I am currently looking for a multiroom speaker system which does not force me to place wiretap into my home. Also it should be able to simultaneously play the same song on multiple speakers. Which device can you recommend me?
Best would be if no additional internet connection is necessary.
What I've done recently is grab one of the bluetooth FM transmitters for cars, that let you connect your phone and it broadcasts that onto a FM radio station.
They actually reach a lot farther than you think. Now any FM radio in your house will be perfectly in sync, and as many as you want. This has a limit depending on how thick your walls are but they're cheap as hell and work well.
Sonos is probably the easiest one as others have mentioned. A bunch of raspberry pi’s with pulseaudio configured for remote streaming from a master audio source could also work for playing the same song in multiple locations if you want a more diy approach
I'd imagine the pulseaudio approach would suffer from lag and inability to sync between devices. That's something that seemingly only Google and Sonos have solved (collaboratively at that - part of the source of the drama between the two in court).
Lag wasn’t terrible when I did it with one speaker, I’ll freely admit I have not tried it as a whole house setup but I’ve seen guides out there from people who have
Admittedly, I just use Sonos myself. However, I do hope to one day move to something else more open.
BluOS is another solution to look at. It's still pricey, but works offline and higher quality than Sonos if you're someone who has lots of high res music files.
Can't vouch for it, but looks interesting and according to the GitHub is still being updated so worth a look if you don't mind putting in some work and tinkering.