Reducing Speaker Volume for Siren Testing

bigcat

Member
May 20, 2010
641
Hartford County, CT
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.
 

shues

Lifetime VIP Donor
May 21, 2010
10,320
NW Indiana
I use four 900 ohm 3.25 watt resistors arranged so that there are two pairs of resistors in series in parallel. This way the circuit provides 900 ohms of resistance to further quiet the output from the speaker, but runs cool enough that the resistors aren't hot to the touch after a few minutes of testing.

900ohms.png
 

jantman

Member
Jun 2, 2010
42
NJ, USA
If you want to keep it in the shop to test, why alter the electrical characteristics? Just put the speaker in a wooden box filled with packing peanuts or foam or something and run the leads out of it...
 

SurfCityCar2

Member
May 20, 2010
156
Jacksonville, NC
jantman said:
If you want to keep it in the shop to test, why alter the electrical characteristics? Just put the speaker in a wooden box filled with packing peanuts or foam or something and run the leads out of it...

My shop used to have a FedSig T-100 inside a small wooden box, stuffed with lots of thick high density packing foam. It allowed full 100 watt output but you couldn't hear the siren tones outside of the tech area...
 

C2Installs

Member
May 24, 2010
477
Tennessee
I have a old Whelen nylon box-type speaker here that I have packed with thick foam sheet in the housing and then wrapped with duct tape. Works well for its purpose.


I needed a second test speaker recently, thanks to my new dual tone siren, and took and old scrapped siren unit, basically just the driver, one that you could use different cones and such with as needed, and simply packed thick foam sheet over the wire screen opening and taped it up again with duct tape. It works even better, is very quiet, and cost nothing.


I still want to do a resistor setup to test new speakers with, prior to install, but not sure where to get the resistors I need. Anyone got some to barter?
 

Jordan_TCFD

Member
May 22, 2010
407
Chattanooga,TN, Bryant,
I have a set up with using the resistors. I think I'm using somewhere around 300 ohms or something. I'll get a picture of my set up and what I used. The local electronics store didn't have the one size I wanted,so I have to use 2 in series.


Jordan,TCFD
 

GSPD

Member
May 21, 2010
159
NY
Here's a couple pictures of the resistors I use. These work great for the grandkids to play with my sirens. They are both Ohmite ceramic, one's 2500 ohms and I think the larger one is 2700 ohms and 50 watt. I picked these up at a hamfest for .25 cents. ai288.photobucket.com_albums_ll196_GSPD44_resistors_IMG_2232_1.jpg
 

toon80

Member
May 24, 2010
2,489
Laval, Canada
I used the 500 ohms 5watts resistor thing. Works pretty well... Still is a bit loud for indoor use. Not that it hurts my ears but it may be a bit much for the neighbours...
 

bigcat

Member
May 20, 2010
641
Hartford County, CT
Props go to shues for (A) the idea/design and ( B) because he sold me the resistors.


Once I saw his drawing I knew exactly how I was going to mount them. 1/8" piece of abs plastic with terminal blocks from an old mx7000. The end terminal blocks have a piece of metal connecting the two terminals. Works like a champ. You could talk with this thing going and not have to raise your voice at all.


Here is the video:


ai130.photobucket.com_albums_p247_ct_bigcat_P1040339.jpg
 

Jarred J.

Lifetime VIP Donor
May 21, 2010
11,593
Shelbyville, TN
old board idea. run a lead into a light socket with a bulb in it.
 

CrownVic97

Member
May 21, 2010
3,352
Hazen, ND
Jarred J. said:
old board idea. run a lead into a light socket with a bulb in it.

I heard from someone on the old board that that was not a good idea anymore. They burned out a Whelen siren amp doing that once and had to send it out to repair it. I did the lightbulb idea a bunch until I read about that possibility, then stopped that and went to stuffing a siren speaker with some old socks and putting it in a box.
 

Shadow-D

Member
Jul 3, 2010
946
Adirondacks, NY
shues said:
I use four 900 ohm 3.75 watt resistors arranged so that there are two pairs of resistors in series in parallel. This way the circuit provides 900 ohms of resistance to further quiet the output from the speaker, but runs cool enough that the resistors aren't on hot to the touch after a few minutes of testing. The resistors cost me one cent each at the local hamfest!
I just did this and it works great! Thanks for the idea.


