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Active 200 (QA8208) White

Q-ACOUSTICS Active 200 (QA8208) White, Active 200 (QA8204) Black Q_Active_White_Paper_Issue-5.pdf

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Q Active
White Paper
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Contents
Introduction ................................................1
Design brief .............................................1
Speaker overview ......................................2
Component detail ....................................3
Balanced mode radiator (BMR) drivers ..4
Why BMR? ...............................................4
Dual BMRs ...............................................5
Asymmetrical positioning ........................5
Integrated subwoofer ................................6
Overview ..................................................6
Boundary control lens ..............................7
Time alignment ........................................7
Balanced subwoofer drivers ....................8
Dual subwoofer drivers in the QA 400 .....8
Dart bracing ...............................................9
Dart bracing for the subwoofer drivers ....9
Q Active stand .........................................11
The Q Active system ...............................12
System connectivity ................................13
Bluetooth® .............................................13
Streaming .................................................14
Connectivity methods ............................14
Using voice control ................................14
Multi-room ..............................................14
Resolution comparison charts ...............14
The hub in detail ......................................16
Optical and HDMI inputs .......................16
Sample rate converter ...........................16
Analogue inputs .....................................16
Clock strategy ........................................16
Low latency 5GHz link to speakers .......16
Configuration ...........................................17
Overview ................................................17
Channel setting ......................................17
Boundary setting ...................................17
Conclusion ...............................................18
Meeting the design brief ........................18
P2P bracing .............................................10
Specification ............................................21
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Introduction
Design brief
The design brief for the Q Active system was to create an exceptional audio system within a pair of compact, high performance speakers, designed to
t seamlessly into a living environment. It was therefore decided early on in
the design process to use wireless technologies to eliminate the wiring of a traditional audio system and require only the connection of mains power.
The brief included connectivity for essential sources such as network streaming, TV sound, and Bluetooth® audio. To enable connectivity with wired sources the system required a wireless speaker pair and a connection ‘hub’ that could be placed remotely for optimal installation. A wireless remote control would complete the system, avoiding the requirement for additional mobile apps, etc.
Each drive unit in Q Active was to be driven by a separate power amplier and
a dedicated digital signal processing (DSP) channel to provide equalisation. This DSP/active topology would enable a more radical approach for the acoustic design of Q Active.
The technologies developed for the Q Active range would be shared
between the two speaker models; a compact oorstander (Q Active 400) and
standmount (Q Active 200).
Whilst this is a fully featured audio system, Q Acoustics heritage is speaker design. This, the most important aspect of the system design, is the best place to start.
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Speaker overview
Q Active speakers strike a harmony between industrial, electronic and acoustic design disciplines, applying creative solutions to perennial speaker
design problems. The compact oorstander and standmount speakers both
incorporate novel technologies and design features.
At the forefront of the design is the driver conguration, which impacts the entire
layout of the speaker including cabinet structure and internal considerations to the electronics such as wireless module positioning and PCB design.
Figures 1 and 2 pinpoint the main mechanical features that are explored in detail throughout this paper.
2 x BMR drive units (58mm)
2 x Subwoofer drive units (114mm) with cast baskets
Reex port
Power amplication
assembly
Figure 1: Q Active 400 detail
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Component detail
Control panel
Acoustically transparent grille
2 x BMR drive units (58mm)
Hi-Res wireless audio receiver
24-bit/96kHz digital signal processor
Reex port
Subwoofer drive unit
(114mm) with cast basket
Low distortion
power ampliers
I/O board
Power inlet
Power supply
Figure 2: Q Active 200 detail
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Balanced mode radiator (BMR) drivers
Why BMR?
At an early stage a BMR driver was reviewed as an alternative to a conventional
dome tweeter as BMRs have a number of benets useful to a system such as
Q Active:
• Super wide dispersion for a panoramic sound stage.
• Seamless mid-range performance resulting in no mid-range crossover distortion.
• Extended lower frequency range to 150Hz for seamless integration with the inbuilt subwoofer.
• High dynamics with low thermal compression due to the relatively large, 32mm voice coil of the BMRs.
• With an actively driven BMR the amplier closely controls the damping of the BMR throughout its spectrum. This removes all passive equalisation
and ltering that would cause the damping factor to change dynamically.
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Dual BMRs
To improve dynamics further and to maximise available sound pressure level (SPL), the speakers use a dual BMR system. Dual BMRs acoustically sum in a more sympathetic manner than conventional pistonic drive units.
