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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Installed Sound/Contracting => Topic started by: Joseph D. Macry on August 12, 2015, 11:15:33 PM
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A school wants the Gym PA system relocated. Run across this crossover being fed by an old Dukane in-wall mixer/amp. The outputs feed two HF lines to biradial horns above and below one central woofer box. (Haven't gone up high yet to inspect it, will post pics here later.)
So I looked up the schematic on the Webs. The underside of this unit contains a resistive network used by the HF Attenuation Selector. The two plastic cubes contain transformers.
What the schematic does NOT show is that big 50-ohm resistor between HF-R and LF-R terminals. What the heck is that resistor doing there?
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That looks like a "add on" by somebody.
That DOES NOT mean it is correct or useful.
Maybe somebody had an idea but did it wrong.
I would take it off and wire it up as it should be.
HOWEVER I would replace the caps in the crossover. Those old paper caps can "dry up" over time.
Get some new electrolytics or better yet some poly caps.
It won't cost very much.
ALSO note that the crossover freq is for a 25 ohm load.
If your load is not 25 ohms, then the crossover freq will the higher or lower.
Just something to consider
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Dust it off for the museum...
JR