The dome of a dome tweeter is the diaphragm, the part that moves the air to create high frequency sound. It is driven by current moving through the voice coil which is in contact with the dome just behind it. Without the dome in place the voice coil itself would not be effective at moving enough air to make the sound level audible. The shape of the dome does affect its dispersion, so having a dent in it will affect its performance to some degree. There are soft and hard dome designs, and neither operates ideally as a perfect piston. At certain frequencies the dome will resonate, and its shape is important at those frequencies since breakup modes occur.
Purpose of Dome on Tweeter...
What is the purpose of the "Dome" on a dome tweeter? Will a dented or dimpled dome effect the sound dispersion coming from the tweeter? If not, why aren't they just pushed in at the factory? Better yet, if a dented dome doesn't effect the sound, it would seem as if it's a non important part in a tweeter so why not just build a tweeter without the dome at all?