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This speaker hangs from a high roof or ceiling and provides excellent quality sound – especially considering how little it costs to build. Its features include: Easy to assemble, with a largely pre-built enclosure Multiple configurations for different applications Excellent quality sound for a pendant speaker Uses a 6.5-inch (170mm) woofer and a dome tweeter Low-cost drivers and crossover 90W rating on normal program material Optional low-cost speaker protection Impedance: 4W (minimum, 20Hz-20kHz) 44cm wide, 40cm high and 7kg in weight High-Performance Pendant Speaker Part 1 by Julian Edgar T his pendant speaker is easy to build, cost-effective and has good performance. It is also an excellent complement to the Outdoor Subwoofer (June 2025; siliconchip.au/ Article/18313). But first, what is a pendant speaker, and why would you want to build one (or more)? Pendant speakers hang from a high roof or ceiling. They are used where floor speakers would be inconvenient or get in the way and in-ceiling speakers cannot be used because there is no ceiling (eg, in a shed or workshop), the ceiling is made of concrete (eg, the ceiling is the underside of the floor above), or there is no space. As they can be placed high, out of reach, pendant speakers are also useful in areas subject to vandalism or interference. Our readers could use them for playing music in home workshops and sheds, but they can also be used for music in large rooms with raked ceilings and in undercover outdoor areas with high roofs. They work well in shops with high ceilings. Finally, they can also be used in public address roles. In fact, we have a specific enclosure variation for when they will be primarily used for voice. Design challenges A pendant speaker is much more challenging to design than a conventional speaker for two reasons. The first is aesthetics. A box-shaped speaker enclosure hanging from the ceiling will look plain weird; instead, what is needed is a curved shape – like a pendant. However, unlike the jewellery, a pendant speaker needs to be three-dimensionally curved. That A single Visaton 170mm (6.5in) WS 17 E woofer/ midrange driver is used. Source: Visaton The tweeter is a 25mm (1in) soft dome unit. They are available inexpensively in pairs. 42 Silicon Chip Australia's electronics magazine normally makes home construction very difficult, but we have a trick that overcomes that difficulty. The second design problem is acoustic. Loudspeakers work by propagating pressure waves in the air; to do that, the moving cone needs to connect with the air. The ability of the cone to transmit energy to the air depends on the acoustic impedance of the system, that is, the opposition that the system presents to the acoustic flow. To put that more simply, the air needs to load the cone, or no energy exchange will occur. This effect is greatest at low frequencies (ie, bass). Acoustic horns load the speaker cone strongly, giving the horn its characteristic high efficiency. A similar increased loading occurs if you put a conventional speaker enclosure at the junction of a floor and wall, and even more loading occurs if you put the enclosure in a corner comprising two walls and the floor (or ceiling). This is why bass response improves at these speaker locations. Now think of a pendant speaker. It’s suspended in mid-air and so cannot benefit from any of those loadings! If we want good bass response, we cannot use a horn, as it would need to be enormous. siliconchip.com.au ◀ The High Performance Pendant Speaker has been tuned to give good performance when hanging in midair. We chose to use an open grille, but alternative grilles with smaller openings can also be used. The tweeters come with two different mounts, cables and crossover capacitors (in the boxes). However, we don’t use these capacitors. The enclosure design we have developed has an option to increase its output at low frequencies. That helps offset the lack of bass augmentation because it’s not positioned near any flat surfaces. However, if you want strong bass, it’s likely you will need to add a subwoofer – for example, the Outdoor Subwoofer we described previously. That will take up floor space, but it’s only one small speaker compared to using multiple large floor speakers. Overall, the pendant speaker design presented here gives excellent sound quality for this type