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GOLDBERG AND MÄKIVIRTA

AUTOMATED IN-SITU EQUALISATION

AES 23RD CONFERENCE, May 23-25, 2003

20

Midrange RMS Deviation

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Figure 10b. RMS deviation for small 2-way systems.

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Summary of Contents for Frequency Response Optimisatio

Page 1: ...ce of calibrating active loud speakers Even with experienced system calibrators significant variance between calibrations can be seen Furthermore with a number of different people cali brating loudspeaker systems additional variance in results will occur For these reasons an automated calibration method was developed to ensure consis tency of calibrations Presented first in this paper is the discr...

Page 2: ...al to significantly improve perceived sound quality The practical challenge is the selection of the best settings for the low order in situ equaliser Despite advances in psychoacoustics it is difficult to quantify what the listener actually perceives the sound quality to be or to optimise equalisation based on that evaluation 13 15 Because of this in situ equalisa tion typically attempts to obtain...

Page 3: ...re determined by the crossover filters The bass tilt control compensates for a bass boost seen when the loudspeaker is loaded by large nearby boundaries 33 36 This typically happens when a loudspeaker is placed next to or mounted into an acoustically hard wall This filter is a first order shelv ing filter The bass roll off control compensates for a bass boost often seen at the very lowest frequenc...

Page 4: ...her than using a least squares type objective function is that the bass roll off tends to assume maximum attenuation to minimise the RMS deviation This type of objective function does not yield the best setting as subjectively a loss of bass extension is perceived This stage of the optimiser algorithm takes six filtering steps three for small two way models 3 2 2 Midrange Level to Treble Level Rat...

Page 5: ...tics of experienced calibration engineers The resulting num ber of filtering steps has been dramatically reduced for the larger systems Table 9 and even the relatively simple two way systems show a substantial improve ment when compared to the number of filtering steps needed by direct search method as summarised in Table 5 There are two main reasons for the improve ment the constraint of not allo...

Page 6: ... there is also a 3 dB roll off with 50 Hz being down by 1 dB and 40 Hz by 2 dB Tolerance lines are set to 3 dB with additional leeway at low and high fre quencies 1 An example of the room equaliser settings output for the large system optimised in Figure 1 is shown in Figure 2 The optimised result is displayed in green and dark grey boxes The green boxes are room re sponse controls that should be ...

Page 7: ...d tonal bal ance improvement This is indicated by a reduction of the median value differences 4 2 Example of Statistical Data Analysis Figure 7 in Appendix C shows a case example where room response control settings are calculated accord ing to the optimisation algorithm The equalisation target is a flat magnitude response straight line at 0 dB level The in situ frequency response of the loudspeak...

Page 8: ...subbands show no changes or a slight increase of the RMS deviation Three way systems show a clear reduction in most cases of both the quartile difference Figure 13 and RMS deviation Figure 14 for the broadband and LF subband Slight and equal numbers of increases and reductions are seen for MF and HF subbands A similar trend is seen for the three large systems in cluded in this study Figure 15 16 M...

Page 9: ...n the median level for the LF subband A similar outcome is noted sepa rately for each loudspeaker type However only in the three way systems is an improvement seen also in the MF and HF subband variance 25 to 75 Percentile Difference Change due to Equalisation All models 3 2 1 0 1 Broadband LF MF HF Level dB RMS Deviation Change due to Equalisation All models 5 4 3 2 1 0 1 Broadband LF MF HF Level...

Page 10: ...d room response control settings The settings achieve im proved equalisation in the form of a smaller RMS de viation from the target response The improvement is not limited by the optimisation method but by the room response controls which are not intended to cor rect for narrow band deviations in the frequency re sponse Examples of these are response variations re sulting from acoustic issues suc...

Page 11: ...Thesis at the Helsinki University of Technol ogy 41 8 REFERENCES 1 Genelec Oy http www genelec com 2003 Feb 2 Walker R Equalisation of Room Acoustics and Adaptive Systems in the Equalisation of Small Rooms Acoustics Proc 15th Int Conf paper 15 005 1998 Oct 3 Cox T J and D Antonio P Determining Op timum Room Dimensions for Critical Listening Envi ronments A New Methodology presented in 110th Conv A...

Page 12: ...2001 Sep 29 Mäkivirta A Antsalo P Karjalainen M and Välimäki V Low Frequency Modal Equalisation of Loudspeaker Room Responses presented in 111th Conv Audio Eng Soc preprint 5480 2001 Sept 30 Karjalainen M Esquef P A A Antsalo P Mäkivirta A and Välimäki V Frequency Zooming ARMA Modelling of Resonant and Reverberant Sys tems J Audio Eng Soc vol 50 pp 1012 1029 2002 Dec 31 Moore B C J Glasberg B R Pl...

