You can export .qb2013 files to .qbb files using the File ► Backup to QuickBooks Windows function in QuickBooks for OS X (possibly only version 2013).
Be careful when restoring older backups, as they might overwrite your existing data. Also keep in mind that it is not possible to use a newer version of the format in the previous version of the program. Ie. you cannot open .qbb file exported from .qb2012 in Quickbooks 2011 etc.