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70 volt distributed audio (PA System) Help

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Jeff Ford:
    I am a complete newbie to audio, been in industrial maintenance for 30 years. I was resently asked to install 8 ceiling mount speakers in the restrooms in our plant so no one would miss an emergency announcement while taking care of business. Being me I started asking questions about the curent system such as current system wattage and load and no one could answer any questions so it was time to dig in. What I found, I believe, is a severely overload system. I found a system with close to 500 watts of speakers on a 120 watt TOA amp. I have been going through the 37 speakers, 31 horns, and now 6 cieling speakers on this 8 to 10 line system and adjusting the wattage taps and am now down to around 250 watts and with about 34 ohms impedance. I know I am over on the wattage but am within line on impedance max of 41 ohms. So my first question is which is more inportant, wattage load or impedance. This system has been running at this load level for probably some 10 plus years with what seems to be some minor feedback issues at some phone locations when paging. Its seem to have helped with feedback after adjusting the speaker wattage level lower but still some issues. The company seems willing to put some money into it just not sure best direction to go as most acticles I have read would direct toward an amp in the 500 watt size to get back to the original speaker tap settings allthough I believe some could stay where I have them now. Looking for some direction.

Caleb Dueck:

--- Quote from: Jeff Ford on October 26, 2021, 02:01:31 AM ---    I am a complete newbie to audio, been in industrial maintenance for 30 years. I was resently asked to install 8 ceiling mount speakers in the restrooms in our plant so no one would miss an emergency announcement while taking care of business. Being me I started asking questions about the curent system such as current system wattage and load and no one could answer any questions so it was time to dig in. What I found, I believe, is a severely overload system. I found a system with close to 500 watts of speakers on a 120 watt TOA amp. I have been going through the 37 speakers, 31 horns, and now 6 cieling speakers on this 8 to 10 line system and adjusting the wattage taps and am now down to around 250 watts and with about 34 ohms impedance. I know I am over on the wattage but am within line on impedance max of 41 ohms. So my first question is which is more inportant, wattage load or impedance. This system has been running at this load level for probably some 10 plus years with what seems to be some minor feedback issues at some phone locations when paging. Its seem to have helped with feedback after adjusting the speaker wattage level lower but still some issues. The company seems willing to put some money into it just not sure best direction to go as most acticles I have read would direct toward an amp in the 500 watt size to get back to the original speaker tap settings allthough I believe some could stay where I have them now. Looking for some direction.

--- End quote ---

Hire a company that specializes in this, no offense intended.  Especially if this is safety related.  What about all the details that we on the forums can't know - intelligibility, coverage, type of cabling, how well it was installed, emergency pre-recorded messages, paging from phone system, etc. 

Mike Caldwell:
What Caleb said!

Some things a professional company should consider and or know about....

- What is the ambient noise in some zones.
- Instead of one big amp consider breaking the system up in zones.
- Some system processing could help the over all sound and maybe feedback issues.
- For the feedback issues there are a few units that record the paging message when
  pick up a phone and dial the paging extension and when you hang the phone up
  it will playback what was just recorded, doing that break the feedback loop.

Jeff Ford:

--- Quote from: Caleb Dueck on October 26, 2021, 02:06:34 AM ---Hire a company that specializes in this, no offense intended.  Especially if this is safety related.  What about all the details that we on the forums can't know - intelligibility, coverage, type of cabling, how well it was installed, emergency pre-recorded messages, paging from phone system, etc.

--- End quote ---

No offence taken, I honestly believe they would leave the system the way it is ( it's working mentality) vs bringing someone else in from comments about past companies. I have no past history of who worked on/ installed but would believe it was not a top name in the business. System coverage is another reason I was adjusting wattage settings as some areas where very loud and others not so much. The loudest aeras in the plant top out at 80db with an occasional spike of a few db with other working areas in the 60db range. This is something I have been walking the plant monitoring so I can make adjustments on the weekends when no one is working. the cabling from what I have found is 18 to 20 awg with the exception of 2 single speakers each ran with data cable. All runs in the ceiling and tied to the beam supports, I haven't found any cabling ran near/with ac lines at this time. The one recorded emergency message (weather) we have is what I have been using to check coverage throughout the building. This system has 5 amps controlling different parts of the plant with each having music, tone and message inputs with the music no longer being used.

Mike Caldwell:
Sounds like they already have the plant divided up into something like 5 zones.

60db is really quite, is that in the office areas. 80db is actually quite for any manufacturing
type of plant on the floor, if that's what kind of plant this is.


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