There are lots of things Roon can be doing in the background during idle, like retrieving updated metadata for all your albums.
Just keep in mind that the Roon Core is designed to be reasonably “heavy” so I wouldn’t get too hung up about resource usage, unless it’s causing other issues.
Are you experiencing any other symptoms? Dropouts? Slow performance in Roon? Resource problems with other apps? It’s ok if you’re just wondering about the numbers, but these don’t look too concerning to me.
The activity per process shown in “Activity Monitor” on OSX is only showing you the CPU usage in relation to one core. Depending on what processor you have, overall CPU usage may be half (Dual Core) or a quarter (Quad Core) or even one eighth (Multi-Thread Quad Core) of that shown next to the Process in the Activity Monitor window.
Have a look down the bottom of that window where it says “System”, “User” and “Idle”.
The actual overall CPU usage is the total of System + User shown there. You should find that there is less CPU usage overall by a factor of 2 or 4, or even 8 if multi-threading is being used.
As an example… See Below - You can see that Roon Appliance on my Quad-Core Mac Mini is using 22.2% of just one core! Look at the bottom and you can see overall CPU usage, including all the other processes I’m running is just 7.8%.
Now… if I do something really processor intensive, such as compressing video in Handbrake, for example, See below… Next to the Handbrake Process, you can see CPU usage is 751.8%! This is because 8 threads over all four cores of my CPU are being used. If you look at the bottom now, you can see the overall CPU usage is just over 98%.
Hope that clears it up a bit. Your 57.2% is just 57.2% of one core… your overall CPU usage should be a fraction of that…
These are great explanations, but the OP is still running Roon Core+Control on his iMac. The Innuos ZENith does not have Roon Core capabilities (but does UPnP server duties and storage) as far as i know. (Added in MkII?)
So basically, the only thing that has changed is that @Matt_Cuttler has moved his media files to the ZENith? If this is wrong i apologize.
I’d recommend returning the ZENith and instead going for a NUC7/8 i3 and adding an externa USB drive with media files. Install ROCK and you are ready to move the processing to that machine.
(Or go for the MkII series of Innuos)
I have found in my systems (Windows as I don’t have a Mac), that if I have first installed Roon on PC as a core server; then later if I point that installation of Roon to another Roon Core to use it as a client interface; that it is still running a Core while the program is active. If I run a Roon install and have it setup initially as a client, then the core “peice” is never installed.
You might try uninstalling Roon on the iMac, and then re-installing it and choosing the option to connect to the new core.
As @Rugby mentioned, I would make sure that none of the old Core server components are still running on that Mac that is now in remote mode. I would perform these steps on the Roon Remote OSX to have a fresh Roon install and then use it only as a Remote: