Fullscreen HTML5Med Res (??MB)HTML4

Installing a Whole-House Sound System Feature by Julian Edgar W hen my wife and I decided to build a new home, there were lots of decisions to be made – literally, hundreds of them. From décor to bathroom design, where to put power points and how high the ceilings should be. As part of the research to answer those questions, my wife and I went to a huge number of new display homes, looking at what features were available and how they were implemented. Unexpectedly, one display home really caught my eye – or more accurately, my ears. This home had ceiling-­ mounted speakers throughout the house, and additional speakers in an outdoor living area. They were playing quietly, and as we walked through the house, it started to change my mind about music in a home. Previously, in all five houses we’ve lived in, the main sound system has been in the lounge room – a traditional stereo hifi system. To get the best quality sound, you sat in a designated area and listened to the music. Except, we never actually did that! Instead, it was more likely that we’d crank up the system while entertaining or even when cleaning the house. We’d not be sitting in one place but instead moving around. It was bad for stereo imaging, and even for hearing tweeters, but it was how the sound system was actually used. So the idea grew in my mind: in the new house, let’s make the sound system a whole-of-house design. There would be inevitable trade-offs in sound quality – but the sound system would be much more practical and useful. Choosing the speakers Three amplifiers, one preamp, thirteen speakers, hundreds of metres of wiring – it all sounds a nightmare! So why do it? There are plenty of good reasons... Having decided that there would be speakers located throughout the house, the next decision was on the type of speakers to use. To minimise the use of floor space and to be aesthetically acceptable, the interior speakers needed to be mounted either in the ceiling or in the walls. These days, with home theatre systems often requiring numerous speakers, speakers designed to be mounted in walls and ceilings are widely available. Most have a glaring deficiency: they comprise bare drivers mounted on a faceplate, with that faceplate then fitted to the plasterboard. The resulting speaker ‘enclosure’ is just the random volume behind the faceplate. Australia's electronics magazine siliconchip.com.au Image source: https://unsplash.com/photos/a-room-filled-withlots-of-different-types-of-speakers-vAHw2myA0EM 54 Silicon Chip Photo 1: seven Bose DS 100F ceiling speakers are used throughout the house. They use a ported enclosure with a 133mm long-throw woofer and a 57mm mid-range/tweeter and suit both 8W and 70/100V systems. These are of much better quality than Bose consumer speakers. Photo 2: the wall in the lounge/kitchen backs onto the roof loft space. From left to right, you can see one Bose speaker, an air intake grille, the two vents for the subwoofers (with a ventilation intake grille in between), another (currently unused) air intake grille, and the second Bose speaker. Another five Bose speakers are distributed throughout the house. I would have chosen white speakers if I had bought them new, but I don’t mind the contrast. With wall-mounting, that volume might be quite small; just the volume between the noggins and studs. With ceiling mounting, that volume might be effectively infinite – the whole volume of the roof space! Thus, such speakers need to be designed with huge compromises, and they cannot use the most efficient common enclosure design: ported bass-reflex. Therefore, I resolved that any speakers would need to have their own acoustic enclosures, meaning that, because of the resulting greater depth, they would usually need to be mounted in the ceilings. I figured I needed up to ten high-­ quality ceiling speakers, and looking at new prices showed that this could very quickly become a huge cost. At this point, I started searching for what was available second-hand, and I found someone selling a complete ex-restaurant sound system. It comprised seven Bose DS 100F ceiling speakers (Photo 1), six Bose DS 16F ceiling speakers, a large Bose DXA 2120 amplifier, three smaller IZA 190-HZ Bose amplifiers, a line-level audio splitter box and various remote controls and cables. The price was very good – in fact, less than the new price of just the big amplifier! (As it later turned out, that was just as well.) To put it mildly, Bose has a variable reputation amongst audiophiles; many hate the brand due to its heavy reliance on processing and compensation to make small speakers sound good. However, in professional sound reinforcement, the story is different. I’ve had a lot of experience with different Bose gear, and I find two things. First, their professional gear is better-­ built than their consumer gear. And second, if you buy their upper-tier products, they can sound quite good. In this case, before committing the gear to the new house, I extensively tested the larger DS 100F speakers working with the DXA 2120 amplifier – and I was impressed. The speakers use a ported enclosure with a 133mm long-throw woofer and a 57mm midrange/tweeter. With a relatively small enclosure volume, and with those drivers, the speakers were never going to sound as good as full-size, dedicated hifi speakers – but then again, in this application they didn’t need to. Still, they had bass down to about 100Hz (more on bass in a moment) and the treble was adequate, although not wonderful. This was with the speakers tested not mounted in a ceiling: if mounted in a ceiling near to a wall, you’d