of enclosure. Design approaches A key aspect of the design that makes it cheap and easy to build is the use of a pre-formed speaker enclosure. It is made from recycled plastic and has reasonably thick, acoustically dead walls. In fact, it’s a pot available from Bunnings! To turn it into a pendant speaker, all we do is make a baffle from particleboard and glue and screw it into place. Then we add a woofer/midrange driver, a dome tweeter and a simple crossover. The woofer and tweeter are quite inexpensive (we already met the woofer in the Outdoor Subwoofer project) and the rest of the hardware – including the grille – is also cheap. Depending on the application, the enclosure can be built as a ported (bass reflex) or a sealed design. More on those options in a moment. siliconchip.com.au The bass/midrange driver (I’ll just call it the woofer from now on) is a single 170mm (6.5-inch) WS 17 E unit made by Visaton. This driver is available in 4W or 8W versions and, in this design, we use the 4W driver. These speakers are available worldwide – a web search will find your nearest stockist. We bought ours from Soundlabs Group, and it cost $54 plus postage. For its low cost, this is an excellent speaker that, in addition to providing good bass response, is quite capable in the midrange. When we used this driver in 8W form in our Outdoor Subwoofer, the measured Thiele-Small specifications differed a little from the advertised specs. The 4W drivers we bought this time were also a bit different from their stated specifications, as shown in Table 1. The bass response of the enclosure was modelled using the freely available WinISD speaker enclosure design software (www.linearteam.org). In this modelling, we used the average of the two sets of Thiele-Small test results. The tweeter we have selected is a 4W “Alpine” DDT-S30 one-inch (25mm) soft dome design that is available online for $30 a pair, including delivery. I’ve put Alpine in inverted commas because it is very likely that these are not genuine Alpine products. The tweeters come with crossover boxes. However, they contain just a single non-polarised capacitor. That is the simplest possible way of preventing bass frequencies reaching the tweeter. By the way, the measured impedance of the finished speaker never drops below 4W. Different enclosure options Two different enclosure designs can be built. The first is used for playing music, while the second is for voice applications. Both designs are quite Table 1: driver measurements vs specifications Specification Listed Tested speaker A Tested speaker B DC resistance 3.2W 3.4W 3.3W 85.5dB 86dB Resonant frequency 45Hz Sensitivity 88dB 44Hz 46Hz Qms 2.35 3.30 3.40 Qes 0.90 0.93 0.89 Qts 0.65 0.71 0.71 Vas 22.0L 24.9L 22.7L Australia's electronics magazine September 2025  43 straightforward to build – the one for playing music uses a ported enclosure, or for voice, a sealed enclosure. A ported enclosure can become sealed just by blocking the port, so if you’re not sure which approach will suit your application, test the ported design first. The ported design has a modelled frequency response that smoothly rises to a peak at +8.5dB at 78Hz (see Fig.1). To put this a different way, on some amplifiers, this is the equivalent of turning the bass control up by about two-thirds. Remember, though, that the pendant speaker isn’t getting any of the bass boost that normally occurs because of the presence of the walls and floor. In this form, its -3dB point is 48Hz. That modelled response is achieved with a port that is 86mm in internal diameter (so quite big) and 100mm long. If you want a peakier or smoother bass response, we will cover that in the section on tuning next month. The sealed design that is better for voice has a bottom end modelled as being only 1dB up by 94Hz, with a -3dB point of 51Hz. What is not generally realised is that speaker simulation and design packages assume that the speaker enclosure is working into ‘half space’, that is, it’s placed in the middle of an infinitely large wall. Therefore, the simulation graphs shown in this article are for a speaker positioned like that, not for one hanging in free air. If you are looking in horror at the ported enclosure’s modelled frequency response, that is very important to The metal grille can be made from open mesh (left) or mesh with small perforations (right). In fact, any metal grille can be