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Bose stereo systems - Interference & Noise


Tom B

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I have a 2002 Eldorado with a Bose stereo. It uses power amplifiers mounted on or near the speakers. There is a separate amp on each of the rear speakers mounted on each speaker magnet. The power amps are powered on even when the stereo is turned "off" by the driver.

I use 2 way radios in the vehicle. There are reports of the same condition I'm describing here when cell phones are used in or near a Bose equipped vehicle.

When a radio signal is transmitted, there is often a buzzing noise from the Bose speakers. Sometimes it is a very loud buzzing noise. Since the stereo power amps are powered even when the radio is "turned off" the buzzing noise appears then, as well as at times when the stereo is shown to be "on." This happens with both a CB and amateur radio (2 meters and 440 MHz.).

The buzz is heard whether the transmitter is powered by the vehicle (13.8 VDC), or whether a battery powered hand held portable transmitter (a "talkie") is used by a passenger in the back seat. That tends to indicate the Bose amplifiers are responding with a buzz from over the air, and not receiving it through the car's electrical system. We did try torroids and chokes to try to shield the wiring running to and from the amps, but there was no change.

A hand held transmitter uses only about 2 watts, and at most, 5 watts. A CB uses 4 watts. An amateur radio transmitter that is powered by the vehicle transmits with 5 to 50 watts. (This is NOT high power.)

I tried to get GM to "repair" this while the car was new in warranty. The dealer tried but could not get any support from the GM office. The woman managing the local GM office ignored me. (I wonder where she is today.)

Looking into this further we notice the enclosures of the power amps on the rear speakers do not appear to have adequate shielding. They have a fairly open enclosure, where air circulates to the circuit board. A lot

of other after market amps are totally enclosed.

I had a previous Cadillac with a regular factory stereo, without the name "Bose" and without extra audio amps mounted near the speakers. It did not have these noise problems when the same 2-way radios were used. (The radio/CD player/tape player sounded good, too.)

I'm looking for others with experience with this problem, either with cell phones or 2-way radios, and for any ideas.

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I have Amateur equipment installed in my Bose equiped '98 Seville; however, the amplifiers are located in an integrated box for a all speaker channels and does not have the RFI problem you are describing.

I would try several approaches. Probabaly the easiest is to triple check the physical mounting of the antenna bracket; a clean tight mechanical connection to the chassis is a must. Also check the feed line between the xmitter and the antenna; clean tight connections and decent quality coax are a must. Depending on how your equipment is mounted in the car, you might need to add a unique ground connection jumper (bonding) between the xmitter chassis and the car chassis.

Mag-mount antennas are not recommended.

You might consider using a relay to power On/power Off the Bose amplifiers. You would need the vehicle wiring diagrams (Service Manual) and it "might" require more than one relay.

Rather than using chokes, I would suggest a very low value of mica capacitor across the speaker + and - terminals to shunt RF to ground. Bose speakers are very low impedance. This might be the cleanest but most labor intensive approach.

Good luck and keep us in the loop.

--... ...--

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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The Bose amplifiers are mounted on the rear speaker magnets. Their enclosures have holes, apparently for ventilation, unlike many other audio amps on the after market, that are shielded.

Here are photos - - Note the sticker that says it's a 100 watt amp, and "Made in Mexico"

Click here:

http://www.n5gar.com/BoseAmp1.jpg

http://www.n5gar.com/BoseAmp2.jpg

http://www.n5gar.com/BoseAmp3-Mexico.jpg

Car buyers interested in adding 2-way equipment, including CBs or cell phones, should test these cars for interference and noise before making their purchases. This can be done with a portable, hand held radio by someone seated in the back seat. If the stereo buzzes or pops or has other noises when the transmitter is on, it indicates a poorly designed vehicle. Buyers should also look for statements in the fine print of owners' manuals about 2-way radio equipment. Some vehicles experience other problems with computers, etc. when a radio is operated.

Police cars are manufactured every day for use with 2-way radios. They do not have these problems.

I paid a lot for this but Cadillac would not resolve the problem. They left me 'stuck.' Now I'm considering several ways of dealing with it, including additional shielding of the amplifier housing, maybe with metal screen material.

In my case the 2-way radio is NOT high power.

