[Rick Hunink]

I found a solution:

1) Record an empty audio track.
2) Place the audio track in timeline FCPX
3) Create new rol for audio track: ’empty for MXF’
4) Export to Master
– Open with Content Browser Exporter
– roles as multitrack exporter
– set al your current roles on mono
– add audio tracks so you have a total of 8 track
– select for every new audio track the role ’empty for MXF’ and make in mono
5) Export