First, let me say that I completely agree that the CPU efficiency in Studio One is definitely behind that of other DAWs. Coming from Sonar and Pro Tools, I would say Sonar, at least, is 2-4 times more efficient than Studio One with large projects. Sonar just did a huge overhaul of it's CPU efficiency and specifically it's multi core efficiency and it's just incredibly powerful now. I see no reason why Studio One shouldn't be able to do the same. Also, I believe Sonar has a feature that temporarily bypasses plugins automatically during playback for tracks that have no content or something like that. Really smart way to save CPU. So yes, PLEASE update the engine to be more CPU efficient!
All of that said, I love Studio One so much I just can't get away from it.
But I'm writing here for another reason that hopefully helps people until CPU efficiency is fixed.
I came to this thread and (the other similar feature request) when I searched CPU spikes in Studio One on Google. I was having horrible CPU spikes that would only show up with larger projects and it was driving me insane. I'm running an I7 6800k with 64gb of Ram, multiple SSDs, etc. and should not be having random CPU spikes. I tried running Latency Mon, disabling all my drivers, reinstalling Studio One, killing all my processes, Disabling C states and EIST in BIOS - everything I could find. Still, the spikes were killing my workflow and making it really hard to get stuff done.
I had read in a few places about disabling Turbo Boost in BIOS (and Turbo Boost Max) but had decided that there was no way I was going to sacrifice CPU power. Well, it got bad enough that I decided to try it and VOILA - for the first time ever for me in Studio One - NO CPU SPIKES!
My CPU is about 10-15% higher without Turbo Boost on but finally I have rock solid consistent numbers. If it's hovering at 35%, it will go up and down maybe 3% but that's it. Before it would spike to 100 every second or so. This should be considered a bug in it's own right because no user should have to go into BIOS and disable a CPU feature hat makes it run a lot faster but at least I have a fix that allows me to get work done.
Anyway, I know this was a super long post but this helped me so much and I figured it could help some of you out there as well - at least until the CPU issues with Studio One get ironed out. Have fun!