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Seldom have we heard hifi speakers which sound so b even $$$$(multi-thousand) commercial models! Never have such high performance hifi speakers been as a d-i-y project in any magazine – anywhere in th You can be justifiably proud that you crafted them y your friends won’ t believe you built them! They’ re big, they’ re beautiful and they’ re mighty po Everything about this superb loudspeaker system is impressive: size, physical presence, power handling, efficiency, extremely wide frequency response and low distortion. Is there a disadvantage? Well, they are somewhat big! On the other hand, if you already have large tower speakers, these won’t take up much more space and will sound far superior. They look better too! Introducing: The Majestic 22  Silicon Chip siliconchip.com.au brilliant . . . n published he world! yourself: owerful! L et’s face it; up till now it has been possible to build your own state-of-the-art amplifier, DAB+ tuner or DAC but SILICON CHIP has never produced what we could claim as a “world-beating” loudspeaker system. Now we believe we have such a design. It can easily handle the power output of amplifiers rated up to 300 watts per channel but at the same time, it is very efficient. How efficient? 97dB/watt <at>1m. To put that in perspective, that is between two and three times more efficient than typical hifi loudspeakers which are rated at around 87-90db/watt <at>1m. What does that mean in practice? There are two answers. First, you don’t need a large power amplifier to drive them to very high sound levels. Say you wanted to produce sound levels of 110dB in your lounge room. That is very loud – about rock concert loud – but you would only need a 20-watt amplifier. Our 20-watt Class-A amplifer would be ideal. Even a 5-watt stereo amplifier will drive a pair of Majestic loudspeakers to more than 105dB in the average lounge room. Second, at the other end of the scale, with a 300-watt/ channel stereo amplifier, you could drive a pair of Majestic loudspeakers to truly deafening sound levels in a large auditorium! In fact, at distance of 1 metre from the front of the Majestic loudspeaker, you would be blasted at 122dBA when fed with 300 watts. That’s way above the pain threshold and well into hearing damage territory. OK, you get the picture. It can handle lots of power and it is very efficient. But the same comment applies to a lot of big public address speakers. However, most of those are just loud; they are definitely not hifi and they typically do not have a wide frequency response. More particularly, they do not have a bass response extending to below 20Hz. In fact, in all our years of listening to high fidelity loudspeakers, we have never come across one that would produce fair-dinkum 20Hz. At the same time, that big 15-inch cone hardly moves at all even when producing high sound levels. That is the advantage of an effective cone area which is more than four times that of an 8-inch driver. A bigger cone means less cone travel and therefore less distortion. Surprise! If you are impressed so far, you will now be surprised. The woofer is Australian-made, an Etone 1525. This has a 2.5 inch voice coil and has a free-air cone resonance of 27Hz. It is teamed with a Celestion CDX1-1730 com- WARNING! By Allan Linton-Smith siliconchip.com.au SILICON CHIP takes no responsibility for broken windows, cracked masonry or porcelain, unstable foun dations, unstable relationships, neighbourhood rioting, replacement of vital organs or loss of bridges, skyscrapers or other infrastru cture resulting from these speakers being driven at high level – especially after midnight. Nor do we take responsibility for air turbulence which may result in unstable or out-of-control airliners , helicopters, hang-gliders or UFOs which may result from use (or misuse) of this speaker system. SILICON CHIP firmly believes in responsi ble sound levels and tasteful music, AC/DC excepted (or is that accepted?). June une 2014  23 +50 “Majestic” Speaker Frequency Response 15/12/2013 16:03:48 10 “Majestic” Speaker Distortion (unsmoothed) 01/01/2014 10:45:23 5 +40 +30 2 Total Harmonic Distortion (%) Relative Amplitude (dBr) +20 +10 +0 -10 -20 0.5 0.2 0.1 0.05 -30 -40 -50 1 0.02 20 50 100 200 500 1k 2k 5k 10k 20k 0.01 20 50 100 200 Frequency (Hz) 500 1k 2k 5k 10k 20k Frequency (Hz) Fig.1: frequency response for the Majestic Speaker – while the overall flatness is very good, what’s astounding is the fact that there’s barely any discernible roll-off in bass response at 20Hz! The dotted line shows the effect of the treble boost network. Fig.2: distortion remains low at most audible frequencies. The spike between 350Hz and 800Hz is likely due to interactions between the drivers around the crossover point, while the spikes below 50Hz are due to the increase in cone excursion and resonances. pression tweeter driver