Page 13: ...User Inputs Model Database Stored Measurement Microphone Compensation CTRL M Measurement Dump Reset Graph and Outputs Get Model Number Apply Mic Compensation Remove DC Window FFT and Smooth Load Impulse Response Set DIPtimisation Range Display Original Freq Response Display Target Response Calculate Target Resp Stored Measurement CLOSE DIPtimiser 1 2 Figure 5 Software flow chart part 1 CLOSE Set F...

Page 14: ...5 2003 14 Is Large System Is Small System Load Filters Model Filters Preset BRO Find ML TL Ratio Set BL BT wrt ML TL Reset BRO Set TT Display Final Tone Control Settings Display Final Frequency Response Set BT Is 3 way System 1 2 Figure 5 continued Software flow chart part 2 Y N N Y ...

Page 15: ...GOLDBERG AND MÄKIVIRTA AUTOMATED IN SITU EQUALISATION AES 23RD CONFERENCE May 23 25 2003 15 APPENDIX B SOFTWARE GRAPHICAL USER INTERFACE Figure 6 Software graphical user interface at start up ...

Page 16: ... AND MÄKIVIRTA AUTOMATED IN SITU EQUALISATION AES 23RD CONFERENCE May 23 25 2003 16 APPENDIX C CASE EXAMPLE STATISTICAL GRAPHS Figure 7 Case example optimisation results Figure 8 Case example statistical output ...

Page 17: ...5 4 0 3 5 3 0 2 5 2 0 1 5 1 0 0 5 0 0 0 5 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A Level dB Low Frequency 25 to 75 Percentile Difference Before Equalisation 0 2 4 6 8 10 12 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A Level dB Low Frequency 25 to 75 Percentile Difference After Equalisation 0 2 4 6 8 10 12 1029A 1029A 1029A 1029A 1029A 1029A...

Page 18: ...2 0 1 5 1 0 0 5 0 0 0 5 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A Level dB High Frequency 25 to 75 Percentile Difference Before Equalisation 0 2 4 6 8 10 12 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A Level dB High Frequency 25 to 75 Percentile Difference After Equalisation 0 2 4 6 8 10 12 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 102...

Page 19: ...to Equalisation 7 6 5 4 3 2 1 0 1 2 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A Level dB Low Frequency RMS Deviation Before Equalisation 0 2 4 6 8 10 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A Level dB Low Frequency RMS Deviation After Equalisation 0 2 4 6 8 10 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A Level dB ...

Page 20: ...Equalisation 7 6 5 4 3 2 1 0 1 2 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A Level dB High Frequency RMS Deviation Before Equalisation 0 2 4 6 8 10 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A Level dB High Frequency RMS Deviation After Equalisation 0 2 4 6 8 10 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A 1029A Level dB H...

Page 21: ...ence Before Equalisation 0 2 4 6 8 10 12 1030A 1030A 1031A 1031A 1031A 1031A 1031A 1031A 1031A 1032A 1032A Level dB Low Frequency 25 to 75 Percentile Difference Change due to Equalisation 4 5 4 0 3 5 3 0 2 5 2 0 1 5 1 0 0 5 0 0 0 5 1030A 1030A 1031A 1031A 1031A 1031A 1031A 1031A 1031A 1032A 1032A Level dB Broadband 25 to 75 Percentile Difference After Equalisation 0 2 4 6 8 10 12 1030A 1030A 1031A...

Page 22: ... 3 0 2 5 2 0 1 5 1 0 0 5 0 0 0 5 1030A 1030A 1031A 1031A 1031A 1031A 1031A 1031A 1031A 1032A 1032A Level dB High Frequency 25 to 75 Percentile Difference Before Equalisation 0 2 4 6 8 10 12 1030A 1030A 1031A 1031A 1031A 1031A 1031A 1031A 1031A 1032A 1032A Level dB High Frequency 25 to 75 Percentile Difference After Equalisation 0 2 4 6 8 10 12 1030A 1030A 1031A 1031A 1031A 1031A 1031A 1031A 1031A ...

Page 23: ...ange due to Equalisation 7 6 5 4 3 2 1 0 1 2 1030A 1030A 1031A 1031A 1031A 1031A 1031A 1031A 1031A 1032A 1032A Level dB Low Frequency RMS Deviation Before Equalisation 0 2 4 6 8 10 1030A 1030A 1031A 1031A 1031A 1031A 1031A 1031A 1031A 1032A 1032A Level dB Low Frequency RMS Deviation After Equalisation 0 2 4 6 8 10 1030A 1030A 1031A 1031A 1031A 1031A 1031A 1031A 1031A 1032A 1032A Level dB Low Frequ...

Page 24: ...e due to Equalisation 7 6 5 4 3 2 1 0 1 2 1030A 1030A 1031A 1031A 1031A 1031A 1031A 1031A 1031A 1032A 1032A Level dB High Frequency RMS Deviation Before Equalisation 0 2 4 6 8 10 1030A 1030A 1031A 1031A 1031A 1031A 1031A 1031A 1031A 1032A 1032A Level dB High Frequency RMS Deviation After Equalisation 0 2 4 6 8 10 1030A 1030A 1031A 1031A 1031A 1031A 1031A 1031A 1031A 1032A 1032A Level dB High Frequ...

