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XL-02 Towers These high-performance tower speakers are very easy to build since no carpentry or soldering is required. The cabinets are precision-made and finished from 25mm medium density fibreboard (MDF). Virtually all you have to do is to install the speakers and the crossover network and fit the base panel. T and with aluminium formers, giving a quoted peak power ower speakers are certainly popular and they have handling spec of 1000W for a 10ms tone burst. a number of advantages in today’s homes and home The woofers are also magnetically shielded, by virtue of units. their double magnets and speaker basket construction. Because of their slim design, they occupy little floor The tweeter is a soft dome combined with a shallow space and even though they are tall, they do not dominate horn and the voice coil is ferro-fluid cooled for high power smaller rooms. And because of their height, their drivers operation. In fact the tweeter has a nominal power rating are at about ear level for most people when they are seated. of 200W (for high frequencies). Note that the tweeter is not These tower models from Delta Loudspeakers each emmagnetically shielded. ploy two 6.5-inch drivers to handle the bass and midrange Fig.1 shows the crossover network which is drawn in two while the 28mm dome tweeter handles frequencies above sections to reflect the way 3.5kHz. Specifications in which it is wired across The tweeter is mounted the four terminal panel on between the two midrange/ the rear of the speaker. bass drivers in the so-called Frequency response ............38Hz to 18kHz within ±2.2dB The two pairs of termiD’Appolito configuration,            (1/3 octave smoothed) nals are normally strapped often used in tower speakNominal impedance.............7.5W (see impedance curve) in parallel for connection to ers, and reputed to give Sensitivity............................93dB/1W <at>1m an amplifier but they may improved stereo imaging for Power handling....................200W separated for bi-amping, if seated listeners. desired. Both the woofers and Crossover frequency............3.5kHz Both bass and treble sectweeter are sourced from Crossover slope...................6dB/octave tions of the crossover have the Israeli manufacturer Dimensions..........................212 x 1235 x 215mm a 6dB/octave slope above Morel. The woofers are Mo           (not including 260mm square base) (or below) the nominal rel MW168H drivers with Weight.................................39.5kg each crossover frequency of huge voice coils – no less 3.5kHz and both feature than 73mm in diameter – Design by Michael Gayler 80  Silicon Chip siliconchip.com.au siliconchip.com.au November 2005  81 UPPER C1 + 6.8 µF 250V UPPER 5.6 Ω 5W R1 2.2 µF 250V C2 – LOWER TWEETER – + MOREL DMS371 L1 + 0.33mH LOWER – 15 Ω 5W R2 4.7 µF 100V C3 WOOFER 1 WOOFER 2 + + – – MOREL MW168H MOREL MW168H Fig.1: there are actually two crossovers – normally they are in parallel but they may separated for bi-amping. The crossover network is wired onto the back of the speaker terminal panel. The air-cored inductor is installed inside the cabinet. This pre-production sample has soldered connections to the speaker wires. Production versions have spade connectors. impedance equalisation by virtue of the RC network across each driver. Both woofers are connected in parallel, which is best for optimum damping effect from the driving amplifier. It also has the apparent effect of increasing the sensitivity by 3dB, by dint of the doubling of power for a given signal level from the amplifier. Perhaps the most unusual feature of these tower speakers is the arrangement of the venting in what is a bass reflex system. Instead of having a relatively small diameter port on the front baffle, these speaker cabinets are raised off their base panels by about 30mm on four metal pillars. This allows the bass reflex port to radiate with less air velocity, meaning no tendency to “chuffing” or rattling of the grille cloth. The downward facing bass reflex port is quite large. In fact, at 10cm in diameter, it is the largest bass port we have ever seen. The combination of the two very rugged but compact bass/midrange drivers and high performance with a well- designed crossover network makes for a highly rated speaker system which will give very satisfying performance in a stereo setup or as part of a great home theatre sound system when combined with other speakers in the Delta range. Power handling is quoted as 200 watts and this relates to normal music signals from a 200W per channel stereo amplifier. Combined with a sensitivity of 93dB/1W/1m, this means that these speakers can deliver very high sound levels. In practice, it can be teamed with amplifiers from 40 watts per channel to deliver highly satisfactory performance in most rooms. Our listening tests confirmed the very wide response of the XL-02s and they have a slight prominence in the midrange which tends to give a little extra “presence” – good for voice and brass instruments. Bass is smooth and extended, although Delta Audio also recommend the use of their subwoofer to augment bass frequencies below 40Hz. Fig.2 shows two curves which demonstrate the high performance of the Delta XL-02 tower loudspeakers. At top Fig.2: this diagram shows both the on-axis frequency response for the Delta XL-02 speakers (top) and the overall impedance curve (lower). Note the very smooth response, without any major peaks or troughs. This photo shows the very large port in the base of the enclosure. At 100mm it is one of the largest ports you are ever likely to (not) see. It faces down onto the base and since it is so large and unrestricted, it will not be subject to chuffing or frequency-doubling effects. 