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Author Topic: PA System Amplifier Speaker Question  (Read 463 times)

Michael Parker

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PA System Amplifier Speaker Question
« on: March 19, 2021, 02:04:19 pm »

I have a unique situation I need help with. I have a old PA system that is composed of 100 speakers. These are older speakers and they do have a transformer and are tapped at the 2k settings. The speakers are wired in parallel with 22awg wire and the run is 120ft from the original amp to the last speaker. The specs I have found on this system are the following:
Sensitivity = (35VRMS @ 1M, 100Hz) 87.5dB
Impedance  = 1050 ohms
Max power @ 80 VRMS = 10W

I am going to be splitting this system up into multiple zones ranging from 10 to 40 speakers. I do not have the original amplifier or the specs on the original amplifier.

My main issue is powering these new speaker zones. I have a 4x300w amplifier that can be used in either a 4ohm, 8ohm, 70v, or 100v system depending on what you set the dip switches to.

My question was can I safely use this amp for this system and not blow up the speakers or burn up the wire? This system once I set the volume on the amplifier will be set and will not be able to be adjusted so this will make it to where someone cant go and crank up the volume.
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Mac Kerr

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« Reply #1 on: March 19, 2021, 03:41:40 pm »

I have a unique situation I need help with. I have a old PA system that is composed of 100 speakers. These are older speakers and they do have a transformer and are tapped at the 2k settings. The speakers are wired in parallel with 22awg wire and the run is 120ft from the original amp to the last speaker. The specs I have found on this system are the following:
Sensitivity = (35VRMS @ 1M, 100Hz) 87.5dB
Impedance  = 1050 ohms
Max power @ 80 VRMS = 10W

I am going to be splitting this system up into multiple zones ranging from 10 to 40 speakers. I do not have the original amplifier or the specs on the original amplifier.

My main issue is powering these new speaker zones. I have a 4x300w amplifier that can be used in either a 4ohm, 8ohm, 70v, or 100v system depending on what you set the dip switches to.

My question was can I safely use this amp for this system and not blow up the speakers or burn up the wire? This system once I set the volume on the amplifier will be set and will not be able to be adjusted so this will make it to where someone cant go and crank up the volume.

Please go to your profile and change the "Name" field to your real first and last name as required by the posting rules displayed in the header at the top of the section, and in the Site Rules and Suggestions in the Forum Announcements section, and on the registration page when you registered.

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Hal Bissinger/COMSYSTEC

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Re: PA System Amplifier Speaker Question
« Reply #2 on: March 31, 2021, 08:34:59 pm »

I have a unique situation I need help with. I have a old PA system that is composed of 100 speakers. These are older speakers and they do have a transformer and are tapped at the 2k settings. The speakers are wired in parallel with 22awg wire and the run is 120ft from the original amp to the last speaker. The specs I have found on this system are the following:
Sensitivity = (35VRMS @ 1M, 100Hz) 87.5dB
Impedance  = 1050 ohms
Max power @ 80 VRMS = 10W

I am going to be splitting this system up into multiple zones ranging from 10 to 40 speakers. I do not have the original amplifier or the specs on the original amplifier.

My main issue is powering these new speaker zones. I have a 4x300w amplifier that can be used in either a 4ohm, 8ohm, 70v, or 100v system depending on what you set the dip switches to.

My question was can I safely use this amp for this system and not blow up the speakers or burn up the wire? This system once I set the volume on the amplifier will be set and will not be able to be adjusted so this will make it to where someone cant go and crank up the volume.
So, you have 100 speakers with transformers tapped at 2k. Each speaker will provide 2.5 watts when supplied with 70.7 volts. 100 times 2.5 is 250. So you should be able to comfortably supply all your 100 speakers with a single channel of that amp using the 70 volt output.

Of course there is no problem with splitting the speakers up and using the other channels to supply each zone if that's what you have in mind.

-Hal
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Keith Broughton

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Re: PA System Amplifier Speaker Question
« Reply #3 on: April 01, 2021, 07:16:28 am »



I am going to be splitting this system up into multiple zones ranging from 10 to 40 speakers. I do not have the original amplifier or the specs on the original amplifier.



My question was can I safely use this amp for this system and not blow up the speakers or burn up the wire?
Should work just fine.
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John Roberts {JR}

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Re: PA System Amplifier Speaker Question
« Reply #4 on: April 01, 2021, 09:27:36 am »

Perhaps search for a white paper about "constant voltage" systems (in the US typically 70V).

These are pretty simple to configure and for multiple zones you can use different smaller amplifiers for each based on how many speakers in each zone.

JR
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Hal Bissinger/COMSYSTEC

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Re: PA System Amplifier Speaker Question
« Reply #5 on: April 01, 2021, 11:45:09 pm »

Perhaps search for a white paper about "constant voltage" systems (in the US typically 70V).
That would be an excellent idea. However, keep in mind that the taps on speaker transformers are labeled in watts today which makes it easy to design your system. Just add them up.

What the OP has must be really old, I believe the original multi-speaker systems labeled the transformer taps with their impedance probably back in the 30's or 40's. You had to do some thinking if you wanted to have some speakers tapped differently than others to provide different volume levels.

-Hal
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Re: PA System Amplifier Speaker Question
« Reply #5 on: April 01, 2021, 11:45:09 pm »


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