mated with an Etone H2017 horn. These are fed through a simple first order crossover network which gives attenuation at the rate of 6dB/octave above and below the crossover frequency for the woofer and tweeter, respectively. We will describe the crossover network in detail later in this issue. Kitchen Cabinet System. Now before you start thinking “Oh no! Not kitchen cupboards!” you really have to see the finish of these panels to believe them. They are anything but “cheap and nasty”. In fact, there is only one word to describe them: Majestic! Construction of the speakers is basically the same as that of a free-standing kitchen cabinet: you first build the “carcase” and then add the glossy piano-finish panels. Because we’re not adding a granite or stone benchtop, we use another panel to create the top of the case. Using these panels means that you can build high quality cabinets for a fraction of what you’d expect. Mind you, if you want to keep your partner happy, you had better let the decorator of the house choose from the large range of finishes available from the Kaboodle cabinet range. Why not try a black piano finish...or be daring and go for “seduction red” in full gloss, or a more conservative Beautiful finish And while you might love the sound quality from the Majestic loudspeaker, that could count for nothing if your partner hates its appearance. After all, DIY loudspeakers and hifi speakers in general seldom win awards for attractive appearance. But we think we also have a winner on this score too, because the cabinets look absolutely superb! Believe it or not, they are based on panels from the German-made but readily available “Kaboodle” Flatpax TheMajestic Power Handling: Sensitivity: Frequency Response: Distortion: Speaker Specifications up to 300W RMS 97dB /1 watt <at> 1m 20Hz – 20kHz, +6/-3dB (see Fig.1) <2.4% 20-50Hz; (typically less than 0.5%) Size (each cabinet): 486 (w) x 864 (h) x 580 (d) (mm) Weight (each cabinet): 48kg Woofer: Etone 1525 15”, 2.5kg magnet Tweeter: Celestion CDX1-1730 compression driver, Etone H2017 horn Crossover: 2-way first order (6dB/octave slope) Cost to build: 24  Silicon Chip ~$1300 per pair (estimated at June 2014 prices). siliconchip.com.au 70 “Majestic” Speaker Impedance 20/02/2014 19:06:58 60 Impedance (Ohms) 50 40 30 20 10 Dotted line indicates effect of treble boost (see crossover description) 0 10 20 50 100 200 500 1k 2k 5k 10k 20k Frequency (Hz) Fig.3: impedance is above 8across the entire audible frequency range, making the amplifier’s job driving the speaker easier and thus keeping distortion low. The two main peaks are at 58Hz (cabinet resonance) and 1.5kHz, due to the effect of the crossover network. “Myrtle gloss”? If you want it all to match with some modern colour schemes you might even like to use “Mocca Latte” and let the speakers blend into the background. Kaboodle Flatpax are sold by Bunnings Hardware and are available throughout Australia and New Zealand. Many Bunnings outlets have samples of their finishes on display so you get to look and touch them before you decide. We originally chose ultra-gloss white for our prototype, mainly because it was immediately available but we had to concede that it wasn’t real pretty – in fact, about as attractive as a bar fridge. But we all liked the sound, so much so, that one of our staff members decided that he must have a pair finished in “Red Oak” (the ones in our main photos with the lovely Tianna showing just how big they are!). These particular panels usually need to be ordered and might take a few weeks for delivery. When we say big, we mean it: the woofer is an Australianmade Etone 1525. This 15-inch powerhouse has a free-air cone resonance of 27Hz. The tweeter (inset at top) is actually a hybrid: a Celestion CDS1-1730 compression driver, teamed with an Etone H2017 horn. Individually, these components are impressive. Combined, they’re formidable! We have probably all experienced PA systems which are painful to the ear, not always because they are too loud but because they have poor frequency response and some frequencies completely dominate everything especially in the painful mid range region. To gain a pleasant sound we have aimed at developing an exceptionally good frequency response combined with So what will it all cost? Our pair of prototypes finished in Red Oak with woofers, tweeters and crossovers, came in at under $1300 (for the pair). That’s an absolute steal compared to anything with even remotely similar performance currently on the market. For example, consider the JBL S4700 3-way loudspeakers. These are taller than the Majestics and are rated at 300 watts and 94dB/W <at>1m. They use a 15-inch woofer with dual 3-inch voice coils and a cast aluminium frame. This is mated with a 2-inch compression driver and bi-radial horn, topped off with a 0.75-inch ultra-high frequency driver and bi-radial horn. Rated frequency