In the case of Q Active, the designers have chosen to drive the BMRs with
separate DSP and power amplier channels. The DSP channel for the upper
BMR runs down to the crossover point with the integrated subwoofer whereas
the DSP channel for the lower BMR includes low-pass ltering set at a frequency
of 5kHz. With this strategy, sound staging is not compromised as ‘point source’ behaviour is maintained for the speaker from the upper positioned BMR at high frequencies.
Asymmetrical positioning
The extended low frequency range of the BMRs enables the bass section to work in a region where its sound is not directional. The bass section can therefore be designed as an integrated subwoofer, built into the back of the cabinet. This creates a more stable, acoustically clean bafe on which to mount the BMRs.
Removing the bass driver(s) from the front of the cabinet frees up the designer to optimise the positioning of the BMR drivers. The asymmetric position chosen breaks symmetry in the acoustic path lengths from the BMRs to the
bafe edges, improving diffraction and interference patterns on the bafe.
Figure 3: Standmount speakers in near eld listening position
A secondary benet of this asymmetric positioning lies in the channel switching
for the speakers - each speaker can be set to reproduce the left or the right
audio channel. This feature gives exibility to position the BMRs toward the
outside or inside to suit user preference, thus optimising the soundstage for the
listener(s). As an example, for far-eld listening the BMRs can be positioned to the inside, or for near-eld listening the BMRs can be positioned to the outside
(Figure 3).
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Integrated subwoofer
Overview
The BMRs require only a slim cabinet section and modest internal volume to
extend to 150Hz. This leaves a full 85% (standmount) and 95% (oorstander)
of the cabinet volume to load the subwoofer drive unit(s).
The subwoofer drive units are substantial, high-power, long-throw bass units built in a 114mm die-cast chassis.
The standmount has a dedicated power amplier that drives a single subwoofer built into a ported enclosure. The oorstander has two subwoofers with one
positioned towards the top and one at the bottom of the cabinet. As with the
standmount both subwoofers are driven by dedicated power ampliers and
the enclosure is a ported design.
One signicant benet of an active subwoofer design is that the ampliers will
drive a known load. They can therefore be optimised to work with the power handling and impedance of the drive units in the Q Active subwoofer.
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Boundary control lens
Q Acoustics have implemented a boundary control lens in front of each
subwoofer drive unit. This low frequency energy guide routes the airow
from the subwoofer drive units to the side vents of the cabinet. This strategy controls the boundary conditions for the subwoofer and ensures that the timing alignment between the subwoofer and BMRs is predictable.
The lens is mounted to a substantial, rigid brace that forms the back of the
cabinet. Its form creates a controlled airow (Figure 4) which would otherwise
break up if the driver were facing a planar surface (Figure 5).
Time alignment
The Q Active includes time delay circuitry that digitally delays the signal reaching the BMRs, keeping the sound from the front mounted BMRs and the rear mounted subwoofer precisely time aligned.
Figure 4: Boundary control lens
Figure 5: No boundary control lens
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Balanced subwoofer drivers
Dual subwoofer drivers in the Q Active 400
A single drive unit mounted conventionally at the top of a oorstander cabinet creates a problem by efciently exciting a standing wave in the speaker cabinet.
This can be seen in the illustration Figure 6 which shows the ‘seesaw mode’
with one driver efciently exciting the standing wave in the length of the cabinet
at 210Hz. The nodal line can clearly be seen in both the pressure and phase.
To address this, the Q Active 400 subwoofer employs twin drive units driven
in phase, one at the top of the oorstander and one at the bottom, effectively
‘locking’ the mode and resulting in uniform pressure throughout the enclosure volume. This can be seen in Figure 7, depicted by the absence of a nodal line and a constant phase within the enclosure.
Figure 6: Conventional driver conguration
Phase
Figure 7: Q Active 400 balanced driver conguration
Pressure
Phase
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Pressure
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Dart bracing
Dart bracing for the subwoofer drivers
A specic bracing formation in the form of an arrow dart is employed to good effect in both the standmount and oorstander cabinets. Figure 8 highlights
this structure in red situated behind each of the subwoofer drive units.
Dart bracing provides high axial stiffness directly to the motor system, effectively providing a mechanical ground to the subwoofer drive unit(s). lt gives superior mechanical stability to the drive unit over un-braced systems
that can otherwise result in drive unit ‘bounce’ on the mounting xtures and bafe.
Figure 8: Dart braces
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P2P bracing
Bracing the oorstander cabinet
Q Acoustics Point to Point (P2P) bracing is employed in the cabinet of the Q
Active oorstander.
