Heya quick question - I'll be connecting the LG C1 OLED tv to my 3080ti pc in the next room via HDMI 2.1. In order to use an Atmos capable soundbar I would need to plug the HDMI into one of the TVs eARC ports and then another HDMI cable between a second eARC port and the soundbar's eARC port? Is that correct? In that case, I don't need a soundbar with a 4K120hz passthrough, right? Sorry for my dumb explanation
Cheers!
A TV only has one eARC port. The TV HDMI sockets are all audio/video inputs. eARC is a seperate audio channel where the audio travels the opposite way.
So if you want to plug the PC into the TV hear audio from the soundbar, plug the PC into any TV HDMI except the one marked eARC. That delivers audio and video to the TV. Connect another cable from the TV eARC socket to the soundbar HDMI output. That is also marked eARC. That gives you an audio connection from the TV to the soundbar.
in TV settings turn on eARC and set the audio to “passthrough” from the TV HDMI input (PC) to the soundbar. On the soundbar set the audio input to Din (on most) which is usually the eARC and optical (if it has that).
Now the audio from the TV passes through the TV.
4K/120Hz passthrough is a different thing. That is video passthrough. If you plug an audio/video device into a soundbar HDMI input, the soundbar can take the audio and process it without interference from an intermediate device (like the TV). The video then passes through to the soundbar HDMI output - the one marked eARC for audio return. Only only soundbar has the ability to pass 4k/120Hz video as far as I know so for those wishing by to see that video feature, they need to connect to the TV.
Some TVs don’t deal with audio passthrough very well and there can be issues with lip synch that can’t be fixed (without a third party expensive device - the audio is behind the video and needs a negative delay), or some audio codecs simply don’t passthrough properly or at all.
Basically if you want the soundbar to get audio as intended, connect the A/V device to a soundbar input and a cable from the soundbar output (marked eARC) to the TV input also marked eARC. That connection delivers the video to the TV and audio from the TV channels and built in apps to the soundbar. HDMI switches are fine if you don’t have enough soundbar inputs.
if you must have 4K/120Hz video, you need to connect to the TB and see what audio passes through to the soundbar. If you are lucky you may get the expected audio from the soundbar without issues.