Page 25: ...tion 0 2 4 6 8 10 12 S30D S30D S30D S30D 1037B 1037B 1037B 1037B 1037B 1038A 1038A 1038A 1038A 1038A 1039A Level dB Low Frequency 25 to 75 Percentile Difference Change due to Equalisation 4 5 4 0 3 5 3 0 2 5 2 0 1 5 1 0 0 5 0 0 0 5 S30D S30D S30D S30D 1037B 1037B 1037B 1037B 1037B 1038A 1038A 1038A 1038A 1038A 1039A Level dB Broadband 25 to 75 Percentile Difference After Equalisation 0 2 4 6 8 10 ...

Page 26: ... 0 5 0 0 0 5 S30D S30D S30D S30D 1037B 1037B 1037B 1037B 1037B 1038A 1038A 1038A 1038A 1038A 1039A Level dB High Frequency 25 to 75 Percentile Difference Before Equalisation 0 2 4 6 8 10 12 S30D S30D S30D S30D 1037B 1037B 1037B 1037B 1037B 1038A 1038A 1038A 1038A 1038A 1039A Level dB High Frequency 25 to 75 Percentile Difference After Equalisation 0 2 4 6 8 10 12 S30D S30D S30D S30D 1037B 1037B 10...

Page 27: ...tion 7 6 5 4 3 2 1 0 1 2 S30D S30D S30D S30D 1037B 1037B 1037B 1037B 1037B 1038A 1038A 1038A 1038A 1038A 1039A Level dB Low Frequency RMS Deviation Before Equalisation 0 2 4 6 8 10 S30D S30D S30D S30D 1037B 1037B 1037B 1037B 1037B 1038A 1038A 1038A 1038A 1038A 1039A Level dB Low Frequency RMS Deviation After Equalisation 0 2 4 6 8 10 S30D S30D S30D S30D 1037B 1037B 1037B 1037B 1037B 1038A 1038A 10...

Page 28: ...n 7 6 5 4 3 2 1 0 1 2 S30D S30D S30D S30D 1037B 1037B 1037B 1037B 1037B 1038A 1038A 1038A 1038A 1038A 1039A Level dB High Frequency RMS Deviation Before Equalisation 0 2 4 6 8 10 S30D S30D S30D S30D 1037B 1037B 1037B 1037B 1037B 1038A 1038A 1038A 1038A 1038A 1039A Level dB High Frequency RMS Deviation After Equalisation 0 2 4 6 8 10 S30D S30D S30D S30D 1037B 1037B 1037B 1037B 1037B 1038A 1038A 103...

Page 29: ...evel dB Low Frequency 25 to 75 Percentile Difference Before Equalisation 0 2 4 6 8 10 12 1036A 1036A 1036A Level dB Low Frequency 25 to 75 Percentile Difference Change due to Equalisation 4 5 4 0 3 5 3 0 2 5 2 0 1 5 1 0 0 5 0 0 0 5 1036A 1036A 1036A Level dB Broadband 25 to 75 Percentile Difference After Equalisation 0 2 4 6 8 10 12 1036A 1036A 1036A Level dB Low Frequency 25 to 75 Percentile Diff...

Page 30: ...ifference Change due to Equalisation 4 5 4 0 3 5 3 0 2 5 2 0 1 5 1 0 0 5 0 0 0 5 1036A 1036A 1036A Level dB High Frequency 25 to 75 Percentile Difference Before Equalisation 0 2 4 6 8 10 12 1036A 1036A 1036A Level dB High Frequency 25 to 75 Percentile Difference After Equalisation 0 2 4 6 8 10 12 1036A 1036A 1036A Level dB High Frequency 25 to 75 Percentile Difference Change due to Equalisation 4 ...

Page 31: ... 1036A 1036A Level dB Broadband RMS Deviation Change due to Equalisation 7 6 5 4 3 2 1 0 1 2 1036A 1036A 1036A Level dB Low Frequency RMS Deviation Before Equalisation 0 2 4 6 8 10 1036A 1036A 1036A Level dB Low Frequency RMS Deviation After Equalisation 0 2 4 6 8 10 1036A 1036A 1036A Level dB Low Frequency RMS Deviation Change due to Equalisation 7 6 5 4 3 2 1 0 1 2 1036A 1036A 1036A Level dB Fig...

Page 32: ...036A 1036A Level dB Midrange RMS Deviation Change due to Equalisation 7 6 5 4 3 2 1 0 1 2 1036A 1036A 1036A Level dB High Frequency RMS Deviation Before Equalisation 0 2 4 6 8 10 1036A 1036A 1036A Level dB High Frequency RMS Deviation After Equalisation 0 2 4 6 8 10 1036A 1036A 1036A Level dB High Frequency RMS Deviation Change due to Equalisation 7 6 5 4 3 2 1 0 1 2 1036A 1036A 1036A Level dB Fig...

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