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Author Topic: Resistor for 100v speakers  (Read 3906 times)

Gary Fitzpatrick

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Resistor for 100v speakers
« on: January 17, 2017, 07:34:01 pm »

Hi

I have an install where the speakers in the bathrooms are too loud despite being on their lowest settings. Can I put a resistor in series with the positive wire to drop the power of the speaker?

Gary
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Ivan Beaver

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Re: Resistor for 100v speakers
« Reply #1 on: January 17, 2017, 08:49:14 pm »

Hi

I have an install where the speakers in the bathrooms are too loud despite being on their lowest settings. Can I put a resistor in series with the positive wire to drop the power of the speaker?

Gary
Yes-technically.  But code issues might be something else.

The BEST way is to simply put a 100V volume control on it-that way it is easily adjustable.

But you can figure out a resistor value.  FIRST you need to know what tap it is on.

Next you need to figure out how much lower in level (dB) you want it to be.

After you have figure out the oh value, you need to figure out what wattage the resistor will be dissipating. 

I would multiply that figure by 4.  Depending on what values you end up with, you may need to figure out how to keep the heat from the resistor from starting a fire.

Hence the suggestion for a simple cheap level control.
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David Sturzenbecher

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Re: Resistor for 100v speakers
« Reply #2 on: January 17, 2017, 10:41:04 pm »

Gary, can you just turn down the gain at the amplifier?


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Steve M Smith

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Re: Resistor for 100v speakers
« Reply #3 on: January 18, 2017, 03:06:16 am »

Speakers?  As in plural?  How about wiring in series?


Steve.
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Ivan Beaver

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Re: Resistor for 100v speakers
« Reply #4 on: January 18, 2017, 07:25:30 am »

Gary, can you just turn down the gain at the amplifier?


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But that would turn down the other speakers as well.

But he may or may not be able to retap all of the other speakers. but they may already be at maximum tap-or not.  We have no idea.
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Ivan Beaver

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Re: Resistor for 100v speakers
« Reply #5 on: January 18, 2017, 07:28:08 am »

Speakers?  As in plural?  How about wiring in series?


Steve.
But that would put the transformers in series.

I have never looked (to be honest) at what the inductance typically is, so that may or may not be a problem.

But it would drop the level a little (6dB).
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Gary Fitzpatrick

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Re: Resistor for 100v speakers
« Reply #6 on: January 18, 2017, 07:34:34 am »

But that would turn down the other speakers as well.

But he may or may not be able to retap all of the other speakers. but they may already be at maximum tap-or not.  We have no idea.

Yes that is the problem...I added speakers onto an existing system. The existing system just fed background music to the toilets and I added speakers to a new beer garden...the new speakers are at their maximum tap, but when I turn the amplifier up to get the desired level outside, it is too loud in the toilets...I think I will just put a volume control on the toilet speakers (only three speakers anyway so not a big hassle)...thanks for the advice
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Steve M Smith

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Re: Resistor for 100v speakers
« Reply #7 on: January 18, 2017, 07:38:28 am »

Going back to my wiring in series suggestion, I think I would try all three of the toilet speakers in series with just one transformer.  I'm sure it doesn't need to be very loud in there!


Steve.
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Hal Bissinger/COMSYSTEC

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Re: Resistor for 100v speakers
« Reply #8 on: January 18, 2017, 04:24:46 pm »

Going back to my wiring in series suggestion, I think I would try all three of the toilet speakers in series with just one transformer.  I'm sure it doesn't need to be very loud in there!


Steve.

That's not going to make a heck of a lot of difference and, besides, it's not a good idea to wire speakers in series especially in this kind of installation. Use a level control as has been suggested, put it wherever it won't get played with. Also, don't know what kind of speakers these are but there are ceiling speakers that have a volume control that is accessible through the center hole of the grill with a small screwdriver in addition to the taps on the transformer.

-Hal
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John Roberts {JR}

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Re: Resistor for 100v speakers
« Reply #9 on: January 18, 2017, 05:51:25 pm »

Far be it for me to be contrary  ::) but I see no problem with wiring 2 or 3 speakers in the same small zone in series, however if there are three speakers in there it may not be that small of an area.

Wiring the speakers in series will definitely scrub off some level, while is not very professional (have some pity on whoever comes behind you to troubleshoot it years from now, maybe tape a wiring diagram to the back of one or more speakers explaining the secret strategy). 

Adding a passive level control for just that one zone should work since you want less level, never more.

JR 
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Re: Resistor for 100v speakers
« Reply #9 on: January 18, 2017, 05:51:25 pm »


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