P2P bracing only supports the parts of the cabinet that need to be stiffened and does not spread unwanted energy randomly. The illustrations show how
effective this methodology has become. A map of an un-braced oorstanding
cabinet wall with respect to its deformation at a test frequency of 873Hz is shown in Figure 9. Where velocity is greatest the area is coloured towards the red end of the spectrum and where it is least it is coloured towards the blue end. A hot spot of vibration has been created at the test frequency. Conventional bracing would allow this movement to be transferred to adjacent panels, but Q Acoustics P2P·allows the design team to apply bracing only in exactly the correct places.
When the test is repeated on the treated enclosure, the deformation map
shows how effectively the cabinet resonances have been reduced. In gure 10
the lower surface displacement of the P2P can clearly be seen. Note that a like for like scaling factor has been applied to the images for illustration purposes.
Figure 9: Cabinet without P2P - high resonance
Figure 10: Cabinet with P2P - low resonance
x10-6m
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Q Active stand
Designed for Q Active 200
The Q Active stand (Q FS75) has been designed specically to partner with
the standmount speaker, providing a stable mounting platform for the speaker
with low resonance and minimal reective surfaces.
The base of the standmount speaker includes xings to enable the Q Active
Stand to be bolted rigidly to the speaker.
Inspired by tensegrity
The striking design of the Q Active speaker stand adopts the principles of a space frame consisting of rods in compression stabilised by cables in tension.
Important benets of this arrangement lie in the skeletal, high rigidity
construction that has minimal parallel or planar surfaces.
Minimising reections
A known problem with conventional speaker stands is that their relatively large surface area acts as a re-radiating surface for the sound waves created by the drivers above them. Sound leaving the drive units will radiate uniformly in
all directions and will reect from any nearby surfaces - such as the speaker
stand - with an accompanying phase shift causing constructive and destructive interference with the direct sound.
Figure 11: Solid MDF stand
Figure 12: Tubular steel stand
Finite element analysis has shown how a real-world radiated sound eld is affected by reections from the surface of the different types of stand.
In the diagrams, traditional solid and steel column stands are compared to
a Q Acoustics space frame design. The radiated sound eld should look like
perfect ripples on a still pond after a stone is thrown into the water. As can be seen, the solid MDF (Figure 11) and column (Figure 12) designs re-radiate far
more of the original loudspeaker signal and therefore contribute signicant disturbance (red and yellow) to the ideal sound eld when compared with the
space frame design (Figure 13).
Figure 13: Space frame stand
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The Q Active system
A complete audio system
Q Active is far more than ‘just’ a pair of high quality loudspeakers. It is a complete audio system. With minimal intrusion into any living space, there is
no requirement for separate amplication, sources, interconnects or cables.
Hub
The compact hub is a key component in the system, combining the functions
of a preamplier and music streaming source.
It includes wired or wireless connection to a local network for streaming, wired inputs for HDMI (ARC), digital audio and an analogue input that is switchable between line level or moving magnet (MM) input for a turntable.
A 5GHz digital wireless link transfers the left and right channel audio from the hub to the speakers.
System control
In use, the system is completely exible for a user to control in whichever way is
most convenient. The system integrates seamlessly with apps when streaming or playing dedicated Q Active remote control is also provided for legacy sources.
Bluetooth
audio and with TV remote controls via HDMI (ARC). A
There is no requirement to install a Q Active app to control these speakers.
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System connectivity
Music streaming
The Q Active hub includes network streaming and requires no special mobile app for this. Any app that features compatibility with these technologies will stream to the Q Active system.
Connecting a TV
The hub features HDMI audio return channel (ARC) connection with consumer electronics control (CEC).
Connect the hub to an HDMI (ARC) outlet on a compatible TV to route 2 channel TV sound through the Q Active system.
If the TV also features CEC, the TV remote can take control of essential functions of the Q Active system such as standby and volume control.
Analogue and digital sources
The hub includes connectivity for wired sources including an analogue input (switchable between line level and phono MM).
A Toslink digital input enables connection to a digital audio source such as a CD or DVD player or a TV.
Bluetooth
Figure 14: System connectivity diagram
Bluetooth
audio is included for universal wireless connectivity.
Sub out
Sub out is an optional feed to connect a separate subwoofer to the system.
This output is a second order low pass-lter set to -6dB @ 450Hz. A connected
subwoofer may be set to extend the response of the system to include low frequency sound effect information for home cinema or just to reinforce bass response in very large spaces.