expect the bass to be better due to the resulting acoustic loading. In addition to the ceiling speakers, we also wanted a pair of speakers mounted outside to service a large undercover deck. This area could also have used ceiling speakers, but the Bose speakers are not weatherproof, and while such speakers wouldn’t be subjected to direct rain, they would be subjected to fog and dew. siliconchip.com.au Australia's electronics magazine So I decided to keep an eye out for good quality exterior speakers. I eventually found a pair of second-hand Niles OS7.5 wall-mounted speakers for an excellent price. The amplifiers The Bose DXA 2120 amplifier was going to be used to drive the DS 100F speakers. But how many speakers could it power? These speakers have a rated impedance of 8W; the minimum impedance this amplifier is happy working with is 4W. Thus, each of the two stereo channels can drive two speakers in parallel, giving a total of four speakers. After a bit of thought, this worked out well. The rectangular-shaped house has two large rooms, one at each end of the house. These rooms have cathedral (raked) ceilings, with internal walls that back onto a roof loft space (Photo 2). If two of the speakers were placed through these walls, we’d have a stereo pair in each room. Within the previously discussed constraints, at least if sitting in these rooms, the stereo imaging should then be good. What about the other speakers? The two end rooms are joined by a wide, open corridor that passes down the middle of the house. Locating the remaining three DS100F speakers in this space would largely cover the rest of the house – there wouldn’t be speakers in every room, but you’d be able to hear sound everywhere. June 2026  55 But how do you drive three speakers from a stereo source? It didn’t make much sense trying to do so! So back to the remaining three Bose IZA 190-HZ amplifiers (Photo 3). These amplifiers all have 70/100V outputs. If you’re not familiar with this approach, each speaker to be driven from such an amplifier is equipped with a transformer with multiple taps, with each tap giving a different power rating (and so speaker loudness). The DS100F speakers were equipped with such transformers, and different power ratings could be selected by turning a knob. A conventional 8W speaker impedance was one setting, explaining how these speakers could also be used with the main amplifier. Multiple speakers can be driven from each output with such a 70/100V system; rather than worrying about impedance, you just need to ensure that the total selected speaker power ratings do not exceed the power output of the amplifier. The IZA 190-HZ amplifiers are also able to be configured with a mono output from a stereo source, making them suitable for driving the three speakers. Only one amplifier was needed to drive these speakers – which is just as well, as it turned out that two of the three second-hand IZA 190-HZ amplifiers were defective! A 70/100V system has a reduced frequency response, but in our case, where these speakers are used to ‘fill the hole’ between the speakers in the end rooms, their more limited frequency response is well masked by the 8W speakers, which are still audible from those locations. All about the bass Now, back to the topic of bass. For our previous house, I’d built two large subwoofers. Each used a JBL 15-inch (380mm) driver and a 200L ported enclosure (Photo 4). I’d mounted them beneath the floor of the lounge room, firing through floor grilles. They’d worked exceptionally well, so I resolved to move them to the new house. There, they could be mounted in the loft space, passing their sound through two wall-mounted openings. As they would also be used for the lounge home theatre sound system (not covered in this article), they would provide bass at only one end of the house – an acceptable trade-off as bass is largely non-directional. But what to power them with? In the previous house, I’d used a four-­ channel amplifier I had built. It had an output of 68W/channel and drove the subs and two full-range speakers. In that small lounge room, the subs’ output had been fine, despite the relatively low amplifier power. However, testing in the new house soon showed that the much bigger room seemed to suck all the bass away – the huge subs sounded quite anemic. So I then built a 200W per channel amplifier, and the subs came alive. Photo 3: a 90W Bose IZA 190-HZ amplifier drives three speakers using a 100V system. Photo 4: two subwoofers are used, each with a 200L custom-built enclosure and a 15-inch, 300W JBL driver. There is audible bass down to 25Hz and strong bass from about 35Hz. 56 Silicon Chip Australia's electronics magazine Photo 5: one of the two outdoor subwoofers for the deck; it is built inside a fibre cement stool. They provide bass support for two Niles wall-mounted speakers. siliconchip.com.au However, in all of this, I had forgotten the outside speakers – surely I didn’t need yet another amplifier to drive them, did I? Instead, I decided to use relay switching to select between driving the inside or outside speakers from the same amplifier. About this time, I developed the Outdoor Subwoofer published in the June 2025 issue (siliconchip.au/ Article/18313) and the improvement it gave to the outdoor sound system audio quality was major. So much so that I decided to build two of these subs (Photo 5). Now things were getting complicated – to switch from inside to outside sound, I needed to simultaneously switch the output of three different amplifiers! But again, Silicon Chip came to the rescue, and we developed the Remote Speaker Switch that was published in the