response is 38Hz to 40kHz at the -6dB points. Cost for a pair is around $20,000. (No mention of 20Hz though!) Frequency response Probably the most important function of any loudspeaker is its ability to accurately reproduce the full spectrum of sound in the audible range, especially at high sound pressure levels. siliconchip.com.au Fig.4: the top trace is a square wave signal being fed into the amplifier while the bottom trace shows the output of a microphone positioned in front of the speaker. The firstorder crossover and good time alignment give excellent waveform reproduction. June 2014  25 TheMajestic Speaker Parts List Timber requirements (per enclosure) Kaboodle Carcase Kit (all 16mm HMR panels) Bunnings Part No. W-51604 Back panel 720 x 418mm Bottom panel 544 x 418mm Side panels 720 x 560mm (2 in kit) Top support panel 418 x 80mm Shelf (becomes angled ‘diffuser’ panel) 416 x 540mm Kaboodle Dress Panels (18mm high gloss finish) Side Panel (2 required) 864 x 580 x 18 (Bunnings part Door panels – 717 x 447mm - 2 required. numbers depend (1) becomes front baffle – used full size on colour chosen) (2) becomes top panel and bottom rear panel    [top panel is cut to 580 x 447;    bottom rear panel (450 x 126mm) is cut from excess] Extra support panels (not supplied in kits) Back top support 418 x 150 x 16mm (particle board) Baffle support 418 x 80 x 16mm (particle board) Horn panel 660 x 125 x 3mm (3-ply) Cleats: cut from 2.4m x 25 x 25mm DAR maple or similar Other components required (per enclosure) 1 Etone 1525 15” Woofer (www.etonesound.com) 1 Celestion CDX1-1730 Compression Driver (www.elfa.com.au) 1 Etone H2017 Horn (www.etonesound.com) 2 rolls bonded acetate fibre (acoustic wadding) 700 x 1000mm 1 Crossover (see article commencing on page 32) 1 2m length of draft exclusion strip (10mm wide) 1 pair heavy-duty panel mount polarised speaker terminals ~ 2m heavy-duty figure-8 polarised speaker wire 1 tube (& dispenser) neutral-cure silicone sealant 14 50mm woodscrews 27 28mm woodscrews 20 20mm panhead woodscrews (for woofer/tweeter mounting) 8 M3 x 20mm machine screws with nuts and washers 2 M6 x 20mm bolts with washers 4 100mm L-shaped brackets One speaker box almost finished – with the top panel still to be cut and glued in place (no screws used here!) and the speakers, crossover, terminals and hyperbolic horn panel to be fitted. Note that we have left the protective plastic covering in place during construction . . . just in case. high efficiency and low distortion. CHIP designs are always better and for many commercial amplifiers they can be markedly better. Ergo, our aim was to have a loudspeaker system impedance which does not drop below 8 ohms at any frequency. In fact, as shown on Fig.3, the Majestic speaker is well above 8 ohms for the whole audio spectrum. So it will be compatible with just about any amplifier – and given its high efficiency, even very low power amps (eg, ~1W!) will drive it, right through to big amplifiers with the rated 300W maximum. The crossover network is quite simple and is covered in a separate article in this issue. In brief, it is a two-way crossover network which provides for minimum phase change across the full audio spectrum. Impedance Frequency response We have paid a lot of attention to the impedance versus frequency characteristics of the Majestic speaker because this can be a major factor in the performance of the driving amplifier. Some amplifiers will misbehave if the impedance drops too low – they will either be over-loaded or their distortion will become quite bad. But even where an amplifier can comfortably drive a loudspeaker with the expected dips in impedance, it will also give lower distortion into a higher impedance load. You can see plenty of evidence of this with the distortion versus power and distortion versus frequency characteristics for driving 4 or 8-ohm loads. The 8-ohm figures for SILICON The graph of Fig.1 says it all: the Majestic’s frequency is within +6, -3dB across the entire audio spectrum from 20Hz to 20kHz. This is one of the best graphs we’ve ever seen in a highpower loudspeaker – again, even many big-name speakers with prices in the stratosphere aren’t this good! Of particular note is the low frequency response – it goes all the way down to 20Hz – but off the graph it keeps going down to 12Hz. That is just amazing! This is bass that you really feel. 26  Silicon Chip Distortion Speakers are still the weakest link in the audio chain. siliconchip.com.au Having gone to enormous effort to build or buy an amplifier with almost immeasurable distortion, there’s not a great deal of point in feeding it into a speaker with high distortion. We measured one popular brand of speaker and found more than 20% THD at the low-frequency end! As shown in Fig.2, the Majestic speakers have distortion figures of less than 1% from 50Hz to 20kHz and for much of the audible range, they’re