DSP-controlled Tannoy array with high-end technology

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1 PROFESSIONAL system Das Magazin für AV-Systemintegration und Digital Signage TEST REPORT FROM Qflex DSP-controlled Tannoy array with high-end technology Established 83 years ago, the Tannoy name has long since become a by-word for high quality P.A. and home entertainment loudspeakers. In addition to studio monitors and home hi-fi speakers with their renowned Dual Concentric(tm) driver, the company located near Glasgow in Scotland also produces a comprehensive range of installation loudspeakers. These range from in-ceiling speakers to twin 18" subwoofers together with dedicated power amplifiers and controllers. Qflex is the most recent addition to their professional installation range, with a Qflex 32 provided by Tannoy Germany being the focus of this review. True to their tradition of producing superior studio monitors Tannoy have chosen two and three way design concepts for the Qflex series depending on array extension. In addition to the usual acoustic and technical advantages of multi-way systems compared to simple wide band loudspeakers, the design also minimises unwanted lobing which is a specific problem when considering an array s dispersion characteristics. Typical Qflex applications are large and acoustically difficult spaces with strong reverberation such as houses of worship, airport lounges, train stations, shopping malls, museums and other public buildings. Since these are often historically important or architecturally sophisticated, loudspeakers should provide for easy, unobtrusive integration. In many cases the sound system is also used for emergency paging requiring additional features, e.g. a minimum speech intelligibility (STI > 0.5) and full loudspeaker/system monitoring capabilities. In short, Qflex can be used wherever room acoustics are demanding and safety is a major issue. As a rule of thumb, the array size must be relative to the acoustic environment, i.e. larger and more reverberant rooms require larger arrays to achieve the desired results due to their dispersion characteristics. While a 1m array should Ill. 1: Qflex 32 frequency response, red = basic setting 1, blue = with EQ 1 see text for details Ill. 2: Qflex 32 phase response, basic setting 1

2 Ill. 3: Qflex 32 maximum SPL at 3% (blue) and 10% maximum THD (red). The dip at 165Hz 2 results from the limiters 2 see text for details QFLEX-Varianten provide appropriate results in a small church that has a reverberation time of 2s, an array of twice the length or larger would have to be recommended for cathedrals with reverberation times of 5s or more. Qflex Components Taking these factors into account, Tannoy decided on a modular approach for the Qflex system. Arrays from 75cm to 300cm lengths can be assembled from two different loudspeaker types (Qflex 8 and Qflex 16) which are both available as master or slave models. The master of an array provides the network and audio connections feeding the slaves of the array. As can be guessed from the model designations, the Qflex 16 features sixteen discrete channels of amplification and DSP, while the Qflex 8 features eight. Looking in a bit more detail, we find the Qflex 16 is equipped with eight 4" low/mid and eight 1" high frequency drivers while the Qflex 8 houses just eight 4" low frequency drivers. Intended as a low frequency extension for larger array configurations, the Qflex 8 may also be used as a stand alone unit for frequencies up to 4KHz. The illustration above is from the dedicated software showing the possible combinations that can be assembled from the two basic models. Since the use of a single Qflex 8 might be considered a limited solution only, the Qflex 16 should be regarded as the typical base unit. When extended with a Qflex 8 as low frequency section it becomes a Qflex 24. Two Qflex 16 assembled with their high frequency units in the centre result in the Qflex 32 reviewed here. This can be extended further by one or two low frequency units turning it into a Qflex 40 or 48 respectively. The model number always refers to the number of loudspeakers/channels employed in the model. Unlike some other systems Qflex has its acoustic centre dead in the high frequency line due to its design principles. This must be considered during installation since it cannot be shifted in any way. Also, orientation is predetermined, i.e. there are no provisions for upside down installation. Both should be of no concern to the user since the QFlex software automatically provides optimum settings. Care must be taken, however, to prevent total or partial obstruction of the loudspeaker by room fittings or the audience more on that later in the software part of this review. Drivers and Electronics The loudspeakers used in the QFlex 8 are 4" drivers, while the QFlex 16 uses 3" drivers and 1" domes. Hardcore Tannoy fans might wonder why the Dual Concentric principle, although omnipresent at Tannoy, has not been put to use here. The explanation is simple: since the acoustic centers of the relatively large coaxial drivers would be too far apart from each other this would at a very early stage result in unwanted lobing at the low frequencies. It was therefore decided to use three different, newly developed drivers with 4", 3", and 1" cones. These drivers have been designed for high power handling and dense mounting, the finite element analysis and a Klippel analyser were used as technical aids. The resulting cone drivers feature neodymium magnets and under-hung voice coils for large excursion and minimum distortion. The tweeters presented even more of a challenge since the distance from each other had to be as small as possible, i.e. the tweeters had to be as small as possible while, at the same instance, a low crossover frequency with acceptable power handling was required. The resulting unit features eight 1" domes with a 30mm distance between their centers. Of course, the latter could only be realized with neodymium magnets. To achieve the desired power handling the eight neodymium magnets are connected with a common heat sink for improved thermal dissipation. The domes are coupled to the baffle via small waveguides matching on the horizontal plane the dispersion characteristics to those of the low/mid drivers while increasing sensitivity as well. All of the eight tweeters are mechanically integrated into a rigid unit which can be seen clearly in photo 2. The number of class D amplifier channels in the QFlex modules is 8 and 16 respectively with each amplifier capable of providing a maximum power of 100W. All the amplifiers of a QFlex unit are powered from a switching supply integrated into the cabinet. The power supply (see photo 4) has been designed to accept all mains voltages from 100 to 230V at 50-60Hz. The average power consumption of the units at full output fed with a 12dB crest factor signal ranges from 220W (QFlex 8) to 1.000W (QFlex 48). The core of the QFlex is a third generation Sharc DSP performing all signal processing functions at a 96kHz sample rate as well as the logging, control, and protection functions. Photo 3 provides a view of the electronics with the connection panel on top, and the DSP and DAC boards located underneath. High quality 4- channel BurrBrown PCM4104DACs are used for DA conversion (4 chips in the centre of the photo). 2

