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Ready-to-assemble, compact, high quality speakers – you decide the finish! M6 KIT LoudspeakerS Would you like to build some high quality speakers and don’t mind doing some enclosure assembly finishing? These M6 compact bass reflex systems from theloudspeakerkit.com could be just what you are looking for. Use them on stands or on a bookshelf. Design by Aaron Waplington* 34  Silicon Chip siliconchip.com.au T he speakers are based on a 6-inch woofer from Peerless Acoustic Engineering, teamed with a silk dome tweeter from Vifa in Denmark. Each kit has a pair of woofers and tweeters, with assembled 2-way crossover networks, plastic tuned ports, bonded acetate fibre (BAF) wadding and precision cut and routed panels of MDF (Medium density fibreboard) to make two enclosures. The two drivers are high quality units which are well matched in sensitivity and overall balance and will make a very good pair of speakers in an average-sized listening room, either as stereo pair or as the front speakers in a home theatre system. They can be used as bookshelf speakers or be mounted on stands which, like the kits themselves, are available from theloudspeakerkit.com In more detail, the woofer is a 165mm (6.5-inch) unit with low-loss synthetic rubber roll and a double magnet system to provide magnetic shielding. The tweeter is the Vifa D27TG4506, a 27mm silk dome unit with a ferrofluid-damped voice coil. It is not magnetically shielded. This means that you will not be able to use the finished speakers in close proximity to CRT video monitors. + 2.7Ω 8.2 µF – FROM AMPLIFIER L1 560 µH D27TG4506 TWEETER 18Ω + – – Fig.1: the crossover network has impedance equalisation for the woofer (22W + 6.8mF). Note the tweeter polarity: it is reversed, as shown in this diagram. 22Ω – 10 µF + L2 560 µH The 2-way crossover network provides attenuation slopes of 12db/ octave for both the woofer and tweeter. Crossover frequency is 2.5kHz. Both the inductors are air-cored, meaning that distortion due to any core saturation will not occur. The 8.2mF tweeter coupling capacitor is a polypropylene type while the woofer crossover capacitors are bipolar electrolytics. The circuit of the crossover is shown in Fig.1. As noted above, the finished cabinets are quite compact, measuring 440mm high, 200mm wide and 295mm deep. Rated frequency response is from SG-18 WOOFER 6.8 µF 40Hz to 20kHz at the –3dB points, as depicted in the graph of Fig.2. Efficiency is 88dB/1W<at>1m, while the recommended amplifier should be in the range from 20 to 100W per channel. Nominal power handling is stated as 90W, for music signals. The nominal system impedance is 8W and the impedance curve, as shown in Fig.3, is typical of a bass reflex system with the double hump at low frequencies. How do they perform? If you are used to listening to large tower speakers it will be quite a surprise to hear how much sound these The kits are supplied complete – enclosure panels, drivers, crossovers, ports, wadding . . . even screws. You need to supply some PVA glue and a Phillips-head screwdriver. siliconchip.com.au November 2006  35 The speaker enclosures (and crossovers) are designed around these specific speaker drivers – Vifa “silk dome” D27TG4506 tweeters and Peerless SG-18 woofers (one of each per enclosure). They are a good match for each other. M6 loudspeakers can deliver. They have an extended bass down to around 50Hz and midrange is quite smooth. At the high frequency end, the silk dome tweeter is very sweet and particularly good on strings. One point which should be mentioned about these kits is apparent in the photographs – they are not supplied with grille cloth frames. This may not be a problem in most households but if you have young children you will want to make sure they are well out of reach of little probing fingers or other implements! Apart from the kits are complete, right down the screws, gold-plated terminals and plastic tuning ports. You won’t need your soldering iron either, because all connections are push-on terminals. Oh, you will need some PVA glue and a screwdriver. The speaker kits are covered by a 7-year warranty and a 14-day money back guarantee. So a client can purchase a kit and then has 14 days to build the kit and listen to them. If they are not satisfied with their purchase then they will get a refund of their money. Assembly It is up to you to assemble and glue the panels together to make the boxes and then finish them in timber veneer, paint or whatever. We chose to glue all the panels together in one fell swoop. It is easier to do, provided you have sufficient clamps to do the job. The alternative, gluing panels together in