being somewhat if not mostly deaf I'm not by any stretch of imagination, an audiophile. But I find myself needing some guidance on speakers and signals.
I am building a gsm gate system for a friend whose gate is half a km from the house and whose daughter was recently traumatised by an unwanted visitor.
the intercom system (gate and mic) is by videx, has an amp inside, an electret mic and an 8Ohm speaker. It takes a single speaker input.
the gsm800L module I have exposes only the SPK1 pins; which are a differential output and can, so the datasheet says, directly drive a 32Ohm speaker.
I have tried directly connecting the module and the speaker, without the amp, and get a very very quiet signal - sometimes. Most often I get an under or voltage warning on the board and it closes down. I imagine because too much current is being sourced from the speaker pins.
I have also tried connecting the SPK1P pin (and the N pin sometimes) to the speaker input of the amp - and just get garbage noise and the occasional under/over voltage warning from the module as it shuts down.
I have read that with differential speaker output it is feasible just to ignore one of the outputs (leave it floating) and for the mic, tie one to ground. this was my intent.
Am I on a hiding to nothing trying to get the amp driving an 8Ohm speaker to accept input destined for a 32Ohm speaker?
If so, can someone point me to a potted primer on the dangers/necessities of impedance matching? or otherwise a pointer to a minimal-component amp circuit to take differential input intended for a 32ohm output and push into a speaker loud enough to be sensibly audible outside on a road?
I don't mind replacing the speaker with a 32Ohm equivalently sized alternative. it would be an annoyance but not fatal.
many thanks in advance for your collective wisdom.