In my quest for compactness, I wanted to get rid of the external speaker and even the earphones when I use the QMX+ to work FT8. Of course the idea is to use an internal speaker.
I was inspired by the video https://www.youtube.com/watch?v=_nVHPMhoixA from George VK2AOE. For his project, George used a very bulky circuit board and a really big speaker. On the other hand, the very nice ABS for QMX+ transceiver project uses a very compact loudspeaker, and no hole in the cover, the authors say, is not necessary. So I didn't drill holes in my pristine case, but in the near future I will probably use another way to pull out the sound from the box.
When I ordered the QMX+ from QRP Labs, I also bought the development kit, which is very handy for making a few additions. My wiring is very simple. The LM386 board (affiliate link below) is soldered to the development kit just for locking. The ground line comes from JP101 and the +12V line from JP105. JP105 is active only after power-up. As the LM386 should not be powered at more than 12V, and my PSU sometimes delivers a little more, I put a diode in series.
I placed the circuit and speaker in the back because I wanted room to accommodate another addition, hence the screw terminals near JP101.
For wiring the audio input lines, I copied what Chris K1NLW did: the two channels (the QMX+ has a stereo audio output) are summed together using 1.2KΩ resistors.
I chose the speaker (affiliate link below) listed for the ABS project because I hope to replace this hack and the next one (internal power supply) with it, so I already have the right speaker. It's attached to the board with double-sided tape.
Once the box was closed, well, it worked! The sound isn't great, but it's good enough to know if FT8 has traffic and that my antenna is properly tuned!
LM386 Audio Power Amplifier Module: https://s.click.aliexpress.com/e/_oFM9vLn
8 Ohm 28 mm Loudspeaker: https://s.click.aliexpress.com/e/_oB3eSG5