SINGLE BEAM VS DUAL BEAM HID BULBS
When you set your mind on upgrading the headlights, apparently this is the question you would like to clarify: what single beam, Bi-Xenon and Low Xenon/High halogen light bulbs are.
Let’s start with a single beam type. The lights of H1, H3, H3C, H4, H7, H8, H9, H10, H11, H12, H13, H15*, 880, 881, 5202, 9004, 9005, 9006 and 9007 sizes can be single beam. The bulbs of this type have one filament which produces one patter: either high beam, low beam or fog light. However, there are cases when single beam bulb performs for both: high and low beams. The reason for this is a movable housing or a mechanism which shifts the position of the light source. In most of cases, the bulbs sizes that are installed to this headlight assemblies are H1, H3, 9011 or 9012.
The bulbs that perform for high and low beams refer to a dual beam type. They can be of H4, H13, 9004 and 9007 sizes. Halogen bulbs of this type have 2 filaments side by side. When you switch on the low beam, the light is produced by one filament. If you switch on the high beam, both filaments light up. There are 2 types of dual beam HID lights. The first one is Low Xenon/High Halogen.
This bulb base has two types of light bulbs, correspondingly you get two kinds of light output. In fact, it is designed with primary and secondary light sources. The halogen bulb which serves for high beam provides yellow color like factory light, while the Xenon bulb is used for low beam and is primary. We want to draw your attention to the fact that when you are purchasing HID conversion kit or Xenon replacement bulbs of this type you select the color only for the low beam, but not for both of them.
The second type of HIDs is Bi-Xenon or Low/High Xenon. This bulb performs for two beams. Its base has one glass part which switches between the beams with a help of an electromagnet. It changes physical position of the bulb. As a result, the focal length changes and the light output adjusts to a wider or narrower angle.
The other specific thing about this type of the HIDs is that they always require a Bi-Xenon relay wiring harness which has a sort of a switcher that makes the use of different beams possible.