The Siren Board

The 508 is designed as a one to one replacement for the Thunderbolt. The 2001 was too but it fell a little short.

When I purchased my Thunderbolt from West Shore back in 2009, Jeff told me that Federal was actually trying to force the RSH-10 into a Thunderbolt replacement capacity. He said there was a lot of pressure from FS to really push the RSH toward the late 80's. Unfortunately that siren ended up being a piece of garbage, with the Modulator not far behind. I am sure the 2001 was already in the works by this time, but I thought it was an interesting piece of info when he told me that.

Somewhat off topic, but when did the modulator come out?

Brendan Ahern wrote:Somewhat off topic, but when did the modulator come out?

This is just a total guess. But I think they came out around the mid to late 90's. I was looking at a old news article about the new Mod sirens that Honolulu was starting to put up. The date of the article was 1999 so I have to guess that they were maybe being made for a few years before that.

Another question here... The 2001 is rated at 130 but the equinox is rated at 125. Now federal could have either gotten those numbers from the rate formula or actually at 100 feet or both... (They test for it better now adays than they used too...) But my question is: why is the equinox so much quieter than the 130? Why hasn't federal signal used a siren with the fully adjustable frequency since the bolt? Is it just not needed?

Mods were out at least on 1997, that's when Chicago installed theirs.

I remember seeing MOD sirens around 1995 or so. First one I ever saw was in Duncanville,TX on Hwy 67.

Yes the Mods were out in the mid to late 90s. Coppell, TX put in a system of Modulators and EOWS-612s around 96 or 97. They have replaced all of the original units with newer Modulators over the past few years. I don't think they have any Mod II's yet.

SirenkiD wrote:I don't think they have any Mod II's yet.

Actually they have at least one by the high school. I figured it was only a matter of time before they purchased one considering how much they have been adding to the system in the past few years.

https://airraidsirens.com/forums/viewto ... c4f40d2788

coastalsyrolover wrote:Another question here... The 2001 is rated at 130 but the equinox is rated at 125. Now federal could have either gotten those numbers from the rate formula or actually at 100 feet or both... (They test for it better now adays than they used too...) But my question is: why is the equinox so much quieter than the 130? Why hasn't federal signal used a siren with the fully adjustable frequency since the bolt? Is it just not needed?

It's quieter because of it's design. the 2001 was built for a 12 port Model 3 rotor vs the 8 port Eclipse series rotor. That's the on paper specs though, I've heard that they can be louder than a 130 in person. They perform about the same with the Equinox maybe being heard better in the distance because of the lower pitch. Overall the 508 made better use of the sound from the chopper and can throw it more effectively. They work well though considering it was something Federal made at the last minute.

They have sirens with adjustable pitch, the DSA, THOR, and Modulator II. Adjusting the pitch actually messes with SPL as seen with Whelen's decision to drop the pitch on their older sirens and slowly bring it up to 560, i.e. a WPS 2810 running at 435Hz and one running at 560Hz produce 126 dB yielding a range of 5200 feet and 129 dB yielding a range of 6100 feet. The same goes with pneumatic sirens, plus the faster the chopper spins the more air escapes the port making the siren louder. Adjusted pitch on UltraVoices and MCPs away from the normal 850 Hz is rather uncommon too; I can only count maybe 3 occurrences in the wild where I've seen a UV/MCP with a custom pitch. Like dual tone, adjustable pitch on a modern siren is not really needed anymore.