I'm also thinking about making a setup where I can use a potentiometer for volume control with maybe less resistors, any ideas?
 

shues

Lifetime VIP Donor
May 21, 2010
10,320
NW Indiana
Make sure you get a pot that can handle the watts you will be feeding it at the lowest resistance it can possibly be set for.
 

toon80

Member
May 24, 2010
2,489
Laval, Canada
shues said:
I use four 900 ohm 3.25 watt resistors arranged so that there are two pairs of resistors in series in parallel. This way the circuit provides 900 ohms of resistance to further quiet the output from the speaker, but runs cool enough that the resistors aren't hot to the touch after a few minutes of testing.

If I recall my electronics correctly, having 4 900ohms resistors in series-parallel like that should be the same as having only 1 900ohms.


Equivalent ohms in parallel circuit is -making the 2 strands 1800 ohms each- (900+900) as follows:


R = 1/( 1/R1 + 1/R2 + ....)


R = 1/(1/1800 + 1/1800)


R= 1/(2/1800)


R= 900 ohms


 

shues

Lifetime VIP Donor
May 21, 2010
10,320
NW Indiana
toon80 said:
If I recall my electronics correctly, having 4 900ohms resistors in series-parallel like that should be the same as having only 1 900ohms.

Equivalent ohms in parallel circuit is -making the 2 strands 1800 ohms each- (900+900) as follows:


R = 1/( 1/R1 + 1/R2 + ....)


R = 1/(1/1800 + 1/1800)


R= 1/(2/1800)


R= 900 ohms



Exactly. I did this to maintain the 900 ohms of resistance, while providing more of a heat sink. I thought that getting one resistor hot was bad, and I found that the four resistors run much cooler.
 

toon80

Member
May 24, 2010
2,489
Laval, Canada
shues said:
Exactly. I did this to maintain the 900 ohms of resistance, while providing more of a heat sink. I thought that getting one resistor hot was bad, and I found that the four resistors run much cooler.

Ah! Clever! :cool:
 

EVModules

Member
May 16, 2010
865
Deer Park, WA
I used LAPD's tech idea of using an in-line speaker plug that can allow a tech to temporarily install a 400 ohm 35 watt sandstone resistor inline for testing the vehicle when it's in the shop since nowdays, many speakers are inaccessible to attempt to muffle the speaker with foam, towels, etc. The test connections was conveniently positioned for easy access.


I also used a rotary switch to install 5 resistors ranging from 200 ohms to 750 ohms for a FedSig rep's demo truck.
 

Henry455

Member
May 21, 2010
513
Houston, TX
EVModules said:
I used LAPD's tech idea of using an in-line speaker plug that can allow a tech to temporarily install a 400 ohm 35 watt sandstone resistor inline for testing the vehicle when it's in the shop since nowdays, many speakers are inaccessible to attempt to muffle the speaker with foam, towels, etc. The test connections was conveniently positioned for easy access.

I also used a rotary switch to install 5 resistors ranging from 200 ohms to 750 ohms for a FedSig rep's demo truck.

Wow, 35 watt resistor, seems like overkill to me.
 

EVModules

Member
May 16, 2010
865
Deer Park, WA
I recently learned from Unitrol that you only need a 500 ohm, 5 watt resistor for testing. You can even hook up a small cone speaker, anywhere from 2 to 5 watts for demonstration setup. Speaker impedance is unimportant: 4 to 100 ohms.


And yes, 35 watt is now overkill. :oops:
 

theroofable

Member
May 23, 2010
1,379
New Jersey
by EVModules

I recently learned from Unitrol that you only need a 500 ohm, 5 watt resistor for testing. You can even hook up a small cone speaker, anywhere from 2 to 5 watts for demonstration setup. Speaker impedance is unimportant: 4 to 100 ohms.


