Several graphs are shown below that describe various common tuning methods along with a couple examples of mal-aligned systems. I was asked to do this a few days ago, and with Till's most recent post, it seemed an opportune time to illustrate the response that can be expected from various systems.
Each of these graphs were prepared using a woofer motor having the following characteristics:
Note that I use the term "optimal" in a way that can be interpreted to mean "critically damped." In other words, when I describe an "optimally tuned cabinet" or one having "optimal size", many would refer to this as being critically damped. There is merit in building systems that are not critically damped for various reasons, and one should not misinterpret the term "not optimal" as excessively derogatory. However, "critically damped" motor cabinets provide the best performance, so the term "optimal" is accurate.