Yeak okay the photo's a bit dark and it's a tad hard to see the drivers so I've highlighted the mid range and top end ones with yellow dots. The red lines join the mid points between them which is the apparent acoustic source for vocals and directional information for both the centre channel speakers and the main left and right speakers.

*New photo required*

The top centre channel speaker with the screen raised. When it's lowered the top of the screen sits just below the woofers. A flipped image of this picture if you like. Below the speaker is a two hinged panel absorption/diffusing screen shown in it's closed position. The gap between the panels is deliberate as is the angle they form. The panels cover the TV when not in use and improve imaging for stereo and multi channel music by creating an acoustically dead area between the left and right speakers. They consist of 18mm MDF covered by 12mm compressed cotton wadding which is then covered by 50mm square and triangular blocks of up to 50mm thick built up from layers of 5mm thick rabbit fur felt.

The Sony STR-DB900 and crossover sit in a small rack below the lower centre channel speaker.

After hearing a demo of a Yamaha 7.1 system several years ago I decided that front effects speakers were a useful addition to any surround sound system when used for movie soundtracks. Yamaha pioneered 7.1 and these days have extended it to 9.1 and even 11.2 in the case of the RX-Z11. THX have a 10.2 system which users three high front effects speakers, left, right and a centre speaker they refer to as "god".

Front effects speakers are placed as high and as wide in the room as possible. In the top left and right front corners of the room is a good place for them. Reflections of the rear and side walls and ceiling caused by this placement aren't a problem at all and probably help achieve the desired result.

The extra two channels to drive front effects speakers don't really exist on 5.1, 6.1 or even 7.1 encoded material but it isn't hard to fake it. All you need to do is take your existing front left and right signals, pass them through a high pass filter, isolate the out of phase components (what used to be called in the good old days of stereo, a "phase or width enhancer"), delay these a tad and feed what's left to a small stereo amplifier.

In this case two channels of a 70w per channel Yamaha DSP E-492 and then to a small pair of speakers that only need to handle from about 500hz upwards. Drivers used are Vifa M10MD39-08 3" mid range and a Vifa D27TG45-06 1" tweeter hooked up with via a modest two way passive crossover.

Front effects speakers add width and more importantly height to a room. They are most effective with soundtracks that have a lot of off screen activity going on. Jungle scenes, streetscapes and the like are simply amazing.

Probably the smallest speaker box I think I've ever built. Sealed of course. Mounted on a bass trap in the top corner of the room. Surprisingly effective.

The front left and right speakers have some serious horsepower. As do the centre channel speakers with their 7 drivers, 5 amplifiers and 500+ watt total output. I needed something at the rear of the room that not only sounded the same but could hold their own, so to speak. What I've ended up with is perhaps more than what's required but I figure that if you're going to go to the trouble of bolting speakers to a masonry wall or lifting roof sheets to get access to the rafters so you can mount threaded rod hangers then you might as well make them as big and heavy as you can.

With the advent of Blu-ray and it's 7.1 soundtracks and A/V receivers that can process 7.1 you now apparently need four rear surround speakers or at a pinch, three. The first pair (Surround) to the side and slightly to the rear of you at between 10º and 30º rear of where you sit and another pair or a single speaker (Surround Back) behind you. To take full advantage of the Cinema Studio EX modes the angle between each of these speakers should ideally be the same, so between 160/3 = 53º and 120/3 = 40º for four enclosures.

A three way sealed box system using a Morel NeoLin MW267 7" bass driver, a Vifa M10MD39-08 3" mid range and Vifa D27TG45-06 1" tweeter. Very solid construction using 38mm laminate MDF/Particle board panels for the sides and 50mm for the front and back. Like the centre channel system it's active/passive with an active 4th order Linkwitz/Riley at 600hz and a passive 2nd order filter at 3000hz. Like the other mid/top passive filters in the system, not that there are many, impedance correction and resonant frequency notch filters are included.

To drive the speakers I'm using four channels of a Sony QS Series STR-DB900 100 watt per channel digital amplifier, the same type that's used for the centre channel. The beauty of digital amplifiers, especially when directly connected to bass drivers as in an active system is the sheer depth and quality of the bass.

And no the photo isn't upside down, it's just that because I wanted to mount these as close to the ceiling as possible it was better to turn the speakers upside down. This gets the tweeters away from the ceiling to avoid reflections, brings the heights more into line with the rear surround speakers and gives better angles (and hence dispersion) to a seated audience. Not obvious in this photo but the enclosure is tilted down and inwards by about 45 degrees. Weighing in at nearly 20kgs they hang by chain to four mounting points from stainless steel ferrules and 8mm threaded rod fixed to 40mm angle iron which spans three ceiling joists.

Okay, so laying gear on its side is probably not the best arrangement but when space is tight you do the best you can and I'm rapidly running out of room. The black 1U rack case is the active crossover and on top of it is the Sony STR-DB900 digital amplifier (actually a full AVR but I'm only using it's amplifiers). It does keep the speaker leads short, to one speaker at least as mounting midway between the speakers and on the ceiling wasn't practical. The big red and green blotches on the active crossover are stick on labels that cover the LED's to dim them so they barely glow in the dark.