And yes, 35 watt is now overkill.
Yeah, this is stated in their Omega 90 manual, and probably others as well. As far as buying them, Radioshack has them in stock, just check their back electronic area, they have cheap automotive switches and leds too. Im sure most other electronic stores has them also. And for the lightbulb, that shouldnt effect it, since a lightbulb is just a resistor, or thats what I remember from physics. I think my teacher said that a few times in class :D :geek:
 

Henry455

Member
May 21, 2010
513
Houston, TX
Although there have been great suggestions presented for reducing the volume of sirens, I believe this one is the most versatile. It's a 100 watt stereo 8 ohm Lpad wired to give a 200 watt 16 ohm mono Lpad. This gives you the ability to adjust the volume from very low to full volume with a twist of the knob. Because of being an Lpad the sirens sees a fixed impedance from low to high. I chose the 200 watt version because I have been using a 100 watt 16 ohm Lpad but with a 100 watt siren and the pad turned to very low volumes it heats up very hot. Applications include man caves, parades, car shows, Emergency Equipment sales demos, etc. The Lpad costs $25.00 so it is not as inexpensive as some of the other solutions. The Lpad part # is 260-264 and can be found at Parts Express: the #1 source for audio, video & speaker building components. Below are some pictures and a short demo video. Click on top picture for video.


aimg.photobucket.com_albums_v691_Henry455_Lpad_20200_20watt_20979fd512ff6755d390e68a6503458d6a.jpg

Lpad wiring.jpg

IMG_20130518_173905.jpg

Lpad wiring back.jpg
 

twodogs603

Member
Sep 7, 2011
1,196
Norfolk,VA
Henry455 said:
Although there have been great suggestions presented for reducing the volume of sirens, I believe this one is the most versatile. It's a 100 watt stereo 8 ohm Lpad wired to give a 200 watt 16 ohm mono Lpad. This gives you the ability to adjust the volume from very low to full volume with a twist of the knob. Because of being an Lpad the sirens sees a fixed impedance from low to high. I chose the 200 watt version because I have been using a 100 watt 16 ohm Lpad but with a 100 watt siren and the pad turned to very low volumes it heats up very hot. Applications include man caves, parades, car shows, Emergency Equipment sales demos, etc. The Lpad costs $25.00 so it is not as inexpensive as some of the other solutions. The Lpad part # is 260-264 and can be found at Parts Express: the #1 source for audio, video & speaker building components. Below are some pictures and a short demo video. Click on top picture for video.




aimg.photobucket.com_albums_v691_Henry455_Lpad_20200_20watt_20979fd512ff6755d390e68a6503458d6a.jpg


Hey Tim,


Is that my powercall??


I will give you $50 for it! :haha:
 

chief1562

Member
Mar 18, 2011
5,840
Slaterville/NY
Stuff full of rags sit on floor with cone pointed to floor.
 

CHIEFOPS

Member
Jan 24, 2011
1,533
NYC
EVModules said:
I recently learned from Unitrol that you only need a 500 ohm, 5 watt resistor for testing. You can even hook up a small cone speaker, anywhere from 2 to 5 watts for demonstration setup. Speaker impedance is unimportant: 4 to 100 ohms.

And yes, 35 watt is now overkill. :oops:

That's how I do it with a standard 4 watt radio speaker for all my siren testing
 

Skip Goulet

Member
Feb 23, 2011
4,241
Midland, TX
CrownVic97 said:
I heard from someone on the old board that that was not a good idea anymore. They burned out a Whelen siren amp doing that once and had to send it out to repair it. I did the lightbulb idea a bunch until I read about that possibility, then stopped that and went to stuffing a siren speaker with some old socks and putting it in a box.

You just stole my thunder. Just what I was going to say: "Just stick a sock in it"! :haha:
 

Torpedo

Member
May 9, 2012
583
USA Fl
The light bulb is safe in series with the speaker but won't attenuate sound level much if at all. Across speaker lines is a no no. Henry 455 has shown the electronically correct way to do this although I would also just stick a sock in it, so to speak.
 

