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Bang & Olufsen BeoLab 90, Technical Sound Manual

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10.3

Power Amplifiers

10.3.1

Tweeters and Midrange Sections

One amplifier per loudspeaker driver

Model

Bang & Olufsen ICEpower AM300-X

Peak Voltage

50 V

Peak Current

20 A

Peak Power

780 W (into 3.2

Ω

)

Frequency Range

<

2 Hz –

>

100 kHz (+0 dB, - 3 dB)

THD+N

0.02% (20 Hz – 20 kHz, 100 mW - 300 W, 4

Ω

, AES17)

Features

DualLoop3 - ICEpower’s third-generation Class-D topology

Custom-modified for BeoLab 90

10.3.2

Woofer Section

One amplifier per loudspeaker driver

Model

Heliox AM1000-1

Peak Voltage

100 V (Software-limited, Hardware capable of 150 V)

Peak Current

40 A

Peak Power

3125 W (into 3.2

Ω

)

Frequency Range

<

1 Hz –

>

20 kHz (+0 dB, -3 dB)

THD+N

0.05% (20 Hz – 20 kHz, 100 mW - 1000 W, 4

Ω

, AES17)

Features

Unified Class-D (UCD)

Custom-modified for BeoLab 90

10.4

Loudspeaker Drivers

10.4.1

Tweeters

Model

Scan-Speak Illuminator D3004/602000

Number

7

Nominal Impedance

4

Ω

Effective Diameter

30 mm

Features

Textile dome diaphragm

Symmetrical drive, SD-2 motor

Non-resonant aluminium rear chamber

10.4.2

Midranges

Model

Scan-Speak Illuminator 12MU/4731T00

Number

7

Nominal Impedance

4

Ω

Effective Diameter

86 mm

Features

Under-hung neodymium motor design

40

Summary of Contents for BeoLab 90

Page 1: ...chnical Sound Guide Bang Olufsen A S April 3 2018 Please note that text in grey indicates features that are not yet released SW Version 2 3 x This manual is for information purposes only and is not legally binding ...

Page 2: ...ers 15 5 1 Beam Width Control 15 5 1 1 Narrow 15 5 1 2 Wide 16 5 1 3 Omni 17 5 1 4 Comment 18 5 2 Beam Direction Control 18 5 3 Speaker Distance 19 5 3 1 Adjusting Speaker Distances with a rotated Beam Direction 19 5 3 2 Adjusting Speaker Distances for more than one listening position 19 5 3 2 1 Automated Measurement of Speaker Distance 19 5 4 Speaker Level 20 5 5 Speaker Role 20 5 6 Active Room C...

Page 3: ... 28 6 1 2 Manual Selection 28 6 2 Individual Input Parameters 28 6 2 1 Re naming 28 6 2 2 Gain Offset 29 6 2 3 Detection Threshold 29 6 2 4 Auto detection 29 6 2 5 Maximum Input Voltage 29 6 2 6 Time out 29 6 2 7 Input Impedance 30 6 2 8 Control Volume of S PDIF or Optical input using Power Link 30 6 2 9 USB Volume enabled 30 6 3 Connection Panels 30 7 System 32 7 0 1 About 32 7 0 2 Max Volume 32 7...

Page 4: ...ers 40 10 4 2 Midranges 40 10 4 3 Front Woofer 41 10 4 4 Woofers 41 10 5 Power Supply 41 10 6 Digital Power Link 41 11 FAQ 42 11 1 Multichannel system setup 42 11 1 1 Bang Olufsen television as source 42 11 1 2 Third party device as source 42 11 2 Does BeoLab 90 support DSD 42 11 3 Does BeoLab 90 support DXD 42 11 4 Why does the BeoLab 90 sound different when I switch to watching television 42 12 S...

