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Why Do Headlights Dim to the Beat of the Music?


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my guesses...

1. Voltage is what determines a normal headlights brightness and there isn't really anything on a car that maintains a constant voltage level even if you have enough alt/battery power for your system. Alts and batteries are always going to be reactive to electrical demands regardless of how much electrical you have.

2. put a voltage regulator on the headlights and make sure you have enough electrical to support your demand or switch them to HIDs.

Those are my guesses.

 

F150:

Stock :(

 

2019 Harley Road Glide:

Amp: TM400Xad - 4 channel 400 watt

Processor: DSR1

Fairing (Front) 6.5s -MMats PA601cx

Lid (Rear) 6x9s -  TMS69

 

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Pussy Magnet . . . lol . . . shit, they run from it.

Your headlight is showing you the voltage fluctuations present on your charging system - just like the needle swinging on an analog volt meter.  This is data that we can easily interpret.  From brightest (maximum voltage available) to lowest (lowest voltage available) and everything in-between.

As enthusiasts, we always want to make use of the maximum voltage available - no matter the design of the power supply of our amplifiers.  To refresh, they are:

Regulated - The amplifier's output power is not affected by input voltage, down to about 10.5V (typically).  The power supply pulls this feat off by making use of Ohm's Law in its simplest form - when input voltage decreases input current increases.  The net result is that power IN is the same and therefore power OUT is the same.

Unregulated - The amplifier's output power is affected by input voltage.  The more input voltage (to a point), the more output voltage.  The greater the output voltage into the load, the greater the current into the load.  Conversely, as input voltage drops so does output voltage and output current.  The Power Law (P = I x E) illustrates this fully [leaving Power Factor out for the propeller heads].

So, utilizing the highest voltage available has benefits for both designs.  This is known as maximizing efficiency and minimizing loss.  But, how do we do that?

You guys gotta' dig deep and do some thinking.  The next generation of car audio experts depends on it.

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Speed plays also. Wont matter if you have a 5000 amp alt,. speed of the regulator turning on, will make the lamp dim ( a lamp that is easily put down with any Vchange) or not "as bright". Maybe, maybe a cap, that actually does something, can help here. 

 

That said, my head lights dont dim,havent in the last many builds,.... only time they did, was when i was 16, in my 81 sdime running way to much, and not giving/feeding it much. 

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1. The beat of music is a regularly repeating pulse. Whereas the pulse is an accentuated piece of the music such as a kick drum, note change, etc. By extension, this means that there requires more power to produce those pulses. Now as to why the headlights dim: I'm going to rely on the assumption that they are standard halogen lights. 

A. Without going excessively far into wavelength emittance along the visible spectrum, or changes in resistivity over heat; A halogen light is a heating element - a resistor. The power this draws from the electrical system can be calculated by v^2/r, where v is the voltage at the headlight, and r is the resistance of the headlight.

B. Everything has resistance. Wiring, battery, will all have voltage drop through them as a result of current demand and resistance. Then you have the differential between charge voltage of the alternator and the resting voltage at the battery when it will begin converting chemical energy to electrical. Add to that there's a response time in the alternator between when the voltage changes from its set point, then the regulator changes the power going to the rotor. 

So what this all means, is if you have a sharp change in power requirements, you get a change in voltage of the system of your vehicle. Each beat, or pulse in the music, will cause this. You can also see the effect if you roll your window up/down then toggle the switch while the window is at the limit of its travel



2. Bearing in mind the info from 1. There are 2 ways you can eliminate this dimming issue

1. Use a headlight that has its own power supply that will provide a stable output independent of the input. An LED or HID would work in this scenario

2. Rig up a capacitor and a diode at the headlight such that the effect of these temporary voltage dips are mitigated such that any dimming that occurs isn't visible to the eye any more

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6 minutes ago, SnowDrifter said:

1. The beat of music is a regularly repeating pulse. Whereas the pulse is an accentuated piece of the music such as a kick drum, note change, etc. By extension, this means that there requires more power to produce those pulses. Now as to why the headlights dim: I'm going to rely on the assumption that they are standard halogen lights. 

A. Without going excessively far into wavelength emittance along the visible spectrum, or changes in resistivity over heat; A halogen light is a heating element - a resistor. The power this draws from the electrical system can be calculated by v^2/r, where v is the voltage at the headlight, and r is the resistance of the headlight.

B. Everything has resistance. Wiring, battery, will all have voltage drop through them as a result of current demand and resistance. Then you have the differential between charge voltage of the alternator and the resting voltage at the battery when it will begin converting chemical energy to electrical. Add to that there's a response time in the alternator between when the voltage changes from its set point, then the regulator changes the power going to the rotor. 

So what this all means, is if you have a sharp change in power requirements, you get a change in voltage of the system of your vehicle. Each beat, or pulse in the music, will cause this. You can also see the effect if you roll your window up/down then toggle the switch while the window is at the limit of its travel



2. Bearing in mind the info from 1. There are 2 ways you can eliminate this dimming issue

1. Use a headlight that has its own power supply that will provide a stable output independent of the input. An LED or HID would work in this scenario

2. Rig up a capacitor and a diode at the headlight such that the effect of these temporary voltage dips are mitigated such that any dimming that occurs isn't visible to the eye any more

 

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Tony Candela - SMD Sales & Marketing
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