Here I'm testing some mini speakers with a small stereo amplifier. I found that the audio output from the RPi was just a bit low for my liking, apparently it's not meant to power headphones directly. So I decided to use USB soundcard, which also meant I then needed a USB hub to split the single remaining internal USB port (for the Teensy and the soundcard). This caused some issues with the USB hub dying when things got hot inside the case, so in hindsight it might of been best to just deal with the lower audio volume.

I put analogue volume control wheel in between the soundcard and the headphone jack, and the speakers are disconnected when headphones are plugged in.

The speakers are contained within the controller body and the gaps around the analogue joysticks conveniently allow sound to pass through, without having to make any extra holes.