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Old 01-20-2011, 10:21 PM   #1
miaM7
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Noise in speakers with engine in idle only - Updated with pics and sound.

As the title says, i am getting some low level noise in my newly installed speakers/amp when in the engine is in idle only. When i rev the engine the noise is gone.

I thaught it was alternator whine, but it cant be as the noise goes away and does not chnge with the throttle application.

I tried different ground location in the trunk, they all gave similar results. Please help?

Last edited by miaM7; 01-30-2011 at 08:47 AM. Reason: master thread.
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Old 01-21-2011, 01:30 AM   #2
95seriesbmw
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give a ground loop isolator a try between your amp signal wire and amp. you will need to do all channels.
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Old 01-21-2011, 06:57 AM   #3
miaM7
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Quote:
Originally Posted by 95seriesbmw View Post
give a ground loop isolator a try between your amp signal wire and amp. you will need to do all channels.
So i guess you're suggesting a ground loop issue? I measured all the different voltages across the different points, and they are equal. Wouldnt that imply it is not a ground loop?

I am just getting tired of all those issues... It seems some lucky fanatics either have issues or dont ... I am one of those unlucky ones.

Thanks for your suggestion.
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Old 01-30-2011, 08:42 AM   #4
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Master summary

Here's a summary of my installs and issues to date based on a recommendation from a user. BTW, i should mention that i did tons of reading and experimenting, so I appreciate not receiving comments like check your ground, its your ground, ...

car audio stock specs: Canadian 6ch HU 06/2004, no amp in trunk, 4 spkrs in front (tweeter/mid or woofer), woofers in back.

I installed a BT (parrot/Connects2) solution, worked fine,no issues with stock HU. Later i decided to install amp/speakers. purchased infinity kappa four and 60.9cs speakers from a fellow fanatic.

Installed the amp without a LOC, tapping into the HU wiring in the back, connecting to RCA on the Kappa 4, which is supposed to take differential, speaker level signals. Also installed infinity woofer/tweeter in the back. i made all the wiring myself, twisted 16AWG. still using the HU output wiring to the rear.

I had hissing noise because gains were a bit high, so i adjusted the rear gain and that helped with the noise floor generated by the HU. thanks Arty.

Next, when i operated the BT system, i was having horrible pops and clicks in the rear speaker. Further investigation showed wrong wiring from the Connects2 connectors. Fixed that by connecting the rear speakers signals from the radio directly to the car harness. Thanks to me ;-)

After all that, one noise was remaining. That ripple noise, only appears when the car is in idle (750rpm), warm or cold. Only in that condition. it does not appear if the engine is off, or if the radio is on and engine off.

The linked audio file, starts by having the noise, then when i apply gently the throttle to 1000rpm, at 2sec into the file, the noise disappears. I've also attached a spectrogram that shows where the noise is.

Experiments/Tests:
  1. by removing the RCA connectors form the amp, the noise goes away.
  2. Checked voltages in the trunk install, all ok and equal to the battery voltage with engine off.
  3. Also check voltages with car running, all ok.
  4. checked the alternator ground, OK. no voltage difference in engine bay
  5. installed a ground loop isolator on the RCA, no change

I'll post a next reply with the Q&A that people have sent me ...

Listen to the noise file: http://www.mediafire.com/?p1xu41pjvm9xwvw
Link to my install pics: https://picasaweb.google.com/1065074...eat=directlink
Attached Thumbnails
Click image for larger version

Name:	speaker noise spectrogram.jpg
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Last edited by miaM7; 01-30-2011 at 08:54 AM. Reason: more info
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Old 01-30-2011, 09:11 AM   #5
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Q&A from fellow fanatics (collected here)

Quote:
Originally Posted by jdstrickland View Post
No worries...I think you have a problem with the stuff you installed ... Basically, you have a factory system that does the crossover stuff inside of the amplifier, and you hooked up stuff that is looking for descreet information to boost and send to the speakers where the crossover typically takes place.
Thanks, i have read all info related to our audio system. i think the HU is sending the full range signal, because i have no separate wires from the front woofer/tweeter. the sedan, Canadian, 6 spkrs install, tweeter is connected in parallel to the front woofer or midrange.

Quote:
Originally Posted by derek0606 View Post
+1 Noise typically comes from bad connections, bad grounds, to many grounds, horrible quality RCAs, or running RCAs to close to a power wire.

... If not then you know its the RCAs.

