Media nav Evolution software downgrade, from 9.1.3 back to 8.0.5 isit possible??

Hi guys, Ive recently had my traffics media nav evolution upgraded to the latest software, but since the update the sound volume doesnt go any louder past number 21 and the overall sound quality isnt as good as before. ive been told by my friend in renault that this has been written into the latest software purposely by renault to save the speakers? isit possible to install the older software (8.0.5) back onto to my media nav to regain the original quality??
thanks in advance!

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