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70v load monitoring


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#1 soundship

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Posted 25 March 2004 - 01:26 AM

I need ideas. We have 2 Crown amps with IQ PIP Lites. The system drives 4x70V lines (impedance ranges 45- 90 at 1K for the 4 lines). The lines need to be supervised because they are part of the voice-evac for the facility. If I use a moderate signal and drive the lines everything is OK. If there is a fault, the Aux puts out 15 volt and it trips a relay. However, the Zoo wantes the system quiet most of the time. The animals (Gorillas) get agitated with constant noise. With out making noise, the "nominal impedance starts to fluctuate and eventually triggers a fault on the fire panel. It was sugested to solve the problem we could run a 17-18K tone and this would be above the range the patrons would hear. The animals do hear this and it would be a problem.
blink.gif Is there a way to make this work? Are there different cards that would work better? Fire Marshal comes Friday.

In a different facility we used USP-2 Ultra Series with the Crown System Interface and it works great. I understand these components are no longer available. We use IQwin with that system.

#2 soundman5150

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Posted 25 March 2004 - 06:09 PM

can you use the fire alarms audio? not sure what you are doing with system. If you want you could run speakers at 25V with the alarms amps which is supervied. these amps would not be as good as the Crowns.

what about end of line resistor? to help keep it line not sure how that math would work.

Or if you like me want to keep Crown stuff use relays to switch feed to and from Crown's amps

so when not in use is connected to fire alarm with 10K resistor on it then when in alarm feed switches to crown outputs to drive speaker or you can switch relays to play music

#3 T Harrison

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Posted 25 March 2004 - 06:46 PM

Have you considered using a sub-audible tone such as 20Hz rather than a super-audible tone (20kHz)? This might act as a suitable stimulus signal, without being in the conscious hearing range of the animals?
You will likely need to experiment with the frequency and level somewhat, as you don't want to saturate the loudspeaker's internal transformers and generate unnecessary heating of the transformer. Also, you need to be careful that a constant low frequency signal which is getting near to DC is at a sufficiently low level not to heat the voice coil too much. Conversely, you may find the heating effect prevents driver problems in very cold temperatures during the winter months, even if it results in earlier driver failure than if it had no stimulus.

Just some food for thought...

#4 Terotec

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Posted 26 March 2004 - 06:34 AM

I agree with T Harrison, although it may be worth consulting with zoo experts as to the hearing ranges of the animals in the different zone areas, some may be have hearing which does not reach 19Khz, but do hear low frequencies so a mix and match policy may have to be deployed.

#5 Bradford Benn

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Posted 29 March 2004 - 09:36 AM

The other thing to consider is what is the frequency response of the speakers? I have a set of 70V speakers on my desk that I run a supervisor tone on. I checked with my RTA and they do not pass anything above 18kHz.

Another option is to put filters between the transformer and the components to remove the disturbing frequencies.
-=Brad

Bradford Benn
Business Development Manager - Crown International
http://www.crownaudio.com/