Along with Dizzie’s comment:
I would add that the divisions of the panel vary depending on the version, ie. The older panel is divided (from bottom to top) with the largest division at the bottom and progressively gets smaller all the way to the top.
The later Bass Focus version of the panel has the narrowest segment in the center of the panel and progressively gets larger divisions towards the bottom and towards the top of the panel.
This affects the imaging and tonal balance relative to the distance from the speaker.