A null test is totaly different from comparing files that are created in different versions of Cubase using it’s native processing.
There are two things going on here; you have the " null test people" that will keep on telling you that you are wrong and imagining things, and the people that just hear a difference when they open a project created in another version of Cubase.
Shure, null tests WITHOUT processing obviously always should null (duh!). But that is not what these posts are about I think…
People expect that after an update, everything sounds the same when they open an old project. Suppose the eq has been altered, but you do not use the eq. You would not notice the difference. But you would if you used it on a few tracks, right?
I had this experience with files in which I had used the cubase eq just on snare and bass, but I noticed something was drasticly different, not as intended right away (using cubase 7 vs 6.5). I just know my mixes. It took me some time to find out the difference was in the eq, using the same procedure as with a ‘null test’.
My experience sofar has been that due to various and constant changes in the software in different versions of Cubase (native eq, filters, group summing), the processed mixes do sound different in different versions, and they do not null at all If you happen to be using Cubase features that have changed in the update.
This means that Cubase is not fully compatible when using different versions, so you better not switch versions while working on a project in witch you use any of the native features of cubase, or you’d just have to accept to have to rebuild your mix a little…
I decided to add cubase version info to my files, and I have 3, 6, 7 and 8 installed for compatibility…
Rebuilding mixes in newer versions sometimes gave better results, sometimes I just gave up…
You could consider to only use 3rd party plugins and avoid using Cubase processing.
It would be convenient if Steinberg would provide a list of incompatibilities between different versions…
I personaly do not mind if they implement better eq, filters or group summing, but I would not mind to be notified about it in a better way…