Batboard

Ok everyone, I couldn't find an answer to this so I thought I would ask...

I would like to have a siren controller/switch box hooked up to a volume controlled speaker so my friend could do on-hand siren demonstrations to his customers in his lights/sirens store without blowing their ears off or disturbing anyone too much..would it be possible to hook the sirens up to like a stereo speaker or a computer speaker or something so they can go from being as quiet as a whisper to as loud as the speaker will take, preferably without having to change the electrical current of the siren or speaker?

It would need the siren and alternative speaker to be hooked up together and then have both of them hooked into a power supply which would be plugged onto an electrical socket on the wall...anyway the idea is to have full siren tones, airhorn, manual, PA, etc function the same as off a standard siren installation in a car, just loads quieter and in a 'bench test' type situation instead of a full install. It would also be pretty cool to have that setup as a bit of fun with a lightbar in my recreation room in my house

It would probably be just 2 or 3 simple sirens on seperate speakers like C3 Microcom 2 or FS PA300 or FS MS4000 and maybe one more complicated model like a FS SS2000SM. Would also need to know the same thing as the siren setup, but would it work with a Federal Signal or Code 3 rocker switch setup at the same time to control any lights for demo/rec. room fun?

If anyone knows how that could work, or another way to get the same effect, plz let me know on this thread or via a PM, with maybe some good yet simple instructions or diagrams....or is what I am trying to do completely impossible???

Thanks,
Nic.

Well, most sirens are either 58, 100 or 200 Watts, so a computer speaker would likely blow in no time. You could probably put a (very) beefy resister in line with a PA type speaker. Someone else could probably give you a better idea if that'd work or not as I've never tried.

I know most Whelen sirens have an internal speaker that works when the external speaker isn't attached, but it's pretty quite. A suggestion would be to hook a normal speaker up and place it upside down on a pillow and press it down, I've seen some people do that at shows and it works pretty well. Sometimes they'll even go straight on the table with it. Grab some ear plugs and try different things out.

Are you sure about that internal speaker? The noise you often hear inside a siren while it's on isn't a speaker, rather it's a capacitor/inductor coil resonating and sounding like the siren.

Whelen sirens do NOT have an internal speaker. What you're hearing is a very unhappy audio amplifier, as it's trying to dump massive power into an open... akin to transmitting with no antenna.

After a while, that noise turns into magic smoke. And the Whelen magic smoke recharge kits are pretty expensive.

Interesting suggestions aside, what you are really trying to do is give the siren a load that will keep its amplifier stage happy, while allowing you to tap the output off at a lower level for your purposes.

If you are not looking to smoke your siren, or win a pillow fight, your best bet would probably be to lay your hands on an 11 ohm load that is capable of handling the siren's full power, and connecting it accross the siren's output. That may either mean one large load, or several smaller (ie 20 watt) resistors paralleled, using the appropriate calculations for power handling and parallel resistance. Please note that you will be turning that 58 to 200 watts of output power into heat, so you will also need to think about heat sinking and / or fan cooling.

Then, with the siren amplifier taken care of, you can work on tapping off the signal for your purposes. The easiest way would be to use an audio output transformer with something like a 1,000 ohm or 10,000 ohm primary, and a secondary in the 8 ohm range. I know a lot of people will go for the 600 ohm load matching concept, but I live in a world where we like low impedance outputs driving high impedance imputs. Connect the high impedance side of the tansformer accross the siren's output, in parallel with the dummy load, and use the low impedance side to drive your computer speakers, or what have you.

This assumes, of course, that you will be driving an amplified speaker that you can control the gain on. If you want a fixed output to drive a speaker directly, you have a little more math to do.

If you want to spend some real money, and let someone else do all of the work for you, go find a "power soak" unit for a guitar amplifier. It's exactly the same idea.

what you actually need is something called an L-Pad.

"An L pad is a special configuration of rheostat used to control the volume of a loudspeaker while maintaining a constant load impedance on the output of an amplifier"

Solves all of the problems without introducing more. Around $20 for the last set I installed.

