Its a well known fact that the audio system in the 2nd gen MINI sounds terrible. It was improved slightly in the facelift but still isn't good.
One of the faults is a lack of bass. The factory stereo has a bass filter built in which limits the bass to the rear speakers, however the rear speakers being 6*9 are more suitable for producing bass than the front speakers. This easy to fit lead plugs in the left kickwell & sends the bass to the rear speakers instead of the front thus improving the bass in the car.
This gives a great result in R55 clubman & R56 hatch pre facelift & a lesser result in facelift versions of these cars.
It is not recommended for the R57 cabriolet.

https://newministuff.com/channel-swap-648-p.asp

 

Hey I was just wondering why the channel swap isn't recommended in the R57. Is the audio system set up differently in the cab?

 

Just bought a 2013 R57, and I'm curious about this as well. Does anyone know why?