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Author Topic: Oddball question for temporary installation  (Read 488 times)

Chuk Gleason

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Oddball question for temporary installation
« on: July 02, 2014, 08:27:37 pm »

OK, here's the deal.

I'm normally a two-way radio tech, but in my current job with a municipality, I've had to pick up on sound distribution.  Because we have a whoooole bunch of fire stations in the city, of all different ages, and quality of installation of what we call the 'ring down' system - Dispatch pages out a station with paging tones, the receiver at the station decodes, trips a relay to light the lights, and audio is fed to a PA for distribution throughout the station.  Except, many firefighters hands on audio systems make for large clustergaggles.  Rats nests.  Poor speaker selection, overdriven speakers, you probably get the idea. 

So I came up with a basic design, radio to 70V amp feeding new decent and decent looking speakers thu the station.  Not hi-fi quality, but the audio is clearer, we have adjustment where needed within a decent range, etc.  Workable.  And documented, so the next yutzhead that comes behind me is not completely lost.  As time and budget allows, we're re-doing stations to rip out crap & install this.

Now:  I've got one station that will be undergoing renovation in about 9 months, but before we can get to it, the guys want a speaker in an area not served.   But if I put in a standard 70V speaker, tap it for a couple watts, run the wire back to the radio and use another (salvaged) 70V matching transformer in 'backwards' configuration, fed off the radio's internal speaker circuit, will this work?

Somewhat graphically:

(radio)(radio speaker, about 4 ohms)--> (transformer, stepping up to 70V)--> (cable)--> (new speaker, with integral transformer). 

Or am I all wet?  Just needs to run decently until other obstacles are out of the way.

Thanks in advance,

Chuk Gleason
Cary, NC


Milt Hathaway

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Re: Oddball question for temporary installation
« Reply #1 on: July 02, 2014, 08:33:41 pm »

Yes, that will work. That's essentially what you are doing now with the new installations, except the 70V amp already has that first transformer built in.
FitzCo Sound, Inc.
Midland, TX

Cailen Waddell

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Re: Oddball question for temporary installation
« Reply #2 on: July 02, 2014, 08:43:13 pm »

Shoot me an email at my work address, Cailen dot Waddell at townofcary dot org.  I'm sure we can help if you would like, I do fair bit of 70 volt work around town... I'm located at the arts center.   

Your premise is essentially correct.  You could also potentially bypass the transformer, unless the distance is a long ways away...

Good luck, and happy to help if needed. 

Sent from my iPhone using Tapatalk

Chuk Gleason

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Re: Oddball question for temporary installation
« Reply #3 on: July 08, 2014, 01:14:55 pm »

Just a quick update, works as desired.  Two-way radio's speaker leads to the 8 ohm 70V. side of the transformer, took the common & 10W. leads of the other side, connected them to the same leads of the transformer of the ceiling speaker, nice level, good adjustment, no distortion. 

What a country!  You can even teach old radio guys new tricks!

Nice quick, not too dirty temporary solution until we can get in there & do our full upgrade.   


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