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Radio speaker high frequency noise


stefank

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Hi everybody,

this topic has been discussed before but I've seen no solution to the problem.

Car: '96 Seville SLS, Bose gold stereo system, all stock.

Situation: As soon as the car starts moving, a high frequency noise is emitted by the radio speakers, regardless whether the radio is on or off. This noise varies when braking hard or going over a bump. Above (say) 35 mph you don't hear it anymore due to road noise.

I suspected the RSS to be the reason for that noise and pulled the respective fuse: noise gone.

So I removed the rear electronics board in the front of the trunk, located the RSS-module and wrapped it in aluminium foil which I grounded with a separate wire. I did the same to wiring loom up to the point where it enters the main loom.

This didn't change the situation at all.

Any ideas to get rid of that annoying noise?

Thanks

Stefan

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Ima really lousy electritian, so I cannot offer much help. The answer is probally no, but have you installed any aftermarket electronics in the car? (I don't remember where it was, but I read something about some Sevilles haveing wiring problems in the raido.)

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I have a 96 DEVILLE and it also drives me crazy! :angry: I have this on AM radio especially in the lower end channels (can't listen to RUSH or Hannity on 660), as soon as the speed hits 6 MPH. I also feel its related to the suspension. I received a suspension code during the summer and the static when away. John Sundeen used to frequent this site. I believe he works for GM in the electronics area, and he specializes in EMF interferance (I believe). Here is a dialog that we had when my car still belonged to my friend and I was attempting to help him with the noise, Mike

PS: the BOLD and LARGE font was affected by me for emphasis

This is a reply to your message (attached below).

The caddyinfo.com post that you referenced below was just the first of many private e-mail exchanges that I had with the other gentleman who requested assistance with the AM radio interference problem. He found that removing the 'RSS' fuse had no effect, nor did many other ideas that I asked him to try out. There were two other possible causes that I had advised him to check out, but before he had an opportunity to do so he decided to trade in his '97 Deville on a new '03 Deville. So, I do not have a definitive solution for the problem, but I can advise you of the remaining possibilities that were never explored before.

I reviewed my archived e-mail messages on this subject, and I have copied the following from one of my last exchanges with the other Deville owner:

Try disabling the exhaust gas recirculation (EGR) valve. Before starting the engine, locate and disconnect the valve's electrical wiring connector. Then start the engine and drive the vehicle to evaluate the radio. The 'SERVICE ENGINE SOON' telltale will be illuminated, and the engine may or may not operate very smoothly. Once you have completed the evaluation, shut down the engine and reconnect the the valve's wiring connector. Then use the onboard diagnostics to clear the PCM codes that will have become set by taking this action with the EGR.

If the AM interference source still has not been isolated, then the next step to try is to disable the transmissions's electrical actuator circuits by disconnecting the wiring connector into the transmission. This is a light gray plastic connector located on the left front face of the transmission; the connector is circular and will have square "serrated" squeeze tabs on opposite sides; you sqeeze the tabs together while pulling on the connector to disconnect it. You may have some difficulty locating this connector. When examining my father's '97 Deville, I could not see the connector when looking doen from above; you may need to first remove the black plastic trim panel that spans the top of the condenser/radiator area. (Do not confuse the trasmission connector with a very similar one located directly above the transmission; the second connector looks the same, but does not "plug in" into the transmission.) With the connector disconnected, the transmission will default to second gear; the vehicle will be drivable, but you should exercise caution while doing so and spend as little time as necessary to perform the at-speed radio evaluation. As you can probably imagine, this action will also cause many codes to be set, and there will likely be warning messages on the DIC. Once again, clear the codes after restoring the original conditions.

Try out these ideas and let me know what you find.

The bad news is that even if you do manage to isolate the interference source using these techniques, actually fixing the problem may not be practically feasible!

Good luck!

John Sundeen

'01 & '03 STS

John, in February of this year you wrote the following post, it does not look like it went any further unless it took place via email. Interestingly I have the exact same problem. If I sit at a red light the AM radio while not perfect is listenable. Once I pull away from the curb I get a static and hiss. Its a 96 Deville with the non-Bose radio. Here was the post, I will pull the RSS fuse when I get a chance and let you know what happens. This car has been back to the dealer, as I know the prior owner very well and he complained about it numerous times, I would love to fix it, AM is impossible to listen to. Thanks, Mike

***************************************************************

The type of problem that you are experiencing falls into the category of electromagentic compatibility (EMC), which is the field in which I work for GM. (In fact, I work in the GM EMC laboratory where ALL GM vehicles undergo EMC tests.) However, as I have stated in my past postings on this board, I do not now, nor have I ever, worked directly on Cadillac models. So, when I first read about your problem, I simply lacked the Cadillac EMC test experience to speculate on the source of the radiated emissions (RE) problem you are apparently experiencing.

Fortunately, one of my EMC colleagues is the original EMC engineer for ALL Cadillac models (going all the way back to the "early days" of EMC testing at GM, in the '70s -- long before my time!). In fact, he is a former colleague of this board's "resident" GM Powertrain expert from the days of the old Cadillac Motor Car division of GM. He is the most experienced EMC engineer in GM, and he is most familiar with the mid-'90s Cadillac models like yours. I asked him to read your post and we discussed what the problem's source may be.

The only likely source that matches your symptoms is the road sensing suspension (RSS) system. This may be especially true if your car is equipped with the "Active Audio" (not Bose) premium audio system. As a test of our hypothesis, use your owner's manual to locate and remove the fuse that supplies power to the RSS control module. (Look carefully at the fuse descriptions in the manual; terminology different than "road sensing suspension" may be used.) Once the fuse is removed, try driving your car again and see if the radio interference problem is still present, or if it has changed in some way. Report the results to me, and we will proceed from there. . .

John Sundeen

'01 STS

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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....

Situation: As soon as the car starts moving, a high frequency noise is emitted by the radio speakers, regardless whether the radio is on or off. This noise varies when braking hard or going over a bump. Above (say) 35 mph you don't hear it anymore due to road noise.

I suspected the RSS to be the reason for that noise and pulled the respective fuse: noise gone....

Thanks

Stefan

Several questions for you Stefan:

Is the noise present with the engine running and vehicle stopped?

Does the frequency of the noise vary with vehicle speed?

Does the frequency of the noise vary with vertical wheel movement?

In addition to the vehicle position sensor input, the RSS module is getting input data from several other sources including a (square wave) signal from the PCM the contains vehicle speed information.

The likehood that one or more of these various signal wires is inducing audio into the speakers is low, but possible. A loose or dirty connector somewhere in all that wiring could magnify the likehood.

You might be in for an extensive visual check of connection points.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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Friends,

thanks a lot for your replies. I believe that the situation is connected to the RSS system. To your questions:

- No noise with engine running and car stationary. Noise starts as soon as the car starts moving.

- Going over a bump varies the frequency of the noise. So vertical wheel movement seems to have an influence

- I can not say much about vehicle speed influence, because over about 35 mph I don't hear the noise any more.

- The noise is present with radio on or off.

- If I switch on the radio, the music is more prominent than the noise, so you hardly hear it.

- The noise does not change with engine speed.

- The radio system is fully stock, as is the whole car, except for parking sensors in the rear bumper. But they are only active with reverse gear engaged.

I have not tried AM stations as Scotty states in his reply, because over here there aren't many. Maybe I should try that to see whether this is also affected.

Thanks all for your help!!

Stefan

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A bit more information, when I am close to the AM station like when I am in New York City, the static is not as bad, once I drive 50 miles away from NYC the static is unbearable. I do plan to check my antenna grounds and connections, but i think John Sundeen has it nailed. Your problem sounds very similar to mine, if the car stands still, the radio is fine, over 6 mph, static... Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Stefan:

Locate the position sensors that will be near the suspension at each corner. The sensor will be attached to the subchassis and there will be a round link that connects to the suspension.

Try disconnecting them electrically one at a time and do a short test drive.

If you have to disconnect all four to get the noise stopped, that would be one kind of problem.

But if you can stop the noise with only one of the sensors disconnected, you have eliminated 99% of the car.

This will set lots of RSS codes but you can clear them.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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Dear Friends,

thanks a lot for your information. I will check as soon as possible. I have not much time available right now, having to visit customers before the holidays etc.

I hope to find some time towards the end of the week, and let you know the outcome of my tests.

Many thanks again

Stefan

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Hi All,

today I tried tuning the radio to a weak AM - station, as soon as the car starts moving the static starts very loud. Same as Scotty described.

Now with the noise well audible, I drove the car as fast as possible (135 mph, legal here) but the noise would not change. When I go over bumps and the car lifts, the noise goes away for a moment, and returns. Same applies when I push the brakes hard.

