirens oxidize and corrode, and need maintenance. The brush-and-collector-ring system i...

There are fiberglass techniques which do not produce that rough outer texture, but they produce a product which is inferior structurally. The Whelen horns are hand-laid fiberglass, which produces one finished side and one rough side. A mat is laid, and then resin is brushed on in several coats, the ...

Actually, those sirens are fed with a signal that's very close to a sinewave. They operate at such high levels that they make nearly 10% distortion but it's still very nearly a sinewave fundamental which is the only part of a siren's sound that carries. There is no good reason why a sinewave fundame...

Whelen's electronic sirens use horns that can have significant pattern control in the vertical plane, which may be easier on the ears of anyone standing below the siren.

It seems to me that from a horn design standpoint, that horn is long enough to be an effective quarter-wave resonator down to at least 45 hz, if not lower. It's way too long to be a siren horn, so I think it's actually intended to produce low frequencies. I think the mouth is not large enough for th...

That array of speakers is really strange-looking. I wonder how well it works at ground level. I think those would be Community M4 compression drivers, though, with horn throats that size. If they are M4s, then that array should be capable of doing something like 150 dB @ 1m!