[Holmz]

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!

An amp with a high damping factor will need a resistor in-line before the capacitor.

If it is the amplifier that is hissing like a pit of vipers, then a DSP will not help.

ideally one probably wants to understand what is happening before just throwing a buchacci of solutions at the problem hoping one of them sticks to it.

 

[cman]

Yeah i think there is a high probability this is just the noise floor of his $hitty OEM headunit...

 

[Raiz]

I tried placing several different value capacitors across the + and - leads. It didn't seem to help at all. The factory tweeter has a 5.6uF cap soldered into it. I desoldered it and tried that on the new tweeter as well but it had no effect.

The hiss is still present.

 

[Raiz]

While it would be nice to go our an spend $1500 on an amp, I'm kind of having fun troubleshooting this issue.

My next plan is to create a low pass filter and start knocking off the higher end frequencies until the hiss disappears. After some reading, a resistor in series and a capacitor in parallel with the tweeter should create the filter.

I'm going to start with a 1ohm resistor and a 14uF capacitor, which will knock off anything above 10khz.... if the web calculators are correct. Should be a good starting point.

 

[Sudoku]

While it would be nice to go our an spend $1500 on an amp, I'm kind of having fun troubleshooting this issue.

My next plan is to create a low pass filter and start knocking off the higher end frequencies until the hiss disappears...

Love your approach to this, I've nothing useful to add really, but hope you nail it.

 

[Raiz]

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?

 

[Raiz]

Some diagrams show the capacitor running to ground instead of the negative side. Something to try in my next attempt I guess.

 

[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.

 

[Raiz]

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.

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.

 

[Raiz]

The ultimate solution, as some of you have pointed out, is to find a way to clean up the signal from the factory head unit before it even gets to the speakers.

Given that I have plenty of volume coming from the speakers, I assume I don't need an amp at all. I just need a way to clean up the signal to the speakers.

 

[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.

 

[Holmz]

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.

An inductor would also do it well, or a bigger cap across the +/-.

A used amplifier with a low noise floor should be easy if the HU had RCA outputs.

 

[Raiz]

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.

 

[Holmz]

You maybe need to figure out where the hiss is coming from? (Otherwise we are back to post #21 and the concept of throwing solutions at a problem)

 

[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.

 

[Raiz]

You maybe need to figure out where the hiss is coming from? (Otherwise we are back to post #21 and the concept of throwing solutions at a problem)

99% certain it's coming from the head unit. I hear the hiss on the stock tweeter as well as the aftermarket tweeter, it's just a bit more noticeable on the aftermarket tweeter (because it's more sensitive). The aftermarket tweeter is still much better than the stock, so it's an upgrade, but I don't have the time or money to make it sound like I want to.

 

[Holmz]

99% certain it's coming from the head unit. I hear the hiss on the stock tweeter as well as the aftermarket tweeter, it's just a bit more noticeable on the aftermarket tweeter (because it's more sensitive). The aftermarket tweeter is still much better than the stock, so it's an upgrade, but I don't have the time or money to make it sound like I want to.

If it is coming out of the HU then how do you explain this:

… The only fix would be an aftermarket DSP with an equalizer built in so I could find the afflicted frequency and drown it out...
…

However the other fix could be a HU with less noise.

but,… we sort of need a way to work out whether either cure is reasonable.

 

[Old'sCool]

The Kappas are 93dB efficient, and 2 ohms. It's going to accentuate hiss. Rolling your highs off at 10k will basically muffle them like the OEMs.

I'm assuming you want to keep the stock HU?

Thomasluke, if car audio is dead, nobody's told me yet.

 

[Raiz]

Yes, I want to keep the highs. We are on a road trip now and the sound out of the new tweeters is much more clear and open compared to the stock.

I need to keep the OEM head unit for navigation, various sensors, car warnings etc.

EDIT: I measured resistance across the tweeters as 4ohm. Unless the crossover combines the woofer and tweeter resistance to make the overall system 2ohm.

 

[dumdum]

A cap across the tweeter pod and neg won’t reduce high freqs, it will load the radio down more as in theory at some freqs it could be a dead short, but it certainly won’t reduce voltage at the tweeter or the current through the tweeter, sorry but that is a waste of time

It’s likely residual noise that the original tweeters couldn’t resolve, a dsp won’t get rid of hiss without removing other parts of the music

in this instance i would consider a helix dsp with a dedicated dap or phone digital input so you can then set the vw hu as a main input and have it switch over for a set time if it senses signal on the main in, but you will get high quality digital audio from the dap