DiyMobileAudio.com Car Stereo Forum banner

1 - 20 of 37 Posts

·
Registered
Joined
·
4,702 Posts
Discussion Starter #1
The noise:
The distortion surfaces in tweeters and maybe midranges. It only occurs with the bass notes. The most obvious occurence is on a track that is all bass so that midrange and high notes don't mask the distortion. It sounds like speaker suspension noise, or maybe a panel rattling but it certainly comes from the tweeters and certainly only during bass passages.

When it doesn't occur:
If I turn the engine off it disappears completely. Everything is squeaky clean. It also disappears if I turn the subwoofer level down from the headunit or, get this, from the bass amp gain knob I have on the dash. However, if the sub output is high enough and the engine is on I can hear it. The bass level can be maxed out with the engine off and it will disappear completely.

My guesses:
It can't be the P99 headunit clipping because I can vary the sub level from the amplifier to make it disappear. The gain can be maxed out on the headunit on the sub but if the amp gain is low enough it won't come up.

It also can't be the subwoofer amplifier clipping because the distortion is in the tweeters.

It can't be a loose ground because it doesn't happen at loud volumes with the engine off.



My best guess on what it is: power noise, either from the fuel tank pump or car computers because it only happens with the engine on. My guess is that it gets filtered through the headunit capacitors really well at low output and that's why I can't hear it when the engine is on but the subwoofer level is down. However, at high output the noise in the powerlines is too strong to be filtered by the headunit capacitors on board.


Weird things:

The noise was there on my old Eclipse CD7200 as well so I sold it thinking it's the headunit. The P99 didn't have this problem when it was new. It's now 5 months old or so and it starting to have the same problems as the Eclipse head. Maybe their caps get old fast and can't filter. Maybe the P99 has a pico fues on board and it blew.

What's your take? It's driving me nuts.
 

·
Premium Member
Joined
·
4,235 Posts
This is usually a grounding problem or a high resistance conection in either the ground or the power leads to the amps. If you have a volt meter, check the voltage across the amps (both of them) power terminals when the distortion happens. You'll probably need to read the little bar graph at the top because the digital display won't display fast enough to read it.
 

·
Registered
Joined
·
12,054 Posts
This is usually a grounding problem or a high resistance conection in either the ground or the power leads to the amps. If you have a volt meter, check the voltage across the amps (both of them) power terminals when the distortion happens. You'll probably need to read the little bar graph at the top because the digital display won't display fast enough to read it.
if it has a min/max setting, that is helpfull too.
 

·
Registered
Joined
·
12 Posts
This is usually a grounding problem or a high resistance conection in either the ground or the power leads to the amps. If you have a volt meter, check the voltage across the amps (both of them) power terminals when the distortion happens. You'll probably need to read the little bar graph at the top because the digital display won't display fast enough to read it.
That was my inclination as well. The noise when the car is running is probably alternator wine. Try a back-seat seat belt bolt connection for ground (assuming your amps are in the trunk).
 

·
Registered
Joined
·
4,702 Posts
Discussion Starter #5
This is usually a grounding problem or a high resistance conection in either the ground or the power leads to the amps. If you have a volt meter, check the voltage across the amps (both of them) power terminals when the distortion happens. You'll probably need to read the little bar graph at the top because the digital display won't display fast enough to read it.
Just to verify, I could be listening to it and then turn the key to off while the music is still playing at the same level and the noise dissapears. Is it still a ground or resistance problem if it only happens with the engine on?


I have a volt meter, I'll give it a try tomorrow. I'm checking at each of the three amplifiers' cable terminals. I have one for tweeter and mids, one for midbass, one for subs. Should i check the voltage at the power distribution blocks instead so all three are joint? Not sure my voltmeter has a bar graph but I'll check.
 

·
Registered
Joined
·
4,702 Posts
Discussion Starter #6
That was my inclination as well. The noise when the car is running is probably alternator wine. Try a back-seat seat belt bolt connection for ground (assuming your amps are in the trunk).
That's the only time I do get a noise, with the engine on. It's not high pitch or changing with revs like alternator whine usually is. Don't have a back seat mate, 2 seater. I was gonna try connecting the ground to the battery directly on the side of the car.
 

·
Registered
Joined
·
197 Posts
The first thing i would try is grounding the amps (and the h/u if poss) straight to the battery, as its an easy test and will rule out grounding problems in one go.

