There are two main types of damper arrangements for upright pianos.
Here we will explore the differences between the two, including the reasons why one is preferred over the other.
The first variety we will look at is the "over-damped" arrangement. The most obvious characteristic of an over-damped piano action (sometimes referred to as a "bird cage action") is that the dampers sit above the hammers.
The second variety is the "under-damped" arrangement. The dampers in an under-damped piano sit below the hammers.
Why are under-damped pianos the preferred choice?
The under-damped action terminates the vibrations from the strings much more efficiently than the earlier over-damped alternative. This is due to the larger damper heads which the under-damped arrangement can accommodate and the better position of the dampers on the strings.
Larger damper-heads offer more surface contact with the strings, facilitating a cleaner and more immediate end to the sound when the sustain pedal is not engaged. In addition, the dampers in the under-damped action are closer to the middle of the string, where they're most effective, as opposed to near the strings' edge as found in an over-damped action.