.cpr sizes go crazy (500mb) for simple unmix stems project

just doing a very very basic test with spectral layers pro 7 in cubase pro 11

  • create a new project
    insert a stereo music track (i used a flac of amy winehouse back to black)
    apply spectral layers and unmix stems
    drag the stems to new tracks
    mute the original spectral layered track
    save the project

result the .CPR is 499mb! :astonished:

Add a second audio mix and do the same procedure as above, save again and its now 820mb :laughing:

I would surmise that SL is creating (lossless) PCM files, which are inherently quite larger than FLAC, MP3, AAC or other “lossy” ‘end user’ formats. PCM files, typically <.wav> can be re-encoded to whatever for end-user distribution in your favorite audio editing, DAW or standalone encoder. I do not think SL has lossy type file encoders.

This isn’t the size of the project folder or the audio…

This is simply the size of the .CPR file
The Audio/ara files are in their own folders

after testing again, the size of the project jumps when saving after performing the “unmix stems” the .cpr file goes from 400KB to 317mb+

new project - save - 361kb
import stereo audio file & save - 362kb
drag audio to audio track & save - 399kb
open event in spectral layers & save - 400kb
process - unmix stems & save - 317MB

and just to add this is with cubase 11 pro, spectral layers pro 7.0.21 on windows 10

These unreasonable sizes have been pointed out before, krevvy, but your demonstration is very useful. I, for one, would very much like it if this cpr size growth could be stopped. Despite of it, I went for the special pricing right now and upgraded to Pro.

It would be fantastic, Robin, if this could be addressed.


What happens when you bounce the event?

if i bounce the event and remove the spectral layers track, the .cpr still stays 317mb+

after bouncing the event/removing SL process, what happens if back up the project and ‘remove unused media’?

krevvy, the “ARA” files you can see outside your project were created by Cubase when the layers were exported out of SL (by drag and drop) - but it’s unrelated to the lossless ARA data itself that SL needs to store somewhere, and the ARA standard recommends storing it in the host project for portability.
Here’s the math, basically:
SL works with float32 data. If you unmix a 4 minutes song into 5 stems, you end up with 6 layers (counting the root layer) 4 minutes long each, which is 6 (layers) *4 (min) *60 (seconds) *44100 (sample rate) *2 (stereo) *4 (float32) = 508 MB.

That being said:
-if you bounce your tracks, including the extracted stems (since they are also assigned as SL layers), completely removing SL after the operation is completed, your CPR file should be back to its original size
-we’re working on a solution to make it optional, so that ARA data could be stored outside the host project as well (but beware that could cause portability issues then)

this has been reported before on V6 - and storing all the audio data inside the CPR isn’t satisfactory for larger projects…your CPR size soon becomes unmanageable. Saves can take several minutes. You say that the ARA standard ‘recommends’ but that is not the same as ‘demands’ ?

Re: portability - I think this is a non issue, as long as it is inside the project folder in a clearly labelled folder then I can’t see why it is any different from ‘normal’ audio - there are even other areas of Cubase/Nuendo that don’t follow this standard…

Previously you have suggested people use Git or Subversion to manage this…I really don’t think that is a sensible solution :open_mouth:


Hi Robin,

It’s wonderful how quickly and promptly you reply to everything here. I am not krevvy, but I have pointed this issue out here before, so I will pitch in. Doing what you say above, does not result in the cpr reverting back to its original size. I did this when I beame aware of the issue: bounced the track/s, removed SL, saved the cpr. It still had the same alarming size, well over 1,5 GB!!! So this doesn’t work. But it would be great if it did. That would save this issue for me completely.



yes - original reports also say this

Indeed, it’s only a recommendation, nothing prevents an ARA plugin to make external saves instead.

However the issue regarding portability is that there is no way for an ARA plugin to know where the host project is saved. SL only has access to memory buffers when reading and writing audio, it doesn’t know anything about your project location and files location.

So I could add an “ARA Folder” setting in SL’s Preferences, but it will be common to every ARA projects then; which can quickly become an issue by itself.

Ah ! Good to know. It’s a Cubase issue then - if SL is not assigned anywhere, there’s no way it could store any data in the project. I’ll report to the Cubase team. Having this issue fixed could already solve most of the inconvenience.

1 Like

that wouldn’t work I don’t think - needs to be handled from the Cubase side then.

A preference to:

“store ARA data in cpr”
“store ARA data in project folder”

it would certainly help - but it’s not the optimum solution obviously. The beauty of a modern DAW is that you don’t need to commit so you can go back and edit later if needed.

It depends - most of the big inflating size (>100MB) is due to this new Unmixing feature; but if you move the unmixed layers out of SL back to Cubase, then SL doesn’t have to store any modification internally.
Small spectral fixes in SL (like removing unwanted noises) should not use that much size.

The Cubase team has now been made aware of the issue, and will try to fix it for the next Cubase patch.

Hi many thanks for the prompt info & making the team aware!

just to confirm that with spectral layers totally gone, the project file is still the same size, so from my example above if i now
remove spectral layers from source audio track
remove the source audio track
render the bounced stems to new files
cleanup & remove trash in the audio pool
“backup” and minimize files… the .cpr still remains 317mb

and just to confirm there is no 3rd party plugins involved… its only a test project, but im so glad i hadn’t used this on a real project (without a backup)

Thanks Steve, I found the thread I think. .cpr sizes go crazy (500mb) for simple unmix stems project

Last post is from Dec 2020, so Cubase should be aware of this.
They talked bout CB11 and SL 7. I have the latest builds of CB11 and SL8. Clearly nothing has happend yet. Dividing to small projekt and then sync all together? Better than loose all, include last saved.cpr file. Pity on a otherwise really good sound cleanup tool. But not very professional. Me doning what computers are ment to do!