Gav
 

·
Registered
Joined
·
93 Posts
Just to verify, I could be listening to it and then turn the key to off while the music is still playing at the same level and the noise dissapears. Is it still a ground or resistance problem if it only happens with the engine on?
Yes it could be. If you have a ground loop issue it might go away when the alternator is no longer in the picture.


Another random idea. Does the distortion mimic the music, or rather the bass track at all? I'm wondering if it is signal bleed through from somewhere that only occurrs at the higher 14.4ish voltage when the engine is on versus the 12.3ish volts when the engine is off? Do the sub speaker wires or RCA's route next to each other anywhere?
 

·
Registered
Joined
·
102 Posts
Problem only occurs with engine on
and
Problem only occurs with sub output high

It seems that it can't be anything associated with the sub output side (sub cables crosstalking with the highs and mids) or you would hear it with the engine off.
It must be something that is different with your system running off of the alternator vice just the battery.
And you said it doesn't sound like alternator whine in that the noise is sub volume dependent and doesn't vary with engine speed.

I'd be looking at your grounding as suggested. What is your grounding layout; are you using a ground distribution block? What size ground wires are you using? Are any of the mid/high interconnects or speaker wires close to the sub ground wire? Does the noise go away if you move any of the mid/high interconnects or speaker cables?

This is an interesting one.
 

·
Registered
Joined
·
4,702 Posts
Discussion Starter #10
The first thing i would try is grounding the amps (and the h/u if poss) straight to the battery, as its an easy test and will rule out grounding problems in one go.

Gav
I'll add this to the list of things to do.


Yes it could be. If you have a ground loop issue it might go away when the alternator is no longer in the picture.


Another random idea. Does the distortion mimic the music, or rather the bass track at all? I'm wondering if it is signal bleed through from somewhere that only occurrs at the higher 14.4ish voltage when the engine is on versus the 12.3ish volts when the engine is off? Do the sub speaker wires or RCA's route next to each other anywhere?
Yeah, the distortion comes in only when there is a lot of bass. I tracks bass perfectly. Bass draws a lot more juice than the other frequencies so I'm thinking it's a power line noise. Maybe there is more distortion in other frequencies as well but I can't hear it as readily as with bass.

I did my best to separate the RCAs and signal wires. They are run on different sides of the vehicle. Both are wrapped separately in flexible tubing. They do cross but for the minimal path possible.

Problem only occurs with engine on
and
Problem only occurs with sub output high

It seems that it can't be anything associated with the sub output side (sub cables crosstalking with the highs and mids) or you would hear it with the engine off.
It must be something that is different with your system running off of the alternator vice just the battery.
And you said it doesn't sound like alternator whine in that the noise is sub volume dependent and doesn't vary with engine speed.

I'd be looking at your grounding as suggested. What is your grounding layout; are you using a ground distribution block? What size ground wires are you using? Are any of the mid/high interconnects or speaker wires close to the sub ground wire? Does the noise go away if you move any of the mid/high interconnects or speaker cables?

This is an interesting one.
There are three amplifiers wired with 4 ga. That run is 1 foot. Then it hits a power distribution block. All three 4ga wires are changed into a 4ga. That run is also a foot and then it terminates into an Anderson power disconnect. Both negative and positive cables are wired exactly the same up to this point.

From the Anderson it's another 2 feet of 0ga cable to the chassis ground. It ends into a 3 screw grounding block. The power cable is 0 ga from the Anderson disconnect to the battery.

So power goes 0 ga to disconnect, 4 ga to splitter, 4ga to each amp. Total length 10feet 0ga, 2 feet 4ga.
Ground is 0ga to disconnect, 4 ga to splitter, 4 ga to each amp. Total length 2 feet 0ga, 2feet 4ga.

I did move the wires around, nothing changes. This is an interesting one, I wish it wasn't haha.
 

·
Registered
Joined
·
222 Posts
any chance it could be noise interference from cars electronics? Leaking plug wires, or non resistor plugs? Just a thought
 

·
Registered
Joined
·
93 Posts
any chance it could be noise interference from cars electronics? Leaking plug wires, or non resistor plugs? Just a thought
I thought the same thing but if it tracks the bass line perfectly and it doesn't change with engine RPM I'm not sure? Maybe try some dielectric grease in the plug boots and see if that helps. It's fixed engine whine issues for me before. And it's not like we have been successful at solving it yet so it's even more worth a shot.
 

