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lower intercom speaker volume
lower intercom speaker volume
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Old 15th March 2014, 06:08 AM   #1
broman973 is offline broman973
diyAudio Member
Join Date: Mar 2014
Default lower intercom speaker volume

My condo association just installed an intercom system for my building. My problem is that my speaker volume is too loud for my preference. My understanding is that the main unit at the building entrance passes the same "ring" tone to any condo whose switch is pressed, so I can't alter my volume at the unit without affecting others.

So, I connected a voltage divider circuit using 1/2 watt resistors in a L-pad configuration. My intercom speaker is 45 ohms, 0.5 W max. I used an online calculator to determine practical values: 22 ohms (series), 47 ohms (parallel) = 5.8335 db = ~33% loudness reduction... good enough for me. I checked the math; works as expected. I know the wiring is right; ringer to series resistor, junction point to speaker, and speaker & parallel resistor both to common.

For some reason, the ringer loudness sounds the same. I don't know what the issue is. Should I have used a U-pad configuration? Is it because the intercom speaker can also act as a microphone?

If it helps, this is the terminal assignments of the intercom circuit board I took from the manual (and confirmed by the wiring):

X = speaker output / microphone input
1 = common
2 = talk (pressing "talk" button shorts 2 with X)
3 = listen (pressing "listen" button shorts 3 with X)
... then there's a "open door" button, which shorts 2 and 3)

Terminals 1, 2, and 3 are daisy-chained among all condos, and X has only one wire... so I know the L-pad should be connected between X and 1 (with the speaker connected at the pad junction point instead of X).

Your help and ideas are greatly appreciated.
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