I have the impression that noise means "signal to the dampers" which implies soft dampening and no noise means "no signal to the dampers" which would be hard dampening. If this is the case, I wonder why the noise had been present at all speeds. I thought the suspension would go to "firm" above a certain speed. I read the appropriate sections in the workshop manual but couldn't find the speed the suspension switches to "firm".

Does anyone know?

Interesting stuff in the workshop manual about reading the in/output signals via the onboard diagnostics. Clever design. Will try to obtain some data tomorrow and compare it with the values given. Maybe I see some irregularities which help me determine what's going on....

Thanks for reading

Stefan

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It's me again...

I played around with the RSS diagnostics today. Really clever design.

I went to "RSS outputs" and let each single strut cycle. As soon as the value went to "high" (soft setting) the noise was present in the loudspeakers. This was true for each single damper!

When I cycled the complete system, the noise was also there with value "high".

Then I disabled the system by pulling both fuses in the trunk. Drove the car and got the "service ride control", of course. No noise, no static on AM radio, as expected.

Well, so we narrowed down the cause of the speaker noise being the pulse-width modulated signal to the struts.

But what now? How to get rid of it? Ideas anyone, pleeeeeease!

Best

Stefan

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Hi Stefank,

John is correct on his points. I work for a company that does EMC testing for automotive and other products. I'm not an EMC expert, but know enough electronics that may provide some relief if you're willing to experiment a bit without being too scientific:

Let's assume that the noise you are experiencing is conducted emission(CE) , which is generated by components (e.g. the RSS system) and travels along the wires in the car to other locations (e.g. - the radio).

Note - If you are experiencing radiated emissions, (RE) which travel through the air as RADIO waves, this is almost impossible to eliminate on a system without extensive analysis, cable shielding and use of various EMC-reducing components.

Go to a local electronics store and buy a couple of 1000 microfarad (uF) capacitors. Make sure they have a voltage rating of at least 50 volts. Connect the "+" lead of one capacitor to the +12 volt lead closest to the radio. The fuse block would be OK. Connect the "-" capacitor lead to a metal point on the car and make sure it has a good connection to the negative side of the 12 volt system.

Note- The best point would be to connect the capacitor to the +12 V at the RSS controller if possible- but not on the RSS sensors!!

Run the car and compare the noise level. If the noise is reduced, add the second capacitor and see if it helps. Note that adding more capacitors does not mean the noise will continue to get lower. In some cases, more capacitance can increase the noise.

Other methods - Buy a "choke" inductor and place it in line with the +12 lead to the radio. MAKE SURE the choke has the same rating as the fuse for the radio. Otherwise, the radio output will "dim" at higher volumes. The choke, in combination with capacitors, will usually kill high frequency noises.

Alternately, you may be able to buy an entire "filter" that contains both capacitors and a choke. Make sure the filter matches the radio fuse value as mentioned above.

For posterity (and respect to EMC guru's out there), eliminating noise from a system usually requires measurements with a spectrum analyzer to determine the specific frequency at which the noise is occuring. From this, the appropriate capacitor and / or choke values can be determined to reduce the noise signal. This is much more precise, but since most of us usually don't have access to a $150K analyzer system, a plug & try method is more common.

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jhall,

thanks very much for your detailed reply!

As I live in Germany, I have no possibility to go to radio shack, but I might find something equivalent over here.

What puzzles me is that the noise is also present with the radio off. That may have to do with the separate amplifiers of the bose system.

I will try to obtain the parts during the next days and then perform the tests you describe, and let you know the outcome.

Thanks a lot again,

Stefan

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I feel your pain...got the "high squeal" last week between Chicago and Atlanta -it's in the passenger front door speaker (BOSE) - replaced the old CD player 4 years ago with a Kenwood 8015 AM/FM/CD player - cool - disappears when car is off, reappears when car is on...anyway - stopped by the car stereo shop yesterday...answer is tomorrow - both front door speakers will be replaced by new, not BOSE, speakers (I don't remember the brand..starts with an M) - front speakers direct to the Kenwood, rear speakers still BOSE, still thru conversion box in trunk which controls BOSE speakers as BOSE have their own amps in each speaker...cost $ 150 and I'm rocking and rolling again...

John B - '93 STS 206,000 miles using Mobil 1 !