3 Ill. 6: EQ and delay settings of the Tannoy V-Net software on a PC. Ill. 4: Horizontal directivity of the QFlex 32. The nominal coverage angle is specified at 120. At 2kHz, a small interference dip can be seen resulting from the mid to high frequency driver crossover. Ill. 7: Protection circuit properties and log diagrams of the Tannoy V-Net software on a PC. Ill. 5: Vertical directivity of the QFlex 32. Coverage was set to a beam spread of 7 with a 0 downward angle. Connection and Networking The connection panel of the QFlex master module provides a mains inlet, two analog audio inputs, and an optional digital input in the AES/EBU format. The analog inputs are on Phoenix connectors with link outputs. VNet is connected via an RJ45 network connector also featuring a link facility. VNet uses the RS-485 format and is easily linked from cabinet to cabinet via conventional Cat. 5 cables. A Tannoy USB-to-VNet interface is required for PC connection, with the maximum possible cable length being 1200m (without using an ethernet repeater). Master to slave connections are made during installation and hidden from view thereafter, the master being the contact for the array assembly. Two additional connections for mode and status provide easy switching between two modes of operation and monitoring of the array. Both modes can be preprogrammed via the software, e.g. in normal operation the input A signal is reproduced, and an EQ setting for music is applied. Switching to emergency paging assigns priority to input B, and the EQ changes to a strong and highly intelligible speech reproduction setting. The operation of the complete array can be checked via the status relay, and fault messages can be triggered if necessary. A powerful blue LED located behind the QFlex front grille lights up whenever there is a fault condition in a module, or when the software search function is activated to locate a module. Ill. 8: Steering file selection and level setting of the Tannoy V-Net software on a PC. Ill. 9: Beam steering setting for horizontal directivity measuring. The speaker was placed upright on a turntable while the beam was aligned with the measuring microphone on the reverberant floor 6m away. 3

