I just installed SONAR X3 and I'm really stymied by this since Line-In automatically went to the speakers in SONAR X1 Studio. My tracks are output to Master and Master is output to "Speakers/Headphones (IDT High ...)". When I play a track the Master volume meter lights up and I hear the track through the headphones/speakers. But when I record onto the track I hear nothing in the headphones/speakers. The volume meter on the track lights up but I hear nothing. The input for all my tracks is "Stereo Line In (ITD High Definition Audio ...)".
 
If I turn Input Echo to "On," then I hear the input but with a substantial delay. The delay gets shorter as I lower the mixing latency but of course the lowest it goes is 30 msec so that's no help. 
 
How do I fix this?
 
Thanks,
John
 
 

go to  your Line-In attributes  and in Listening tab switch on "Listen this device" option.

Thanks, sounds promising. Where do i find the line-in attributes? I can't find it anywhere in the Audio Preferences.

Yes, it's very well hidden.  It is windows  mixer  component.

Right click  in  speaker icon near the Clock , it  open a menu, where choose  "Recording  devices"  command.   It open a recording devices dialog,   here you can open Line-in attributes.

Are you talking about Windows Mixer?  In the Windows Control panel, under Sound Devices, the Line-In properties are already set to "Use this device (enable)." 
 
So I'm hoping that you're talking about a Line-In attributes dialog in SONAR.

yes it's windows thing  not  sonar.  it can from open control panel too.
 
Control Panel > Sound. Click on the Recording tab. Select Line-In. Click on the "Listen" tab and check the "Listen to this device".
 
look this image:
 
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//remove spacebars

You will (almost) never get low latency with a stock computer sound card.
For best performance, an audio interface designed for recording is recommended.
Also, this is the wrong forum for X-series questions; it's for older versions of Cakewalk software.