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Too much hiss from speakers, what to do?

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=85430
Printed Date: March 29, 2024 at 9:03 AM


Topic: Too much hiss from speakers, what to do?

Posted By: hemanjoyman
Subject: Too much hiss from speakers, what to do?
Date Posted: November 10, 2006 at 10:39 AM

When I had my Pioneer DEH-P9600MP which had 4V preouts, I was able to set the gain on my amps just fine, and when I turned the volume all the way down, there was no noise. Now, I have my Kenwood KVT-717DVD, which has 5V preouts, I have to turn the gain up a lot higher to get the right settings, but there is a lot of hiss coming from the speakers. What I had to do was turn the gains down and got rid of most of the hiss, but now I have to turn the deck volume up quite high to get good volume, and I'm not liking the sound too much. The thing is, now the RCA cables are a bit long, about 8-9ft too long, and I wrapped up around itself and set it on top of the brain unit under the passenger seat, I am wondering if that is what is causing the hiss??? Any Suggestions??? By the way, my amps are a JL Audio 500/1 and a JL Audio 300/4.



Replies:

Posted By: master5
Date Posted: November 10, 2006 at 11:39 AM

As far as the excessive rca cables causing hiss that is doubful, but it can pick up other kinds of inducted noise, you might want to move those cables around and listen for changes.

The odd part about your post is you are now using a unit with more preamp voltage but claim you need to set the gains higher. Kind of defeats the benifit of the higher voltage as that if anything should allow a better s/n ratio, as hiss is a byproduct of a poor (or lower) s/n ratio. However the output voltage rating is not the s/n rating. Without knowing the specific s/n ratings of each unit (which I don't) I can't say for certain that this is or is not the problem.

You might also be sensitive to certain frequecies that you didn't notice with the pionner, you could try adjusting the eq settings on the kenwood and lose or lower the hiss to an acceptable level without sacraficing too much SQ.

Best of luck.



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Posted By: hemanjoyman
Date Posted: November 10, 2006 at 12:18 PM
Well, I looked at the specs. of both units, and the Pioneer has 4V/100Ω preouts, while the Kenwood unit has 5V/600Ω preouts. I'm guessing that could be the problem there. Do you think if I used a signal amplifier (having a brain fart right now, can't remember what they are called) before I go into the amp, then adjust the gain at the amp it would work?   

I think I'm just going to end up buying RCA cables anyway, the ones in there now are just regular unshielded and non-twisted pair....I am going to get shielded twisted pair RCA's that are shorter because the ones I have now are too long anyway.




Posted By: DYohn
Date Posted: November 10, 2006 at 1:45 PM

While the noise you hear could be caused through your RCA cables, this is unlikely.  Much more likely is improper gain setting or poor quality ground, or a poor ground inside the head unit.  Make sure your RCA cables are not damaged and are properly seated.  Read the ground stickies at the top of this forum and make sure you have good grounds for your amps.  Run a separate ground for the HU (do not use the factory wiring harness ground.)  In fact, some times the best results can be had if the HU and the amps are grounded at the same point.

It is also possible that the new HU is simply noisier than your old one.  If this is the case there's nothing you can do about it other than change the HU.



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Posted By: hemanjoyman
Date Posted: November 10, 2006 at 2:02 PM
I will try what you suggested DYohn, see if that helps any. Oh, by the way, I finally remembered it's called a "Line driver," do you think this would help me at all?? So I won't have to turn the amp gain so high??? I guess if the noise is really coming from the head unit, it won't help as the noise will be amplified anyway, right, but the noise does seem to go away when I lower the amp gain, but it has to be lowered quite a bit, almost all the way off?

I think the amp ground is fine because with my previous head, a Pioneer, which are notorious for causing noise, as I have recently found out, was dead silent.




Posted By: DYohn
Date Posted: November 10, 2006 at 2:14 PM

hemanjoyman wrote:

I will try what you suggested DYohn, see if that helps any. Oh, by the way, I finally remembered it's called a "Line driver," do you think this would help me at all?? So I won't have to turn the amp gain so high??? I guess if the noise is really coming from the head unit, it won't help as the noise will be amplified anyway, right, but the noise does seem to go away when I lower the amp gain, but it has to be lowered quite a bit, almost all the way off?

I think the amp ground is fine because with my previous head, a Pioneer, which are notorious for causing noise, as I have recently found out, was dead silent.

I doubt a line driver would help you at all.  It also sounds to me like your gain is way too high.  How did you set it?



