# H4-4 Bulbs - Question



## Digital (Jun 29, 2012)

If you have a H4-4 bulb and wire both the high and low on together at the same time would you get twice the light output or would they combine?
Can anyone show me a math equation to figure that out? For arguments sake lets say it's a H4-4 100w 4300k bulb.


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## Benson (Jun 29, 2012)

Digital said:


> If you have a H4-4 bulb and wire both the high and low on together at the same time would you get twice the light output or would they combine?
> Can anyone show me a math equation to figure that out? For arguments sake lets say it's a H4-4 100w 4300k bulb.


Could you be more clear what you mean by "H4-4 bulb"?

H4-4 is not AFAIK standard terminology.

H4 is an automotive headlight bulb with two filaments; the references I'm finding googling H4-4 seem to be various types of HID bulbs (which fits with your saying 4300k) meant to replace an H4, but there's several types being referred to as "H4-4" -- ones with two HID burners, ones with an HID and a halogen bulb, and ones with a single HID sliding back and forth with a solenoid.

The last type (solenoid) simply doesn't have a "both energized" state, because there's only one bulb. The others will all put out more light with both elements energized, but may overheat (because they're only designed for one filament/burner at a time). Because of the differing position, only one element will contribute to a spot beam, so you'll get a spot and flood together -- it'll only throw as far as one element alone (whichever one's in focus).


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## Digital (Jun 29, 2012)

H4-4 requires two ballasts, one for each HID in the bulb. It's essentially like having two H4-1s in a single housing.
My question is for H4-4 bulbs if you turned both the high and low HID on at the same time would you get twice the light output?
Essentially is this the same principle of people putting three CREE LEDs into a single head and combining the output?
What's the math equation for that?


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## PhillyRube (Jun 29, 2012)

No additional light output. I have a THOR, with a H-4 bulb. Each filament is energized by a separate switch, so you can run both, and no appreciable output noticed.


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## Digital (Jun 29, 2012)

PhillyRube said:


> No additional light output. I have a THOR, with a H-4 bulb. Each filament is energized by a separate switch, so you can run both, and no appreciable output noticed.


Good to know thanks man.


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## Benson (Jun 29, 2012)

Okay, you'll get pretty much twice the output, but half of it will be flood. No extra throw.

It's not at all the same principle for multi-LED lights. They have individual reflectors for each LED, so they each contribute to throw; of course this makes the reflectors smaller (= broader beam), so you don't get _more_ throw from the same size flashlight (you actually get a bit less), but you do get more light in the beam. The light from the second HID burner won't focus into the beam at all.


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