Another thing that comes to mind is what kind of LOC did you use and where did you tap it in?
...
Also, just to double check; how are the speaker wires ran?
Check my install pics. HU rear wires running on the driver side all the way to the trunk. check how my RCA/spkr wires are to the left, amp+ is going to the right, and GND is freakin 4" to chassis, sanded, cleaned, applied special chemical for increased connectivity, bolted !

Noise is definitely carried by the HU twisted pair that is connected to my amp's RCA. see above post. remove RCA, noise is gone.

No LOC used, see above post. rear speaker wiring along the deck into the trunk.

Quote:
Originally Posted by albarran9 View Post
Are you using the stock amp or an LOC with a DICE unit? If your using an aftermarket amp and DICE unit, a "humming noise" seems to be a normal thing with speakers on startup. Some people may even experience a pop when turning the radio on. With your new speakers installed, depending on your set up and speakers you might be able to hear details in the music that you didn't before. With that, you will also hear any flaws in the wires, ground, and equipment. It's like having some crappy headphones that came with your MP3 player and then upgrading to a nice set that has better sounding music with detailed sound.
No LOC and no DICE. Noise appeared before installing my USA spec. i subscribe to your theory that with an aftermarket amp/speaker that we may hear noises that werent there.

Last but not least, and the most interesting revelation that Art provided...

Last edited by miaM7; 01-30-2011 at 09:15 AM.
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Old 01-30-2011, 09:16 AM   #6
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Quote:
Originally Posted by Arty View Post
Do your speakers run from one cable or two? Like all speaker level output, it's a balanced differential signal. That is why you cannot connect the negative terminal of the speaker to the chassis GND. The BMW amp output is not different to any other car audio system.
Of course the speakers have two wires.

Quote:
The low ripple noise - Is it there when the engine is off?
No, it is only there when the engine is on, only during idle.

Quote:
Edit: Missed this bit.
You did what? Did you check the RCA outer cores aren't chassis GND (which they will be in 90% of amplifiers that don't float the low level inputs)?

You have Grounded one half of the HU amp output. Expect it to get hot and fail.

Fix this as your noise profile may change. You have funky short circuit current flowing in the audio GND path.
WHAT ???? i thought that Infinity kappa amps can take speaker level out, diff balanced inputs ?
"Differential Signal Inputs eliminate ground loops that cause engine noise and work with a variety of output configurations. Speaker-level, line-level single-ended and line-level balanced output signals from any source unit can be connected directly to the Kappa amplifiers' RCA-type input connectors."
now i am really puzzled ! so i should check the RCA outer core of the connector on the Kappa amp without the RCA connector i made coming from the HU? is that what you're referring to ? so measure DC voltage across amp + lead and the RCA outer core ? or check continuity (or impedance?) between RCA outer core and chassis GND ?

How could i be getting acceptable sound if I was grounding one of the HU amp output ??? thanks for your help !
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Old 01-30-2011, 09:20 AM   #7
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Can you bypass the amp, connecting outputs to inputs to see if the noise persists?

Can you temporarily reroute the HU speaker outs (eg over the seats) to get them away from any other cables.

The source of your noise may well be the DISA or ICV or something enginey. You want to find how it's getting onto the audio if you can.
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Old 01-30-2011, 09:23 AM   #8
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Quote:
Originally Posted by miaM7 View Post
WHAT ???? i thought that Infinity kappa amps can take speaker level out, diff balanced inputs ?
"Differential Signal Inputs eliminate ground loops that cause engine noise and work with a variety of output configurations. Speaker-level, line-level single-ended and line-level balanced output signals from any source unit can be connected directly to the Kappa amplifiers' RCA-type input connectors."
You should be fine. IF the manual says you can send speaker signals into the RCAs, they must be using the differential inputs on the amp. A neat config. Quick check is a resistance test with the multimeter to chassis GND from the RCA outer.

Should not be a dead short.
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Old 01-30-2011, 10:56 AM   #9
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Quote:
Originally Posted by Arty View Post
Can you bypass the amp, connecting outputs to inputs to see if the noise persists?

Can you temporarily reroute the HU speaker outs (eg over the seats) to get them away from any other cables.

The source of your noise may well be the DISA or ICV or something enginey. You want to find how it's getting onto the audio if you can.
I will follow up on those suggestions shortly. Something came to mind when i fixed the connects2 wiring, that loom that connects the HU radio to the connects box and back to the car harness is about 4-5 ft of untwisted cables, even smaller in gauge. Given that those wires are behind the radio and untwisted, could they be more susceptible to noise from ignition and oher surrounding enginey things?
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Old 01-30-2011, 10:59 AM   #10
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Quote:
Originally Posted by Arty View Post
You should be fine. IF the manual says you can send speaker signals into the RCAs, they must be using the differential inputs on the amp. A neat config. Quick check is a resistance test with the multimeter to chassis GND from the RCA outer.