82  Silicon Chip siliconchip.com.au This side view of the Morel MW168H midrange/woofer clearly shows the very large blue aluminium voice coil former. That and the rugged suspension assure very high power handling. The woofer itself might look a bit small but it is a standard 6-inch driver; we should not have used such a big hand to hold it! is on-axis frequency response from 20Hz to 20kHz. As can be seen, the overall response is very smooth from below 50Hz to 18kHz, with no apparent peaks or troughs within that range. This agrees substantially with listening tests although in practice, the bass response in typical rooms appears even more extended, to below 40Hz than in the published curve. This accords with the manufacturer’s claimed response of 38Hz to 18kHz within ±2dB, using one-third octave smoothing. The lower curve of Fig.2 is the speaker impedance and as can be seen, it exhibits the classic double peaks of a bass reflex enclosure. In this case though, the two peaks are quite modest and nor are there any dips which would cause some amplifiers to misbehave. Speaker kits The Delta XL-02 oozes “class” – even down to the deeprouted DELTA logo at the base. Also in this photo you can clearly see the slightly oversize base and the speaker stand-offs. These are not just for show – as explained in the text (and photographed at left) the oversize ports aim down from the speaker boxes with air movement allowed by the space between the bottom of the box and the base. siliconchip.com.au These XL-02 tower speakers are very easy to put together since no carpentry or soldering is required. Literally the only tools you will require are a hammer, Phillips screwdriver and an Allen key. The enclosures are supplied fully assembled (apart from the base plate and grille cloth frame. They are also lined with acoustic wadding and have the crossover inductor and port already installed. Virtually all you have to do is to install the speakers, grille cloth frame and base plate. The accompanying photos tell the story and you can probably comfortably assemble a pair of speakers in an evening. Delta Audio loudspeaker systems are available only from www.kitaudio.com Log on to find full details of all Delta Audio loudspeakers. November 2005  83 Constructing the Delta Audio XL-02 Tower Speakers 1 Check to ensure that all components are included, according to the parts list shown on page 84. You will also need the following tools: Phillips head screwdriver, Allen key, hammer, scissors and a 1.5V battery for speaker polarity checking. 4 Place the small end of the female socket into the holes on the front of the cabinet. Carefully tap the sockets into the holes with a hammer until the bottom is flush with the front face of the cabinet. Before placing the drivers, foam must be fitted to ensure that no air can escape around the drivers. Apply foam tape to the driver cut outs at the front of the cabinets, as close to the edge as possible. 3 Place all cables connected to the terminal plate into the cabinet, then secure terminal plate to the cabinet with the four small screws provided. 84  Silicon Chip Pull the driver cable out through the driver cutout. Push the spade lug on the cable with a line down the front onto the “+” speaker terminal and then attach the other wire to the “–” terminal of the same driver. Place the driver in the cutout and carefully push down on the driver edges until it is properly in place. Repeat this step with the second driver. 5 2 Pull wire through from the inductor inside the cabinet (it has already been installed at manufacture) through the terminal hole. Connect the male and female connectors to the input terminal plate. 7 8 Pull the tweeter cable out of the cabinet and once again, locate the cable end with a line down the front. Push its spade lug onto the “+” driver and then attach the other wire to the “–” terminal of the same tweeter. Place the tweeter in the cut out and carefully push down touching only the edges until the tweeter is properly in place. 6 When installing the foam for the tweeter, ensure that you place it on the inside of the cutout. 9 Screw in all three drivers with the provided screws. Be very cautious not to slip; at this stage the drivers are very fragile. siliconchip.com.au 10 Briefly touch a 1.5V battery across the input terminals while watching the driver cones. The drivers should move in the same direction. If the drivers move in opposite directions, the connection to one or more drivers has been reversed and will need to be corrected. Parts List – Delta Audio XL-02 Tower Speakers* 2 XL-02 Cabinets – with wadding 8 Steel stand offs 2 Bases 2 Crossovers (with attached terminal plates) 2 Grilles with male clips attached 8 Base mounting screws 2 Metres of foam tape 8 Grille clips – female 4 Drivers 2 Tweeters * These are the contents of the XL-02 Tower Speaker pack from KitAudio, who are licenced to sell Delta Audio products 13 11 Turn the cabinets upside down so that you are facing the base. Place the four steel stand-offs in the outer corners of the cabinet so that they surround the predrilled holes. 12 Turn the speakers up the other way, connect your amplifier, wind up the wick . . . and enjoy! Where from, how much: Locate the base onto the top of the steel stand offs so that it sits flush. The base has predrilled holes to allow for the steel standoffs to fit snuggly. Insert the four long screws through the holes and standoffs into the cabinet and tighten with an Allen key. siliconchip.com.au Delta XL-02 towers and other speakers in the Delta range are available exclusively from www.kitaudio.com Three options are available:   Fully assembled ...................................................$1999.00 pair    Kit with fully assembled cabinets...........................$1699.00 pair    Kit without cabinets...............................................$1199.00 pair November 2005  85