Phone project: Same speaker for headphones and loudspeaker

Projects General Guidance
1

Hey all,

i am building a small phone project and have a question regarding the usage of speakers.
I'm using an Arduino Nano, SIM7670 module and a PAM8302A amplifier.
The SIM module has a mono output, and i can either directly connect my headphones (62 Ohm) or my loudspeaker (8 Ohm via amplifier), both work fine.

Because of space issues, i was thinking to use the same hardware for both cases.
So to have a loud volume when the phone is ringing, and a very low volume when i'm picking up.
Since they have different impedances, i was thinking of using a SPDT switch after the amplifier to put a resistor in series to the speaker, so i can change the impedance, hence the outgoing volume.

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Do you think this might work, or did you maybe even build this once?

Thanks and have a good weekend!

2

Sure it will work. An 8 Ohm resistor will reduce the volume by half. A 16 Ohm resistor will reduce it even more.

3

I wish to differ, an 8 Ohm resistor will reduce the power by half, it will reduce the volume by 3dB, which is barely noticeable.

4

Yeah. Wrong choice of words!

1 Like
5

Actually I'm wrong too, the power in the speaker will be reduced to one quarter, so 6dB drop. Total power will be half.

6

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