-Shawn

There are a couple of potential problems with an L-pad type attenuator in this application, which is why I didn't bring them up before.

The biggest one is that you will need to stay at the very bottom of the output range, given the input powers that you are dealing with. This will mean that barely touching the knob will cause a big swing in the output. Additionally, if someone decides they can't resist playing with (or accidentally moves) the knob, your speaker is probably going to be headed for an early retirement.

That is the main reason why I suggested a fixed load with a tap over an L-pad.

Additionally, most high-power L-pads are a step type, rather than continuously variable, which further limits your control.

tvsjr wrote:Whelen sirens do NOT have an internal speaker. What you're hearing is a very unhappy audio amplifier, as it's trying to dump massive power into an open... akin to transmitting with no antenna.

After a while, that noise turns into magic smoke. And the Whelen magic smoke recharge kits are pretty expensive.

Cool, do you know where I get get a few extra recharge kits? I want to stock some spares on my shelves

SG

spectragod wrote:Cool, do you know where I get get a few extra recharge kits? I want to stock some spares on my shelves

SG

Yup... last I checked, the part number was a S01RCHG* where * is the color of smoke you'd like. Now, don't think that you can replace a red LED's smoke with blue smoke and have it work... you don't want ghey purple lights, do you?

Oh yeah, lead time is about 36 weeks, like every other fuggin Whelen LED product.

35 watt, 340 ohm upwards to 500 ohm sandstone resistors.

Give or take a few 60 ohms to adjust output volume but 340 is something you can start with.

Never got to use the blue smoke recharge kit sitting on the shelf since 94'.

Enjoy.

I had a setup to demo my sirens indoors. I used a standard wall mounted volume control knob for home audio. I forget where I bought mine, but you could prolly get them at Tweeter, BestBuy, Home Depot ETc.

http://www.partsexpress.com/pe/showdetl ... er=300-548

Follow that link, that is what you want. It is impedance matching to prevent you from smoking your amp. It was very easy to install, just wires in between the siren amp and thesiren speaker.

was looking up something today, and saw this from FedSig:

7: SIREN QUIETING
To protect your hearing as well as the hearing of those
around you, reduce the siren loudness while testing.
For in-vehicle testing, place a 500 ohm, 5watt resistor inline
with one speaker wire as shown in the diagram below. The resistor is available in most electronic parts stores.

For bench testing, install the 500 ohm, 5 watt resistor inline
with one wire of a small cone speaker. Speaker
power rating can be 2 to 5 watts. Speaker impedance is
relatively unimportant: 4 to 100 ohms.

Straight from the manufacturers' mouth. And, this was in a manual for a newer solid state unit. Just be careful, some sirens get very pissed if there isn't any load there, even for a second or two...

and, for the record, I still like my Lpad...

-Shawn

I used to stuff a motorcycle speaker with foam rubber and test Unitrol 80H and 80K sirens all the time. Worked great and I can still hear!

Fowler

Just hook it up to a reflex-type PA speaker (with a center cone) and unscrew the cone. Without the speaker reflex-horn to concentrate it, the driver doesn't really put all that much sound power into the air. You can plug the driver with some closed-cell foam as needed if it is still too loud.

This also takes care of loading the amplifier safely.

Much adoo about nothing. Simply amazing how many off the wall ideas the in-experienced can come up with.

Use a TS-100 speaker or equivalent. Take a Motorola 5-803001 (the old part number) hole plug, trim off the small part, remove the reentry cone from the speaker and glue in the previously removed Motorola hole plug with RTV. Carefully screw the cone back on so the glue doesn't ooze out and glue the cone on.

Make noise.

DONE!

IF YOU USE A REAL EMERGENCY VEHICLE PAINT THE REENTRY CONE PINK, RED OR SOME OTHER BRIGHT DISTINCTIVE COLOR.

TWEMARS wrote:Much adoo about nothing. Simply amazing how many off the wall ideas the in-experienced can come up with.

So you felt the need to Lazarus a 3-month-old post, just to be insulting? Smooth.