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TQ-440SP Test Report (Reprinted from Production Partner, February 2000)
"The 6.5" mid frequency system is very successful. Indeed, it offers tangible advantages, particularly with respect to distortion values, when compared with a 2" driver." At the end of 1999 Turbosound launched the TQ-440SP, a newly developed compact active speaker system. This offers simple solutions as a universal loudspeaker with many applications. The following test on the first series of the product sets out to demonstrate the sound and technical qualities of this speaker which - at a price of around DM 8,000 - is located in the high-end class of loudspeakers. Nearly all manufacturers are busy within the compact class of loudspeaker. The generally classical 12"/2" combinations are mostly available either as an active or passive system with a front loaded low frequency (bass) speaker in a very compact enclosure. This allows them to be used as full range systems or, if necessary, to be enhanced with a subwoofer. They can be set up to run as individual systems or can be used to make small clusters or can be used as side fill or front fill. These loudspeakers are always much sought after, and there is particularly large demand for them amongst rental companies. Besides this, there are innumerable applications for them in installations and in congress halls, theatres or sports halls. As a result of their high quality components and professional design, these loudspeakers move in the high-end class and are clearly different from the low cost models in the MI market. Naturally this is reflected in the individual price which exceeds DM 3,000. Typical examples of such speakers are the CT212 from KS, EAW's JF3000, HK-Audio's VT112, d&b's 1202 or GAE's 122T. Sometimes these loudspeakers can be used either actively or passively as chosen; in such an event they require an additional controller or controller amp. A few manufacturers also offer systems with, or exclusively with, onboard amplifiers. Meyer UPA or Duran T-2112 belong in this category. Turbosound gives its customers a free choice in offering the new product in both designs, with or without integral final amplifiers. Even without its own final amplifiers, active operation with an external controller is still provided for. The TQ-440 and TQ-440SP differ from most of their competitors in that the customary 2" high frequency speaker and 12" low frequency speaker combination has been replaced by a combination of a 6.5" mid frequency speaker with horn and a 1" high frequency driver mounted coaxially to the to the 12" chassis. The EAW KF300 has a similar arrangement in that the high frequency driver is mounted coaxially. For
and Against Self-Powered Loudspeakers Critics deduce for the most part that the disadvantages of greater weight and the threat of a higher interference level both have justification and need closer examination. What does this mean? With regard to the TQ-440SP which is the active self powered version the weight is 39kg, exactly 9kg heavier than the passive version. An external amplifier rack with two amplifiers and a controller supplying four TQ-440s would presumably be just as heavy as four modules at 9kg each. This weight is not too much for hanging points in the event the speakers are to be flown. With a fixed installation there is the additional issue of ease of servicing in the event that the electronics in the speaker are inaccessible. This is particularly critical with open air installations where the electronics are more sensitive to the damp than the loudspeaker driver is. The advantages and disadvantages of the different versions can certainly be listed in more detail. As a result of much discussion Turbosound has decided to offer the TQ-440 in both versions. Three-way,
bi-amplified (twin horned) To begin with, one cannot see the high frequency driver since it is mounted coaxially on the back of the 12" low frequency speaker. The French low frequency loudspeaker made by PHL has an integral high frequency horn, which forms part of the loudspeaker magnet assembly. At the front of the driver this horn is continued by the 12" loudspeaker cone. This apparently unusual solution has certain advantages. Tight beamwidth control is maintained by crossing the 1" driver over at such a high frequency and natural time alignment is achieved by mounting the high frequency driver in the same plane as the 6.5" driver. A further advantage is, of course, the front dimension of the speaker, which, being three-way and bi-amped, would otherwise have been noticeably bigger. The combination of mid and high frequency speakers as used in the TQ-440 and TQ-440SP is a new approach from the otherwise customary 2" driver on a horn arrangement so commonly used by most of the manufacturers. Turbosound claim that this arrangement results in significant distortion improvements in the mid frequency range and a better reproduction of the highest frequencies by a 1" driver. The separation of the mid high frequency combination to the low frequency speaker takes place in any case actively with Linkwitz Riley filters (24dB/octave) at 1300 Hz. When the TQ-440 is used with external amplifiers, Turbosound recommends that it is used with the LMS-D6 digital controller, which is manufactured for Turbosound by XTA. Low frequency (bass) section Figure
3: Impedance The 12" driver in the TQ-440 and TQ-440SP works in a small capacity, compact enclosure, part of which is occupied by the large mid frequency horn and the three drivers. This results in the need for a high level of equalisation. The bass reflex openings are neatly placed centrally on the longest sides of the front of the speaker. This means that the deepest natural frequencies of the enclosure are not emitted above their maximum stress level at the top and base. The tuning frequency is approx. 65Hz as can be seen from the impedance minimum in figure 3. To measure frequency response the low frequency was firstly measured individually at a distance of 2m. The two near sound field measurements were evaluated according to the root of their area ratio and then added to the far sound field measurement. That then allows the low frequency graph to be combined with the far sound field graph so that possible interference below these frequencies up to which the test room is anechoic no longer appear. The far sound field measurement provides the level and time reference. Figure
1: Sensitivity, 12" low frequency
driver For the measurements in figure 1 (sensitivity @ 1 watt, 1 metre) the combined frequency was set at 100Hz. The individual near sound field measurement of the tunnel is interesting here, showing as it does the effect of the resonator at low frequencies and an enclosure resonance at 700Hz. If the bass reflex tunnel were not centrally positioned, but placed at the upper or lower end of the longest enclosure side, then not only would the natural frequency of 700Hz be emitted, but also the deeper frequency at 350Hz. Above 1kHz further resonance appears which is partly dispersed via the tunnels and the diaphragm. The only really relevant resonance is at 700 Hz and at 1400 Hz, which is near the dividing frequency of 1.3kHz. Figure