Should not be a dead short.
The four outer RCA amp connector show anywhere from 1Mohm to 5Mohm to chassis GND. So we're ok tx for your help.
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Old 01-30-2011, 01:06 PM   #11
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What are the connections like behind the radio and what wires did you decide to tap into?

Better yet, where did you tap the signal wire in?

Also, by the looks of your amp location.... Does the power and signal wires ever cross?

Last edited by derek0606; 01-30-2011 at 01:19 PM.
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Old 01-30-2011, 01:52 PM   #12
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Quote:
Originally Posted by derek0606 View Post
What are the connections like behind the radio and what wires did you decide to tap into?

Better yet, where did you tap the signal wire in?

Also, by the looks of your amp location.... Does the power and signal wires ever cross?
See above, the radio is connected to the connects2, then this sends some signals to the car harness. Most of those wires are 18/20 AWG, and are untwisted.

I tapped in the HU rear wires in the rear deck/trunk. The signals do not cross at all with power or GND. Pic says it all. Signal on drivers tunk side, power going to the battery side along spare tire, GND to frame rail newly created spot.

My theory is related to ICV, Disa, injection or now i think even some ignition noise. Will have to buy a 2200uF cap and install it in parallel with radio power and GND.
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Old 01-30-2011, 02:15 PM   #13
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Untwisted? Seriously man.... RCA Signal Cables have a shield all the way around the wire.... At least do that much... I'm sorry but my questions may seem stupid but its because I do not trust other peoples work and how they slap stuff together assuming yea it will be ok. It is very unclear where the signal wires run in the trunk.

As I have been asking in all your threads and this thread.... WHAT IS THE AC VOLTAGE ON THE SIGNAL WIRES?

Further more, most amps that accept line level input have a different harness for this sort of thing.... Are you using the harness or did I read correct and you made your own RCA's? Which is why I was curious if you used a LOC.

I am an experienced MECP certified installer and all my questions are not based on assumption but experience and things I have seen in the past... Like I tell customers who come in wanting to buy stupid Ground Loop Isolators; save your money and quit trying to buy more components to fix the problem because that is what got you there in the first place..... You added an extra component to the car and that is what caused this; Not BMW's ignition system... BMW's get stereos in them every day... I have never experienced a problem with noise in any of mine.
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Old 01-30-2011, 02:28 PM   #14
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http://manuals.harman.com/INF/CAR/Ow...t.friendly.pdf Is this your amp? Looks like they short cut on that speaker level input now.
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Old 01-30-2011, 02:56 PM   #15
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The connects2 wiring is not done by myself, it comes as is, untwisted. surely for few feet, it wouldnt matter ?

THE AC VOLTAGE ACROSS THE +VE AND OUTER CORE of the RCA connector using the twisted cabled coming from the HU = 0.15V AC, so ? music moderatly loud, fader full to back.

I didnt use a LOC, just soldered a RCA connector on the twisted pair cables coming from the car harness. Now onto the amp, yes that is my amp, infinity Kappa four. what do you mean they short cut the speaker input level ? thanks very much for you help and patience.

http://www.infinitysystems.com/car/p...=US&Region=USA

Last edited by miaM7; 01-31-2011 at 08:05 AM.
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Old 01-30-2011, 05:15 PM   #16
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Quote:
Originally Posted by miaM7 View Post
My theory is related to ICV, Disa, injection or now i think even some ignition noise. Will have to buy a 2200uF cap and install it in parallel with radio power and GND.
33nF would be resonant at 33Hz, assuming the timebase on your graph is in seconds.

I wonder if the car would run when the DISA or ICV was temporarily unplugged?

Naturally you want to check the audio wiring routing by bypassing the amp before hacking at the power supplies.
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Old 01-30-2011, 06:36 PM   #17
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Hi Arty, i see you calculated based on the period of the noise signal in my spectrogram! did you use the jpeg and a ruler ;-) the resonant frequency is close to what you calculated. but i didn't think to use a cap based on that.

No, i don't think the car would run without the ICV. if no air goes into the engine during idle, the engine will definitely choke or give some errors.

So I did wire the HU wires to the crossovers that are connected to the rear new 2ohm speakers. with car on idle, no damn noise!!! so what does that mean ? also with the amp on, when i disconnect the HU wires coming to it, no noise.