4 BESCHALLUNG TEST LAUTSPRECHERZEILEN Ill. 10: Measurement of a 41 downward angle 8 beam. Ill. 11: Measurement of a 32 downward angle beam. ally, with the help of a download from the Tannoy page or the included installation CD and caused no problems at all for this review. Ill. 12: Measurement of a 20 downward angle beam. The VNet software lists every Tannoy loudspeaker found in the network and provides a selection facility. Here, the master module and the accompanying slaves of a QFlex system are indicated. Clicking a module opens a small control window showing amplifier, power supply, and driver status of the module as well as the current levels at both inputs and possible limiter activity. There is a gain control and a mute switch for the master module only which operate on the connected slaves as well. The system is fully operated from the master module, only the status functions of all the modules are shown individually facilitating the location of a module with a fault condition. Changing over to the master module display there are the EQ/delay, setup, and properties/options windows shown in illustrations 6, 7, and 8. Operation is intuitive, and there is hardly any need for instructions. After calculation by the QFlex software, the desired steering file for the system is loaded in the setup window. Ill. 13: Measurement of a 7 downward angle beam. The QFlex software automatically calculates the optimum settings of a preselected QFlex loudspeaker for one or several listening areas as well as quiet zones. The result is shown as level distribution within the room and on the areas in octave bands, or predefined frequency ranges. After calculation, which takes only a few seconds even on slightly dated PCs, the corresponding settings for the loudspeaker s DSP system can be saved. Also, the QFlex software can directly export ASCII files with the loudspeaker s balloon data in the EASE XHN or any CATT Acoustic compatible format, export in the CLF format is not possible...yet. When using these files in EASE or CATT simulations, one must be aware that they are valid in the loudspeaker s farfield only and do not contain any phase information. In the future, the possibility to generate EASE GLL files for the QFlex series would be welcome. These could be used to precisely calculate nearfield and farfield directivity including phase information from the data and filter settings of the individual system loudspeakers. QFlex and VNet Software The QFlex PC software currently consists of two parts, the VNet software in version , and the QFlex beaming software. The latter calculates and optimizes filtering and delay for the desired directivity, and saves the settings in a steering file. The Matlab-based beaming software requires the Matlab runtime library version 77 for installation and use of the current version b1. Also, the obligatory driver is needed for the USBto-RS485 interface. This may sound complicated but is quite easy, actu- Measuring For the measurements, a QFlex 32 was installed in an anechoic room, and a relatively narrow beam with a 0 vertical angle was set to radiate from the centre of the QFlex unit. The frequency response in fig. 1 was measured at a distance of 4m. The red curve shows the response with a neutral EQ setting making it evident that the array has been originally designed for a linear frequency response without the need of user intervention. The blue curve represents a variation with minor EQ cor- 4

5 Ill. 14: Setting for two beams with +7 and 15 angles. Ill. 15: Directivity measurement of two beams with +7 and 15 angles. A QFlex 32 on the turntable in the anechoic measuring room ready for directivity measuring rections. With the exception of a narrow dip at 24.2kHz the result of the tweeter measuring is strikingly impressive showing a smooth uniform response without the interference of partial oscillation and other parasitic effects. Take note that unlike in common plots the frequency axis of the diagram extends to 40kHz. Taking the 6dB corner frequencies as a base in contrast to the average between 100Hz and 10kHz the QFlex 32 has a frequency response of 150Hz 20kHz. The accompanying phase response in fig. 2 shows 360 phase angle rotation at the crossover frequency of approx. 2kHz and at the end of the frequency band due to highpass filtering. As usual, 185ms sine bursts were used for the maximum SPL measuring. The values at a distance of 1m and 3% and 10% maximum THD in fig. 3 were gained from calculation. Above 300Hz both curvers converge indicating that the 3% value was not exceeded before limiting. In general, the QFlex 32 limiters proved to be very conservative with early action taking precedence thus reducing the tweeter levels above 2kHz significantly during the 185ms bursts. Also, sudden limiting occured at 165Hz and remained inexplicable throughout various measurements with varying parameters. With this measuring method, the QFlex 32 achieves a calculated maximum SPL of 120dB at 1m. With shorter impulses or speech and music signals without limiting the value might increase by 6-10dB. Without further details, the technical data specify 100dB at 30m equalling 129dB calculated for a distance of 1m. This is easily verified using the QFlex software. Directivity Array directivity on the horizontal plane is independent of the beam settings and identical to that of a single system unit. In that sense the QFlex is a small 2-way sytem with a crossover frequency of 2kHz and a side-by-side arrangement of the low frequency driver and tweeter. For measuring, the QFlex was placed upright on a turntable (see photo 1), and the beam was vertically aligned with the measuring microphone on the floor 6m away (fig. 9). This approach was necessary since the anechoic half space measuring room requires microphone 5

