TiK Master Sub - JBL Audio Service Manual (repair manual). Page 3

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2.  The Sub LP crossover is temporarily extended from 100Hz to 500Hz. The sub output 
gain is then ramped to a pre-determined level. The Output gain is then adjusted as 
before, to achieve a reference level at the Mic. This gain (SubGainRef) is stored, as is 
the difference between the final meter reading and the desired target 
level(SubRefDiff). An FFT is then carried out on the Sub and the average level is 
stored (SubZeroLine). 
 
3.  Pink noise is passed through 20Hz to 100Hz crossovers and into the main system 
amplifier. The Cal output gains are ramped to the level stored in Step 1. The 
difference between the level measured at the input (Fed from main amp “Sub Out”) 
and the output level is stored as MainSysGain and is a measure of the position of the 
Volume control on the users amplifier. The signal is band-limited to ensure that an 
amplifier with a band-limited sub output will read the same as an amplifier that does 
not band-limit it’s sub output.  
 
4.  When the above steps are complete, enough data has been obtained to set the final 
output gain for the sub so that when both systems are excited from the main 
amplifier, (fig. 3) the mean sub level is at the same amplitude as the reference level in 
the main response.  
 
 
 
 
 
 
 
 
 
Main Amplifier
preAmp
LineIn
SubOut
Sub Amplifier
MainAmp
PRBS
CalGain
Cal Out
Mic In
AEQ Measuring Configuration
SubGain
SubAmp
Figure 2 
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