less than 0.3%. Even at 20Hz, distortion doesn’t rise above 2.4%. By the way, this performance graph was taken at a power level of 1W. Of course, part of the reason for the low distortion is the use of that 15-inch woofer – its cone hardly deflects at all unless you are driving it to bedlam levels. Drive the Majestics hard and all you’ll experience is arguably the best bass you’ve ever heard! Incidentally, our distortion measurements were made using some very high performance microphones but even the very best will introduce their own distortion. We measured our microphones at 0.38% so the actual distortion could be lower than in the graph! Cabinet vibration It is vital that a speaker enclosure be as rigid as possible, to prevent the panels vibrating and resonating at different frequencies and power levels. Any panel vibration is bad as it will add colouration to the sound in the best (least worst?) case and simply unpleasant buzzing and rattles in the worst case. One of the advantages of using the “Kaboodle” panel system is the rigidity of the cabinets. The thermoformed side panels are almost 19mm thick and the HMR chipboard inner panels are 16mm thick. Glued and screwed together, this near35mm thickness of the two side walls provides excellent damping and also means that no internal bracing is required. Top and front of the cabinets only have the thermoformed panels but these also have support brackets and cleats, further assisting in their rigidity. We used two rolled-up 700 x 1000mm sheets of bonded acetate fibre wadding inside each speaker to minimise internal standing waves and damp resonances. On completion, as a test we placed piezo sensors on the cabinet panels and found no major problems across the siliconchip.com.au audible range. If you do find any vibrations in your Majestic speakers, they will probably be caused by insufficient attention being paid to assembly – particularly loose screws or lack of silicone sealant between joints. How it works The speaker box is essentially a bass reflex design with a tuned port but there are a number of important refinements. It is referred to as a bass reflex because the sound waves from the back of the woofer pass through the port and are radiated from the front to reinforce the sound from the front of the cone. Most of this reinforcement only takes place at low frequencies and it leads to a considerable extension of the very low bass response. The tuning of a bass reflex enclosure results in two low frequency impedance peaks which straddle the free-air resonance of the woofer, which in this case is at 27Hz. As you can see from the impedance curve shown in Fig.3, these two peaks are at 58Hz and 12Hz. Now there are two ports in the enclosure, the main one Fig.5: front elevation, side elevation and plan (from underside) of one Majestic speaker box, which can also serve as an assembly aid. The other prototype boxes were made mirror image but in hindsight, we don’t think it matters: both left and right boxes can be identical. June 2014  27 FRONT SIDE RAIL BACK PAN E RT PPO TOP SU L EL N K PA PAN E BAC L BOTTOM PANEL SIDE PPORT TOP SU STEP 1: after cutting any panels required as per the parts list and diagram overleaf, fasten back panel to bottom panel using silicone sealant and 50mm woodscrews (these holes are pre-drilled in kit). Attach the side panels to bottom panel and back panel using silicone sealant and 50mm woodscrews. Allow sealant to dry. STEP 2: Drill holes in top of side panels and attach front and back top support rails. Plae 50mm woodscrews in the holes and temporarily assemble (ie, tighten woodscrews) to ensure everything is in the right place. If OK, loosen the screws and again run a 5mm bead of silicone sealant in the join. Retighten and allow to dry overnight. being the 110mm hole in the base and this is tuned to about 20Hz. However, while the main port itself is tuned to 20Hz, that is modified by a second port formed by the 416 x 540 x 16mm angled panel inside the enclosure which is mounted to produce a gap of 1.5mm and an overall port area of 63cm2. This lowers the enclosure tuning and results in a low frequency peak at 12Hz. The angled panel also reduces effect of sounds from the back of the woofer being reflected back through the cone and also damps (smooths) the low frequency response. The low frequency energy emerges from the downward firing port and is then radiated by a half-hyperbolic horn with a mouth area of 559cm2. However, this horn has no real effect at very low frequencies and its main function is to damp any “chuffing” which may result at high signal levels from the port. Just incidentally, the horn also encloses an area underneath the box to accommodate the crossover network PCB. boodle covers until the speakers are complete. They’ll minimise damage from any “oopses”. (b) All joins must include a bead of silicone sealant to ensure they are airtight. We