TQ-440SP Test Report (Reprinted from Prosound, April 2000) "The Turbosound speaker sets the sound free within the room with a pleasant quality which makes you forget the attendant technology."     Turbosound's Three Ways By Dirk Wedell A full range or PA mid-high section is a two-way speaker. Why? Because it is, it always has been and it is right that it is so. So there's no more to be said on the matter. At last a clear, unambiguous position on the subject. But we're not quite finished with the topic. Altogether we haven't had all that many three-way speakers to test. All those tested have done well, although sound advantages have had a decisive impact on the test results. A prominent example was in edition No.2 / 97 - Martin Audio's W3P - which in terms of audio impression simply performed better than the other two-way systems. Current representatives of the three-way family are speakers equipped with a BMS coaxial driver. We've listened to one of these speakers and were very satisfied with the sound, although the manufacturers are still having to work on a small problem with frequency behaviour. So the 2-way/3-way debate is far from concluded. The new speaker from Turbosound First of all, just a small observation on Turbosound. The English company has undergone (how shall we put it?) a root and branch renewal, also in terms of new products. The TQ-440SP is an active three-way system. The speaker has as components a 12" cone loudspeaker, a 6.5" mid-frequency driver and a 1" high-frequency driver. In order to make the phase response as inconspicuous as possible, in two places developments have been made which are very unconventional. The 12" cone and the 6.5" cones are physically time aligned with the mid-frequency horn to equalise distance and to eliminate phase jumps. Internal mid-frequency horn delays are equalised also by means of a phase plug. You can't see the high-frequency speaker even when removing the front grille. It is positioned within what is termed a "dual concentric" coaxial construction under the sound-transparent dust cup. This manner of construction also demonstrates the particular importance placed on the phase response. Firstly bass and treble are emitted from one point on the common axis, and secondly the high-frequency speaker is so far back in the loudspeaker that time delay differences are not noticeable. The problems listed in the section "Advantages / Disadvantages" have been very much in the minds of the developers, and the manner of construction shows how they have got round and solved phase problems. The birch plywood enclosure (black, semi-matt paint) of the speaker has a trapezoidal basic shape with a rounded front. Such a design is an aspect which should not be underestimated with the demanding clientele targeted by the speaker. The speaker has two recessed carrying handles and an integral pole mount. The front grille is secure and covered with reticulated foam. The rounded front makes the grille even more secure, but whether you would particularly want to install such a high-quality system in a sports hall with balls flying around is a different question … No matter. Flying equipment There are several variations for flying the speaker. In the side panels under the recessed handles are found key-hole fly points on the centre of gravity on each side. There are in addition rigging points at the top and bottom ends of the side panels and in the top and base of the speaker. Steel flying strips and flybars are obtainable for fitting into these rigging points. The flying equipment which is an optional extra from Turbosound has one thing in common. The force created by the weight of the speakers suspended underneath each other is transferred always from one flybar to the next and never from speaker to speaker. This means that you can suspend virtually as many speakers as you like underneath each other, without bringing any pressure to bear on even part of the wooden surface. You can of course use simple eyebolts to suspend individual speakers. A T-bar (T for television) is also available. If using the optionally available FB-58 Flybar from Turbosound for assembling an array of speakers, the number and inclination of speakers suspended in groups next to each other can be freely configured. This is because the flybar can be added to in a modular fashion both on the right and left, and the inclination angles are continuously adjustable. If you need a complete flying frame with you can obtain these from Thomas Frame. The amplifiers exemplify the technology of these active speakers. Two are installed, one amplifier with 250W for the low-frequency speaker and one with 160W for the mid- and high-frequency section. The amplifiers are convection cooled and have therefore no fans which create noise. This makes the speakers suitable for use in theatres very close to the audience. Buzzing and hissing are extremely slight. The signal input is an XLR connector, the power supply is fed via Neutrik Powercon. The XLR connector has a parallel link-connector for further connection to other speakers; the power supply for some illogical reason doesn't. The TQ-440SP is equipped with a music/speech switch. Sound We set up this speaker in our hall without a subwoofer. We synthesised a normal audio output on the MediaMatrix