Hmm, I see that I’m not the only one confused about this subject of bit depth. On Mudgels advice I edited the subject line of my post as “Solved”, now I have edited it again as unsolved.
 
According to Mudgel the resulting export file will contain 16 bit audio, and according to Sandxpander a decisive “no” it will actually be 24 bit. So who is correct?
 
Just to reiterate my OP, I imported the audio with my import bit depth settings (found under Edit > Preferences > Audio Data) set to “Original”. And I am aware of the options of bit depth both for rendering and for export.
 
One would assume that if the audio clips are 16 bit and you export choosing the 16 bit option in the export window that it would be a straight match, so to speak, requiring no dither down processing. However this assumption is in contrast to Sandxpander’s answer.
 
Normally I don’t mess with MP3s; and I had never tried to use Sonar’s built in “Burn to CD” utility until yesterday. I simply record in Sonar’s standard 24 bit mode and export in 24 mode without dither, then I master in Wavelab and add dither only at the final stage of mastering using Waves UltraMaximizer. I have used this method for so long I haven’t needed to delve too deep into the bit conversion question – nor the MP3 – .wav file question.
 

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Dilaco1
Hmm, I see that I’m not the only one confused about this subject of bit depth. On Mudgels advice I edited the subject line of my post as “Solved”, now I have edited it again as unsolved.
 
According to Mudgel the resulting export file will contain 16 bit audio, and according to Sandxpander a decisive “no” it will actually be 24 bit. So who is correct?

If you make the selections in the export dialog. If not being up sampled to 24 bit don't dither on export. The fact that internal process is Ng maybe at 32bit float is no reason to dither when going back to 16 bit.
 

Dilaco1Just to reiterate my OP, I imported the audio with my import bit depth settings (found under Edit > Preferences > Audio Data) set to “Original”. And I am aware of the options of bit depth both for rendering and for export.
 
One would assume that if the audio clips are 16 bit and you export choosing the 16 bit option in the export window that it would be a straight match, so to speak, requiring no dither down processing. However this assumption is in contrast to Sandxpander’s answer.

If you have Sonars default set so that all project are created at 24 bit. If that's not the case then you're right no change in bitrate no need to dither.
 

Dilaco1Normally I don’t mess with MP3s; and I had never tried to use Sonar’s built in “Burn to CD” utility until yesterday. I simply record in Sonar’s standard 24 bit mode and export in 24 mode without dither, then I master in Wavelab and add dither only at the final stage of mastering using Waves UltraMaximizer. I have used this method for so long I haven’t needed to delve too deep into the bit conversion question – nor the MP3 – .wav file question.

If this is you normal process then that is perfectly fine. If you use Sonars CD burner then you obviously don't need to do it in wave lab nor export files from Sonar.
 


A very confusing initial post with gradual revelation of info makes it real difficult. Sorry for any additional confusion.

I wrote a post to try to summarise this thread but happened to go back to your first post. And subsequently replaced it with this

For anybody following this thread I bet they are confused. I've just gone back to your first post and you've heavily edited it so that the following answers pretty much don't make sense anymore. Had we been given that information first your real question could have been answered in a few words.

In future perhaps just leave previous posts because not only are you getting an answer but anyone who follows along can get answers too. Now that's no longer the case.

Anyway I'm out a here now.

Mudgel, my original post is absolutely untouched, no edits whatsoever – not a word. The only editing I did was to the subject title at your request. Remember, you told me to! You said, "Would you please go back to your first post, select edit from the bottom right corner of that post and edit your thread title to say Solved." So I did that. Then when Sanderxpander gave me a different answer to yours and I got confused, I went and changed the title back to being unsolved.
 
I am very sorry to have to say that you couldn’t have read the original post properly. But I’m used to that, which is why it was no surprise to me when people were telling me all about the bit rate options for import and export and rendering which I had already mentioned in the original post.
 
Still confused.  

OK then I'm obviously having a brain disturbance of some sort My apologies then. What?
 
Until my previous post I have been using my ipad (just updated to ios 8.3 yesterday) to work on this thread and scour the forum generally. I have been having all sorts of screen issues which for whatever reason didn't show me the last part of your initial post until earlier when I opened my PC to use Sonar and also checked this and a few other threads.
here's what I saw.
 

Dilaco1I have an atmospheric soundtrack in MP3 format. I want to extend its duration, and then burn it to CD, but I need to do so with as little alteration to the original audio as possible – i.e. without dithering, rendering, decoding, etc. any more than I have to.
 
I don’t know much about MP3s but I tried importing the MP3 to Sonar (Import bit depth setting: “Original”), then copied the audio clip and pasted it on to the end of itself – doubling the audio’s duration. Then I tried using Sonar’s Burn to CD function. When I clicked on its Add button to bring up the audio file, it only added the original audio and not the cloned audio. So I thought of doing a “Bounce to Clips” to render the two clips together. The problem is that this bouncing is at the wrong bit depth –32 bit. I thought of changing my rendering setting to 16 bit was concerned it would be low quality/accuracy.

 
Hence my comment that if you had posted the additional information yadayada and carry on about MP3s. I'm a pretty thorough reader and usually read all posts in threads and all the posts.
 
the main thing is are you clear now on what to do?
 
if you use 32 and or 64 bit float for internal processing then you don't need to dither for that reason alone.
If you go up in bit depth. process then go down in bit depth you dither as your last stage in processing which you already know by your comments in post #13. BUT there is some discussion on dither which suggests that the kind of material itself would decide on the use of dither when reducing bit depth. Higher frequency more likely need dither than low frequency material. Its one of those long ongoing debates with no winners I would reckon. You can always experiment to see which you think sounds better. Dither or don't and the choice of dithers  to use.
 
In the meantime I've had a look at Sonar's CD burner tool and didn't realise that it required exporting files in the first place. BUT in any case it clearly states in the online help for the CD Burner that even if a file that is not at 16 bit is selected, the burner software will take care of that in the whole process of uploading (to the program) and burning the files to CD.
 
And as sander said by default Sonar will only spit out files at the bit depth to which it is set in the preferences section he described, I actually specified making those various selections because the export dialog is that comprehensive that you may select all manner of things including bit depth etc.
 
I hope that's clear now.
 
 
 

Further: with respect to Sonar's CD burner process you need to select the actual files. A cloned file does not exist as such.
 
Because Sonar is non-destructive, Sonar's cwp (Project file) just keeps records of all editing. You never get new audio files unless you bounce the actual clip.
 
 
If you want to check you can simply open the audio folder where your file is located in Windows explorer and by right clicking and selecting Details you will be able to find out various audio properties like bit depth.

All I meant is that Sonar, by default, will be set to export a file at the project bit depth. You can change this easily. But the fact that you, at one point, dragged a 16 bit file into the project doesn't change this behavior.

Sanderxpander
All I meant is that Sonar, by default, will be set to export a file at the project bit depth. You can change this easily. But the fact that you, at one point, dragged a 16 bit file into the project doesn't change this behavior.

Yes I understand sander. thanks.

dilaco1, you may be over-thinking the process and looking for options that just don't exist.
 
Leave your SONAR settings at their defaults. SONAR is going to convert the MP3 into a 32-bit wave file when you import it. There won't be any modifications to the file beyond the decoding process. Quality will depend almost entirely on the bitrate of the original file and unfortunately there's nothing you can do to improve it. 
 
Of course, when you ultimately export the final file it will be truncated to 16 bits and have dither noise added. But that's required for CDs so there's no point in fretting about whether you could have done something better. As long as the original MP3 was decent quality, chances are you'll not hear much difference between the original and the final CD version.