I didn't even know that was a feature. It works now and I am extremely sorry for wasting your time!

I am bad at this game, but not that bad

https://i.imgur.com/svtMQ53.jpg

Here's how it looks with all mods enabled expect electric furnaces: https://i.imgur.com/sBHIGR1.jpg

Extremely weird. It were the last mod I disabled, since it seemed so unlikely.

Modlist: https://i.imgur.com/hutYepC.png

And thanks for the quick response!

EDIT:
I tried in sandbox again. It seems my speakers only work, when I disable the mod on my main save. But they work in sandbox, even when ...

I have searched for a solution both here and on Reddit, so either I am a idiot or there is something funky about the speakers. (Properly the first)

The speakers should play a sound, when the total amount of coal in the chest = 0. But there is no sound and no coal in that chest.
The light function ...