What is the correct way to combine 2 audio outputs?

[bitter bluff]

To be clear, I want 2 physical audio devices plugged into the same speaker.

[loud dome]

audio interface or basic switch

[drowsy stone]

Use a simple interface like Fifine

[plain sky]

If you want to blend them you want an "audio mixer" broadly looks like fifine a company that makes them.

[jagged lava]

IDK what you have as hardware. But what I did back in 2012 was to get a a p2 audio cable to plug my iPad to my desktop line in 3.5mm jack. This solved my problem, since i enabled the "listen to this device" option so I could listen my computer`s audio together with the iPad

[bitter bluff]

To be clear, I am talking about physically separate devices.
Specifically a console and my PC

[still scarab]

You would need a device that mixes the audio. You can't just splice the wires.

You can also use the Line In port on your PC, then select "Listen to this device", but if we are talking gameplay, the listening feature often has about a second of lag.

So music this way is fine, synced gameplay/video is generally not.

[bitter bluff]

If I do splice, will it just half the volume?

[loud dome]

It would backfeed the device not sending audio, potentially frying it

[still scarab]

It would halve the volume if you sent one signal to two different devices (speakers/headphones).

Splicing the signal from two outputs together would at best cause interference and at worst, one device would try to drive the other and fry it.

[loud dome]

this is also assuming a perfect world where both devices have the same impedance

[still scarab]

Sure

[bitter bluff]

Not necessarily, from my tests. My speakers have a high input impedance. Now, 2 headphones, definitely.

[still scarab]

Yes, they would require equal impedance for the volume to actually halve cleanly.

[bitter bluff]

I have attached a similar load in parallel to the PC speakers and it didn't change anything beyond measurement error.

[bitter bluff]

Ooo, frying would be bad...

[loud dome]

output splitter is fine, input merger is not

[bitter bluff]

I will see about fixing the powered signal merger I made in response to the initial response and the cost of them online.