Halloween Snob

New Member
Jul 30, 2013
3
pa
Henry455: Thank you!! I just purchased this component from parts express today. Just to be clear, I have a Whelen 295sl101 and a 100 watt federal siren speaker. I want to be able to adjust the volume of the siren tone itself (not the PA, not the radio rebroadcast) to a level that is tolerable for demonstration. Will this part do the job well? My siren says the speaker impedance is "11 ohm minimum" whereas I think I read the OHMS on this part is 8ohms?

Henry455 said:
Although there have been great suggestions presented for reducing the volume of sirens, I believe this one is the most versatile. It's a 100 watt stereo 8 ohm Lpad wired to give a 200 watt 16 ohm mono Lpad. This gives you the ability to adjust the volume from very low to full volume with a twist of the knob. Because of being an Lpad the sirens sees a fixed impedance from low to high. I chose the 200 watt version because I have been using a 100 watt 16 ohm Lpad but with a 100 watt siren and the pad turned to very low volumes it heats up very hot. Applications include man caves, parades, car shows, Emergency Equipment sales demos, etc. The Lpad costs $25.00 so it is not as inexpensive as some of the other solutions. The Lpad part # is 260-264 and can be found at Parts Express: the #1 source for audio, video & speaker building components. Below are some pictures and a short demo video. Click on top picture for video.




aimg.photobucket.com_albums_v691_Henry455_Lpad_20200_20watt_20979fd512ff6755d390e68a6503458d6a.jpg
 

Henry455

Member
May 21, 2010
513
Houston, TX
Yes it will, the part I used is actually 2 100 watt 8ohm lpads mounted back to back, if you follow my wiring instructions it becomes a 200 watt 16 ohm lpad. The impedance is close enough not to cause any problems in fact a higher impedance is less draw on the siren amp.
 

HILO

Member
May 20, 2010
2,781
Grand Prairie Texas
I use the 'Hush you speaker' from Jazz Dad Industries. It was $79.99 and came shipped in popcorn you could eat.


jdihk.jpg
 

Halloween Snob

New Member
Jul 30, 2013
3
pa
Henry455 said:
Yes it will, the part I used is actually 2 100 watt 8ohm lpads mounted back to back, if you follow my wiring instructions it becomes a 200 watt 16 ohm lpad. The impedance is close enough not to cause any problems in fact a higher impedance is less draw on the siren amp.

Henry,


I looked at your video and pictures, thanks!!


Question: I am hooking the speaker and siren up to just the positive side of both? I only have one speaker and I assume that part assumes the user is using two speakers. I will use the jumper and wire in parallel to increase the ohm to 16 as you suggest. I am thinking run the speaker prongs to the positive side of the speaker and the siren prongs to the positive side of the siren. Is that correct?
 

Henry455

Member
May 21, 2010
513
Houston, TX
The lpad is wired for ONE 100 watt speaker, the reason I used 2 was to double the power handling capability. I 100 watt lpad will get very hot if the pad is turned to low volume. There is no positive/negative on the speaker or amp, the signal is AC. Wire the Lpad as shown in this picture:

Lpad wiring back.jpg
 

Halloween Snob

New Member
Jul 30, 2013
3
pa
Henry455 said:
The lpad is wired for ONE 100 watt speaker, the reason I used 2 was to double the power handling capability. I 100 watt lpad will get very hot if the pad is turned to low volume. There is no positive/negative on the speaker or amp, the signal is AC. Wire the Lpad as shown in this picture:

Thank you. I am still unclear. Let me try again. I am having trouble understanding what wires to plug into the white terminal connections you use for "speaker" and "siren". My siren Whelen 295sl101 has two wires as output for the speaker. One is brown (negative) and one is orange (positive). See page 4 here: http://www.whelen.com/install/140/14045.pdf


My 100watt Federal siren has two wires coming out of it. One is white, one is black.


Which wires for the devices go where in your picture??


What I have done so far:


I tied the two speaker prongs on the attenuator together and terminated to the positive side of my speaker. I then tied the two siren prongs for the siren on the attenuator and terminated to the positive side of the siren. I tied ran the last two prongs together. Everything works. It gets louder and softer as I turn the dial. I wish it would get even lower though. It is still relatively loud even at the very minimum.


Is this not an advisable alternative?
 

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