This is how to set up Sonar with OBS,
NOTE: This mix will transfer over from Sonar to OBS, (this will include any levels and configurations you made in your streaming mode) along with your mic sound settings as well.
Hop into OBS Settings, click on Audio, and disable everything. Then, in ‘Desktop Audio’, set it to ‘Steelseries Sonar – Stream’.
Press apply and you're all set!