used. Source: Bunnings keep in mind! When it is suspended in free air, the design sounds nothing like the modelled response curve; instead, its bass is smooth and effective. Before going any further, why can’t you use the ported design for voice, or the sealed design for music? You can, but there are some disadvantages. With the ported design, on some voices (eg, a man’s deep voice), the speaker may sound too chesty, especially if the source also has bass boost applied to the signal. More importantly, it will be harder to work out what the person is saying – intelligibility will be worse. Conversely, the sealed design on Fig.1: the modelled bass response of the 27L ported (green) and sealed (blue) enclosure versions. The response of the sealed enclosure has been designed to strongly augment bass, compensating for the lack of cone loading caused by the absence of flat surfaces near the hanging speaker. The ported enclosure design is best for music, while the sealed version is best for voice applications. 44 Silicon Chip Australia's electronics magazine music will sound tinny, especially if being fed a flat signal (with the bass control on the amplifier set for zero boost). Remember, all these comments apply only when the speaker is being dangled in midair! We chose a welded steel mesh for the grille. It has openings that are 12.7mm square and it is available from Bunnings (I/N: 0082424). This grille allows you to clearly see the woofer, tweeter, port and (optional) speaker protection lamp, and gives the speaker an ‘industrial’ look. If you want a more conventional grille, Bunnings also sells steel mesh sheets with much smaller openings One of the prototype speakers deliberately being over-driven. Note the glowing protection lamp that is limiting the power. siliconchip.com.au (eg, I/N 0647223 has 3.2mm round holes). Optional speaker protection In our previous Outdoor Subwoofer project, we used a specific halogen lamp as a speaker protection mechanism. The lamp was wired in series with the speaker and, as current through the lamp increased, so rapidly did its resistance, limiting the power that reached the speaker. In that design, the protection was needed as it was easy to over-drive the subwoofer without realising it. With the full-range pendant speaker presented here, the situation is somewhat different. If the speaker is overdriven, it is easier to hear distortion than in the subwoofer. However, a good outcome requires that the listener knows what distortion sounds like and then immediately turns the amplifier power down! The nominal peak power rating of the speaker is 90W, but if there’s any possibility of the speaker being overdriven, we recommend that a protection lamp be installed. The lamp mounts on a bracket behind the grille, so it’s visible when the speaker is hung in position. If the speaker is constantly over-driven, it is possible for the lamp to become very hot. Because of this, the lamp needs to be spaced away from the baffle, and a metal grille (rather than cloth grille) should be used. The suggested protection lamp is a Narva 24V 55W bulb, part number 48701. At around $10, it is cheap insurance. A halogen incandescent light bulb is used as the optional speaker protector. It rapidly rises in resistance as its current flow increases, limiting the maximum speaker power. Source: Narva siliconchip.com.au The simple crossover can be built on a piece of plain punched laminate. In our tests, using a 50W amplifier to drive the pendant speaker, the lamp did not light at all on any program material, even at full volume. This is what you would expect to see in normal use – the lamp filament not glowing at all. Using a much more powerful amplifier, the light would glow dimly on some passages at about 70% volume; at 80%, it would glow more brightly on bass passages. At volume settings above that, it would glow very brightly. No distortion was audible and the speaker was not damaged – so the simple lamp protection mechanism works very well! Finally, while testing the speaker, I made an interesting mistake. I was swapping line level inputs to the amplifier, not realising the amp was still switched on and at full volume! As I pulled an RCA plug, a huge 50Hz hum was fed to the speaker, but the protection lamp immediately lit, and no damage was done. Performance I have built many speakers over the decades, and normally, you test them sitting on