4: disintegration spectrum, 12" low frequency
driver Even this can be categorised as harmless, where in the disintegration spectrum (fig 4) a rapid fading can be noted with the result that the chassis can be operated uncritically up to this frequency. The sensitivity of the PHL chassis increases strongly up to 250Hz and then runs clearly above the 100dB line; the driver being just right for such a speaker which depends on a good, dynamic low-mid reproduction. Less important is the bass region in which the sensitivity sinks to values of between 90 and 92dB. Seen in relation to this value, the lower frequency limit could be given as approx. 65Hz. Mid/high
frequency combination Figure
7: disintegration spectrum, 6.5" mid frequency
driver The disintegration spectrum in figure 7 also looks very good, having only some small resonant points. Although a typical 2" driver might, in comparison, turn out better in the region up to approx. 8kHz, typical problems of big diaphragms at high frequencies with partial vibrations do however appear most of the time - of these there as good as none here. Particularly impeccable is the successful integration of the mid and high frequency speakers in the phase relationship, as illustrated in figure 6. The pattern at high frequencies allowed no suspicion that two loudspeakers were here in play. Figure
6: phase relationship, mid and high frequency
drivers Electronics On the other side of the amplifier panel is the transformer and a large PCB board which houses both power amplifiers, the active frequency crossover along with some other filters, the limiters and usual safety switches. The two power stages are so designed as to be able to deliver a very high peak performance at the relevant impedance of 8 to 12 Ohms. Despite the compactness of the construction this is most possible since it can certainly be assumed that it will not be required to drive any low impedances. Filter frequency responses for both ways are shown in figure 9, although the settings "music" and "speech" also exist for the low frequency. The speech setting does not require the bass range to be raised and overall it emphasises the presence range of 3-4 dB, thus increasing the clarity of speech. Figure
9: filter frequency responses Enclosure
construction The enclosure measures 588mm by 409mm by 363mm with a weight of 39kg. There are of course further accessories such as flybars, T-bars, strips etc. as one would expect from an experienced manufacturer such as Turbosound. A pleasant surprise is provided by the documentation with detailed technical data, polar diagrams, isobar graphs and drawings of the enclosure and rigging equipment. On Turbosound's Homepage (www.turbosound.com) there is further information together with data records for simulation programmes. Measurements Figure
13: disintegration spectrum The disintegration spectrum of the TQ-440SP shows in the overall picture (figure 13) small resonance points already familiar from the individual measurements at 700Hz and 1.4Hz for the low frequency speaker and at 2kHz and 3kHz for the mid frequency speaker. Also noticeable here is the effect of filtering; here the overall bass range in contrast to figure 4 without filter is raised and from approx. 500Hz a delay arises through the filter. The same results are presented in a different form in the delay graph in figure 12. Figure
12: group delay Maximum
Level at low distortion However, what is noticeable in the TQ-440SP is that the curve in the graph is reached almost continuously with a harmonic distortion factor of 3%. The 10% curve is not, for the most part, different from the 3% curve, signifying that these values were not reached before the internal limiter prevented a further level increase. Therefore a third series of tests were then carried out, setting the distortion factor limit at an extremely low 1%. This value is otherwise only found in studio monitors. Even here the TQ-440SP demonstrated noticeable values clearly surpassing 120dB without any weak spots on the graph. One can thus conclude that although the low frequency driver breaks into low frequencies really early, the system does, however, work from 200 Hz very loudly and with minimal distortion. The mid/high frequency unit is capable of operating far above 6kHz giving a performance of a good 2" driver. Moreover, it achieves these values with a 3% harmonic distortion factor instead of the otherwise customary 10%. Directivity
Somewhat unusual is the leap at approx. 900Hz and the proceeding widening of the horizontal angle. Causes for this are likely to be found in bowing effects at the enclosure edges. The large mid frequency horn keeps very well to the nominal departure angle within its working range before again slight turbulence appears through the high frequency speaker. The departure angle at first widens a little here, only then to become very narrow at the highest frequencies. Here too an unsettled zone appears through the overlapping working range in the vertical plane. This is unavoidable and a result of the system; when a transition between two ways occurs at such a high frequency with a very short wave length. The narrow but forceful widening in the horizontal plane at 8kHz is a typical effect of the relative presentation of isobar graphs. Since all data is standardised to the corresponding value of 0 degree measurement i.e. on the central axis, a selective drop at 0 degrees in the isobar presentation can lead to the widening, even if this is under observation is not the case. The alternative absolute presentation of isobars is, however, not a practical alternative since it no longer allows a good reading of the directivity. Audio
Test The TQ-440SP moved to the real peak of its form with material containing voices; these were reproduced with uncommon dynamism and exactness. Here again it needs too be clearly stated that there is no question of a nasal or screeching quality to the reproduction. Small concessions had to be made, of course, in reproducing deep bass sound which this loudspeaker simply cannot deliver. Whoever requires this, however, will soon find assistance from Turbosound, when the self-powered 2x15" bass extension comes on the market. The level reserves of the TQ-440SP were similarly astonishingly large, and even when the limiter was activated the reproduction remained dynamic and accentuated. Conclusion Click here to download a pdf version of this article. |
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"The
TQ-440SP moved to the real peak of its form with material
containing voices; these were reproduced with uncommon
dynamism and exactness."