Page 5: ...s 48 14 6 AC mains cables 48 15 Appendix 2 Introduction to Parametric Equalisers 49 15 1 Filter Type 49 15 1 1 Low shelving Filter 49 15 1 2 High shelving Filter 49 15 1 3 Peaking Filter 50 15 2 Gain 50 15 3 Centre Frequency 50 15 4 Q 50 16 Appendix 3 The Influence of Listening Room Acoustics on Loudspeakers 52 16 1 Early Reflections 52 16 2 Room Modes 54 16 3 Reverberation 55 16 4 Solutions 55 16...

Page 6: ...1 20 Appendix 7 Thermal Compression Compensation 62 20 1 Introduction 62 20 2 Voice coil temperature 62 20 3 Loudspeaker response changes 63 20 4 The solution 63 20 5 Some extra information 64 21 Appendix 8 Control of BeoLab 90 using the BeoRemote 1 65 21 1 Introduction 65 21 1 1 Customising the Product Name 65 21 2 Input Selection 65 21 2 1 Source Selection 65 21 2 2 Customising the Input Names 6...

Page 7: ...tening when sitting in the sweet spot Finally imagine that you invite your friends for a party or you re just walking around the room Imaging is of no interest to anyone you want a loudspeaker that can deliver the same experience to the entire room at the same time by sending sound in all directions simultaneously Again with your controller you change the BeoLab 90 s acoustical behaviour to suit t...

Page 8: ...ount of energy that is reflected off the side walls If we do not want to change the room one way to do this is to change the behaviour of the loudspeaker by focusing the beam of sound so that it stays directed at the listening position but it sends less sound to the sides towards the walls This is one of the options that BeoLab 90 gives you to make the beam of sound directed out the front of the lo...

Page 9: ...ects of your room s acoustical behaviour in different zones in the room and subsequently select optimised compensation filters for different situations For example you can customise a filter for the sofa and another for your dining area In cases where you are moving between these locations you can simply select a combination of both filters to create a single compensation filter that improves the so...

Page 10: ... 0 60 40 100 80 140 120 1 000 2 000 4 000 8 000 16 000 32 000 64 000 Threshold of Pain BeoLab 90 Maximum SPL Threshold of Hearing Cymbals Figure 1 10 The approximate frequency ranges of example sound sources The darker grey bars show the frequency ranges of the fundamental frequencies The gradient bars show the harmonic content The white line in the Piano range shows Middle C BeoLab 90 s frequency...

Page 11: ... to switch to the edit mode for the current screen Presets Easy Chair Party Sofa Left Presets Easy Chair Party Sofa Left Figure 2 3 Circular selection buttons al low for one item from the list to be cho sen Room Compensation Sweet Spot Sofas Entire Room Dining Table Room Compensation Sweet Spot Sofas Entire Room Dining Table Ro Swe Sofa Entir Dinin Figure 2 4 Rounded square selection buttons are t...

Page 12: ...m Compensation Gain Offset Listening Preset Detect Threshold Max Input Voltage Control Volume Input Impedance Time Out INPUTNAME About Guide Network Reset Power Enhance Max Volume Default Volume System Automatic Update UTC Time Search for Update Submit Log Product information About Speaker Preset Input System etc Advanced Figure 2 5 Simplified and generalised navigational map for the BeoLab 90 int...

Page 13: ...ng the icon on the top right of the screen Press the icon to create a new ARC filter Follow the instructions for microphone placement and perform the three measurements Once the measurement procedure is complete select the ARC filter you have made to apply it to the listening Preset Enter the Advanced menu Verify that the Latency Mode is set to Auto If your source is a Bang Olufsen television take...

Page 14: ...eset enter the edit mode as shown in Figure 4 2 and press the icon in the Preset menu This will start a process where you can name the preset and edit its parameters Easy Ch Party Sofa Le Easy Ch Party Sofa Le Presets Easy Chair Party Sofa Left Presets Easy Chair Party Sofa Left Presets Easy Chair Party Sofa Left Presets Easy Chair Party Sofa Left Presets Easy Chair Party Sofa Left Figure 4 3 Pres...

