If I change the speakers in a new BMW 528i does that void the warrant on the soundsystem?
No, unless dealer can directly prove that it caused "what ever " to fail.
Evolution is correct they will only void the warranty if they can prove that the speakers caused the problem and only the part that the speakers caused to fail will not be covered.
I have not heard of speakers voiding a warranty but changing speakers along will not improve auido sound. If you don't have the Premium sound your issue is the head unit not the speakers.
If you change your speakers you can be assured that you will have effectively voided your warranty. You may not be told that straight out but when you do have a problem with your sound system you will have a real problem at the dealer. The burden of proof that you did not damage it with the speakers or during there installation will fall on to you.
Out of curiosity, what upgrades did you have in mind? I am assuming the the Bang and Olufsen package did not come with your ride?
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