January 2026 issue (siliconchip.au/Article/19561). It’s a very flexible system and does this job neatly using three interlinked switches (Photo 6). Photo 6: the Silicon Chip Remote Speaker Switch is used to simultaneously switch the output of three amplifiers between different speakers, with three modules required. The preamp The next step was to consider how the amps were to be fed signals, and where all these amplifiers were going to be mounted. Looking at the second point first, I decided to place the three amplifiers on a shelf in the roof space loft. The loft is accessed by a dropdown ladder, with the area used primarily for storage. If the amplifiers were remotely switched, and if volume control was also able to be achieved remotely, there was no need to have the amplifiers located in the living space. Making this decision easier was the fact that we would stream music from our phones via Bluetooth, with the volume also controlled by the phone. So, a series of plywood shelves were made, and the three amplifiers installed in the loft. How to feed signals to all these amps? The ex-restaurant sound system installer had faced the same dilemma and had used the powered line-level signal splitter to divide the source signal between the amplifiers. However, he or she had not had an extra subwoofer amplifier to contend with. Not only did the audio signal have to be sent to the different amplifiers, but a subwoofer crossover needed to be implemented as well. Here I took a step that is unusual in home sound siliconchip.com.au Photo 7: unusually in a home system, a Clarion EQS755 car sound preamp is used. This drives the three amplifiers from a single Bluetooth streaming input adaptor, provides the subwoofer crossover and allows frequency equalisation on seven bands. It runs from a 12V DC plugpack. systems and decided to use a preamplifier designed for a car: a Clarion EQS755 powered by a 12V plugpack (Photo 7). I’d used it in our previous house, and it had worked well. Now out of production, it has surprisingly good audio specifications, unbeatable at the price. It has a 7-band equaliser and a variable-level subwoofer output, with the sub crossover frequency able to be set at either 60Hz or 90Hz. In addition, it has a further two full-range outputs, for car use, dubbed ‘front’ and ‘rear’. However, in my application, I could use these outputs to feed the two Bose amplifiers. As a bonus, using the preamp would give me a seven-band EQ. Disaster! As an owner-builder, a lot of the house was being built by me, and I Australia's electronics magazine wanted to listen to music as I toiled. Therefore, the whole-of-house sound system was running quite early in the house build process – as soon as the house was made weatherproof. The ceiling speakers were mounted temporarily on plywood panels. It’s just as well the system was trialled before the house was completed, because I started experiencing major amplifier failures! First to go was the home-built subwoofer amplifier. It used two offthe-shelf modules, each comprising a switch-mode power supply and a Class-D audio amplifier. This amplifier lasted just weeks before it started blowing supply fuses at switch-on. I could have attempted to fix it, but truth be known, I was a bit suspicious of the quality and design of these modules, anyway. June 2026  57 Photo 8: two LD Systems amplifiers are used to drive the main and subwoofer speakers – an XS-400 (2 × 200W) for the main speakers and an XS-700 (2 × 350W) for the subwoofers. These fan-forced commercial amplifiers were purchased after multiple amplifier failures – the demands of providing a lot of power and working in a hot loft space proved to be extreme. When John Clarke saw them, he was scathing about their design layout! So I replaced this amplifier with another, more conventional design I’d built long ago, an amplifier that I was sure was of good quality. Next to go wrong was the big Bose DXA 2120 amplifier. This one developed a ‘splat! splat!’ in the audio output, then just died completely. What on earth was going on? My replacement amplifier for the subwoofers gave me the clue. Despite this amplifier having run in my previous home office for years, and despite my having used it to occasionally test loudspeakers at quite high power levels, the passively cooled heatsinks had never run warm. But here in the loft, driving the subwoofers, it was getting darn hot – over 55°C external heatsink temperatures... and still rising. Two aspects were at play. The first is that the ambient temperatures at which the amplifiers were working were high. In a normal domestic setting, ambient temperatures are seldom very high; after all, that’s why people have air conditioning! But in the loft, within the roof space, temperatures were up to 35°C; potentially even higher in some weather conditions. The second aspect was that the amplifiers were working really hard. Especially with the house unfinished, and so without plasterboard walls and ceilings in place, the house volume was very large. To get adequate sound levels in such a large volume meant using a lot of power. Put those two things together, and the amplifier working conditions were extreme. So I decided to buy two new amplifiers, both fan-cooled and both aimed at commercial (rather than domestic) use. After an extensive search, I found two LD Systems amplifiers – the XS-400 and XS-700. The XS-400 has an output of 2 × 200W into 4W, and the XS-700 develops 2 × 350W into 4W – see Photo 8. Both are Class-D amplifiers that have a maximum distortion of less than 0.1%. Not hifi, but good enough for a whole-of-house sound system. The amplifiers were