If you hook them up like as per the manual, everything should work the same as on your R4 Speaker Manual  As for sound cutting out, some have reported this due to Dell support Assist and/or AWCC. I would suggest trying the things out from this thread: Support Assist You can always reinstall it if it made no difference.
Have just purchased the R15. But no speakers as did not see any and maybe dumb but i took it as having onboard sound. Set it up and have no sound. Looking at the back you have sockets for speakers. My last one was an R4 and i had Logitek Z506 surround speakers with it. I have added these but the sound keeps cutting out. Is there anything i can do or are my speakers to old?  Did have a look on Dell web for speakers but can only seem to find headsets which i do not want. Thanks in advance
Aurora R15, Sound Issues