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Streaming
Overview
Q Active is capable of streaming music or radio from a wide variety of providers using the different connectivity methods described below. The user can use any app which supports one of the listed methods, or alternatively use voice control via compatible smart speakers or mobile devices.
Connectivity methods
All Q Active systems include these connectivity methods:
• AirPlay 2
• Spotify Connect
• Roon ready
• UPnPTM*
•
Bluetooth
Q Active is available in two different versions making it compatible with either:
1. Google Home system
• Chromecast built-in
• Google Home assist voice control
TM
Using voice control
The ‘Chromecast built-in’ version integrates with other ‘Google Home’ compatible devices. Voice commands to any Google smart speaker or setup via the Google Home app will control the playback selection and volume on the Q Active system.
Similarly, the ‘Works with Alexa’ version forms part of an Amazon ecosphere with other compatible devices. Voice commands to an Echo device or via the Alexa app will control the playback selection and volume on the Q Active system.
All Q Active systems can be operated using Siri voice control once the speakers have been added to the Apple Home App. Voice commands can then be made via any Siri enabled hardware, or using a compatible iPhone or iPad to control the playback and volume of Q Active.
Multi-room
Q Active can form part of a multi-room speaker group using the following connectivity methods:
• AirPlay 2
• Roon ready
2. Alexa system
• Works with Alexa
*Both versions of Q Active can be used with many Universal Plug and Play (UPnP) servers and control apps. The Q Active system will appear as a selectable speaker system on the UPnP control app. Many Network Attached Storage (NAS) drives are supplied with UPnP server software, and can provide
a library of compatible digital music les which can be played through Q Active.
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• Chromecast built-in
• Amazon multi-room music
Resolution comparison charts
The charts opposite show a graphical comparison of the connectivity methods supported by Q Active and the most popular streaming services available
(gures correct at time of print).
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Connectivity methods comparison
Sounds
Music
Music
Ultra-High Resolution 32-bit/192kHz*
High Resolution 24-bit/96kHz
CD Quality 16-bit/44.1kHz
Compressed Audio e.g. mp3
*Q Active downsamples to 24-bit/96kHz
Streaming services comparison
Ultra-High Resolution 32-bit/192kHz*
High Resolution 24-bit/96kHz
CD Quality 16-bit/44.1kHz
Compressed Audio e.g. mp3
Other streaming services are available
Roon
Amazon
Music HD
Amazon
UPnP
Apple Music
Chromecast
built-in
BBC
Works with
Alexa
Deezer Primephonic Qobuz Spotify Tidal
Airplay 2 Spotify
Connect
Bluetooth
Masters
Tidal
Youtube
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The hub in detail
Optical and HDMI inputs
Digital audio from the optical and HDMI inputs is routed through the sample rate converter (SRC) and re-sampled to 24-bit/96kHz, regardless of native bit depth and sample rate.
Sample rate converter
A key element in the hub topology is the SRC. This accepts the signals from the digital and HDMI wired sources and converts any incoming audio signal to 24-bit/96kHz digital audio. The 96kHz sample rate ensures that any aliasing due to the sampling process is shifted up in frequency and well away from the audio band.
Analogue inputs
The analogue input is switchable to match either a turntable with moving magnet cartridge or a line input. Analogue inputs are routed through a 24-bit analogue to digital converter (ADC) that runs at a sample rate of 96kHz to also minimise aliasing.
Clock strategy
Jitter in digital signals causes dynamic time domain distortions that are not
harmonic in nature. Although difcult to measure precisely in an audio signal,
jitter artefacts can be quite audible when listening to a digital audio system.
To address this, the hub includes a single, low jitter ‘master’ clock in the circuit responsible for receiving streamed and clock is also used to time the re-sampled data out from the SRC, effectively minimising jitter that could otherwise have been present in a clock recovered from the input signal.
Bluetooth
audio. This reference
Figure 15: Hub detail diagram
HDMI
Decoder
Sample Rate Converter
High resolution Network
and Bluetooth player
Dual Core Coretex Processor
Low Latency 5GHz Wireless Link to Speakers
Optical
Receiver
24-bit/96kHz
Audio processing unit
24-bit/96kHz
AnalogueDigital
Phono MM
Line Level
24-bit ADC
Master clock
Low latency 5GHz link to speakers
The hub connects wirelessly to the speakers over a dedicated 5GHz digital link. This is designed with super-low latency to ensure left and right channels
stay precisely in step for a stable stereo image.
