double-ended lightsaber 双头光剑
The lightsaber is the weapon of the Jedi, but it is also used by the evil Sith. The deadly Darth Maul used a double-ended blade as his primary weapon. In his skilled hands, the swinging blade becomes an arc of destructive energy, capable of cutting anything it comes into contact with. The Sith lightsaber is basically two lightsabers end-to-end. It can be selectively used with only one end ignited.
As the Jedi had not faced the Sith for centuries, lightsaber dueling had become a lost art. To focus their training and their skill, Jedi still partake in practice duels and sparring contests, but to face an actual saber-wielding opponent was not something any Jedi expected before the Naboo crisis. In the past, the double-ended lightsaber was reserved only for training purposes.
Unlike the Jedi, who use natural crystals mined from such worlds as Ossus in the Adega system, the Sith prefer synthetic crystals to generate their lightsaber blades. While the crystals are being forged in a blazing furnace, it is not uncommon for a Sith to reach out with the Force and manipulate the process, focusing his hatred for the Jedi to increase the potency of the crystals.
Millennia ago, the Sith Lord Exar Kun fashioned a modified lightsaber with two blades. During the events of the Great Sith War, Kun modified his existing weapon to increase its lethality. Customized controls allowed him to extend the length of each blade from half a meter to one-and-a-half meters.
Ben Burtt specifically designed the sound of the double-bladed saber to be more "ragged" and threatening, to subtly suggest that being cut by this weapon would be far more painful than being sliced by a standard lightsaber.