I have problems with some stereo-recorded sounds from synths disappearing in the soundscape when playing via bluetooth in mono equipment. I suspect that some kind of phase shift is the cause. Is there a way to control this when mixing in Cubase and how to avoid this phenomenon?
I use Cubase 13
Phase shift isn’t the right term for that, since it doesn’t shift anything.
It’s better to call it phase issues.
Don’t use too much out of phase sounds on stereo channels.
A quick search brought up that article.
Thank you for the fast reply but first I would like to apologize for poor English. Since I use GoogleTranslate it can be a little wrong sometimes 
I have read the article that you googled for me and it gives many interesting answers to how my problem arises. However, not how I solve them. Therefore, I still wonder if there is a “mono button” in Cubase where you can control how certain instruments are rendered in mono? Or do I have to download some plugin to find a solution?
The best solution is not to use those sounds that have loads of artificial widening if you care about mono compatibility.
You can create width by using different mono sounds panned left right instead of this fake stereo using phase.
Otherwise you have to find a balance between too loud in stereo and not loud enough in mono, or you can try to narrow the stereo field with dual panner mode or a plugin (The freeware A1 Stereo Control for example) to lessen the difference.
If you’re using Cubase’s Control Room, you can switch temporarily from monitoring in stereo to monitoring in mono so you don’t have to be surprised later when playing a stereo mix back on mono hardware. Independent of specifically stereo sounds, that is a good practice to do periodically when mixing since stereo field placement can affect how things sound in mono and in non-ideal listening positions when listening to actual stereo playback.
As for ways to address problems in this area, that’s going to depend on the cause of the problems (some of which have already been mentioned in the responses above). A few things I tend to do when dealing with stereo sounds include:
-
Using the stereo combined panner instead of the standard left-right panner for placing stereo sounds. The standard panner just adjusts the balance between the left and right channels, so, for example, if you pan full left, you won’t hear whatever was on the right side of a stereo sound at all. The stereo combined panner lets you shift the stereo field, so, for example, if you wanted a stereo sound to be mostly on the left side of the soundstage, you could either put both the left and right sides on the left or maybe put the left channel at full left and the right channel at 50% left. Of course, how this affects a stereo sound that uses phase differences to create width will vary, but, at the overall stereo mix level, you won’t have the left and right sides of the same sound cancelling each other (i.e. in the extreme case where the width is created by the two sides being out of phase with one another).
-
Using a plugin designed for manipulating stereo information to tweak things for best results in a given situation. It may be that Cubase has something of this sort (not sure), and I know of and use a few different plugins (e.g. from Waves and iZotope) for stereo field manipulations, but the key one that comes to my mind for dealing with actual problems and/or making very fine manipulations is PSP StereoController2 (https://www.pspaudioware.com/products/psp-stereocontroller2). This can let you separately manipulate high-end and low-end width and gain (and set the crossover frequences for the low/high definitions), delay one side of the signal compared to the other (which could potentially be useful if phase issues are causing the cancellation, in addition to being useful for creating artificial width), and a lot more.
In general, I think it’s a matter of checking mono compatibility fairly regularly as you go through the mixing processing and experimenting to resolve any mono/stereo compatibility issues until you find the best tradeoffs for the specific mix.
Many thanks to those of you who have been involved in my problem. I have learned a lot by reading your posts and found a working solution by combining your suggestions.
The problem was a saxophone solo from a synth that disappeared completely in mono. By selecting that section of the audio track and then selecting menu “Audio-Processes-Invert Phase” and delaying the left channel by a few milliseconds, the solo became audible in both mono and stereo and the problem was solved