Sliding vertical location for matrix elements

[OmarIthawi]

There is a problem the size of the brackets, and the vertical space between symbols. The problem appears when you have a lower script number like x_1. See the result of this script for which is more clear. Script:

\left[\begin{array}{c}f\\f\\f\end{array}\right]
\left[\begin{array}{c}x\\x\\x\end{array}\right]
\left[\begin{array}{c}x_1\\x\\x\end{array}\right]
\left[\begin{array}{c}x_1\\x_2\\x\end{array}\right]
\left[\begin{array}{c}x_1\\x_2\\x_3\end{array}\right]