sequence, means that you have top be absolutely sure that each 36  Silicon Chip panel is exactly at right angles to its neighbour; otherwise the panels will not fit. Once you have all panels clamped, wipe off any excess PVA glue while it is still wet. Once dry, it is virtually impossible to remove and you will have to sand any excess flat – which spoils the very smooth finish of the panels. We left the boxes to dry overnight. Then we used a special router bit to machine a 5mm radius on all the corners. This removes the very sharp edges on the panels and the end result looks better. This is of course optional. Finishing the enclosure. As noted on the LSK website, there are a number of different options for finishing your enclosures and this must be done before the drivers and crossovers are assembled into the boxes. We elected to paint our prototypes, using a high gloss, oil-based enamel. We started by using an all-purpose acrylic primer after having thoroughly sanded off all the rough edges. We also used an acrylic filler to fill the inevitable fine gaps in the joins between the panels. We used a 50mm brush to apply the primer and the finish coat. Big mistake. It is impossible to get rid of the entire brush stroke. We learnt by doing! After thoroughly sanding it all back, we then used a 50mm foam roller to apply the finish coat. This gives much better results and while you won’t get the glass-smooth finish that is attainable with a spray gun, it is much quicker and easier. The slightly dimpled finish from the foam roller is also better at hiding any surface blemishes. Make sure you do not get a paint build-up in the rebated holes for the tweeters otherwise they will not fit properly. Final assembly When your boxes have been painted, veneered or whatever, the end of the process involves assembling the crossover network and drivers into the box. First step – insert the plastic tuning vent into its hole in the baffle. Push it down hard to make sure it is flush with the baffle. ‑Next, mount the crossover network inside the panel, adjacent to the hole for the speaker terminals. You will need to drill a hole for a selftapping screw, to secure it through one Here’s one of the two crossovers. It is supplied as you see it here – fully assembled. All you need do is connect the three sets of flying leads to the input terminals, woofer and tweeter (watch the switch of polarity on the tweeters!) and mount the board to the inside back of the enclosure. siliconchip.com.au WHERE can you buy SILICON CHIP Fig.2: the speakers have a very smooth frequency response (from 50Hz to 20kHz,) as shown in this graph. You can get your copy of SILICON CHIP every month from your newsagent: in most it’s on sale on the last Wednesday of the month prior to cover date. You can ask your newsagent to reserve your copy for you. If they do not have SILICON CHIP or it has run out, ask them to contact Network Distribution Company in your state. SILICON CHIP is also on sale in all of the holes in the crossover PC board. (With 20/20 hindsight, we would have drilled these holes before assembling the boxes!). Next, pass the input wires through the back panel hole and push the connectors onto the spade lugs of the terminal panel. Note that they polarised – push the red connector on to the lug for the red (positive) screw terminal and the blue connector to the black (negative) screw terminal. Then pass the tweeter wires through the tweeter hole in the baffle and attach them to the tweeter terminals. Note that this time the connectors are not coloured but the wire with the black strip must go the tweeter’s negative spade lug. Once the wires are on, carefully place the tweeter into its hole and make sure it sits flush with the front surface of the baffle. Carefully secure it in place with five screws – do not over-tighten. Then place the piece of BAF (bond- ed acetate fibre) wadding into the enclosure via the woofer mounting hole. Then connect the remaining crossover wires to the woofer. The connectors for these are different sizes to match the spade lugs on the woofer, so you cannot make a mistake. Finally, secure the woofer with six self-tapping screws. Do not overtighten. Connect to your amplifier, select an input source, sit back . . . and relax! stores . . . again, you can ask the store manager to reserve a copy for you. Or, to be sure that you never miss an issue and save money into the bargain, why not take out a subscription? The annual cost is just $89.50 within Australia or $96 (by airmail) to New Zealand. Subscribers also get further discounts on books, and other products we sell. * Designer, Theloudspeakerkit Availability The kit of two M6 speakers, as described in this article, is available for $599.00 plus shipping. For further information, contact: The Loud Speaker Kit 21 Harrogate St, Leederville WA 6007 Tel: (08) 9382 8588 Fax: (08) 9382 8087 Website: www.theloudspeakerkit.com Fig.3: the impedance is a nominal 8W. Note the double hump below 100Hz which is typical of bass reflex systems. OVERLEAF: Putting the speakers together, step-by-step siliconchip.com.au November 2006  37 Putting them together . . . step-by-step ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; 1 2 Before you start (especially on carpet!) , lay out a sheet of plastic . . . 