Building my own powered 12v speaker?

[SirJ]

Does this sound like a cool project? In my mind it does.

Over the years I have collected a lot of Motorola, Kenwood, Tandy corp speakers. My favorite speaker is the Motorola used with Astro spectra and xtl series. Yes I know there are a few different models of the Motorola speakers.

I could install this inside the housing with pigtails etc but I need to know if the 4 terminals on the board are used for 12v in and speaker out? As I do see a input and variable resistor for volume.

4.2US $ |LM386 10W Mono Amplifier Board Mini Desktop PC Speaker DIY radio Boombox 3.5mm DC3 12V|Amplifier| - AliExpress

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[RFI-EMI-GUY]

You are not going to get much more than 1/2 watt audio from an LM386. That plus a bunch of distortion.

 

[AK9R]

Might look at the ST Micro TDA series for a little more power with less distortion.

 

[slicerwizard]

I need to know if the 4 terminals on the board are used for 12v in and speaker out?

Yes, they are, but as noted the claimed audio output power is a joke. There's a reason that IC doesn't have a heat sink - it ain't no 10 Watt powerhouse.

 

[RFI-EMI-GUY]

Whatever amplifier board you choose, be careful how you interface to your radio. Most radios have BTL , or bridge tied load, audio amplifiers. They want to see a speaker, period. Any load that goes to ground or voltage will damage the radio, or at best make bad distortion. You can fool the radio into thinking you have attached a speaker with an audio isolation transformer and avoid damage.

 

[slicerwizard]

A series-connected non-polarized capacitor should suffice. Assuming the radio and amplifier share a common ground, nothing needs to be connected to the ground side of the amp's audio input.

The amazing AliExpress 10 Watt LM368 board already has a series cap in the audio amp input circuit. And it's still a POS...

 

[GregOH]

Those class D amps perform best with 24 volts. I have one to be used with a sub and have a 20v laptop brick powering it for a home theater application. There are many of those boards for sale at Amazon cheap and if being used in an automobile, I'd get a 12 to 24 volt step up converter and you will get plenty of audio output from it.

 

[prcguy]

The few times I've built a powered speaker I made a resistive attenuator with a couple watt 10 ohm resistor across the input to give the source amp a reasonable load. Then depending on if the source can live with a grounded speaker line a simple variable resistor to the input of the amp feeding the speaker or a 600/600 ohm transformer with 600 ohm resistor in transformer primary to DC isolate the source amp then a variable resistor at the output of the transformer to the input of the speaker amp.

A problem I've seen is most powered communications speakers have an equalized response for voice and using a wide band hi-fi amp results in a lot more hiss and noise than a communications specific powered speaker. You almost have to build a low pass filter in the 3-5KHz range to cut down the hiss and noise.