Led question

Upon looking at all the different manufacturers that make these LED bars, I see a lot of them have posted the input voltage range. Typically this runs from approximately 9 V to 32 V. Obviously if you're hooking it up to the vehicle with the regular car battery you're going to run at approximately 12 to 13 volts.
If you were to put 32 V to one of these LED light bars are you going to make it any brighter or would it be dimmer if you only had 9 V available?
With the lightbar perform at the same light output whether it has 9 V or 32 V?

 

I would guess there is some voltage regulation going on and they will perform the same anywhere in the range of 9-32V.