When we buy new device such as Sennheiser 9920 we often through away most of the documentation but the warranty.
Very often issues with Sennheiser 9920 begin only after the warranty period ends and you may want to find how to repair it or just do some service work.
Even oftener it is hard to remember what does each function in Headphones Sennheiser 9920 is responsible for and what options to choose for expected result.
Fortunately you can find all manuals for Headphones on our side using links below.