bought second-hand, and while it was an additional cost I wish I didn’t have to outlay, they were much cheaper than buying similar quality amplifiers new. As you can imagine, I tested these amps very thoroughly, only to find that certain internal components were running very hot! However, a simple modification to the airflow path within the amplifiers, as described in my articles on amplifier cooling published in the August & September 2025 issues, improved this greatly (siliconchip.au/ Series/444). To give you an idea of the required power levels, I found that the 350W/ channel amplifier driving the two subwoofers was quite near clipping at times. The amp has a clipping indicator on its front panel, so it’s easy to see how hard it is working. The final system Fig.1: a Bluetooth adaptor feeds a preamp/subwoofer crossover that in turn feeds three amplifiers. These power internal and external speakers, both main and subwoofers, with inside/outside selection via three interlinked relay switches. A mixture of 8W and 100V systems is used for the main speakers. Fig.1 shows the layout of the final system. A Bluetooth adaptor feeds the Clarion EQS755 preamp. The preamp also drives the LD Systems XS-400, XS-700 and Bose IZA 190-HZ amplifiers. These power the four 8W speakers as two stereo pairs, and the three mono 70/100V speakers located down the middle of the house. The preamp’s subwoofer output also drives the LD Systems XS-700 subwoofer amplifier, which powers the two 15-inch subs. The speaker switch turns off all the interior speakers and swaps the XS-400 output to the outside wall speakers; simultaneously, the XS-700 amplifier’s output is switched to the two outside subwoofers. Power to the Bose IZA 190-HZ, LD Systems XS-400, preamp and the switching relays is controlled by a single wall-mounted conventional switch in the living area, with one LED indicator showing when they are active. That is, this part of the system is powered by a remotely switched power point. Australia's electronics magazine siliconchip.com.au 58 Silicon Chip Lessons learned Test at every step! Without testing, you cannot be sure what you’ll end up with. For example, until I had temporarily mounted the speakers in the half-built house, I wasn’t sure that seven interior speakers would be sufficient. Until I had tested over a period of many weeks in summer, I had no idea that amplifier cooling would prove to be so critical – and that so much power would be needed. Would the Bluetooth adaptor continue to work if I took my phone out onto the exterior deck? (It did.) Did all the gear purchased second-hand actually work? It took me many hours to discover that two of the Bose amplifiers were defective – I was chasing down blind alleys with their remote switching and volume control functions, sure that their lack of output was something I was doing wrong! (Their power LEDs came on and then slowly went off – the amps weren’t totally dead.) Finally, consider how you actually use a sound system in a house and develop a system to suit that application. Silicon Chip Binders REAL VALUE AT $21.50* PLUS P&P Are your copies of Silicon Chip getting damaged or dog-eared just lying around in a cupboard or on a shelf? Can you quickly find a particular issue that you need to refer to? Photo 9: this is a mock-up design shot of what I hope the finished house will look like, with the landscaping done. Another wall plate switch operates the LD Systems XS-700 subwoofer amplifier – it’s on a separate switch, so only this part of the system can be switched on for home theatre use. Finally, all the speaker wiring was made using 3.4mm2 cross-sectional area low-­voltage garden lighting cable – the cheapest cable I could find that had plenty of copper cross-section. It was much cheaper than dedicated speaker cabling of the same gauge. The results So, are we happy? Yes, we are. The interior system doesn’t have the subtle nuances of a good hifi system being listened to from the sweet spot – but then, with seven distributed speakers, it never could have. But it fills the house (or outside deck) with quality sound and has enough power to listen at ‘party’ levels. Conversely, it still sounds good at very low listening levels. siliconchip.com.au Despite the presence of the large subwoofers (and their 700W amplifier), the bass is set to give body and depth to the sound, rather than bump thump. In the two main rooms, the stereo imaging is clear, and when walking from these rooms to the hallway, the transition from stereo to mono is unnoticeable. The ability to balance the output levels of the separate amplifiers also means that the sound volume doesn’t change throughout the house. The outside speakers are ideal for listening at normal levels and, if required, can work at much higher levels (however, even in this semi-­rural valley, that can annoy neighbours). The best aspect of the system is that operation is seamless; you just flick the wall switches, connect your phone via Bluetooth, and play music. The system was complicated in development and implementation, but in use, SC it just works. Australia's electronics magazine Keep your copies safe, secure and always available with these handy binders These binders will protect your copies of S ilicon C hip . They feature heavy-board covers, hold 12 issues & will look great on your bookshelf. H 80mm internal width H Silicon Chip logo printed in goldcoloured lettering on spine & cover Silicon Chip Publications PO Box 194 Matraville NSW 2036 Order online from www. siliconchip.com.au/Shop/4 or call (02) 9939 3295 and quote your credit card number. *see website for delivery prices. June 2026  59