I have a pair of Edifier R200DB connected to my PC via a Rodecaster Pro (Speakers > Rodecaster Pro > PC). Due to the layout of my ultrawide monitor, I had to mount them about a feet higher than my ears and cannot point them downwards, so the sound comes from above. Can I add a center speaker such as this one so I can put it below the monitor? If so, do I need additional equipment?
You can do it but you’ll need an amp to power the passive speaker. Might be able to use the headphone out on your interface.
And software shenanigans to do what you want because nothing except films and even in that case will use the center channel, in the movies case you’ll be on 5.1 tracks so you need to downmix the remaining channels. And for music and random content either the center will play the same thing as the edifiers so effectively lose stereo or you do some custom upmix in software. If they play the same content you also need to time align all the speakers to not suffer huge cancellation issues.
All in all not recommended unless you wanna throw 10s of hours of messing with software at the problem for questionable gain