used bathroom caulking compound which has good adhesive properties. Too much sealant is better than not enough – but be sure to clean up any excess as you go. (c) Openings for the woofers and tweeters need to be cut in the ‘door’ panels. These are best cut from the nonglossy side with a jigsaw fitted with a fine-tooth blade. Construction The “Kaboodle” system is very easy to assemble and you really only need to follow the instructions provided for a really professional look. Bunnings also have available a DVD to give you some guidance. Most of the construction follows the same steps as building a kitchen cabinet, the main difference between basic 450mm-wide kitchen cabinets and our Majestic speakers is just the drivers! OK, so we’ve made a few modifications – these are all explained in the step-by-step diagrams. There are a few important things to keep in mind: (a) Leave the protective plastic coating on the gloss Ka- It looks just like a kitchen cupboard carcase (!), albeit with a couple of extra braces. The angled panel (made from the cupboard shelf) is visible in this shot, taken before the dress panels were fixed in place. 28  Silicon Chip siliconchip.com.au 126 CK BA P TO T OR PP SU FRON TOM BOTPANEL T TOP EL N E PA FF LE SU CLEAT BA PP PAN E OR T (AN GLE DP AN EL) C CLEAT R A RT SU PP O M O TT EL BO AN P IL CLEAT L KP AN EL RT RAIL AT SID SIDE BAC SUPPO CLE CLEAT 72 126 93 LE AT STEP 4: Turn E box back to upright SID EL N position and use a PA shelf to make the angled diffuser panel. Fasten panel in position using 50mm woodscrews through side panels (first drill appropriate holes) and plenty of silicone sealant. (Remember the 1.5mm gap between the diffuser panel and back panel). Add baffle support using 50mm woodscrews. Cut and place six cleats around front edge of box (cleats cut from 25 x 25mm DAR maple), secured in position with silicone sealant and 32mm woodscrews. The same comments apply when you cut the top of the other ‘door’ off to become the top of the cabinet. (d) You will need some extra 16mm MDF or particle board cut to the dimensions given in the parts list to make up the three support panels. (e) The four adjustable feet supplied with the Kaboodle kit are used only to ensure the side panels are mounted in the right place, after which they are removed and discarded. (f) The angled panel (the Kaboodle shelf) is secured by placing it inside and use some strips of masking tape to secure it at the bottom. Check the measurements. Set the top gap 1.5mm out using some pieces of scrap pc board held in place with masking tape and then use a liberal amount of silicone sealant on the sides because there is a gap to fill. Allow plenty of time to dry. (g) The hyperbolic horn is made from a piece of 660 x 125 x 3mm plywood bent into the appropriate shape. 100mm “L” brackets hold this in position. Mounting this in the position indicated in Fig.5 should result in FR O N T STEP 3: Up-end the box and cut 110mm diameter port hole in bottom panel, centred 72mm from back and 93mm from side. Temporarily attach the four adjustable feet to the bottom of the box with four x 28mm woodscrews on each foot, first drilling appropriate holes. Using a straight edge, adjust all four feet so they are 126mm above bottom panel. Wiring the speakers: this is done immediately before STEP 8 above - ie, just before the top is glued on. Note the extensive use of silicone sealant around the seams to ensure they are totally air-tight. The holes where the wiring passes through should be similarly treated. This photo was taken of the first (white) prototype – in the final version cleats were added to support the panels. siliconchip.com.au There’s a 1.5mm space between the top panel and side panels. Here’s a nifty way to ensure that space is constant: use some offcuts of PCBs or similar and place in the gap while the sealant dries. Be careful not to get any sealant on the panels. June 2014  29 GLOSSY SIDE PANELS HORN PANEL STEP 5: The glossy dress panels are secured using a ‘criss-cross’ pattern of silicone sealant and 28mm long woodscrews screwed in from the inside of the box (drill only 5mm pilot holes into the dress panel to ensure they don’t emerge from or marr outer surfaces). Use five screws on each panel in addition to silicone sealant. The bottom of the dress panels should line up with the bottom of the adjustable feet (ie, 126mm below the bottom of the box). the hyperbolic shape. (h) Cut the 110mm hole in the base before assembly (i) The glossy side panels are criss-crossed with silicone sealant, then clamped and drilled before the screws are fitted. (j) When cutting holes for the woofer and tweeter, mark out the woofer on the underside of the glossy door panel with a large compass or better still use the cutout provided in the Etone box as a template. Be very careful and check your measurements twice! Then gently drill a 9mm starting hole well inside