Using an Asus Zenbook, Sonar plat, Focusrite Clarret Thunderbolt interface.  Windows 10, 16 GB RAM, PCIe SSD drive, 4 core 2.6 GHZ I7 with Hyper thrreading.
 
I can play a guitar/bass through an amp sim no issue at all with a 32 sample buffer.   Mostly TH3 and some other cheapware ones.
 
when running a synth through MIDI (USB controller, not using the MIDI in on the Focusrite if the polyphony of the synth goes above 8ish notes or so it kinda freaks out, snap crackle and poping noises.   Not using greedy synth either, DM pro, True Pianos, Korg legacy stuff, all low-power synths.
 
The CPU meters in SONAR barely show any CPU activity. No other apps on the PC, AV turned off makes no difference, same with turbning off blue Tooth, wireless, and pretty much every Windows Service that isn't needed.
 
All works fine at a 64 sample buffer, which is playable and I can live with this if this is how it is.
 
But what throws me if is live instruments work fine at the 32 sample buffer - midi ones don't.   Are there any optimizations I might have missed or settings in SONAR that would help? 

Have you tried a different midi interface or using the Focusrite midi in?
Also, does it still happen if you also enable input monitoring on a dummy audio track simultaneously?

You are running ASIO driver mode?  Do the problems go away at 64 samples?
 
And, what are your reported latency values in Sonar Preferences?
 
I actually run at 128 samples, typically, though can usually get it down to 64 and sometimes 32, but 128 still gives me decent performance with no discernible latency lag, so I just normally leave it there.
 
Bob Bone
 

Most synths will use more CPU the more polyphony is used (Truepianos which is partially 'modeled' definitely does), but this could also be a disk-streaming issue, epecially on a laptop with 5400rpm disks. If Performance meters are staying low, I would try increasing disk I/O buffer size. But if perf meters are going above about 60% and/or are extremely variable, you should check DPC latency. WiFi and Bluetooth drivers commonly cause DPC spikes that will wreak havoc with audio streaming at low latency.
 
Unless that interface has loads of hardware/firmware/bus latency, soft synths should be eminently 'playable' at buffers up to 128 samples or so.

robert_e_bone
You are running ASIO driver mode?  Do the problems go away at 64 samples?
 
And, what are your reported latency values in Sonar Preferences?
 

Asio yes, issues go away at 64.


What's concerning me is Audio works fine at 32, and that's supposed to be greedier.

brundlefly
Most synths will use more CPU the more polyphony is used (Truepianos which is partially 'modeled' definitely does), but this could also be a disk-streaming issue, epecially on a laptop with 5400rpm disks. If Performance meters are staying low, I would try increasing disk I/O buffer size. But if perf meters are going above about 60% and/or are extremely variable, you should check DPC latency. WiFi and Bluetooth drivers commonly cause DPC spikes that will wreak havoc with audio streaming at low latency.
 

PCIe SSD, what laptop in 2017 still has a 5400 RPM drive?
 
CPU usage is BARELY above 1% -  disk also shows no activity.

Sanderxpander
Have you tried a different midi interface or using the Focusrite midi in?
Also, does it still happen if you also enable input monitoring on a dummy audio track simultaneously?

LOL . . . my cheap MIDI controller doesn't actually have MIDI out, USB only.   I do have a set of MIDI Taurus pedals I can try by, hard to hit enough notes on that.

gprokap
PCIe SSD, what laptop in 2017 still has a 5400 RPM drive?
 
CPU usage is BARELY above 1% -  disk also shows no activity.

Sorry; didn't read carefully enough. I'm not sure what else might be going on, then, but would still check DPC latency. I can play handfuls of sustained chords on TruePianos and Dim Pro at 32 - or even 16 - samples here so I know it's not an inherent limitation of SONAR or the synths you're using.
 
 

128 samples is probably a good starting point with soft synths.

abacab
128 samples is probably a good starting point with soft synths.

 Maybe using a USB interface on a 10 year old computer