speedbar-ignored-directory-expressions

speedbar-ignored-directory-expressions is a variable defined in `speedbar.el'.
Its value is

("[/\\]logs?[/\\]\\'")

Documentation:
List of regular expressions matching directories speedbar will ignore.
They should included directories which are notoriously very large
and take a long time to load in. Use the function
`speedbar-add-ignored-directory-regexp' to add new items to this list after
speedbar is loaded. You may place anything you like in this list
before speedbar has been loaded.

You can customize this variable.