[Thomasluke7899]

The reason why the hiss is so prominent has nothing to do with ground loops.
Sensitivity is not to blame either.
It is the factory eq in the head unit. The factory tweeters response most likely rolls off around 10k and is crossed over at 8 or 10k with a cap.
The cheapest way to get the response except able is to use a massive amount of eq all the way up to 30k hertz in some cases 15 or 20db of boost. And thats at 30k.
So when you swap in a half decent tweeter you hear the hiss. Prominently. In some cases the hiss can be louder than music at all volume levels.
Some audiocontrol units get blamed for white noise when in reality the loc simply can't knock down 20 dB of boost at 30k.

 

[Thomasluke7899]

So..... how do I fix it? It's a brand new 2021 VW Tiguan R-Line if that helps at all.

Without a dsp there is not much you can do.
You could add an inductor in in line and lowpass the tweeter around 20k you would need a 0.03 inductor in line with the positive wire.

 

[Thomasluke7899]

If the cap across the tweeter doesn't fix it when I try it tomorrow, I'm down to move to the next step. If that's a DSP, give me a recommendation for an inexpensive yet decent one!

Stop wasting your time man.
What car is this? Make year model

 

[Thomasluke7899]

2021 Volkswagen Tiguan R-Line

You need the dsp. The easiest way these days is a 5 channel amp dsp combo.
Jl audio vxi amps are great. They use a Bluetooth app works.
They will take care of any eq and correct any all pass filters they may be using.
Then you have a full blown dsp to play with.
They also different set up modes. 3 from beginner to pro.
Kinda pricy but I feel like you got the coin.
Do yourself a favor and put the capacitors away and don't try and reground anything.
The car is less than 6 months old. The factory grounds are still flawless.

 

[Thomasluke7899]

More updates.
The stock speakers DO have the hiss, it's just much more minimal. This confirms that it's just a crappy signal from the head unit. The reason it's so minimal on the stock tweeters is because they constantly sound like they have a pillow over them, so the hiss is hard to hear unless you put your ear up to them.

I created a few low pass filters and didn't have great results. Adding the resistor in series definitely lowers the overall volume of the tweeters (as it should), but the capacitor in parallel doesn't appear to do anything. It should be cutting out the high frequencies as I increase the size of the cap, but it isnt... or at least it doesn't sound like it to my ears. I'm simply jumping a bipolar cap it across the + and - lines going to the tweeter. Am I doing something wrong here?

A cap will not filter any high frequency from the signal path.
You will need an inductor. At 4 ohm the value is 0.03 millihenrys.
A cap will not filter high frequencies.

 

[Thomasluke7899]

Thanks for the reply. My reading has shown that a low pass RC filter should filter out high frequencies using a resistor in series and a capacitor in parallel with the signal. Could you further explain why a cap won't filter high frequencies? It's not that I don't believe you, but rather I just want to understand.

Technically they do. It's just at about 100000 hertz.
They are used in class d amp to filter out the switching frequencies.
You need to filter 20000 hertz.

 

[Thomasluke7899]

An inductor would also

Well, I gave up.

Couldn't get rid of the hiss no matter which way I hooked it up. The only fix would be an aftermarket DSP with an equalizer built in so I could find the afflicted frequency and drown it out.... but then I'd need a amp... the cost keeps going up and it's more than I want to spend on this project, so I installed it as is. If you're driving or the AC is blowing, you can't hear the hiss, but I will always know it's there and it will bother me.

The very reason car audio is dead.

 

[Thomasluke7899]

I can only see that parallel load increasing load and distortion from the amp if I’m honest and don’t see how it would help at all as per my previous post

Bro...I tried like a week ago to explain.