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Conguration
Overview
Q Active is a highly exible system that can be optimised for both the room
environment and the listener’s system needs.
Channel setting
A channel setting switch on the back of each speaker enables it to be set to the left or right channel. This, with the asymmetrical design of the speakers
allows the BMR drive units to be positioned optimally for near-eld or far-eld
listening.
Boundary setting
A 3-position boundary setting switch on each speaker enables the DSP to change the speaker’s voicing. Consequently Q Active speakers may be optimised for a number of different listening environments including:
Positioned close to a corner.
Positioned close to a wall.
Free-space.
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Conclusion
Meeting the design brief
Q Active speakers are the fusion of rened, innovative acoustic and industrial
design, with modern connectivity in a compact and powerful package.
Acoustically, the Q Active speakers embody many new and interesting design ideas:
• BMR and integrated subwoofer driver conguration.
• Separate DSP and power amplication for each individual driver.
• Precision braced cabinet design including an asymmetrical front bafe and boundary control lens.
The acoustic design is integrated into a system that offers expertly considered components:
• Wired HDMI, optical and analogue or phono connectivity to a separate hub.
• High resolution 24-bit/96kHz wireless connection from the hub to the speakers.
• Streaming via Chromecast built-in, Amazon Alexa and Apple Airplay 2 for smart home integration.
All these elements allow the user to create immersive hi- sound without
any intrusion of traditional audio component stacks and wiring. A thoughtful approach to the entire system design has culminated in an experience that combines traditional audio and the future of enjoying music in the home.
Q Active has been developed from an idea to a nished product by a creative
and great group of people that make up the Q Acoustics team and we would like to thank all those who have contributed.
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Specication
Product Q Active 200 Q Active 400 Hub Acoustics
Enclosure type Reex (ported) Reex (ported) ­Full range driver 2 x BMR 58mm (2.25in) 2 x BMR 58mm (2.25in) ­Subwoofer (high excursion) 1 x 114mm (4.5in) 2 x 114mm (4.5in) ­Crossover frequency 150Hz TBC ­System frequency response (free boundary) 46Hz to 20kHz (-6dB) TBC -
Power (per speaker)
Continuous power 100W TBC ­Peak power 280W TBC -
Power requirement
Voltage range 100 - 240 VAC, 50/60 Hz 100 - 240 VAC, 50/60Hz 100 - 240 VAC, 50/60Hz
Weight and dimensions
Un-boxed weight (per speaker) 7.5kg 17.5kg 0.5kg Dimensions (per speaker) H x W x D 284 x 170 x 290mm
(11.2 x 6.7 x 11.4in)
Dimensions on stand H x W x D 922 x 286 x 338mm
(36.3 x 11.3 x 13.3in)
Wireless connectivity
Bluetooth
Wi-Fi - - IEEE 802.11 a/b/g/n and 802.11ac compliant Hi-Res Wireless Link frequency 5.8GHz 5.8GHz 5.8GHz Remote control - - 2.4GHz
Audio playback
Codec formats - - AAC, WAV, FLAC, MP3, Vorbis, WMA & ALAC
Sample frequency 96kHz 96kHz 8 – 192kHz (depending on codec) Bit depth 24bits 24bits 8 – 32bits (depending on codec)
Wired connectivity
Digital optical - - 96kHz/24bit Toslink Digital HDMI - - 96kHz/16bit ARC (2 channel) Analogue (set to line level) - - 300mV/18kΩ Analogue (set to phono MM) - - 2.6mV/47kΩ (RIAA Equalised) Subwoofer output - - 1.20V (0-300Hz)
- - v4.1 Low Energy
825 x 320 x 290mm (32.5 x 12.6 x 11.4in)incl. spikes & stabiliser
- -
40 x 180 x 112mm (1.6 x 7.1 x 4.4in)
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We reserve the right to change the designs and specications without notice.
Our policy is one of continuous product improvement.
Google and Chromecast built-in are trademarks of Google LLC.
Amazon, Alexa and all related logos are trademarks of Amazon.com, Inc. or its afliates.
Apple, AirPlay, are trademarks of Apple Inc., registered in the U.S. and other countries.
The Bluetooth® word mark and logo are registered trademarks owned by Bluetooth SIG, Inc. and use of such marks by Armour Home Electronics Limited is under license.
The term HDMI and HDMI High-Denition Multimedia Interface, and the HDMI Logo are trademarks or
registered trademarks of HDMI Licensing LLC in the United States and other countries.
Issue 5
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