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Posted By: druidpagen
Date Posted: November 10, 2006 at 2:34 PM

many factors could be your problem.

"Much more likely is improper gain setting or poor quality ground, or a poor ground inside the head unit." Dyon is on the money, start there first.

i disagree with some ideas though through personal experiance. Rca's can pick up noise-and fairly easily.

" about 8-9ft too long, and I wrapped up around itself and set it on top of the brain unit under the passenger seat"  there is a couple "no no's" here. your rca's should never be longer than you need them. (i actually cut mine down and resolder and heak shrink to my cars length". since you wrapped them up and there so long they could be picking up inductance and acting like a coil (providing unwanted resistance). it's possible but not likely you could be picking up noise from your brain as well, but not likely. also make sure your RCA's are not running next to your power wire as this will pick up alot of noise as well.

hopefully if you take these easy steps it will clear up your problem. if not let us no and we can help you further. good luck.





Posted By: hemanjoyman
Date Posted: November 10, 2006 at 3:55 PM
Actually the gain is set pretty low, even lower than it was set with my previous head unit, and still some hiss. It is set about, let's say it goes from 1 to 10, it's set at 2 or 3. With my previous head unit it was set to about 5.

The first two things I am going to do is shorten the length of those RCA cables, and then I am going to put a better ground to the head unit, and see what happens.

The RCA's and the power wires run on opposite sides of the car.....the remote turn on wire does run on the side of the RCA's, but I don't think that will have much of an effect, if any.




Posted By: DYohn
Date Posted: November 10, 2006 at 4:34 PM

hemanjoyman wrote:

Actually the gain is set pretty low, even lower than it was set with my previous head unit, and still some hiss. It is set about, let's say it goes from 1 to 10, it's set at 2 or 3. With my previous head unit it was set to about 5.

The markings on the amplifiers are really meaningless.  Did you use test tones?  Did you set by ear?  Did you use a multimeter as JL Audio suggests?  Or did you just guess?  I really bet your gain is high and this is exaggerating any noise in your system, if not introducing it.  And I still bet your HU ground is bad.



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Posted By: hemanjoyman
Date Posted: November 10, 2006 at 5:02 PM
I actually did it using test tones and a multimeter like JL recommends, and that is the exact same way I did it to set up the Pioneer unit I had in there before. By the way, the amp gain doesn't have markings on it, I was just mentioned the numbers to give a reference point.

With the Pioneer, on the 500/1, to get the level to 44.7V on the DMM, I only had to turn the gain about half way, on the Kenwood unit, I have to turn the gain about 3/4, if not a little bit more. Same for the 300/4, to get it to 17.3V, I only had to set the gain to about 3/8 of the way with the Pioneer, with the Kenwood, I have to turn it about 5/8 to 3/4 of the way up.

It could very well be a bad HU ground.....by this you mean the ground to the HU harness, or internally???




Posted By: master5
Date Posted: November 11, 2006 at 12:52 PM

Any ground issues of course could be a problem and noisey but I don't think it will cause "hiss". Are you sure this noise is hiss and not something else?



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Posted By: stevdart
Date Posted: November 11, 2006 at 6:48 PM
hermanjoyman, you've GOT to stop referring to a corresponding position on the gain's travel path when you are talking about your gain setting.  Nobody who sets their gains by the book should pay the least amount of attention to the gain position once it's all set.  The referral to position makes the very act of proper gain-setting suspect.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.




Posted By: hemanjoyman
Date Posted: November 11, 2006 at 6:48 PM
Yeah, it's hiss or a staticky kind of sound....kind of like when you tune into a radio station with a bad signal. The thing is, you can only really hear it when the volume is turned all the way down, as you turn it up, you can't hear it anymore....I am going to turn up the gains and see If I can still hear it when I turn up the volume. I went to a installation shop and they told me I won't be able to get rid of it because it was the nature of the head unit. I know it's not the amps because when I disconnect the the RCA's from the brain unit, the hiss goes away. My friend has a Kenwood head unit also, and it does the same thing I just found out yesterday when he told me, it's a different model Kenwood, but it's a Kenwood.

I just finished making the RCA's shorter, cut off about 8 feet from all 3, I moved around the power wires for the brain unit to make sure they don't run parallel to the speaker wires or RCA's, but still that hiss/static sound persists....The only thing left to do is give the head unit and the brain unit a better ground....but I still don't think that will solve it. I might finish it up tonight, might not, tired of doing all the other things already...I will let you know what happens if I do it tonight, or whenever it is I do it.




Posted By: stevdart
Date Posted: November 11, 2006 at 6:55 PM

]I am wrote:

going to turn up the gains and see If I can still hear it when I turn up the volume.

Dude, you just reinforced what I posted at the same time you did. 

Set your gains using the true methods you said that you used.  After that, leave them alone.  They are not to be fooled with for even the purpose of troubleshooting odd sounds.  They are set accurately...and that is a checkmark on your list of troubleshooting steps.  You can then go to step two knowing that the gains are not a contributing factor.



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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.




Posted By: DYohn
Date Posted: November 11, 2006 at 6:55 PM

Like I said several posts ago...

DYohn] wrote:

hile the noise you hear could be caused through your RCA cables, this is unlikely.  Much more likely is improper gain setting or poor quality ground, or a poor ground inside the head unit.  Make sure your RCA cables are not damaged and are properly seated.  Read the ground stickies at the top of this forum and make sure you have good grounds for your amps.  Run a separate ground for the HU (do not use the factory wiring harness ground.)  In fact, some times the best results can be had if the HU and the amps are grounded at the same point.

It is also possible that the new HU is simply noisier than your old one.  If this is the case there's nothing you can do about it other than change the HU.




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Posted By: hemanjoyman
Date Posted: November 11, 2006 at 9:48 PM
Dude, stevedart, I only gave those reference points because Kenwood claims 5V preouts, while the Pioneer I had before claimed 4V...so, it would only make sense that the gains should have to be set lower, not higher. Setting the gain "by the book" only makes the hiss louder....the only way to do it is to set it by ear, to get the minimum hiss as possible. The amps are the same amps, so the gain on those amps is the same as it has always been. The only difference now is the head unit...obviously this head unit is the cause of the noise since it wasn't present before. The Pioneer I had before must have preouts closer to the 4V it claims, and the Kenwood must not be close to the 5V it claims, and also most likely the Kenwood must have a ground problem that is inherent to their units, since my friends does the same thing. That is the only explanation I can see.




Posted By: druidpagen
Date Posted: November 12, 2006 at 2:16 PM

sounds like it's just a noisy head unit. your probably gonna have to live with it :(  a better ground should help. the only  other thing i could sugest is this. i had a head unit with the same problem. i ended putting a diode on the ground to prevent ground loop. it was still there but it greatly reduced it. make sure you get the right one!





Posted By: hemanjoyman
Date Posted: November 13, 2006 at 12:05 AM
Did you use a 12V zener diode, or a 15V zener??? I am assuming the band side (cathode) of the diode will go to ground, is that how you set it up???




Posted By: hemanjoyman
Date Posted: November 14, 2006 at 11:10 PM
I just wanted to add.....I took some measurements of the preout voltage on the Kenwood head, using an 80hz test tone, with 3/4 max volume, with all the processing off, no eq's...and I get a reading of 1.45 volts on the sub preout and 1.045 volts on the front and rear outputs.

When I took the same measurements, with the same conditions on the Pioneer head, back when I was setting up the gain for that head, I read about 3.3 volts on all the preouts.

So, now I have proven that the Kenwood definitely has lower voltage output on the preouts than it claims, most likely not high enough to clear the noise floor....most likely why I hear the hiss........again I ask, will a line driver help me in this case???




Posted By: stevdart
Date Posted: November 15, 2006 at 7:37 AM
If you've narrowed it down to the head unit as the culprit, wouldn't it be the wisest thing to do to trade up to a better deck rather than adding another device in the signal path as an attempt to fix the deficiencies?

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.




Posted By: DYohn
Date Posted: November 15, 2006 at 8:18 AM
A line driver will likely only make the hiss worse.  I agree with Stevdart.

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Posted By: hemanjoyman
Date Posted: November 15, 2006 at 12:51 PM
Sure, it would probably be the wisest, and most likely the simplest thing to do to fix the problem. But, I want to see if I can minimize the hiss to an acceptable level, while having the gains set correctly because I really like the look and feel of this head unit.

Plus, I already cut up all the harnesses, and I bought from the Best Buy Outlet through ebay....don't know if they will make it a pain to return it...most likely I will be out a 15% restocking fee, don't know if they will charge me for the harnesses or not....but that will be the last resort. For now, I will borrow my friends line driver and see how it goes in the next few days.





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