E82 Logic 7 slight static noise on bass hits

[siddhartha]

Hi all, (my first post here)

I've had my 128i with the Logic 7 Premium Hi-Fi Package for about a month now. Just in the last couple days I've notice some sort of distortion/noise interference on songs with loud bass. This is definitely not a vibration and is an almost indiscernible sound, but it is noticeable if you are listening for it (as I am now). It's interesting that the sound only appears to be there while the car is moving. It does not get louder or softer with acceleration, so it is not an alternator noise. For it to happen all-of-a-sudden like this, it doesn't seem symptomatic of a ground loop.

Basically, it is a static-type distortion that happens milliseconds after a loud bass hit. Again, because it is only noticeable while the car is moving, I do not think it is a blown speaker, and it doesn't sound like a blown speaker normally would. It is slightly more noticeable on songs with fast and hard bass hits like trance or techno.

I listen to all my music as MP3s through a USB flash drive. I currently have a 16GB stick, which I recently upgraded from an 8GB. I didn't notice the sound on the 8GB, so I am going to test that out, although I would think the voltages and draw would be the same. The sound happens on many different songs and the MP3 files are all different bit rates by different encoders, so it is not the quality of the encoding.

I don't listen to music on CDs and I haven't heard the distortion on the radio (I don't have HD radio, only standard definition). I am testing out the CD sound tonight.

I am taking it in to the dealership, but unfortunately the soonest appointment is two weeks into September.

Has anyone else experienced any issues like this?

[AZ135]

My car has been doing this since I got it a month ago. It's not really noticeable, but now that I listen for it, it's really annoying.

[backtoreality15]

Originally Posted by AZ135

My car has been doing this since I got it a month ago. It's not really noticeable, but now that I listen for it, it's really annoying.

+1, I just put down the windows a little if it bothers me. :wink:

[siddhartha]

Wow, so other people do have the problem...

I find it is most noticeable on the song "Too $hort - I Need A Freak" about 5 seconds in.

I burned that song as an MP3 onto a CD and the noise is still there. I also burned it as a straight audio track and it is still there also, so it's not the MP3 decoding. I also tried removing the USB stick and the sound is still there on the CDs, so it is definitely not due to the memory stick being present.

The sound is also audible with the DSP set to MUSIC, CINEMA/MOVIE, and OFF.

It will be interesting to see what the dealership can do. It sounds like a difficult problem to diagnose since it only happens when the car is at speed.

I am bringing it in though; it's quite annoying. I would hope everyone else who has the problem will do the same.

[bimmertech]

We replace a lot of Logic 7's. they're junk.

[siddhartha]

Originally Posted by bimmertech

We replace a lot of Logic 7's. they're junk.

Would that be the head unit you normally replace or other components?

[bimmertech]

the issue you have seems to be caused by the actual logic 7 dsp amplifier and not the head unit.

[backtoreality15]

Originally Posted by bimmertech

the issue you have seems to be caused by the actual logic 7 dsp amplifier and not the head unit.

No "fix" currently? Just a shitty amp?

[Swift135]

It's only on MP3's in my car, I have the same song on CD and MP3 via USB, the little electronic buzz with the bass is only heard when playing the song in MP3 form.

[Mad Dragon]

Originally Posted by siddhartha

I listen to all my music as MP3s through a USB flash drive. I currently have a 16GB stick, which I recently upgraded from an 8GB. I didn't notice the sound on the 8GB, so I am going to test that out, although I would think the voltages and draw would be the same. The sound happens on many different songs and the MP3 files are all different bit rates by different encoders, so it is not the quality of the encoding.

I don't listen to music on CDs and I haven't heard the distortion on the radio (I don't have HD radio, only standard definition). I am testing out the CD sound tonight.

...

I burned that song as an MP3 onto a CD and the noise is still there. I also burned it as a straight audio track and it is still there also, so it's not the MP3 decoding.

The sound is only going to be as good as the source, and MP3 is a lousy source. If you burn an MP3 onto a regular audio CD, it's still an uncompressed copy of a compressed copy.

[siddhartha]

Originally Posted by Mad Dragon

The sound is only going to be as good as the source, and MP3 is a lousy source. If you burn an MP3 onto a regular audio CD, it's still an uncompressed copy of a compressed copy.

Obviously, but I am just trying to narrow down the MP3 decoding versus the DAC from CD audio. Being that the noise happens on both MP3 and CD-Audio versions of songs, I can remove the MP3 decoder as the source of the noise.

[siddhartha]

Originally Posted by bimmertech

the issue you have seems to be caused by the actual logic 7 dsp amplifier and not the head unit.

I was actually thinking since it only happens at speed that it might be a problem with the speed sensor that tries to adjust the volume level of the stereo.

[Dafdos]

Wow, I never thought I´d find someone else experiencing the same problem! I had an USB stick while picking up my car 5 weeks ago and stumbled across this sound also from the high/mid-range speakers. It happens on a defined bass range, you cannot hear it while the engine is running but still standing, but during driving you can hear it then. I´ve done various tests on all input devices (CD, USB, AUX-IN and also RADIO), its there on all devices.
I was at the dealer already, they heard it, but diagnosis and a BMW Test-CD didn´t show it. However I´m not satisfied with their answers and will involve some persons at my dealer to get a replacement for my amp to see if it solves this problem.

