Reducing Speaker Volume for Siren Testing

I have a BP100 that I'm going to keep around the shop to test sirens on. I want to reduce the output. Is there something commercially made that I can put inline on the speaker wire to do this? Or can someone tell me how to make something to do it?


I recall an install on an engine where they had the feature via a switch on the dash. I'm looking to do something like that.
 
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So I am not totally clear and have 2 different projects I am thinking of.

The first is to use a Motorola speaker with a Federal or Whelen siren on the display (so pretty quiet). The speaker is 3.2 ohm/30 watt. A volume adjuster would be nice to fine tune it but I wouldn't need to adjust after setting it. Without knowing the voltage put out by the siren I am not sure how to be sure I would have the correct resistors. Looking for a volume level equivalent to quiet television or office speakerphone.

The other possible (and lower priority) would bet to run an above siren with a 58 watt speaker quieted down for the display.

Thoughts or info?
 
shues said:
For the voltage produced by the siren, 33 volts AC comes to mind.

The L-PAD design from @Henry455 would be ideal for your application.
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I have read this thread several times, done some other research and still not comfortable. I dont want to play around with expensive stuff when I don't understand it all. I totally get low voltage/wattage/amperage for lights. I do not have a good understanding of the siren ac output and speaker properties (been reading up on it but not comfortable enough to test it out without recommendations from those in the know).

I know enough to know I don't comprehend enough to do this properly and safely!
 
Review post #26 it can't be easier- install the resistor inline on one of the speaker leads and your work is done, you can use a simple radio speaker
 
CHIEFOPS said:
Review post #26 it can't be easier- install the resistor inline on one of the speaker leads and your work is done, you can use a simple radio speaker
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I am looking for the reasoning and effects behind something, that does not explain any of it. I have a hard time believing that one resistor is compatable with every siren and every speaker. If so, why have others used different values with results that they are happy with? I have and continue to research it but not coming up with an answer I am comfortable with testing.
 
@Jennifer Rose Towing
I don’t fully understand how it works either. But the L-Pad is designed for the audio world and designed for speakers and amps. So in my mind it works for me reducing my siren output for indoor use. I can’t find where I bought mine from. But I am sure it was relatively cheap. ($20-$40 I am guessing. I wouldn’t have paid more than that for my project)
 
Jennifer Rose Towing said:
I am looking for the reasoning and effects behind something, that does not explain any of it. I have a hard time believing that one resistor is compatable with every siren and every speaker. If so, why have others used different values with results that they are happy with? I have and continue to research it but not coming up with an answer I am comfortable with testing.
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It's straight from FedSig, for well over 10 years I've been using this method testing sirens indoors running for as long as 5-10 mins on a simple 2-way radio speaker. I'm not an electrician so I don't know the science but it's simple, reliable and safe.
 
CHIEFOPS said:
It's straight from FedSig, for well over 10 years I've been using this method testing sirens indoors running for as long as 5-10 mins on a simple 2-way radio speaker. I'm not an electrician so I don't know the science but it's simple, reliable and safe.
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Do you have any bulletin or paperwork where they say that is ok? I would be fine with the specs/info from the manufacturer (or someone here who could give a basic explanation of it all).
 
Have a look at the Federal Signal Unitrol Omega 90 manual at https://www.fedsig.com/resource-document/file/8143 and you will see the following:

98JJLtH.jpg
 
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shues said:
Have a look at the Federal Signal Unitrol Omega 90 manual at https://www.fedsig.com/resource-document/file/8143 and you will see the following:

98JJLtH.jpg
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Thank you. That should be fine then for a siren speaker, any idea about a smaller speaker? Says 4-100 ohm but the main speaker I want to use is a Motorola external 3.2 ohm for its size and portability. I figure only w couple of watts to the little speaker would be more then plenty. I'll try to reverse engineer the numbers for the Omega and see what else I can learn.
 

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Jennifer Rose Towing said:
Thank you. That should be fine then for a siren speaker, any idea about a smaller speaker? Says 4-100 ohm but the main speaker I want to use is a Motorola external 3.2 ohm for its size and portability. I figure only w couple of watts to the little speaker would be more then plenty. I'll try to reverse engineer the numbers for the Omega and see what else I can learn.
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I keep telling you it will run a speaker as small/low watt as a 2-way radio speaker
 
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