Hi all - I haven't had this issue historically, so must be doing something wrong.  My mix sounds fine when playing back - however when I export to MP3, it sounds odd - the reverb is much more prominent in the mix, EQ has changed, etc. 
 
I've triple checked to ensure all my tracks output to the master bus & my master bus outputs to the audio card outputs.  I'm using the normal settings I always use when exporting - 44.1khz, 16bit, stereo, triangular dithering and using 'audio outputs' for the source.  I've also used 'master bus' as the source and it still sounded weird.   Additionally, I tried exporting to MP3 with no dithering and with power3 dithering and again, the MP3 sounded strange. 
 
Any thoughts?
Thanks
Russ
 

Yeah, a couple of thoughts.

Start by doing an export to wav format - export @ 16 bit, 44.1KHz and make sure dither is turned on.

Now import your export back into the same project, route it directly to your soundcard (bypassing any master buss Fx) and solo it - does it sound the same as your project?

If yes, you can go on and use the 16 bit wav for MP3 conversion.
If no, there's something not quite right with your export settings/configuration and you'll need to investigate further.

I normally bounce to tracks first and check the resulting track.
If it needs some "mastering" I adjust FX and PC on the master buss and, when all sounds ok, then export that soloed track to mp3 (44.1, 16) through the master buss to the main outs.
Sonar prompts with a dialog box and I set the slider to slower/higher quality - I don't change anything else.

How much overhead is there in your project, and what MP3 quality are you using?

If your track is limited to something like -0.1 dB, you should lower the level to -0.3 at least to prevent clipping.
Is it SONAR or Media Player you use to audition the MP3? There might be a compressor on in Media Player, and that
pushes the reverb to front and inevitably affects the perceived EQ as well.

Hi all..
Thanks for the recommendations - to answer some of your questions:
- I exported to MP3 using both medium and "best" options for MP3 quality in the export dialog box
- I was using Windows Media Player to audition the MP3, but also used another MP3 player and it still sounded very odd. 

I'll check the levels & also try the method Bristol Jonesy recommended and will post results.
Thanks
Russ

You need to check that the export sounds ok in Sonar before converting to Mp3 by re-importing it like i described above

Hi guys.. thanks for the suggestions.  

Jonesey - I exported to WAV using all the same settings I used previously when exporting to MP3 (e.g. 16 bit, 44.1 khz, source = audio outputs, etc) and it sounded fine.  

So I'm happy to know I'm not doing something completely stupid with the export settings.  But I'm a bit baffled why a WAV export would sound fine and an MP3 export would sound garbled using the same settings.  I lowered the levels in case the MP3 roundign was causing errors, but that didn't help.  I also tried exporting to the highest quality MP3, also to no avail.  I'm baffled.
   

If the wave file sounds fine then use that for MP3 conversion - DON'T export directly to MP3 from Sonar - use the wave file as an intermediate step.

Bristol_Jonesey


If the wave file sounds fine then use that for MP3 conversion - DON'T export directly to MP3 from Sonar - use the wave file as an intermediate step.

So, is there a quality (or other) advantage to exporting to WAV over bouncing to track and exporting from there?

Jonesey - yes, I'll use the WAV as an intermediate step - will try that today, although I've always exported directly to MP3 without any issues historically, so I'm confused why this issue suddenly appeared, particularly as this is such a simple tune - just an acoustic duo - a few tracks, whereas I've exported much larger projects of 50+ tracks directly to MP3 without issue.

I'll give that a shot today and post my results.
Thanks
Russ