It almost sounds like the amp is amplifying some noise there, or some funky interaction between the amp and the radio during idle only. please dont say ground loop
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Old 01-31-2011, 04:02 AM   #18
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I'm pretty sure the ICV just controls the idle. (heh), but removing it may cause your engine to pick up revs as the car goes to a default RPM, hence masking the problems.

I think the DISA has a click period that is audible, there are a few videos on youtube you could watch to see if they are comparable speeds.

So you have two choices

1) Find the source and kill it
2) Stop it getting onto your soundsystem

Find the source and kill it:
Could it be the ignition? 33Hz/6 cylinders * 60seconds = 330RPM = roughly 1/2 engine speed.


Stop it getting onto your audio:
If you look up CMMR, you will see that it is not a perfect science in amplifiers. The diff amp won't be able to cope perfectly (instantaneously) with CMMR transients, as shown on your 'scope trace. Some will get through before the amp can react and cancel them out.

Things to try

1) In line 40A inductors on amp supply or GND (large and expensive)
2) A cap with low ESR tuned to the noise frequency
3) Star grounding and for the audio. In practice all you will need to do is run GND to the HU. They should then float about together and your CM voltage will go down. But then the length of the cable may bring in inductance that negates that star GND arrangement a bit
4) Consider feeding the amp differently or moving it. An optical link is not that expensive (although you'll need a good automotive supply to run it), or a LOC at the last minute GNDed to the amp EDIT: On second thoughts you are then simply relying on the CMMR of the LOC, so forget that idea.

Last edited by Arty; 01-31-2011 at 04:30 AM.
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Old 01-31-2011, 08:19 AM   #19
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Quote:
Originally Posted by Arty View Post
I'm pretty sure the ICV just controls the idle. (heh), but removing it may cause your engine to pick up revs as the car goes to a default RPM, hence masking the problems.
i am not a mechanic, but the ICV lets air in the engine when you are not pressing the throttle. hence its name Idle control valve. when you apply the throttle, air flows in the engine based on throttle application. no ?
...
Quote:
Find the source and kill it:
Could it be the ignition? 33Hz/6 cylinders * 60seconds = 330RPM = roughly 1/2 engine speed.
Ha ! thats exactly why i started the fuel injection thread, because I reached the same calculation as you but was off by a factor of two. you must be an EE !
Damn, after thinking about this, i tried just turning the key to position 2 (ignition on), and i do get additional noise (different that the attached file), but there's some ignition induced noise ! so your suggestion to reroute and i will twist the wires behind the HU. but thats for the weekend :-)

Now, I cant kill the ignition or fuel injectors BTW, do you think 3-4 ft of untwisted speaker wires behind the HU can pick up that noise ?

Quote:
Things to try

2) A cap with low ESR tuned to the noise frequency
3) Star grounding and for the audio. In practice all you will need to do is run GND to the HU. They should then float about together and your CM voltage will go down. But then the length of the cable may bring in inductance that negates that star GND arrangement a bit
I will try 2 & 3 and see ! thanks again for your help !

Last edited by miaM7; 01-31-2011 at 08:29 AM.
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Old 01-31-2011, 04:33 PM   #20
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Originally Posted by miaM7 View Post
i am not a mechanic, but the ICV lets air in the engine when you are not pressing the throttle. hence its name Idle control valve. when you apply the throttle, air flows in the engine based on throttle application. no ?
I think so, but moreover I thought it's job was to finetune the revs down to reduce fuel consumption. I don't know to be honest either.

Quote:
Originally Posted by miaM7 View Post
Ha ! thats exactly why i started the fuel injection thread, you must be an EE !
I am.
Quote:
Originally Posted by miaM7 View Post
because I reached the same calculation as you but was off by a factor of two.
You must be Management
Quote:
Originally Posted by miaM7 View Post
Damn, after thinking about this, i tried just turning the key to position 2 (ignition on), and i do get additional noise (different that the attached file), but there's some ignition induced noise ! so your suggestion to reroute and i will twist the wires behind the HU. but thats for the weekend :-)

Now, I cant kill the ignition or fuel injectors
But you could add a HV filter or just plain clean up the grounding on the stuff that spikes.
Quote:
Originally Posted by miaM7 View Post
BTW, do you think 3-4 ft of untwisted speaker wires behind the HU can pick up that noise ?
Yes. It's not your install, more that any cable is vulnerable to pick up. What's either a concern is that you picked a noisy route or your ignition system is struggling a bit with a corroded ground strap or something.


Quote:
Originally Posted by miaM7 View Post
I will try 2 & 3 and see ! thanks again for your help !
NP. Let us know what fixes it!

Last edited by Arty; 01-31-2011 at 04:35 PM.
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