Page 15: ...ding Vega s voice should appear to float at a position between the two loudspeakers If her voice does not appear to be located exactly mid way between the two loudspeakers it is likely that you are sitting slightly closer to one loudspeaker than the other in other words to one side of the sweet spot Try moving slightly side to side and pay attention to the lateral movement of Vega s voice in space...

Page 16: ... of the directivity of the Narrow Beam Latency Long Frequency Hz Horizontal Angle Beam Width Narrow 100 1000 10 000 150 100 50 0 50 100 150 12 10 8 6 4 2 0 Figure 5 8 Full frequency range direc tivity plot of the Narrow Beam Latency Long Contours in steps of 3 dB nor malised to the on axis response 5 1 2 Wide As mentioned above when the BeoLab 90 s are set to a narrow beam width they are somewhat ...

Page 17: ... 5 14 A map of the phantom im age locations of instruments and voices in Jennifer Warnes s recording of Bird on a Wire Beam Width Wide Compare to Figure 5 4 Thirdly the overall timbre or tone colour of the sound may change as a result of increase influence of the sidewall reflections at the listening position Finally as mentioned above the overall punch of the bass will change when compared to the...

Page 18: ...omment Note that the above illustrations connecting Beam Widths to listener position are merely that illustrations It should also be said that changing the Beam Width of the BeoLab 90 has non intuitive consequences on the perceived sound of the loudspeakers For example the overall sensation of punch in the bass may be different for the three Beam Widths regardless of your location in the listening ...

Page 19: ... menu should be the distance from the listening position to each loudspeaker The result of this alignment is that the closer loudspeaker s signal is delayed to match the time of arrival of the sound from the more distant loudspeaker Note that since the Listening Position can be different for different Presets these distances may not necessarily be the same from Preset to Preset Units Metres Feet Ran...

Page 20: ...nd Slave loudspeakers is done in the Beam Control menu shown in Figure 5 1 Master Left Slave Right Slave Left Master Right Master Right Slave Left Slave Right Master Left Figure 5 28 An example of a loud speaker configuration where the Mas ter loudspeaker should be assigned the Speaker Role of right Master Left Slave Right Slave Left Master Right Master Right Slave Left Slave Right Master Left Fig...

Page 21: ...Dining Table adding the Dining Table zone to the Sweet Spot zone will reduce the quality of the ARC filtering in the sweet spot location This is due to the fact that some of the filtering required to compensate for the room s acoustical effects in the dining area may not be required in the sweet spot Also note that changing Room Compensation zones will cause an approximately 20 second break in the ...

Page 22: ...pplied to all Presets It is also is independent of the settings of other equalisation controllers in the system such as the Frequency Tilt Sound Enhance and Parametric Equaliser controls The range of the controller is from 6 0 dB to 6 0 dB in steps of 0 5 dB 10 100 1 000 10 000 6 4 2 0 2 4 6 Frequency Hz Gain dB Figure 5 36 Magnitude Responses Bass controller Note that this filter is applied to bo...

Page 23: ... the relationship between Latency Mode and a Narrow Beam Width over fre quency The black curve shows a High latency mode The red curve shows a low latency mode Note that the high frequency beam width is the same for both latency modes Only the beam width of the low frequency bands widen for lower latencies 5 10 2 Loudness Sadly human hearing is imperfect One of the issues that we all suffer from is...

Page 24: ...n the signal path to give the loudspeaker a final sound design The BeoLab 90 is no exception to this as a result it has a custom tuned factory default sound design for every combination of beam widths beam directions and latency modes However there may be some specific cases where this tuning is not applicable One example of this is a case where the BeoLab 90 is used in a listening room such as a ...

Page 25: ... from 0 5 to 8 0 where the Q is based on a bandwidth defined by the half gain points4 The gain ranges from 6 0 dB to 6 0 dB in steps of 0 5 dB The peaking filters have a range of 5 octaves with differing limits as follows Four low frequency filters with a range of 25 0 Hz to 400 0 Hz Three mid frequency filters with a range of 250 0 Hz to 4 0 kHz One high frequency filter with a range of 2 5 kHz to...

