Is there a specific advantage of rotational sirens over omnidirectional sirens?

[archizackture]

Is there a specific advantage of rotational sirens over omnidirectional sirens? Since omnis spread maximum sound for 100% of the time and have fewer moving parts that can break, I just don't get why rotational sirens still have so much market share. Is there something more technical that I don't know about? Please shower your knowledge upon me.

[Brendan Ahern]

Basic answer is power. It takes a considerable amount of power to project sound in all directions. Which is why a 40v2t has a 40 horsepower motor, and a 2001 has a 6.5 horsepower motor. Yet both are similar in sound output. So to have an efficient battery backup siren, less is more. Same with the eclipse and the 508, and the t121 and t128.

[archizackture]

Basic answer is power. It takes a considerable amount of power to project sound in all directions. Which is why a 40v2t has a 40 horsepower motor, and a 2001 has a 6.5 horsepower motor. Yet both are similar in sound output. So to have an efficient battery backup siren, less is more. Same with the eclipse and the 508, and the t121 and t128.

I see, that makes sense. Thanks!

[Tuba]

Is this the same with electronic sirens?

[archizackture]

Is this the same with electronic sirens?

Based on my understanding of energy physics, I'm gonna say yes. It would still take more energy to broadcast a sound wave 360 degrees than to broadcast it 90 degrees.

[Snowcube]

With an omni siren, all sound is being pushed everywhere at once where as a rotating siren is only going to cover an area for something like 25% of the time. In a situation like severe weather with really strong wind an omni siren is preferable as more people are likely to hear it.

[DJ2226]

Is this the same with electronic sirens?

It's applicable to electronic sirens as well. Switching to electronic sirens you actually use less power in general since the tone generation is solid state instead of mechanical, and because of that electronic sirens aren't handicapped in the same way mechanical sirens are in terms of their ability to perform. You have a much easier time running big omnidirectional electronic sirens on battery power.

The biggest omnidirectional DC-powered mechanical siren on the market right now is the 16V1T-B, which is rated for a mile range and 129 dB. It's electronic siren counterpart would be the Whelen WPS-2910, rated for roughly the same spec. I've heard both, and they both perform about the same in the field. With that said, the 16V uses dual 8 HP 72VDC motors vs the 10 400 watt drivers and amps in the Whelen. It takes 6 batteries to run the 16V vs the 4 for the 2910. Once you go beyond that for omnidirectional mechanical sirens it becomes less practical. I have no doubt that the 40V1T will outrun a 2910, but now your're talking about a siren with a 40HP 208/240/480VAC motor. Not only are you stuck without the battery backup, now you're stuck with expensive 3 phase. Ultimately that is why Sentry never brought the 40V1T-B to production, at least officially anyway. It's not impossible for them to do it. Their 14 HP motor from the 14V-B can drive one of the siren's choppers, so they could very easily stick two of them together and make it work, but it would draw a hell of a lot of amps. That's what kept the siren from hitting the market to begin with. The rectifier, if the company they source theirs from even can supply one with the required output, would draw some serious amps on the line voltage side, and the batteries wouldn't take too kindly to it it either in a straight DC setup. If I had to guess they could develop a 96 VDC 14 HP motor to use in the siren. It wouldn't change the situation with the rectifier, but as a DC only siren it might take some of the heat off the batteries. Problem now is you have 8 batteries that are needed to run the siren. Even if the 2910 can't keep up in the field it now looks more practical and will cost less to maintain over the years, possibly less upfront as well, compared to the 40V1T-B.

The solid state property of electronic sirens also applies to rotating sirens. The ASC T-135 and a 560 Hz Whelen WPS-4008 will both hit 133 dB at 100 feet and get roughly 2 miles of range, but the Whelen can do it with 48VDC at 3200 watts vs the 72VDC 20 HP motor in the ASC. 4 batteries vs 6.