Speaker Diagnosis
Tools Required
J 39916-A Audio System Diagnostic Kit
Important: Always compare the front speakers to the front. Always compare the rear speakers to the rear. Do not compare front speaker to rear speaker because they could be different speakers or their mounting environment could cause them to sound different.
Tones are used to test and to evaluate coaxial speakers or other complex speaker systems. The following are the three basic tones used:
| • | 50 Hz sine tone is used. |
| • | 500 Hz warble tone is used. |
| • | 9 kHz spectral tone is used. |
A combination tone is a blend of the above three tones.
Bass/Sub-woofer Test (50 Hz sine tone)
Use the 50 Hz sine tone to evaluate the bass response of an audio system. This tone is also helpful in evaluating audio systems which have separate subwoofer amplifiers and woofers.
Midrange Speaker Test (500 Hz warble tone)
Use the 500 Hz warble tone to evaluate midrange speaker response. This tone is qualified as a warble tone because it has different audio characteristics than a sine tone. This tone produces a warble sound. At these tone midrange frequencies it is better to use a warble tone than a since wave because the location of a warble tone source, such as a speaker, is easier to identify. A normal sine tone can set up a standing wave within a vehicle which can make it difficult to determine its source location.
Tweeter Test (9 kHz spectral tone)
Use the 9 Hz spectral tone for tweeter or high frequency evaluation. This tone is a section of frequencies of equal amplitudes ranging from 8.5 kHz to 9.5 kHz. This sounds like a group of crickets chirping. This type of tone is used for the following two reasons:
| • | Much like the warble tone, it is easy to locate its source. |
| • | This type of tone is easier to identify for those people with high end hearing loss problems. |
All Speaker Test
Use the combination tone for numerous audio problems such as distorted or no sound from speaker(s). Comparative AC voltage measurements can be made on the speaker terminals provided the fade and balance controls are in the detent position when using the combination tone. A determination can be made in the diagnosis of speaker or amplifier with these voltage measurements.
Speaker/Grill Rattle Test (50 Hz to 8 kHz swept sine)
Use the next portion of the tape to diagnose speaker and grill rattles. The first test is two tones played back to back. The second test is a variable frequency tone (the frequency change is at a much slower rate). Both tests can be used to repair a speaker rattle or buzz. If the problem is already isolated the fade and balance controls can be set to the proper location and the test tones can by played in the specific problem area.
