Mister_Penetrator
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Pro's and con's between an electronic and mechanical siren?

Sun Jul 02, 2006 3:59 am

What are the pros and cons between the electronic and mechanical sirens? Also, what is the most powerful electronic siren?

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Whelen Rules
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Sun Jul 02, 2006 4:17 am

Both Mechanical and electronic sirens are good. Both can be heard for a good several miles depending on models and companies. Both the Whelen Vortex R4 and the T-128 can be heard for aproximatly 2 miles 3 in some cases primarily because the low tone travels further and penetrates better than say the high pitch of an ATI which does good for only a mile or less. The only problem with electronic sirens is they only last about 30 years(according to whelen) Where as a mechanicl siren can last a good 50-60 years.But once again both are dependible sirens just depends on your communitiies needs. The current most powerful electronic siren would have to be both the Whelen WPS 4004 and the Vortex R4 both rated at 129dB @ 100 feet. Both sirens can be for about 2-3 miles at the most. The current most powerful Mechanical siren would of course be the T-135 which can be heard for about 4-5 miles at the most.
Last edited by Whelen Rules on Wed Sep 06, 2006 1:27 am, edited 1 time in total.
Tyler Lund

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SirenMadness
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Sun Jul 02, 2006 1:28 pm

The problem with mechanical sirens is that they have too many mechanically moving parts; the problem with most electronic sirens is that the speaker-drivers can only go for around thirty years, as Whelen Rules said, without blowing from the vibrations.
~ Peter Radanovic

Jim_Ferer
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Sun Jul 02, 2006 4:48 pm

Most municipal bodies don't think about equipment life much; they all figure they'll be retired by then and it's someone else's problem.

The advantage electronic sirens have is lower current draw - easier for battery backup - and easier for SCADA. Easier programming of signals would be another advantage.

High Low Boy 2
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Mon Jul 03, 2006 6:57 pm

+ dat if you follow maintance rules (with nobody does they just test em till one just stops working then they got a problem) thats how they figure out if it works just sound em & if one or two (or all of em) dont sound then they got a prob.. just my two cents

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va_nuke_pe
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Let's get our facts straight

Tue Jul 04, 2006 4:19 am

ACA P-15 alerting frequency = 450 Hz
ATI RHPSS16 alerting frequency = 460 Hz
Sentry sirens typical alerting frequency = 460 Hz (some are dual-tone 460/920 Hz)
Whelen WPS-2800/WPS-2900 alerting frequency = 465 Hz
ASC T-128, T-121, T-112 alerting frequency = 500 Hz
Federal Eclipse series (8 and NH) alerting frequency = 520 Hz
Typical T-bolt 1000 alerting frequency = 550 Hz
ATI HPSS16 or HPSS32 alerting frequency = 550 to 575 Hz
ACA P-10/ASC T-135 (P-50) alerting frequency = 465/698 Hz (dual-tone)
Federal 2001SRN-A alerting frequency = 705 Hz
Federal 2001SRN-B (since 2003) alerting frequency = 790 Hz
Federal Modulator alerting frequency (typical) = 850 Hz to 1020 Hz

These are FACTS taken straight from the vendor manuals. Now, WHO'S got the high pitched sound that doesn't travel very far?

As far as the electronics versus electro-mechanicals are concerned - the advantages and disadvantages depend on what you want to use them for. Yes, electronics tend to be more efficient so they draw less power to make the same sound output. AND, if you live in a location where power outages are frequent and prolonged, then electronics can last longer on battery power. But for most locations, that doesn't matter much since the event that took aout the grid should be well understood as having already occurred by the local populace. Any siren with battery back-up should be capable of operating at least 24 hours on standby followed by 15 minutes of full power output. Electronics can be on standby for several days typically followed by 15 minutes of full sound output.

As far as complexity is concerned, the least reliable part of the siren is the rotation function (or in the case of electronics, it is better described as oscillation). That goes for T-128's, 2001's, Defenders, Vortex, HPSSR16, WPS-4000 series, whatever.

If I don't need voice function, then give me omni-directional electro-mechanical sirens - ANYBODY's - over the "stereos on a pole." The E-M omni's are simpler, and far more rugged. IF I realize they are going to be up a while, then I spend the extra bucks to get stainless steel housings, etc.