Page 26: ...ab 90 s connected to a Bang Olufsen television such as a BeoVision 11 or BeoVision Avant as shown in Figure 5 51 then it is possible to automatically trigger presets in tandem with the television s Speaker Group This selection is done in the Speaker Group menus on the television where you can select the Speaker Preset number for the BeoLab 90 as one of the parameters in the Speaker Group See the B...

Page 27: ...a pair of BeoLab 90 s connected to two third party sources an AV Surround Processor using XLR and a separate audio player using S PDIF Note that in this case the latency of the BeoLab 90 s must be carefully managed in the setup of the loudspeakers and the AV Surround Processor in order to ensure that the multichannel system is behaving correctly Audio Player AV Surround Processor Power Amplifier X...

Page 28: ...the BeoLab 90 This prioritisation can be personalised by changing the vertical order of the inputs on BeoLab 90 interface in the Input Select menu press the icon at the top right to enter the edit mode Inputs Power Link XLR S P DIF RCA Optical USB Audio WPL WiSA Automatic AUTOMATIC SENSE MANUAL SENSE Inputs Power Link XLR S P DIF RCA Optical USB Audio WPL WiSA Automatic AUTOMATIC SENSE MANUAL SENS...

Page 29: ... different from the detection of analogue signals since the digital inputs are triggered by the presence of a any non zero signal on the digital audio stream rather than a signal above a user defined level Options On Off Factory Default On Note that the Auto detection parameter is only available for the USB Audio S PDIF and Optical inputs Note that for the XLR and RCA analogue inputs the Detection T...

Page 30: ...ntrol of a Bang Olufsen source sent via a Power Link connection and apply it to an audio signal coming into the BeoLab 90 via its S PDIF input Note that in order for this option to function properly the S PDIF input must be assigned a higher priority than the Power Link input in the Selection Priority This function is also independently available for signals on the Optical input When the volume of...

Page 31: ...B 5V 0 5 A USB AUDIO DPL DPL DPL ETHERNET USB 5V 0 5 A DPL ETHERNET DPL DPL Figure 6 6 Audio connection panel Slave loudspeaker Note that the only audio connectors on this loudspeaker are for the Digital Power Link connection to the Master loudspeaker If you are familiar with XLR connectors you will notice that the push button lock is missing on the XLR input This is intentional and has been done ...

Page 32: ...ange 0 90 Resolution 1 dB Factory Default 90 Note that the Max Volume parameter is not available for the Power Link and Wireless Power Link inputs 7 0 3 Startup Volume The Startup Volume control allows you to determine the volume level when the BeoLab 90 wakes as a result of a detected signal or is manually turned on Range 0 90 Resolution 1 dB Factory Default 42 Note that the Startup Volume parame...

Page 33: ...PL 51 53 3 dB SPL 50 52 3 dB SPL 49 51 3 dB SPL 2 4 3 dB SPL 1 3 3 dB SPL 0 dB SPL Table 8 3 Unweighted Sound Pressure Level SPL of the audio signal from a BeoLab 90 at 1 m in a free field 200 Hz 2 kHz Input signal 30 0 dB FS Note that these values consider only the output level of the audio signal and assume that thermal protection has not been engaged 8 3 Parametric Equaliser Type Range Hz Filte...

Page 34: ... x x 1 7 x 1 8 x x 1 9 x 2 0 x x x x x 2 12 x 2 24 x x 2 36 x 2 5 x x x 2 65 x 2 8 x x x 3 0 x 3 15 x x x 3 35 x 3 55 x x 3 75 x 4 0 x x x x x 4 25 x 4 5 x x 4 75 x 5 0 x x x 5 3 x 5 6 x x x 6 0 x 6 3 x x x 6 7 x 7 1 x x 7 5 x 8 0 x x x x x 8 5 x 9 0 x x 9 5 x Table 8 7 ISO standard frequency centres for fractional octave spacing 34 ...

