Question

For example it says in Focal Alpha manual:

In order to allow you to plug up to two audio sources to the monitors using RCA and XLR inlets, please note that both inputs will remains on. If you want to take benefit of this feature by plugging two audio sources, make sure only one audio source is on to avoid any unwanted interaction or sound from the second audio source. 

Question is, is this possible with R65/80? 

Answer 1

The R Series have XLR and TRS 1/4 inch (balanced) inputs and an RCA (unbalanced) input connections.  The manual states that if you connect XLR and TRS, the TRS will take priority over XLR.

The manual does not specify the nature of the RCA inputs.

So it will either work along with the balanced inputs or it will not.

Ultimately, it isn't really good practice to "mix" or "merge" audio source at your speakers.  This is what mixing consoles are for.

Even the quote you used generally covers this.

" make sure only one audio source is on to avoid any unwanted interaction or sound from the second audio source.  "