the floor. Depending on their application, it might be a big room or a little room, but they’re always on the floor (or sometimes on short stands). However, in the case of the pendant speaker, I had to test it 4m above the ground. Two different testing venues were used. The first was in a partially built house with a 10 × 6m room with a raked roof peaking at 6m high. The second test location was a large shed, 24 × 8m, again with a 6m peaked roof. In both cases, the speaker was positioned 4m from the ground. As described earlier, this position is a tough test for a speaker’s bass response, and developing adequate Using the Pendant Speaker with the Outdoor Subwoofer In the June 2025 issue of SILICON CHIP, we introduced the Outdoor Subwoofer. This uses a fibre-cement stool as the ported enclosure, with two Visaton WS 17 E 8W drivers mounted in an isobaric (face-to-face) configuration. As its name suggests, the sub is designed primarily for outside use. Still, it can also be used indoors, especially in large spaces. The Pendant Speaker works very well in combination with this subwoofer. We performed some testing using the pendant speaker and the subwoofer in the previously described 10 × 6m room with a 6m roof. Using a 100Hz electronic crossover, we found the sub’s input power needed to be less than the pendant speaker’s. In other words, with equal amplifier power to the pendant and sub, the bass was too strong. However, with the sub pulled back, the sound quality on music was excellent. That led to another thought. This combination of the pendant speaker and sub is likely to give excellent sound quality in large shops, especially those without suspended ceilings, where the room volume is very great. Certainly, we’d back the system over the small cube speakers and subwoofers often seen (and heard) in such environments. In that application, we suggest fitting protection bulbs to both the sub and pendant speakers. Australia's electronics magazine September 2025  45 sound output in such large room volumes is also a difficult task. However, it also reflects how the speaker will likely be used. I also purchased a commercial pendant speaker for a similar price, allowing direct comparisons during development. The commercial speaker used a 6.5inch coaxial (two-way) driver, a complex crossover and a small enclosure. My aim was to get a much better result with our project than the commercial speaker – and that was achieved in spades. In comparison to our final design, the commercial speaker had very poor bass, with a rapidly falling response below about 150Hz, accompanied by a buzz. Furthermore, there were clear resonances at 260Hz, 210Hz, 170Hz and 120Hz. In comparison, our project speaker had no loud resonances at all. Also, there was no bass buzz in our speaker and our speaker has an audible response down to 45Hz. The mid-range of the commercial speaker was also overly bright – but perhaps that was intentional, for better voice intelligibility. On the other side of the ledger, the commercial design was quite sensitive, being louder than our project speaker on the same Fig.2: the simple crossover circuit uses a non-polarised 4.7μF capacitor and two 5W resistors. volume control setting, despite the commercial speaker having a higher impedance (8W versus our 4W). The treble of the commercial speaker was initially better than our project speaker, but development of the crossover (covered next) gave treble in our design that matched the commercial speaker. Again, these comments apply when the speakers are tested in mid-air. The crossover During testing and development, the wiring for the woofer and tweeter were run outside the enclosure so that external tuning changes to the crossover could be easily made. In the final version, the crossover components are mounted inside the enclosure on the back of the baffle. The “Alpine” tweeter comes with a simple 6dB/octave high-pass crossover: a single 3.3μF non-­polarised capacitor. This gives a nominal crossover point of 12kHz. That’s a bit high for the 6.5-inch woofer, which has specifications showing it has a good response only until about 7kHz. Using a 4.7μF capacitor drops the nominal crossover frequency to 8.4kHz. However, the tweeter was then a little bright, so it was pulled back by about 3dB by using an L-pad comprising a series 1W resistor and a 10W parallel resistor. The final crossover circuit is shown