Page 35: ...t of measurements of each loudspeaker driver s mechanical and acoustical behaviour and a custom created set of filters for it 9 2 Phase Optimised Filtering Like all audio devices in order for the BeoLab 90 to deliver its level of sound performance filters are used in the Digital Signal Processing DSP Generally an audio filter is a device that changes the overall response of the the audio signal In...

Page 36: ...en its gain is reduced to attempt to protect it from destruction It is important to state that this does not mean that the BeoLab 90 is indestructible but it does make it very difficult to destroy More information can be found in Appendix 6 ABL Adaptive Bass Linearisation 9 4 Thermal Compression Compensation BeoLab 90 s processing includes automatic compensation for changes in loudspeaker driver res...

Page 37: ...ee sections Preamplifier and Processor equivalent to a surround processor preamp or receiver Power Amplifiers Loudspeaker Drivers Stereo Preamp BeoLab 90 Power Amps Loudspeakers Figure 10 1 A block diagram of the BeoLab 90 showing the comparative sections in terms of competing devices 10 2 1 Overall Specifications Note Hardware only measurement All filters and equalisation bypassed or removed from...

Page 38: ...RMS produces 88 dB SPL 1 m on axis free field XLR Line Input Impedance Single ended 50 kΩ Fixed Input Impedance Balanced 100 kΩ Fixed Maximum Input Voltage 2 0 4 0 6 5 V RMS Selectable Features Differential and impedance balanced Pin configuration Pin 1 Audio ground Pin 2 Positive signal input hot Pin 3 Negative signal input cold Note that the XLR connector casing or shell is connected to the chass...

Page 39: ...Linear PCM Sampling rate Standard WiSA sampling rates up to and including 96 kHz Word length 24 bits 10 2 3 Digital Signal Processor Model Analog Devices ADSP 21489 Number 2 Instruction Rate 400 MHz Sampling rate 192 kHz fixed Notes 32 bit floating point 10 2 4 Digital to Analogue Converters Note that these specifications include the analogue stages that follow the DAC outputs Model Texas Instrume...

Page 40: ...000 1 Peak Voltage 100 V Software limited Hardware capable of 150 V Peak Current 40 A Peak Power 3125 W into 3 2 Ω Frequency Range 1 Hz 20 kHz 0 dB 3 dB THD N 0 05 20 Hz 20 kHz 100 mW 1000 W 4 Ω AES17 Features Unified Class D UCD Custom modified for BeoLab 90 10 4 Loudspeaker Drivers 10 4 1 Tweeters Model Scan Speak Illuminator D3004 602000 Number 7 Nominal Impedance 4 Ω Effective Diameter 30 mm Fe...

Page 41: ... Impedance 4 Ω Effective Diameter 212 mm Features Anodised aluminium cone Fibre glass dust cap 10 5 Power Supply Power Consumption Low Power Standby 0 5 W Network Standby 2 W Low level audio Idle Approximately 150 W continuous Sustained Max Average 250 W Peak 18 000 W Duration 1 ms 10 6 Digital Power Link Technology Audio Video Bridge AVB Sampling Rate 192 kHz fixed Bit depth 24 Features Includes p...

Page 42: ...signals a conversion of DSD to PCM is required somewhere in the audio chain Placing this conversion process ahead of the loudspeakers inputs gives the user the option to choose his or her preferred filter for the process 11 3 Does BeoLab 90 support DXD DXD is not currently supported by BeoLab 90 since its digital inputs will not operate at sampling rates above 216 kHz In order to play DXD files on...

Page 43: ...ab 90 s Speaker Distances for larger listening areas When measuring the Speaker Distances for larger listening areas with more than one person it is sometimes better to measure the distance from a given loudspeaker to the closest listener This is particularly true in multichannel systems For a Party Mode where there is no single listening position either due to the size of the crowd or the fact th...

Page 44: ...ce an audible echo relative to other loudspeakers in the system It may be possible to trick some surround processors into compensating for BeoLab 90 s latency in High Latency Mode by adding 34 3 m 112 5 feet to their actual distance from the listening position This value corresponds to a 100 ms latency When used in Low Latency Mode 8 6 m 28 1 feet should be added to the actual distance from the li...

