70V Audio System: Junction Boxes Needed?

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  #1  
Old 10-01-14, 10:07 PM
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70V Audio System: Junction Boxes Needed?

I'm going to be changing some 70V outdoor speakers tomorrow. Currently, the speaker wire runs to connections right on the back of the speaker, which have since corroded away. On the new speakers, there is a length of SJO-like cord that runs out of the speaker housing. I will be running that into the building, where I will be making my splices inside. Will these splices need to be in a box, or is this still considered class 2?
 
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Old 10-01-14, 10:26 PM
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No.... junction boxes are not required for class 2 70v speaker wiring.
 
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Old 10-03-14, 05:26 PM
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Thanks for your reply! Speakers are in and all is good!
 
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Old 10-03-14, 05:53 PM
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You are da man.
 
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Old 10-03-14, 06:13 PM
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You are da man.
Thanks! Now just to get the equpiment into a real vented rack and replace most of the tired equipment with new modern equipment.
 
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Old 10-04-14, 05:52 AM
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Drip loop between the speakers and wall?

Just an FYI -- The new amp should be at least 20% overpowered after you add up all of the speaker wattages you've tapped. IOW if you have 100 watts on the speaker lines the amp should be at least 120 watts.
 
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Old 10-04-14, 09:46 AM
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Drip loop between the speakers and wall?
I left a rather large drip loop, and went through the building with a wet-rated box cover and compression cord grip. Inside the buildings I soldered my splices and covered them with adhesive-lined heat shrink.

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Old 10-04-14, 01:34 PM
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The shrink with glue makes an excellent waterproof splice.
 
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Old 10-05-14, 07:10 AM
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Beautiful! Too many people forget or ignore the details!
 
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Old 10-05-14, 07:30 AM
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The amp should be at least 20% overpowered ...
Note that a published speaker wattage is the maximum wattage the largest speaker (driver) in the speaker unit can take without danger of burning out.

While a lower powered amplifier will usually provide adequate sound volume, it is important not to turn it up so high that distortion is noticeable. In a multi-speaker unit, the tweeter(s) will burn out before the power rating is reached if the audio is unusually rich in higher frequencies. Such speaker burnout is likely if an amplifier is overloaded or can occur if the content is not representing sounds heard in nature or from performances using non-electronic instruments.

A system reproducing music with a lot of bass requires more power than a system used for background music or voice announcements.
 

Last edited by AllanJ; 10-05-14 at 07:48 AM.
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Old 10-05-14, 02:42 PM
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While a lower powered amplifier will usually provide adequate sound volume, it is important not to turn it up so high that distortion is noticeable. In a multi-speaker unit, the tweeter(s) will burn out before the power rating is reached if the audio is unusually rich in higher frequencies. Such speaker burnout is likely if an amplifier is overloaded or can occur if the content is not representing sounds heard in nature or from performances using non-electronic instruments.

Because this is a 70V system, the amplifier stays at "100%" volume the whole time. Each speaker or set of speakers has its own volume control mounted nearby, and the volume is limited by the transformer taps. I have the one pictured at the 50W tap, it goes all the way up to 200W on this model. The amplifier has to be sized greater than the total speaker load, as it will burn out otherwise.

A system reproducing music with a lot of bass requires more power than a system used for background music or voice announcements.

This system in particular is used for background music and paging.


Beautiful! Too many people forget or ignore the details!

Thank you! The details are everything!
 
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Old 10-05-14, 02:49 PM
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You should set the amp level so that when the remote volume controls are at maximum the level is where you want it. Running an amp at 100% volume and then setting each volume control to low will cause the amp to overheat.
 
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Old 10-06-14, 05:34 AM
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Don't confuse constant voltage speaker systems with low-impedance speaker systems.

Each CV speaker will draw wattage according to its transformer tap settings. The standalone volume controls in these systems are actually autoformers. They take no portion of the signal to ground. As you turn down the volume the impedance increases (into the thousands), so the load presented to the amp gets lighter as they are turned down. Turning them all the way down opens the circuit. The only limitation on the volume control is, again, the wattage tap of the speaker. The VC must be rated for equal or higher wattage than the speaker tap.

Potentiometers that are incorporated into a CV speaker (for example, in the center of a ceiling mounted speaker baffle) are inserted on the low-impedance side between the transformer and the voice coil. In this case, they take a portion of the signal to ground when turned down. The effect on the primary side of the transformer -- and therefore the amp -- is minimal.

Justin, are those Community R series speakers?
 

Last edited by Rick Johnston; 10-08-14 at 05:41 AM. Reason: "effect", not "affect"
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Old 10-07-14, 02:00 PM
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Justin, are those Community R series speakers?
I know they are Community, however I don't know which specific series. They had a really nice sound when I bench tested them.
 
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Old 10-07-14, 08:21 PM
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Probably the R25's. An 8" coaxial speaker in a gray cabinet. Those bad boys are like $400 a pop.
But they do sound good.
 
  #16  
Old 10-08-14, 05:40 AM
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The company I work for used 120 R1's and R2's at Coca Cola Field (MiLB) in Buffalo. The system is really clean.
 
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Old 10-08-14, 09:31 AM
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Those are cranking speakers...... I can imagine how good that must have sounded.
 
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Old 10-09-14, 08:54 PM
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Those are cranking speakers...... I can imagine how good that must have sounded.

They sounded beautiful at home on my Bogen amp. When installed, they sounded like crap, like the rest of the system. I believe it's how the original installer set the GraphiQ, as well as heat buildup from being in an airtight cabinet and other useless pieces of equipment that are no longer needed. Once we're done with this I'm going to have all of the equipment in a vented, fan-cooled rack, as well as a new Samson S-Zone mixer and 2 4-channel QSC amplifiers.
 
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Old 10-09-14, 09:09 PM
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4 channel QSC amps ?
Are you bridging amp channels to get the 70v line ?
 
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Old 10-09-14, 09:56 PM
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4 channel QSC amps ?
Are you bridging amp channels to get the 70v line ?

QSC makes 4-channel 70V amplifiers.
 
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Old 10-09-14, 09:59 PM
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Perfect.... wasn't aware of that unit.
 
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