7 Now it’s time to run a bead of glue around the front panel rebate . . . 13 Clamp the box up firmly and allow it to dry. If you have glue runs, 19 You may need to squeeze them on with pliers. Note the polarity! 38  Silicon Chip 3 . . . and do a “dry run” so you can work out how the pieces fit together. 8 It saves any mistakes later on! If you’re satisfied, pull it all apart . . . 9 . . . and the back panel. Once again, too much glue is better than too little. 14 Push the front panel into position on the box, 15 simply wipe them off with a just-damp cloth. Leave until the glue dries. 20 Screw the input terminals to the back of the case with the screws provided. (Optional): we rounded the box edges with a router make it less “boxy”, 21 Then turn the box over and push-fit the port into its hole. siliconchip.com.au ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; 4 . . . and start running glue along the bottom rebates. Don’t be measly! 10 5 Push both side panels into the bottom rebates. They should be a snug fit. 11 followed by the rear panel. Make sure the edges are all flush. 16 22 Pull the “tweeter” wires through and connect them in the right polarity. Last of all is the top panel. Run the glue in the rebates . . . 17 then sanded and painted the boxes an off-white colour to match our decor. siliconchip.com.au 6 The crossover has to be screwed to the inside of the back panel. 23 7 If necessary, give them a push down or even a gentle tap with a mallet. 12 13 . . . an place the top in position. Push it down (or tap it down) into place. 18 19 Poke the input wires through the hole and attach them to the terminals. Place the tweeter in its hole and align its holes with those in the box. 24 25 Fasten the tweeter to the front panel with the screws provided. Don’t slip! November 2006  39 ; ; ; ; ; ; ; STOP 25 The acoustic wadding is placed inside the box through the woofer hole. 28 Drop the woofer back into its hole and align its screw holes. 28 27 26 As you did for the tweeter, pull the woofer wires through the hole . . . 29 . . . and connect them to the woofer, again taking note of polarity. 30 Screw the woofer into place with the screws provided. Repeat for the other box, connect them to your amplifier . . . and enjoy! Radio, Television & Hobbies: the COMPLETE archive on DVD YES! NA MORE THA URY T N E C QUARTER ICS N O R T OF ELEC HISTORY! This remarkable collection of PDFs covers every issue of R & H, as it was known from the beginning (April 1939 – price sixpence!) right through to the final edition of R, TV & H in March 1965, before it disappeared forever with the change of name to EA. For the first time ever, complete and in one handy DVD, every article and every issue is covered. If you’re an old timer (or even young timer!) into vintage radio, it doesn’t get much more vintage than this. If you’re a student of history, this archive gives an extraordinary insight into the amazing breakthroughs made in radio and electronics technology following the war years. And speaking of the war years, R & H had some of the best propaganda imaginable! Even if you’re just an electronics dabbler, there’s something here to interest you. • Every issue individually archived, by month and year • Complete with index for each year • A must-have for everyone interested in electronics Please note: this archive is in PDF format on DVD for PC. Your computer will need a DVD-ROM or DVD-recorder (not a CD!), Windows 98 or higher and Acrobat Reader V6 or later (free download) to enable you to view this archive. This DVD is NOT playable through a standard A/V-type DVD player. Exclusive to SILICON CHIP ONLY 62 $ + $ 00 7 P&P HERE’S HOW TO ORDER YOUR COPY: BY PHONE:* (02) 9939 3295 9-4 Mon-Fri * Please have your credit card handy! 40  Silicon Chip BY FAX:# (02) 9939 2648 24 Hours 7 Days <at> BY EMAIL:# silchip<at>siliconchip.com.au 24 Hours 7 Days BY MAIL:# PO Box 139, Collaroy NSW 2097 # Don’t forget to include your name, address, phone no and credit card details. BY INTERNET:^ siliconchip.com.au 24 Hours 7 Days ^ You will be prompted for required information siliconchip.com.au