Page 45: ...volume control of the Optical input using Power Link has been enabled then it is important to set the priority of the Optical input higher than that of the Power Link If this is not done then the Power Link signal will override the Optical input and the latter will not be heard 13 12 Automatic switching of inputs not behaving as expected If you are using the Automatic input selection there may be ...

Page 46: ...ce between the two loudspeakers If possible the height of the listening chair should be set so that the listener s ears are level with the centre of the vertical beam shown in Figure 14 1 This point is 108 6 cm above the floor The next consideration is symmetry within your listening room It is commonly recognised that the best stereo imaging will be achieved if the listening configuration the tria...

Page 47: ...se the ratios of the room s dimensions would have non simple values e g 1 2 16 2 96 so as an example 3m x 6 48m x 8 88m 1 A second issue in many listening rooms is that of hard reflective surfaces particularly in locations where the sound from the loudspeaker is directly reflected to the listening position There are two ways to alleviate this problem absorption and diffusion In order to absorb a so...

Page 48: ... and Installation by Philip Giddings is highly recommended Although this is book intended for installation of audio devices in recording and mastering studios the practices and recommendations detailed therein are also applicable to consumer level audio equipment 14 5 2 Optical cables It is recommended that high quality optical cables are used for the BeoLab 90 particularly for longer cable runs T...

Page 49: ...ng Although there are up to 7 different types of filters that can be found in professional parametric equalisers the BeoLab 90 contains the three most used of these Low shelving Filter High shelving Filter Peaking Filter 15 1 1 Low shelving Filter In theory a low shelving Filter affects gain of all frequencies below the centre frequency by the same amount In reality there is a band around the centre...

Page 50: ... uses reciprocal peak dip filters 15 2 Gain If you need to make all frequencies in your audio signal louder then you just need to increase the volume However if you want to be a little more selective and make some frequency bands louder or quieter and leave other bands unchanged then you ll need an equaliser So one of the important questions to ask is how much louder or how much quieter The answer...

Page 51: ... filter with a gain of 6 dB and a Q of 4 will actually have a gain of almost 13 dB and will attenuate by almost 7 dB This over and undershooting of the filter s magnitude response is the reason the Q of the high shelving and low shelving filters in the BeoLab 90 s parametric equaliser have been limited to a maximum value of 1 Note that when the Q is set to a value of 1 then the resulting overshoot...

Page 52: ...speaker The question is what effect does the wall reflection have on the measured response of the loudspeaker Very generally speaking the answer is that you will get a higher level at some frequencies because the direct sound and the reflection add constructively and reinforce each other and you will get a lower level at other frequencies because the direct sound and the reflection work against eac...

Page 53: ...ison 10 100 1 000 10 000 20 15 10 5 0 Frequency Hz Gain dB Figure 16 5 Distance to loudspeaker 2 m Distance to wall 1 m Wall is ab sorptive and or the loudspeaker is direc tional at high frequencies The red line is the magnitude response of the direct sound The blue line is the magnitude response of the reflected sound The black line is the magnitude response of the combination 10 100 1 000 10 000...

Page 54: ...g at a note The longer the pipe the lower the note because the speed of the sound wave moving in air in the pipe stays the same but the longer the pipe the longer it takes for the wave to bounce back and forth This is basically how all woodwind instruments work What s interesting is that in terms of resonance a room is basically a big pipe If you pluck the air in the room say by making sound with ...

Page 55: ...densely packed together in time that we can t separate them so we just call them reverberation or reverb although you ll often hear people call it echo which is the wrong word to use for this Reverb is what you get when you have a lot of reflective surfaces in your room but since it s so irregular in time and space it just makes a wash of sound rather than a weird comb filter effect like we saw wit...

Page 56: ...two different loudspeakers will behave differently from each other in two different rooms In other words if you listen to loudspeaker A and loudspeaker B in a showroom of a shop you might prefer loudspeaker A but if you took them home you might prefer loudspeaker B This would not be surprising since what you hear is not only the loudspeaker but the loudspeaker filtered by the listening room This is e...