Electronics are far more sensitive to environmental effects than electro-mechanicals. As far as equipment life is concerned, electronics may be capable of 30 year design life, but the vendors don't tend to keep the parts in stock that long. Somewhere at the 15 to 20 year point, if you want to keep the electronics, you will have to replace their guts because you won't be able to get the original replacement parts anymore.

One other advantage of electronics, however, is that they tend to be modular so if I blow a speaker-driver, I still have close to full sound output.

For the battery back-up sirens, as sure as God made little green apples, the batteries will be the weak link because people will not do the maintenance and testing necessary to keep them in top condition - nor will they want to be replacing them every 3 to 4 years. Municipalities are famous for their "penny wise, pound foolish" ways.

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Tue Jul 04, 2006 5:36 am

My personal experience with electronic sirens is unfavorable, at least on moving emergency vehicles. For stationary electronic sirens, I can't comment because I've never heard one in person.

On vehicles, I can't hear electronic sirens anywhere near as well as mechanical ones. Today in fact, I was driving in Los Angeles and I thought I heard a siren, but I couldn't be sure. I just couldn't tell where it was coming from, or whether it was a siren or an angry bird in a nearby tree! Then I saw a LAFD ambulance about 1 block ahead, heading my way with light bar running. Still all I could hear was a faint WHOOP WHOOO WOOO, but VERY faint. NO WAY could I have heard it at all if I had been playing the radio as many drivers do. Then he blew the mechanical siren becase the other traffic also couldn't hear him and was not yielding. WOW what a difference!!!! I could FEEL the mechanical one, and it was very clear to me from what direction it was coming. I have noticed that on LAFD ambulances, there seem to be both mechanical and electronic sirens. LAFD fire engines are all mechanical, but LAPD police cars are all electronic, as evidenced by MANY wrecks.

I wrote a little editorial for the LA Daily News earlier this year on this very subject. I did so on a day when there had been two serious collisions involving LAPD police cars with electronic sirens the previous day, which were evidently NOT heard by cross traffic.

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Rory Buszka
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Tue Jul 04, 2006 2:05 pm

A loudspeaker driver whose voice coil and diaphragm are intact can, in theory, operate indefinitely as long as those operating factors are maintained and as long as the magnetic structure retains its field. It is fatigue of the diaphragm's suspension component or any of the adhesive bonds that could cause a failure of the siren driver unrelated to thermal dissipation. Siren drivers such as the Whelen driver undergo tremendous heating when operating at full power, and that heat is transmitted by the voice coil former to the adhesive bond at the rim of the diaphragm, therefore selection of adhesives is important.

The Whelen compression driver is truly a standout in the world of power handling, though -- even the Community M4 only handles 200W continuous sine-wave power (RMS).

Where is this 30-year number coming from, WRT Whelen sirens? Is there some failure mode that causes Whelen siren drivers to always give up the ghost at 30 years? Something about that number seems arbitrarily-chosen.
Say NO to excessive siren testing - overtesting desensitizes the public.
Say NO to voice siren systems - multiple origins = unintelligible audio.

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Tue Jul 04, 2006 5:30 pm

kx250rider wrote: Then he blew the mechanical siren becase the other traffic also couldn't hear him and was not yielding. WOW what a difference!!!! I could FEEL the mechanical one, and it was very clear to me from what direction it was coming. I have noticed that on LAFD ambulances, there seem to be both mechanical and electronic sirens. LAFD fire engines are all mechanical, but LAPD police cars are all electronic, as evidenced by MANY wrecks.
Not to take this thread off track, LAFD ambulances are utilizing the Timberwolf siren, mounted in the bumper as an adjunct warning device.

If you'd like to hear it, click on this link:

http://www.timberwolfsirens.com/Assets/ ... ds/T6C.mp3

Here's a picture:
http://lafirephotos.com/articles/lafdst ... ove/20.jpg

John

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Tue Jul 04, 2006 5:53 pm

Many emergency vehicles use only one 100-watt speaker. Many of the speakers are very small because today's cars don't have space for bigger ones. I've heard true 200 watt set-ups and they're pretty good.

Obviously, the problem with mechanical vehicle sirens is size and current draw.

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