[Dafdos]

Originally Posted by siddhartha

I was actually thinking since it only happens at speed that it might be a problem with the speed sensor that tries to adjust the volume level of the stereo.

There is a service mode for the professional radio (maybe you got it), switch it off, switch it on and hold the "m" button on the left for more than 8 seconds. You can switch trough different menus on the right by pressing +, there is a parameter called "GAL", thats a parameter for audio speed adjustment, I´ve played around with it from 1 to 6, but it didn´t help for the problem.

[siddhartha]

Originally Posted by Dafdos

There is a service mode for the professional radio (maybe you got it), switch it off, switch it on and hold the "m" button on the left for more than 8 seconds. You can switch trough different menus on the right by pressing +, there is a parameter called "GAL", thats a parameter for audio speed adjustment, I´ve played around with it from 1 to 6, but it didn´t help for the problem.

I can adjust the audio speed from the "S-Level" setting in the normal menus, but I'm still interested in what other things are shown in the service mode.

Please post back if an amp swap solves your problem. I don't think it will though, as there seems to be many people having this problem and I doubt we'd all have defective amps. I would think it is an engineering flaw in some sort of grounding wire placement, either that or speed sensor inadvertently introduces noise. I've had ground loop problems in stereos in the past, but they would be audible whether the car was turned on or off. There's a whole set of problems/solutions here, but I'm certainly not going to rip apart the dash of my brand new bimmer to create my own chassis ground to the head unit.

[siddhartha]

Oooh, interesting:

VIII. Don't connect all of your amplifier ground wires under one bolt. Contrary to belief, this is not required if the rest of the system is installed properly. If you do connect more than one power ground wire under a single bolt, you run the risk of amplifier ground modulation. This is caused by the current demands of, for example a woofer amp, modulating the power ground wire of a tweeter amp. This results in a squeaking noise that can be heard over the tweeters whenever bass notes hit.

(http://www.termpro.com/articles/noise.html, emphasis added)

I wonder if the amplifier is powering more than just the subs...

Edit: And it is, according to this: http://www.e90post.com/forums/showpo...82&postcount=1

[Mad Dragon]

If that were the case, every multi-channel amp on the market would have multiple grounds.

Originally Posted by Dafdos

There is a service mode for the professional radio (maybe you got it), switch it off, switch it on and hold the "m" button on the left for more than 8 seconds. You can switch trough different menus on the right by pressing +, there is a parameter called "GAL", thats a parameter for audio speed adjustment, I´ve played around with it from 1 to 6, but it didn´t help for the problem.

GAL is for speed-dependent volume control.

[Dafdos]

Originally Posted by siddhartha

I can adjust the audio speed from the "S-Level" setting in the normal menus, but I'm still interested in what other things are shown in the service mode.

Please post back if an amp swap solves your problem. I don't think it will though, as there seems to be many people having this problem and I doubt we'd all have defective amps. I would think it is an engineering flaw in some sort of grounding wire placement, either that or speed sensor inadvertently introduces noise. I've had ground loop problems in stereos in the past, but they would be audible whether the car was turned on or off. There's a whole set of problems/solutions here, but I'm certainly not going to rip apart the dash of my brand new bimmer to create my own chassis ground to the head unit.

Sorry, as Mad Dragon wrote, this GAL setting is of course the speed-dependent volume control - I found tis parameter in a german service manual for BMW E87 (hatchback).

Values in the service mode:
1. Serial Number
2. Radio Type
3. Software Version
4. Revision
5. GAL parameter
6. Antenna
7. Frequency and signal quality
8. DSP YES(1)/NO (0) and current volume
9. Traffic announcement volume (TP)
10. A display check

There was another setting for me when using the service mode in my car that is not documented in the manual which is region setting (EU, US, JP).

Do you have other threads discussing the problem, I rarely found one - I had a look on german boards and found only 2 with 3 users complaining about it.

I´m still confused though why we cannot hear the sound while not driving (then I would think it is a ground problem).

[siddhartha]

I hope everyone who has the problem takes it in.... maybe there should be a recall on the amp or whatever is causing the problem. It definitely sounds like amplifier ground modulation.

If you look at the pic here from this post, you can plainly see multiple wires going to a common ground. From the same post but a reply, you can see this pic, where there is only one wire going to the ground. Looks like one is the L7 amp and the other is not. Interesting...

[Mad Dragon]

Do you have any idea how much our cars would cost if the wiring harnesses had individual ground points for every component?

[siddhartha]

Originally Posted by Mad Dragon

Do you have any idea how much our cars would cost if the wiring harnesses had individual ground points for every component?

What are you talking about? First off, all it takes is a single, stand-alone ground point for a single amplifier mounted in the trunk. It has nothing to do with the wiring harness for the head unit. The extra cost for that is what, maybe $10 for a foot length of wire, a hole, and a bolt? Do you have any idea how important grounding is for car stereo amplifiers? Do you have any idea how annoying the sounds are if it is not properly grounded?

Or should I just keep on going listening to a sub-standard stereo system because you are afraid your car might cost more for something that shouldn't have been a problem in the first place?

This is my second thread that you've brought an ignorant attitude to, just piss off.

[Mad Dragon]

You've only made two threads... :wink: