Running Sonar X3 64-bit on a Win10 64-bit box (6-core AMD CPU, 16Gb RAM, twin SSD) so more than enough grunt to run X3 which it has done happily for many years. Soundcard is a firewire Saffire LE (getting on a bit but still works fine).
 
I have a few soft synths, Dim Pro, Pianissimo, TruePianos & EzKeys, some of which can be played in stand alone mode. When I do this (using ASIO drivers) they play perfectly and sound as they should - using a midi controller or digital piano. When I load them in Sonar however, the sound like they are being played underwater, tinny, horrible echoey type noise, reminiscent of a really cheap and nasty reverb. Oddly however, if I import a midi track and use the playback in Sonar - the sound renders perfectly.
 
So I'm guessing it isn't the soundcard as they play perfectly in stand alone mode and I'm down to a setting somewhere in the Sonar Preferences - but which one is the problem - I really don't have clue. Have been through the X3 manual and defaulted all the settings - no change. Have tried switching from ASIO to a different driver and running wave profiler - same problem and even uninstalling and reinstalling the LE.
 
Slightly at my wits end here - appreciate there is not much to go on and a whole of potential causes but anybody have any idea what might be causing this or how I might go about troubleshooting it? Short of a full uninstall and reinstall of Sonar - I'm about out of tricks and I really don't want to go down that route.
 
Any assistance very much appreciated - latest Sonar X3 patch is installed btw.
 
Andy

I am having a very similar problem. I saw your post topic and thought Great! someone has solved it, and then I saw that you posted it one hour ago :(.
 
1) I have Sonar Artist and am using midi input via USB from my Yamaha DTX-532k set. When I play and when I do playback the session drummer 3 sounds also sound distorted and have additional reverb (sound terrible!). I switched to less sampled drums (instead of the Steven Slate sizzlekit wet) and also purchased a proper audio interface (Steinberg UR-12) but am still having the same problem with sound quality during playback and when I down-mix into an audio track. However, if I just bang on the session drummer interface while monitoring it sounds fine.
 
2) On a side note, some of the midi tracks really seem to be saturating the output channel (snare and kick). Even when I turn the snare volume down 2/3, the master bus is still redlining. I also set the drum map velocity to 90%. I have no idea what is happening here. I found a youtube video from 8 years ago that said you should turn down the "output trim by 6 dB to avoid overloading your inputs" but I couldn't find a control for that in Sonar Artist. I assume that the midi track has some audio track analog properties to fit in with Sonar's physical plug and play analogy, but I have no idea how to adjust it.
 
I am new to Sonar last week and am assuming that this is an esoteric, versionitis issue. Finding answers in their help documentation that applies to your particular version is challenging. I have had more success with Youtube videos.

I think I have an idea. Because I am using a laptop, I have not seen the top half of the track inspector view, but there is an input "gain" knob at the top. When I get home I am going to reduce that by -6dB and see if that helps. I am thinking we are maybe getting artifacts from redlining the track. Let me know what you find.

AndyB01
....
I have a few soft synths, Dim Pro, Pianissimo, TruePianos & EzKeys, some of which can be played in stand alone mode. When I do this (using ASIO drivers) they play perfectly and sound as they should - using a midi controller or digital piano. When I load them in Sonar however, the sound like they are being played underwater, tinny, horrible echoey type noise....

Is this happening in a brand new project?  If you haven't already, you might try deleting the aud.ini file and restarting to let Sonar recreate it. 
 
If that doesn't help, you might as well do a complete uninstall of Sonar (including leftover folders and registry entries), then reinstall.  Reboot, then do same with interface drivers.

Hi Michael and Andy:
There are 2 ways to get a soft synth going in Sonar.
First is the creation of 1 track soft synth, and second is the creation of 1 midi track and an audio track.
So which one are you using?
If one does not work well, then try the other way.
Also you mentioned that you are using Asio, did you have the latency to low, like 128 samples?
dan
 

I insert a soft synth, with synth track folder . Using a drum map for my Yamaha DTX-532k drums which only took me an entire week to figure out how to do. (its now saved as a track template thank jebus) (9 tracks + midi control track + audio track with guitar)
 
I am trying to use Sonar to jam to some guitar tracks a friend is recording. So I am importing an audio file as well. I then play along to the audio file and the synth sounds bad. Prior to recording, session drummer steven slate sizzlekit wet sounds great. 
 
I have a steinberg UR-12 using ASIO drivers with current settings:
Sampling rate: 44100kHz
triangular dithering selected
 
ASIO Panel: 512 samples, 11.6 msec latency
roundtrip reported latency: 35.9 ms
 
file system: 
write and read caching enabled 1024 kb buffer
using ASIO reported latency for adjustment 
 
playback: 
1024 ms buffer always echo current midi track turned on
 
Note: I just adjusted the input gain on the midi control track which takes my drums as input and outputs to the synth tracks to -6. It seems to have made some improvements. But I still seem to be getting audio drop-outs on playback and terrible sounding drums. And if I double click the session drummer icon and tap the drums with my mouse they sound fine. 
 

system properties
 
OS Name Microsoft Windows 10 Pro
Version 10.0.10240 Build 10240
OS Manufacturer Microsoft Corporation
System Manufacturer LENOVO
System Model 11433BU
System Type x64-based PC
System SKU Unsupported
Processor Intel(R) Core(TM) i3-2310M CPU @ 2.10GHz, 2100 Mhz, 2 Core(s), 4 Logical Processor(s)
BIOS Version/Date LENOVO 8HET44WW(1.26), 8/7/2013
SMBIOS Version 2.6
BIOS Mode Legacy
BaseBoard Manufacturer LENOVO

Glad it's not just me! Some great suggestions here thanks that I will try later. I did delete the aud.ini file but the problem persists. Will post how I get on, I know it's fixable hopefully without resorting the nuclear option. I don't use read/ write caching as I thought that was only recommended for older IDE drives and not SATA or SSDs like mine - but happy to be corrected if that's not the case.

Thanks all for your replies so far.

Sounds like there could be doubling of MIDI events from the controller. You could try setting the track midi input to accept only one port/channel. Or check your keyboard's config. 

Sounds like combfiltering to me. As bvideo pointed out, make sure you are routing ALL midi correctly and not duplicating the input to the soft synths.