in Fig.2. The crossover is built on a piece of bare punched laminate board. We chose to use input and output terminal blocks, but you could solder directly to the components on the board for these connections, then fasten the flying leads in place with cable ties. If you don’t have any punched laminate board, you could glue the three large components to a piece of board and then wire them together. Next month That’s all the space we have for this month. In the second and final part next month, we will show you how to build the speaker, test it and (optionally) tune its performance to suit your taste and listening environment. SC Parts List – Pendant Speaker 1 Eden 44cm Black Faux Planter pot [Bunnings I/N 0118235] 1 Visaton 170mm (6.5-inch) WS 17 E 4W woofer [Soundlabs etc] 1 pair of “Alpine” DDT-S30 1-inch soft dome tweeters [eBay etc] 1 4.7μF 100V non-polarised crossover capacitor [Jaycar RY6904] 1 10W 5W ±5% wirewound resistor 1 1W 5W ±5% wirewound resistor 1 80 × 70mm piece of plain punched laminated board 1 1000 × 500mm piece of 18-22mm thick particleboard (or two 500 × 500mm pieces) 1 600 × 900mm piece of steel mesh with 12.7mm square openings [Bunnings I/N 0082424] 1 1.5 × 1m piece of 150 GSM quilt wadding [Spotlight] 1 500mm length of thin-walled 90mm OD PVC stormwater pipe 1 can of black spray paint 1 Narva 24V 55W bulb, part number 48701 (optional) [auto parts store] 2 cartridges of Liquid Nails water clean-up building adhesive [Bunnings] 1 40mm saddle clamp or 8mm eye bolt Assorted hardware, eg, 40mm particleboard screws, spacers & solder tags Machine screws, bolts, washers and Nyloc nuts Assorted lengths and colours of hookup wire double all quantities except these for two speakers this may only be available in large sheets. You can buy a large sheet and have the store cut it into manageable pieces. If new homes are being built where you live, approach a carpenter and see if they have any offcuts of particleboard flooring to give away. Testing a pair of the pendant speakers during development. The stepladder is 3.7m high. Australia's electronics magazine siliconchip.com.au 🔸 ▪ 🔸 🔸 🔸 🔸 ▪ 46 Silicon Chip Two of the pendant speakers hanging in a shed converted to a living space. Using different sized enclosures After considering many different sizes, we chose to make the High-­Performance Pendant Speaker quite large. The enclosure volume is nominally 27L, while the enclosure as a whole has a volume of about 35L. Selecting a relatively large enclosure has benefits, especially in bass response. Because it is hanging in mid-air, so not taking up any floor space, the downsides of going large are minimal. But what if you want to use a smaller enclosure? In addition to modelling the 27L enclosure, we also modelled two smaller enclosures in both sealed and ported designs. Table 2 shows the results, with the ported designs tuned to give a strong lower end bass boost, as needed in a pendant speaker. Table 3 shows the length and diameter of the port needed with each smaller enclosure, and the frequency each enclosure has been tuned to. Silicon Chip PDFs on USB ¯ A treasure trove of Silicon Chip magazines on a 32GB custom-made USB. ¯ Each USB is filled with a set of issues as PDFs – fully searchable and with a separate index – you just need a PDF viewer. ¯ Ordering the USB also provides you with download access for the relevant PDFs, once your order has been processed ¯ 10% off your order (not including postage cost) if you are currently subscribed to the magazine. ¯ Receive an extra discount If you already own digital copies of the magazine (in the block you are ordering). EACH BLOCK OF ISSUES COSTS $100 NOVEMBER 1987 – DECEMBER 1994 JANUARY 1995 – DECEMBER 1999 Enclosure Vol. Sealed -3dB Sealed peak Ported -3dB Ported peak JANUARY 2000 – DECEMBER 2004 27L 51Hz +1dB <at> 94Hz 48Hz +8.5dB <at> 78Hz JANUARY 2005 – DECEMBER 2009 20L 54Hz +1.5dB <at> 90Hz 52Hz +8.5dB <at> 85Hz JANUARY 2010 – DECEMBER 2014 15L 56Hz +2dB <at> 96Hz +8.5dB <at> 94Hz JANUARY 2015 – DECEMBER 2019 59Hz Table 2: bass performance with reduced enclosure volume OUR NEWEST BLOCK COSTS $150 JANUARY 2020 – DECEMBER 2024 Enclosure Vol. Port diameter Port length Tuned frequency (modelled) 27L 90mm 100mm 63Hz (55Hz measured) OR PAY $650 FOR THEM ALL (+ POST) 20L 75mm 100mm 66Hz 15L 50mm 45mm 69Hz WWW.SILICONCHIP.COM. AU/SHOP/DIGITAL_PDFS Table 3: port tuning September 2025  47