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QUOTE (Tom B @ Jul 25 2009, 08:50 PM)
The Bose amplifiers are mounted on the rear speaker magnets. Their enclosures have holes, apparently for ventilation, unlike many other audio amps on the after market, that are shielded.

Here are photos - - Note the sticker that says it's a 100 watt amp, and "Made in Mexico"

Click here:

http://www.n5gar.com/BoseAmp1.jpg

http://www.n5gar.com/BoseAmp2.jpg

http://www.n5gar.com/BoseAmp3-Mexico.jpg

Car buyers interested in adding 2-way equipment, including CBs or cell phones, should test these cars for interference and noise before making their purchases. This can be done with a portable, hand held radio by someone seated in the back seat. If the stereo buzzes or pops or has other noises when the transmitter is on, it indicates a poorly designed vehicle. Buyers should also look for statements in the fine print of owners' manuals about 2-way radio equipment. Some vehicles experience other problems with computers, etc. when a radio is operated.

Police cars are manufactured every day for use with 2-way radios. They do not have these problems.

I paid a lot for this but Cadillac would not resolve the problem. They left me 'stuck.' Now I'm considering several ways of dealing with it, including additional shielding of the amplifier housing, maybe with metal screen material.

In my case the 2-way radio is NOT high power.

I use a CB in my cars on long trips with a magnetic mount antenna - I have no issues with interference on any of my cars. It sounds like you have a lazy dealer - find another dealer.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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It's not clear to me if you are looking for a forum to bad-mouth Cadillac or if you are open to effective "fixes". And I would not expect to find a dealer technician with RFI experience.

You can count on the fact that GM does test their vehicles for "external" RFI. You could drive your car within 500 feet of the antenna farm of a clear channel AM b'cast station with no ill affects on any of the vehicle systems.

Consider the possibility the source of the RFI is your equipment installation.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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I agree with JimD...check and possibly add, better grounds from your radios and antennas to ground.

Make sure you have GOOD coax and GOOD quality connectors at each end of the coax.

My current Cadillac has the BOSE system.

I use my cell phone a lot. :D:D

Typical monthly usage is 4000 to 5000 minutes a month.

I have NEVER had an issue in any Cadillac I have ever owned.

My Brother in Law is a Amateur Radio operator.

He has used his radio in the front AND back seat of my Cadillac A LOT of times with no issues what-so-ever.

I have had other Cadillacs, in which I had some pretty high power radio equipment installed.

The one I had just before this one, had a CD that had been clipped and put out 8.5 watts.

That 8.5 watts drove an old tube type Palomar 300 linear amplifier, which, after it got warmed up good...would put out about 800 watts.

Power was transmitted thru a Shakespeare antenna (tuned for low SWR, naturally) bolted to the front of the trunk lid, with an extra ground wire from the antenna to the frame.

No issues with it at all, except that it would bleed all over any other CB radio that was within a block or two of it. :D:D

DISCLAIMER...as soon as I found out that this was slightly illegal, I disposed of all the radio equipment and amplifiers including the 2000 watt base station and the 82 foot tall tower and set of beams.

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My transmiter is well within specs. It's also very low power, compared to what amateurs are licensed by the FCC to use.

This is why I bring up testing with a hand held, battery powered walkie talkie. Hand held radios like this are self contained and intended to be used without a separate ground. They are like hand held cell phones. My experience is that when one is transmitting with 2 watts or less by a passenger in the back seat on a 2 meter (VHF) frequency, the Bose stereo has interference. I've heard about simlar problems with cell phones operated by passengers in the back seat.

When a radio with more power is used, the interference with the stereo is much louder, even though the signal transmitted is within all the legal specs.

I'm interested in finding someone with the same experience who resolved it. The best advice I have so far is that since the Bose package appears to be unshielded, to re-engineer the package with shielding, similar to that found on a lot of aftermarket amplifiers.

Even if the local dealer does not have a technician with RFI experience, the problem should be moved through channels at GM and Bose to get an answer that will work. I tried my best to get it resolved that way.

It's not clear to me if you are looking for a forum to bad-mouth Cadillac or if you are open to effective "fixes". And I would not expect to find a dealer technician with RFI experience.

You can count on the fact that GM does test their vehicles for "external" RFI. You could drive your car within 500 feet of the antenna farm of a clear channel AM b'cast station with no ill affects on any of the vehicle systems.

Consider the possibility the source of the RFI is your equipment installation.

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