6 BESCHALLUNG TEST LAUTSPRECHERZEILEN Tweeter Array with small waveguides and 3" mid-low chassis in the QFlex placement on the floor, and because the acoustic centre of the 1.39m tall QFlex is the geometric centre as well. For the vertical measurements the cabinet was simply placed on the side and aimed at the microphone. Fig. 4 shows the horizontal directivity of the QFlex which is the same for all the 2-way models and variants. Minor deviations might result if the QFlex 8 is added as low fequency extension. The 6dB isobars show an average beam spread of approx. 120 at the transition from yellow to green as specified in the technical data. The small asymmetric dip at 2kHz results from the crossover between the low frequency QFlex electronics with connection panel, DSP and DAC- section plus amp board. For DA conversion high class 4 channel BurrBrown PCM4101 DACs (four chips in the middle of the picture)are used. 6

7 Prices Model Price (Eur) QFlex 8 (8 4") 840 mm ; 15,25 kg 3.570,00 QFlex 16 (8 3" + 8 1") 744 mm ; 14,25 kg 5.057,50 QFlex 24 (8 4" + 8 3" + 8 1") mm ; 26,25 kg 8.627,50 QFlex 32 (16 3" ") mm ; 25,25 kg ,00 QFlex 40 (8 4" " ") mm ; 38,5 kg ,00 QFlex 48 (16 4" " ") mm ; 51,5 kg ,00 Cabinet (all models) 171mm width, 150mm depth Understandably, precise statements on vertical directivity cannot be made although the actual dispersion can be checked against settings. Fig. 5 shows what can be accomplished with an array of the given length. At first, beam spread was set to 7 with 0 vertical angle. Unsurprisingly, the isobar diagram is sharp as a needle. It is really impressive, however, that there are essentially no side lobes up to the highest frequencies. The few blue foothills are 12dB or more below the value on the center axis illustrating the huge advantage of a 2-way configuration with separate tweeter array. Fig show further measurements on the vertical plane with various beam spreads and tilt angles. Again, the results are highly impressive. Very large tilt angles cause small side lobes on the 0 axis, but these occur above 8kHz only. Diagrams of the frequency response on the main axis at various settings have not been included. While many similar loudspeakers require EQing of the central radiation direction depending on the beam setting the QFlex does not. It immediately provides uniform response since its beaming filters also set the appropriate EQ as well, and a measuring system is not necessarily needed for correction during installation. Fig. 14 and 15 show a deliberately chosen extreme with two beams at +7 and 15. Precise separation is possible only above approx. 3kHz since the unit reaches its limit at the lower frequencies due to its restricted length. However, even in this case the settings were calculated correctly and adhered to. Photo 4: The switching power supply of a QFlex unit. drivers and tweeters. Increasing convergence is evident above 6.3kHz since the effect of the waveguide starts to diminish while the tweeters begin to converge themselves due to their diaphragm expanse. Conclusion In recent years, Tannoy have extended their product portfolio into all areas of loudspeaker technology, including high-end consumer systems, studio monitors, PA and installation loudspeakers. Now they have added the DSP controlled QFlex arrays to their range. QFlex arrays have been designed as modular 2 and 3-way systems with lengths from 75cm up to 3m intended for high quality sound reproduction in acoustically difficult environments. After extensive testing and measuring it is safe to say that remaining true to their high standards, Tannoy have come up with a true high-end array loudspeaker system. The 2-way concept featuring a dedicated high frequency array has strong advantages absolutely clean reproduction without annoying side lobes, the software is operated easily and intuitively producing immediately usable settings, and the loudspeaker meets the highest demands on tone. Attention has been paid to the remote control and monitoring facilities which are so important in practice, and without which an installation system is unthinkable today where safety is of major relevance. Qflex pricing structure reflects its position in the upper end of the market but fully justified considering performance and quality. Review and measuring: Anselm Goertz Photos: Dieter Stork and Anselm Goertz 7