TiK Master Sub - JBL Audio Service Manual (repair manual). Page 2

To enable long impulses to be measured, auto-EQ uses a lower sample rate than the normal 
audio sample rate. This is not a limiting factor for room equalisation, which rarely extends beyond 
500Hz. 
 

Auto-EQ sample rate: 

 

 

6kHz 

MLS sequence length:   

 

4095 

Number of averaged sequences: 

8 

Maximum impulse response length: 

682ms 

FFT 

length: 

   4096 

FFT window type: 

 

 

Raised cosine bell 

Log-frequency domain resolution: 

1/50

th

 Octave 

Number of EQ filters: 

 

 

12 

Level matching is carried out prior to the first AEQ measurement. It is essential that the average 
level of the sub is accurately matched to the level of the main system so that the combined LF 
response curve lies within the limits set by the maximum allowed eq cut and boost . The process 
is carried out in 4 steps: - 
 

1.  The DSP is loaded with a patch to realize the system in Fig.1. The main system gain 

is ramped to a fixed level. The level from the Microphone meter is used to adjust the 
output gain so as to achieve a reference level at the Mic (-12dBFS). This gain ( 
MainGainRef )is saved for later calculations, as is the difference between the final 
meter reading and the desired target level(MainRefDiff). An FFT of the main system is 

then taken. The average FFT level across a range of frequencies, not affected by 
room response, is measured (MainZeroLine ). 

Main Amplifier

preAmp

LineIn

SubOut

Sub Amplifier

MainAmp

PRBS

CalGain

Cal Out

Mic In

SubGain

SubAmp