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GOLDBERG AND MÄKIVIRTA

AUTOMATED IN-SITU RESPONSE OPTIMISATION

APPENDIX A – SOFTWARE FLOW CHART

START

DIPtimiser

Display GUI

Reset GUI

Variables and

Graph

Add Supported

Models

Await 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

DIPtimiser

Figure 9. Software flow chart, part 1.

Set Frequency

Range

START

Содержание Optimisation of Active Loudspe

Страница 1: ...en loudspeakers in one space and performs robustly and systematically in widely varying acoustical environments The algorithm is currently in active use by specialists who set up and tune studios and listening rooms 1 INTRODUCTION This paper presents a system to optimally set the room response controls currently found on full range active loudspeakers to achieve a desired in room frequency respons...

Страница 2: ...lemented using a separate equaliser Some equalisers on the market play a test signal and then alter their response according to the in situ transfer function measured in this way 8 but the process can be so sensitive that a simple press the button and everything will be OK approach proves hard to achieve with reliability consistency and robustness It is possible that equalisation becomes skewed if...

Страница 3: ... used to shape the broadband response of a loudspeaker They control the output level of each driver with frequency ranges that are 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...

Страница 4: ...nge and treble driver band 500 Hz fHF Bass roll off region fLF 1 5 fLF Bass region 1 5 fLF 6 fLF 3 2 1 Pre set Bass Roll off In this stage the bass roll off control is set to keep the maximum level found in the bass roll off region as close to the maximum level found in the bass region Once found the bass roll off control is reset to one position higher for example 4 dB is changed to 2 dB The reas...

Страница 5: ...es are permitted The default values are the 3 dB lower cut off frequency of the loudspeaker and 15 kHz This part of the optimisation algorithm takes 35 filtering steps There are no driver level controls in two way or small two way systems so these virtual controls are set to 0 dB The bass tilt control can then be optimised using the same objective function Only five filtering steps are required fo...

Страница 6: ...kHz for the large systems to reduce the aggressiveness of sound at very high output levels 2 dB slope from 4 kHz to 15 kHz to reduce long term usage listening fatigue 3 dB slope from 100 Hz to 200 Hz for Home Theatre installations to increase low frequency impact without affecting midrange intelligibil ity 3 Another Measurement allows the user to optimise a loudspeaker s frequency response mag nit...

Страница 7: ... The Schroeder curves indicate a smooth linear and short decay in all octave bands except 62 5 Hz which shows some stepping caused by reflections There is a high level 5 dB reflection about 3 ms after the direct sound 2 Genelec 1031A 1 due to the floor reflection The loudspeaker suffers from a strong cancellation due to the floor reflection at 160 Hz There is some ripple in the bass and midrange h...

Страница 8: ...case study of a compact three way loud speaker3 placed in a very well damped listening room In this case a reasonable improvement is shown to the in situ response however the fundamental acoustic problems in the room are not solved and can still be seen in the final response 3 Genelec S30D 1 The loudspeaker has an eight inch bass driver with a low frequency cut off of 35 Hz There is also a 3 5 inc...

Страница 9: ...dB Bass Roll off 0 dB After equalisation the response Figure 8 is closer to the target of a flat response The broadband rms deviation between the original responses 2 8 dB and the optimised responses 2 6 dB shows a reduction of 7 0 2 dB The gain increase at 35 Hz has been flattened due to the bass tilt setting The midrange treble balance is flatter due to the 1 dB decrease in the midrange level re...

Страница 10: ...ce the number of alternatives by dividing the task into subsections that can reliably be solved independently A significant part of the heuristics is the order in which these choices should be taken A considerable improvement in the speed of optimisa tion was achieved The optimisation algorithm is relatively robust to a wide variety of situations such as varying room acoustics different sized loud...

Страница 11: ...Society Vol 23 pp 178 186 Apr 1975 7 STAFFELDT H and RASMUSSEN E The Subjectively Perceived Frequency Response in a Small and Medium Sized Rooms SMPTE Jour nal Vol 91 pp 638 643 Jul 1982 8 JBL http www jblpro com Dec 2002 9 GEDDES E R Small Room Acoustics in the Statistical Region 15th Audio Engineering So ciety Conference on Audio Acoustics and Small Spaces pp 51 59 Sep 1998 10 ANSI SMPTE 202M 19...

Страница 12: ... Society Convention Preprint 5590 May 2002 30 FIELDER L D Practical Limits for Room Equalization 111th Audio Engineering Society Convention Preprint 5481 Sep 2001 31 MOORE B C J GLASBERG B R PLACK C J and BISWAS A K The shape of the Ear s Tem poral Window Journal of the Acoustical Society of America Vol 83 pp 1102 1116 Mar 1988 32 MARTIKAINEN I VARLA A and PARTANEN T Design of a High Power Active ...

Страница 13: ...atabase 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 9 Software flow chart part 1 CLOSE Set Frequency Range STAR...

Страница 14: ...LANDS 2003 MARCH 22 25 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 9 cont d Software flow chart part 2 Y N N Y ...

Страница 15: ...ND MÄKIVIRTA AUTOMATED IN SITU EQUALISATION AES 114TH CONVENTION AMSTERDAM THE NETHERLANDS 2003 MARCH 22 25 15 APPENDIX B SOFTWARE GRAPHICAL USER INTERFACE Figure 10 Software graphical user interface at start up ...

Страница 16: ... e D ata Finland H elsinki D em o Room 1031A Centre Time ms 340 320 300 280 260 240 220 200 180 160 140 120 100 80 60 40 20 0 Pres Pa volts Linear 2 1 0 1 Figure 12 Case 1 impulse response data solid line time window dotted line Tim e D ata Finland H elsinki D em o Room 1031A Centre Time ms 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 5 Pres Pa volts Linear 2 1 0 1 Figure 13 Case 1 zoomed impu...

Страница 17: ...tion time Schroeder Curve Finland H elsinki D em o Room 1031A Centre Curve7 DIPtimiser Practices 1031AC HelDemRm wmb BandPass 62 5 Hz 1 oct Curve6 DIPtimiser Practices 1031AC HelDemRm wmb BandPass 125 Hz 1 oct Curve5 DIPtimiser Practices 1031AC HelDemRm wmb BandPass 250 Hz 1 oct Curve4 DIPtimiser Practices 1031AC HelDemRm wmb BandPass 500 Hz 1 oct Curve3 DIPtimiser Practices 1031AC HelDemRm wmb Ba...

Страница 18: ...e Tim e D ata Finland Genelec Listening Room S30D Right Time ms 340 320 300 280 260 240 220 200 180 160 140 120 100 80 60 40 20 0 Pres Pa volts Linear 1 0 Figure 18 Case 2 impulse response data solid line time window dotted line Tim e D ata Finland Genelec Listening Room S30D Right Time ms 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 5 Pres Pa volts Linear 1 0 Figure 19 Case 2 zoomed impulse r...

Страница 19: ... time Schroeder Curve Finland Genelec Listening Room S30D Right Curve7 DIPtimiser Practices GenListRoomS30DR wmb BandPass 62 5 Hz 1 oct Curve6 DIPtimiser Practices GenListRoomS30DR wmb BandPass 125 Hz 1 oct Curve5 DIPtimiser Practices GenListRoomS30DR wmb BandPass 250 Hz 1 oct Curve4 DIPtimiser Practices GenListRoomS30DR wmb BandPass 500 Hz 1 oct Curve3 DIPtimiser Practices GenListRoomS30DR wmb Ba...

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