I don't use OpenHAB or Home Assistant, but I'd be extremely surprised if they don't have existing functionality for connecting microphones, speakers, and LLMs to set up voice-controlled stuff.

searches

https://heywillow.io/

Willow Is a Practical, Open Source, Privacy-focused Platform for Voice Assistants and Other Applications

Willow is an ESP IDF based project primarily targeting the ESP32-S3-BOX hardware family from Espressif. Our goal is to provide Amazon Echo/Google Home competitive performance, accuracy, cost and functionality with Home Assistant, openHAB and other platforms.

100% open source and completely self-hosted by the user with "ready for the kitchen counter" low cost commercially available hardware.

https://rhasspy.readthedocs.io/en/latest/

Rhasspy (ɹˈæspi) is an open source, fully offline set of voice assistant services for many human languages that works well with:

• Hermes protocol compatible services (Snips.AI)
• Home Assistant and Hass.io
• Node-RED
• Jeedom
• OpenHAB

For passive, and even now some active loudspeakers, very much so.

Links for passives: https://sites.google.com/site/undefinition/diy https://www.zaphaudio.com/ https://www.madisoundspeakerstore.com/speaker-kits/ (etc)

Active speakers are usually things like this and use commercially available parts with commercial software. But if you want you can build a DIY DSP and DAC and DIY amplifier. Note that there are tons of other designs for both available.

The DIY audio community is very vibrant. There are tons and tons of forums collaboratively iterating. You can build DIY headphones and DIY headphone amplifiers. Hell, you can even build DIY speaker drivers.

Anything I missed was not an intentional omission, lol.