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Hi John,

seems that your problem is related to the stereo system itself, then your approach is right for sure. I think on my car the reason for the noise is the RSS system.

I guess you're right, I could rip out the complete Bose system and replace it with a generic stereo which may not be so sensitve to radiation, but then I'd loose the steering controls, and beside that, I love to keep my car as stock as possible. Also the radio blends into the dashboard so niceley...

Thanks for your input

Stefan

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Stefan, I found out from the guys on this site that you can purchase a radio and retain your steering wheel controls (which I like also), Mike

http://caddyinfo.ipbhost.com/index.php?showtopic=4417

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Stefan:

On my cars, the warning chime for DOOR OPEN (and others) is produced in the sound system which means at least one audio amplifier is powered on with the ignition regardless of radio being "on" or "off". Your model is probably a similar design.

If I had your noise problem, I would want to know if disconnecting the radio antenna produces a noticeable difference in the noise level. In order for you to "hear" the difference in noise level, you would have to change the level by approx. 3 dB. If disconnecting the antenna lead yields that much change, that would be useful information.

Season's Greetings over there......

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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Scotty;

I have looked into this and will keep it in mind, in case I'm replacing the sound system some time in the future. Thanks!

JimD;

on my car the audible warnings are also emitted by the driver's door speaker. So the Boses must be powered all the time.

I will check disconnecting the antenna feed tomorrow, then we'll see whether there is an influence.

Merry Christmas and a beautiful holiday season to all of you!

Many thanks,

Stefan

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Stefan, thanks! You have a Merry Christmas and a beautiful holiday season also! Let us know how this turns out! If I can help at all, let me know, Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Dear Friends,

I removed the radio from the dash today and unplugged the antenna.

The noise is gone !!!

When I reconnect the antenna the noise ist back as soon as the car starts moving.

I guess the antenna lead (going from the back to the front) is routed alongside the signal lines of the RSS system, thus picking up the noise.

The antenna lead is tied into the main wiring looms, so I will leave that alone and install a new lead separateley, maybe along the center of the car.

What do you think?

I will have to find an antenna lead with these GM-specific plugs on both ends, perhaps I have to order it from the GM dealer. Will look up the parts microfiche later today....

Best

Stefan

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Dear Friends,

I removed the radio from the dash today and unplugged the antenna.

The noise is gone !!!

When I reconnect the antenna the noise ist back as soon as the car starts moving.

I guess the antenna lead (going from the back to the front) is routed alongside the signal lines of the RSS system, thus picking up the noise.

The antenna lead is tied into the main wiring looms, so I will leave that alone and install a new lead separateley, maybe along the center of the car.

What do you think?

I will have to find an antenna lead with these GM-specific plugs on both ends, perhaps I have to order it from the GM dealer. Will look up the parts microfiche later today....

Best

Stefan

Do install a second piece of coaxial cable. I would try one on a temporary basis before working on where and how to hide a new cable.

Perhaps the original cable is nicked or cut somewhere along the path, or one of the end connectors is damaged?

Well done, Stefan!!!

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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John that is a different problem you are having. That is a problem with your BOSE amp. Yoiu can send it away and have it rebuilt, the capacitors leak and age from heat and it whines till it just stops totally.

I had the same problem in my 91 Seville. If you find out that your 93 takes the same amp as my 91, I have a drivers side door complete with BOSE amp for my 91 and you are welcome to it, just pay shipping. Here is a schematic of the BOSE amp, maybe you want to do some diagnostics.

PS: I converted this to a GIF to get under the allowable posting size, if you want it in JPG better quality, send me an email address, Mike

post-3-1104425684.gif

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Dear Friends,

I removed the radio from the dash today and unplugged the antenna.

The noise is gone !!!

When I reconnect the antenna the noise ist back as soon as the car starts moving.

I guess the antenna lead (going from the back to the front) is routed alongside the signal lines of the RSS system, thus picking up the noise.

The antenna lead is tied into the main wiring looms, so I will leave that alone and install a new lead separateley, maybe along the center of the car.

What do you think?

I will have to find an antenna lead with these GM-specific plugs on both ends, perhaps I have to order it from the GM dealer. Will look up the parts microfiche later today....

Best

Stefan

Terrific Stefan! Good detective work.. Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Thanks,

it may take a while until I proceed, as this is not an fast-selling item. If it's not in stock in Europe, I'll have to wait.

I will let you know whether this solution works.

Best

Stefan

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