·
Premium Member
Joined
·
6,214 Posts
Is your voltage dropping when hard bass hits?
Also, does your amp have low voltage protection? If the protection doesn't work, that can lead to distorsion on strong dips in the voltage...

Kelvin
 

·
Registered
Joined
·
4,702 Posts
Discussion Starter #14
Is your voltage dropping when hard bass hits?
Also, does your amp have low voltage protection? If the protection doesn't work, that can lead to distorsion on strong dips in the voltage...

Kelvin
It happens way before the voltage drops. Also the distortion is in the tweeters and midrange but somehow related to the power pulled from the sub amp. Those amplifiers can't possibly clip and why would they trail the sub? Oh, and since it happens only with the engine on it's even less likely, the power comes from the alternator and augments whatever there is in the battery.


I'll look into this dialectic grease, but it sounds messy. :D
 

·
Premium Member
Joined
·
6,214 Posts
It happens way before the voltage drops. Also the distortion is in the tweeters and midrange but somehow related to the power pulled from the sub amp. Those amplifiers can't possibly clip and why would they trail the sub? Oh, and since it happens only with the engine on it's even less likely, the power comes from the alternator and augments whatever there is in the battery.


I'll look into this dialectic grease, but it sounds messy. :D
IMO, your problem comes from the HU... Time for a HU capacitor maybe :D

Something like the Helix Cap33

Kelvin
 

·
Registered
Joined
·
93 Posts
I'll look into this dialectic grease, but it sounds messy. :D

It's pretty cheap and comes in a nice little squeeze tube. Just slop some in the plug boots and snap back on to the plug and wiggle it around a little. Shouldn't take a more than a few minutes unless they hid some plug boots under air intakes and other junk.
 

·
Registered
Joined
·
4,372 Posts
This is a Pioneer HU..... Using DEX-P99 does not mean it is a problemless HU... The problem(s) signature will be more or less the same....
Where you take your measurements? Suggest to include Hu's power also, if it is working at 10V, you will have some funny behaviour. It will just lost its noise filtering abilities... Lower end HUs, yes, higher end no? Think again, even my DEX-P9 combo also have this problem....
Lay another ground directly from the amps back to battery would be good idea, but I'll put this on last....
 

·
Registered
Joined
·
4,702 Posts
Discussion Starter #18 (Edited)
So I did more troubleshooting today.

First I took the removable IB baffle out and placed it in my passenger seat. The noise disappeared!



So then I figured, it must be because the sub wire is not touching the RCAs and stuff. So I moved the baffle back in the trunk but made damn sure that sub wire went around the RCAs like an Italian man scarf:

Blue wire is sub cable, red wires are RCAs, snug:


Here's where the baffle was, like in a bucket:


NO noise!


So I figured it must be that when I mount the baffle into the car it shakes the ground or power connections or something. So I doubled the number of screws the fiberglass scheleton has, added more dynamat, added dynamat over the power connectors between the fiberglass baffle and grounds. I even moved the figerglass scheleton out an inch.

Mounted the baffle back, and the noise is back. SOB!

Andy I won't be able to put a voltmeter on the amps. I can if I remove the IB baffle, but then the noise is gone. With the IB baffle bolted on (so that the noise is there) I can't reach the amplifier power terminals, it's a physical impossibility. My voltmeter also only has a digit counter, I checked, no bar.

Step 2 and 3 tomorrow at the So. Cal. meet. I'll run a ground cable to the bat and maybe even install power filters. This is really annoying.

This is the setup, fiberglass scheleton. The ground is on the left right behind the fiberglass mold:



I don't have a fresh picture of the Vifas, but here is how the baffle looks like as bolted to the scheleton.



Something happens when it's bolted and the only way I can justify the noise is that the fiberglass shakes the grounds a bit. It can't be a filtering story anymore because it doesn't happen if the baffle is off but powered with the engine on.
 

·
Registered
Joined
·
4,702 Posts
Discussion Starter #20
How long is your bolt? Maybe it's touching your ground when your baffle is in place...

Kelvin
No, the ground is like a foot to the left. I basically made the figerglass mold that's not detachable by fiberglassing over the chassis and the ground. So the fiberglass piece is really close to the grounding point. From there the power wires are wrapped in tubing and freely moved away from the baffle. There is no way the screw is touching the wire. The bolts are 4"! The baffle is 2.25" alone.

The red circle is where the grounding point is behind the fiberglass. The arrow points to the wire loom that bring the ground and power to the amp rack.

 
1 - 20 of 37 Posts
Top