which only had a conventional high pass filter at different frequencies. Since the speaker is supposed to work free of any sort of predetermined audio surroundings (without processor or other parameters) no correction of distortion was programmed. The first impression on listening to music on CDs was the homogeneity and compactness of the sound. As with a good studio monitor, it is not possible to "fix upon" in aural terms any transitions or even jumps between the frequency bands. I write "fix upon" in inverted commas because there isn't a word for it. Whenever you think this is where the treble begins and the mid-range ends, another instrument or a different vocal register appears, and the impression is postponed. The audio structure of the speaker does not predetermine anything. Aural impressions do not come from the speaker but from the musical material itself. Indeed, the TQ-440SP is one of those speakers which make it hard for a tester trying to do his job and to earn his crust by doing what he is supposed to do, because without intending it you keep listening to the music and to a lesser extent to the speaker. The Turbosound speaker sets the sound free within the room with a pleasant quality which makes you forget the attendant technology. This is how a speaker of this class should sound, and only because of this neutrality is this speaker suited to all musical styles and directions. If you take the TQ-440 as the first representative of the new Turbosound company and product philosophy, then what is demonstrated is undoubtedly a new way in objective development which is not exclusively characterised by the personal preferences of the developer. The price of the TQ-440SP as given by the distributors ProAudio Marketing is DM 7,350. Advantages / Disadvantages Two-way advantages A simple construction (one consequence of which is good value for the customer). Only one transition between the two neighbouring frequency bands (which means that the ranges not disrupted by dividing frequencies are very large: 100Hz-2kHz and 2kHz up to upper roll off are usual). Possible distortions caused by each frequency division are irregular phase response, irregular frequency response off axis, occurring mostly when the axial frequency response is smooth. Two-way disadvantages Primarily the higher frequency range from 2kHz to the furthest limit for 1" drivers and 1kHz upwards for 2" drivers is too large. All these drivers function with partial vibrations. A 1" driver hasn't in reality any fewer partial vibrations as its 2" counterpart. A second, essentially suppressed form of distortion are double-distortions occurring when a higher-frequency distortion rides on a lower one. Both forms of distortion, partial or double, are promoted by large frequency ranges transmitted from a single source. Three-way advantages The sound of a high-frequency speaker with its feather-light membrane is finer, more transparent and more natural. The sound of the mid-frequency speaker is often very good because this transducer has either been specially selected for this frequency range or specifically developed for this range by firms which also produce chassis speakers. A transducer specifically developed as a mid-frequency speaker does not have to be raised with brutal DSP force to 18kHz. One should always bear in mind in such considerations, however, that the 12" which is working at the lower level remains neutral (often it is also one or two 8" or 10" drivers), because in the end it always needs to be raised as high as the 2 or 3 way system installed above it demands. Three-way disadvantages An additional transition frequency somewhere around 4-8 kHz may lead to difficulties with the phase and frequency response off axis. These points must be dealt with very carefully in the development stage, thus incurring costs which have to be borne in the end by the customer. A high-frequency speaker can sustain neither thermal nor mechanical loads. The desire to make it more resistant in these areas would lead to a much heavier system thus reducing its advantages. Only very precise and reliable forms of protection provide a remedy, but these must initially be developed at a cost. The passive crossover is more extensive and complex. Since it must work very precisely, even obtaining the individual components is somewhat more expensive. There are users who also want to use actively each way individually when using a three-way system. There are of course considerably higher costs for these users. Moreover, a high-frequency speaker has to be set at the processor with quite different (dynamic) parameters than a 1" or 2" compression driver. On account of the scarcity of high-frequency speakers in PA technology these are not generally known. Illustrations Diagram 1: Frequency response at 0 degrees and 30 degrees off axis Diagram 2: The effect of the speech/music filter The speaker demonstrates an even, rapid outward vibration. In the high-frequency range one can see both in the waterfall effect and in the wave-let analysis the somewhat broad-band reflections on the cone membrane; there are no narrow-band side-wall reflections as is usual with horns. Diagram 3: Waterfall analysis Diagram 4: Wavelet analysis Click here to download a pdf version of this article. Back to top of page