It´s a strange thing whit the BOSE-system.
In my first 147 i had a BOSE,after a while i discoverd that there where no tweeters behind the covers were the Bose logo stands,there are no speakers whatsoever.They are FAKE!!!!
Not in the front and not in the back.
There are whires and connections behind these covers.
Afther a visit to my dealer,he orderd them on warrenty.
In the manual i later discoverd that the Bose only have the 4 big speakers.
When you have the normal radio,then there are also tweeters.
Whit the 147 I have now it was just the same.
The dealer orderd them again,i got them for free again.Normal price 48£ for the 4.
Now i have the bose system whit al 8 speakers,it´s a little less loud, but it sounds match beter.
You can see some pictures here,it´s in dutch of course,sorry for my bad English writhing.