Page 57: ...ntion the distance information the relationship between the direct sound and the reflections has been captured in the recording This means that when you listen to the recording you not only can tell where the instruments are from left to right but also their relative distances 17 3 Combining the Two So we know that early reflections tell your brain how far away the sound source is Now think to a l...

Page 58: ...e roughly the same as the height of that person s ears typically 100 120 cm above the floor Figure 18 2 Recommended micro phone placement height for one listener shown in gray If the ARC measurement zone is intended for more than one listening position or for listeners of different heights then it may be beneficial to change the vertical position of the microphone for the three measurements For exa...

Page 59: ...e ARC microphone placements in red for a passive listen ing and background music situations at a dining table Note that in cases where there is overlap between different ARC Zones the measurements can be combined by combining ARC Profiles in the BeoLab 90 interface instead of duplicating measurements An example of this is shown in Figure 18 6 Figure 18 6 An example of avoiding duplicate microphone ...

Page 60: ... contours If you tune a loudspeaker when it s playing loudly you ll wind up with a loudspeaker with less bass than if you tuned it quietly This is because you re automatically compensating for differences in your own hearing at different listening levels After that tuning is done then we go back to the measurements to see where things will misbehave For example in order to compensate for the relativ...

Page 61: ...ping quickly maybe it s because I hit the brakes maybe it s because I hit a concrete wall the seat belts just lock up when they re asked to move too quickly Your woofer s voice coil doesn t know the difference between Eminem and Stravinsky with a bass boost it just knows it s hot and it doesn t want to get hotter 19 2 ABL and BeoLab 90 In spite of BeoLab 90 s massive power reserves and four capable...

Page 62: ...f you know how each of these components behaves and you know the correct values to put in for a given loudspeaker and you know how to do the right math then you can come close to getting a prediction of the response of the loudspeaker that you re modelling with the circuit However if you just put in one value for each component then you re assuming that they never change in other words that you re...

Page 63: ...a low pitch As the voice coil resistance goes up its resistance increases and we generally lose sensitivity i e level or loudness from the woofer In other words the hotter it gets the quieter it gets However this only happens at the frequencies where the resistor is not overridden by another component say the mechanical resonance of the woofer or the inductance of the voice coil The total result i...

Page 64: ... the music gets loud the woofer heats up so you lose output so we add a filter that compensates by putting more signal into the driver However this means that the problem is caused by the signal being too loud and the result is that we make the signal louder However there is one more trick up our sleeve Appendix 6 ABL Adaptive Bass Linearisation describes BeoLab 90 s Thermal Protection algorithm T...

Page 65: ...there that are scrollable using the UP DOWN buttons and selectable using the GO button on the remote control Firstly you will need to customise this list as follows 1 press LIST 2 Scroll down to SETTINGS and press GO 3 Scroll down to MUSIC sources and press GO 4 Select SHOW and press GO 5 Use the GO button to place a check mark next to the following items in the following list It may also be helpf...

Page 66: ...er parametric 24 33 Fc 50 features 35 features disabled 44 filter high shelving 25 49 low shelving 25 49 peaking 25 50 phase response 35 Q 50 reciprocal peak dip 50 formats DXD 42 frequency tilt 23 gain 50 equaliser 50 filter 50 gain offset 29 Hertz 50 high shelving filter 25 49 Hz 50 imaging 7 15 impedance input 30 input auto detection 29 detection threshold 29 gain offset 29 impedance 30 maximum i...

Page 67: ... signal detection automatic 29 sound design 24 35 sound enhance 24 speaker distance 19 speaker group 26 speaker level 20 Speaker Preset 26 speaker role 20 specifications technical 37 SRC 38 stereo imaging 7 15 technical specifications 37 temperature 32 thermal compression compensation 36 62 thermal protection 35 threshold detection 29 time out 29 treble 22 USB Audio 39 volume 30 volume control 21 ...

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