the line and cut the hole with a jigsaw keeping the glossy side DOWN. Then mark the rectangle for the tweeter and drill and cut this with the jigsaw. (k) Test the holes by carefully lowering the speaker drivers. They should fit easily and not bind. Remove the speakers then add felt “weather seal” strips under the edges of both the woofer and tweeter to form an airtight seal when they are permanently fitted. (l) The wiring to the speakers pass through suitable holes (only as big as necessary) in the bottom panel. These holes need to be made airtight with silicone sealant. (m) Connnections to the Etone woofers need to be soldered but the Celestion tweeter takes spade connectors. If WHERE IS STEP 6: Turn box upside down again and remove the (BOX UPSIDE DOWN temporary adjustable TOP PANEL NOT YET FITTED) feet (from now on the speaker will sit on the dress panels). Cut the “door” panel to 580mm and use the offcut as the support panel at the bottom rear of the box. Cut the holes for the woofer and tweeter in positions shown earlier and secure the panel in place with silicone sealant, then fit the horn panel (660 x 125mm strip of 3-ply) and secure in place with right-angle brackets. Seal the ends of the horn panel to the side and back panels with silicone sealant. you use crimped connectors, ensure they are firmly crimped in place and when fastening to the speakers, that they cannot come loose. (n) Soldering heavy duty wire requires more heat than a typical 20 or 30 watt hobby iron can deliver. A 50W iron or gas-powered iron is much better. (o) The driver units are mounted using 10g x 18-25mm stainless steel woodscrews or screws with T-nuts. (p) Two rolls of bonded acetate fibre are used in each box. Mount the rolls side-by-side to make it possible to access the speakers between them. Breaking in and testing Out of the box you will find that the bass drivers are very stiff and won’t deliver their optimum performance until they have had a ‘break in’ period. Simply allow them to run under normal conditions with various types of music played at different levels. You should notice an improvement over time. Even though they are rated up to 300W RMS this is the rating for normal music. Don’t be tempted to run a continuous tone from a signal generator or test CD at high levels – you risk permanently damaging your speakers (and your ears!). Even with the high power handling of this system it can TheMajestic CROSSOVER? As the crossover is suitable for many other speakers, we decided to make it a separate article – you’ll find it starts on page 32. 30  Silicon Chip siliconchip.com.au TOP PANEL TOP PANEL [TRIMMED] (FITTED LAST, USING (FITTED LAST, USING ONLY ONLYSEALANT SILICONE– IE, ADHESIVE) SILICONE NO SCREWS) (ACOUSTIC FILLING) USE THIS OFFCUT AS REAR PLATE UNDER BOX (ACOUSTIC FILLING) (ACOUSTIC FILLING) STEP 7: Attach front baffle board (another piece of glossy panel) from the inside, using 28mm woodscrews through the baffle support and edge cleats. Fill interior of box with two rolls of acoustic wadding side-by-side and mount your prewired speakers (woofer and tweeter) to the outside of the baffle using suitable woodscrews or screws and “T-nuts” which grip the timber on the inside (ie, place the nuts via the top of the box with the wadding pushed out of the way) . be damaged by a relatively small amplifier which clips severely. The only 100% certain way to tell if the amplifier is clipping is to observe the signal on a scope – but if the speaker output sounds harsh and unnatural, the chances are the amplifier is clipping. Finally, note that once the top panel is secured in place with silicone sealant, it is difficult – if not impossible – to remove without major damage. Make sure it works first! If you need access to the box internals, you’ll need to remove the woofer and work via its mounting hole. Because the top panel is secured only with silicone sealant, it’s essential that the join is compressed so the sealant spreads over all and forms an airtight seal. Use a heavy weight to force the panel down – but protect the surface! siliconchip.com.au STEP 8: Wire in the crossover and terminals drilling holes as required (see photo below). Check that the speaker works before fitting the box top (it may not sound real good without the top fitted – just ensure it works!) The trimmed door panel, which forms the top of the box, is secured in place using only silicone sealant (no screws!). Ensure that sufficient silicone sealant is spread along entire length of support panels and cleats to form an airtight join and is weighed down until the sealant has dried. Fitting the crossover: actual position is unimportant but make sure all wiring is secured to the panel and/or cable clipped. The 3-ply “horn” panel looks much thicker here than it really is – we’ve attached some selfadhesive tape to prevent the speaker scratching our polished floor. SC June 2014  31