Audio System - Test CD/Tape
GROUP 65Sound Systems, Cruise, Alarms
Engineering
65 04 99
Woodcliff Lake, NJ
August 2000
Service
SUBJECT:
Audio System Test CD/Tape
MODEL:
All
SITUATION:
Troubleshooting sound problems ("distortion", "rattle", "noises") from the area of the loudspeakers, in all operating modes of vehicle's audio system.
CAUSE:
Based on an extensive analysis, in a majority of the cases, speakers of the audio systems were improperly diagnosed as defective, and should have not been replaced.
Audio system sound distortion can be caused by:
-- loose elements of speaker surroundings (e.g.: securing components, clips, trim panels, etc.)
-- loudspeakers not properly secured, or fixtures over-tightened loose speaker grill
-- loudspeaker seal (between speaker and the trim) in contact with the speaker's membrane, or seal permanently attached (cemented) to the membrane.
-- control units installed in the vicinity of the loudspeaker being loose, or generating noises agitated by a specific frequency of the speaker (e.g. as a result of a loose printed circuit board inside the module).
CORRECTION:
A new Audio System Test CD/Tape was developed to help you properly diagnose sound system reproduction problems in BMW vehicles equipped with radio/cassette or CD changer, and to avoid unnecessary replacements.
Every BMW center will receive two copies of the Audio System Test CD/Tape through the Automatic Tool Shipment Program. Additional copies may be purchased from the BMW Parts Distribution Centers.
The following type of sound systems complaints can be diagnosed by using the Test CD/Tape:
-- Sound quality complaints related to distortion in speakers (treble, mid-range, bass and subwoofer)
-- Refer to Section 1
-- Sound quality complaints related to resonance within the vehicle (trim panels, loose wires/fixtures)
-- Refer to Section 2
-- Sound quality complaints related to the lack of continuity ("breaks") in CD/tape reproduction.
-- Refer to Section 3
-- Sound quality complaints related to amplifier/radio malfunctions (only for vehicles with CD changer)
-- Refer to Section 4.
PROCEDURE:
Before diagnosing the sound system with the Audio Test CD/Tape, make sure that:
1. Battery is fully charged (if necessary use a battery charger during the test).
2. "Treble" and "Bass" controls are set to their respective middle positions.
3. On vehicles equipped with a spatial sound switch (Harman-Kardon) or DSP amplifier, both functions are turned OFF.
4. The volume level has to be adjusted before the test. To adjust the volume:
play the music track number 17 (on cassette tape Side B track number 5) and increase the volume to the upper limit of the output stage before reducing it slightly.
NOTE:
If necessary, wear ear protection devices.
Section 1: Diagnosing sound distortion from the individual speakers
To individually test each speaker of the sound system, from the Test CD/Tape select a suitable track:
-- To test a subwoofer; CD (or cassette) track 09 - 63 Hz
-- To test a woofer; CD (or cassette) track 10 - 125 Hz
-- To test a mid-range speaker; CD track 11 (or cassette tape Side B track 1) - 2500 Hz
-- To test a tweeter speaker; CD track 12 (or cassette tape Side B track 2) - 12500Hz
When using those tracks, keep the preset volume level, and use the "Balance" and "Fader" controls to shift the sound output from "Front left", through "Front right" and "Rear left" to "Rear right" speaker.
To test the spatial stereo effect (on vehicles equipped with Harman-Kardon system), select a suitable track:
-- To determine the stereo center point - CD track 15 (cassette tape Side B track 4)
-- To check spatial stereo distribution - CD track 16 (cassette tape Side B track 5)
For those tests, retain the preset volume level, and adjust the "balance" and "fader" controls to their respective middle positions.
Section 2: Diagnosing sound reproduction problems related to resonance
within vehicle
In sequence, select tracks from 01 to 08 from the Test CD/Tape. Vehicle resonance tracks (01 to 08) generate sinusoidal oscillations in the following frequency ranges:
-- Track 01 - 8 to 80OHz
-- Track 02 - 32 to 63Hz
-- Track 03 - 63 to 125Hz
-- Track 04 - 125 to 250Hz
-- Track 05 - 250 to 500 Hz
-- Track 06 - 500 to 1 kHz
-- Track 07 - 1 to 4 KHZ
-- Track 08 - 4 to 16 kHz
For those tests keep the preset volume level, and use the "Balance" and "Fader" controls to shift the sound output from "Front left", through "Front right" and "Rear left" to "Rear right" speaker.
Section 3: Diagnosing sound quality problems related to lack of continuity ("breaks") in CD/Tape reproduction
Select CD track 13 (cassette tape Side B, track 3), which generates a sinusoidal wave with frequency of 1200 Hz. This track allows you to detect any reproduction breaks caused by the CD/Tape head. For this test, retain the preset volume level, and adjust the "balance" and "fader" controls to their respective middle positions.
Section 4: Diagnosing sound reproduction problems related to amplifier/radio malfunctions
This test is available only on the Audio Test CD.
Select CD track 14, which reproduces a digital "zero" (no sound, silence). This test allows you to detect sound reproduction faults caused by the amplifier or radio (also with engine running). For this test, retain the preset volume level, and adjust the "balance" and "fader" controls to their respective middle positions.
PARTS INFORMATION
Part Number Description Quantity
99 00 001 773 Audio Test 2
CD
99 00 001 774 Audio Test 2
Tape
Every BMW center will receive two copies of the Audio System Test CD/Tape through Automatic Tool Shipment Program.
WARRANTY INFORMATION
For information only