Unfortunately my lovely Cleaninglady made a mistake and damaged the tweeter of my 683 but after the process of replacing it I am glad she did. First, it was fun to change it and I learned something new about my speakers.
To access the tweeter you have to remove the mid driver. In order to do so you have to remove the outer ring by gently pull it out using your fingernails as shown in the first picture. After you pulled out the ring you can access the screws with an Allen wrench. All screws were kind of loose so I realized that this was a great opportunity to maintain the speaker so I removed the rings from all drivers and tightend all screws. Believe me or not, there was a difference. The sound is now cleaner, smoother like in the beginning.
As the middriver is out you have to unscrew a small plastic nut from the back of the tweeter and can then push it out from behind. Take care when unplugging the cables.
Put it all back together and here you go.
What it also shows is the great support of Bowers & Wilkins. After ordering the tweeter by my local dealer it arrived in no time.