A three way active system each powered by yet another 70w per channel Yamaha DSP E-492 amplifier. In case you're wondering what the story is with these amps, it's that I got a good deal on a few of them. These were a great little add on unit for two channel systems that provided Dolby Pro Logic decoding with three amplifiers to power the centre and rear channels. I'm only using the very good amplifier sections, rated at 60W but actually putting out 70W at the same distortion levels.

Drivers are Vifa PL26WR09-08 (OEM version of paper coned M26WR-09-08) 10" bass, Vifa M10MD39-08 3" mid range and a Vifa D27TG45-06 1" tweeter. All are mounted in sealed boxes. Front and back panels are 50mm, others are 38mm. Crossover points are 600hz and 3000hz and that's the crossover sitting on top of the amplifier, both of which are sitting on a shelf that's bolted to the wall.

They just appear to hang there like something that shouldn't but a look around the back reveals a very substantial welded steel bracket and five fixing points to the wall. The stepped enclosures are to reduce baffle effects and to also time align the drivers. The enclosures are also angled downwards and inwards enough to align them with a nominal centre of room seating position.

Every home theatre system needs a subwoofer or so the salesmen keep telling us. Not just to make up for any bass deficiencies your main speakers might have but to take full advantage of the .1 signal. But if you're going to have one, then why not have two. In fact why not have four spread around the room and this is exactly what I've done. For further reading on the use of multiple LFE drivers you could read the AES paper #5062 titled "Subwoofers: Optimum Number and Location" by Todd Welti.

At the front of the room are a pair of dual driver subwoofer which uses Peerless 831857 12" drivers each with its own enclosure and 125W amplifier. Both enclosures are sealed boxes, constructed from laminated 25mm MDF for 50mm wall thickness, heavily braced and damped and stuffed with long fibre wool at 48gm/litre. It's really two subwoofers, one sitting on top of the other that happen to be joined, rather than one subwoofer, in fact the Q's of both boxes are slightly different. Along the rear and one side wall are two additional subwoofers which use Vifa M26WR-09-08 10" drivers and the same 125W amplifiers. The enclosure is a standard double folded tapered transmission line.

Whilst each enclosure has an amplifier built into it there is no crossover, just a buffer. All six subwoofers are driven from a common control amplifier via three channels with adjustable levels and filtering.

I'm still a fan of transmission lines and people are generally impressed with the size of the things and tend to ask questions. You can achieve much the same result though with a much smaller low Q sealed box.

Just in case you're reading this and thinking that there sure are a lot of speakers and amplifiers in this room, well yes there are but it is a fully active 9.1 system. Anyway here's a summary of the current state of play...

29 Amplifiers (as in individual channels) total power 2600 watts ^[1], driving 37 Drivers (consisting of six 12", four 10", seven 7", ten 3" and ten 1") mounted in 14 Cabinets (speaker boxes).

^[1] Actual watts RMS into 8 ohms at rated distortion levels but the effective power of active speaker systems is always higher than a single amplifier driving a multi speaker passive system. As a general rule for a three way active system you add the total power of the three amplifiers and then double it.

Right at the start of this article I said I had a normal home with a more or less normal lounge/living area that I use for audio and video related activities as well as it's usual functions. Well I'm sticking to this story even though some people would say I have a far from normal home and that's apart from this room. It has been suggested that I'm heading into "bat cave" territory and whilst I think that's a slight exageration the room probably has gone way past the bounds of what some people, especially spouses, might consider reasonable.

In my defence though getting a decent picture or for that matter decent sound does require that some work be done to the room. No projector is ever going to achieve anything like it's true performance in a room with a white ceiling, light coloured walls, flooring and furnishings. This is especially true for absolute black levels, shadow detail and scenes with high contrast as any light reflected back from the room will degrade the image. The better the projector the more important all this becomes because the limitations of the room will simply drag it back to the same level of performance as a lesser machine.

Image depth or if you prefer "pop" as some people like to describe it is dependent on the ANSI (the ability to show something dark right next to something bright and maintain the contrast between them) and On/Off (the maximum output for an all white scene compared to the minimum output for an all black one) contrast of a projector with a fair bit of interplay between the two. In high APL (Average Picture Level) scenes (ie. bright) ANSI contrast is more important and in low APL scenes (dark) On/Off contrast becomes more important. Nothing kills either of them quicker than light bouncing back from the room and onto the screen. Light spill back onto the screen can also desaturate the colours so they appear washed out and not as vibrate as they could be.

Achieving excellent audio quality opens up a whole other can of worms with things such as getting the reverberation time right, taming first reflection points, controlling room modes and putting all the speakers in the right place. The most important aspect is of course the room shape and dimensions because if you get this right then it reduces the number or at least the severity of problems that you have to solve later. Luckily for us work by the likes of O.J. Bonello, M.M. Louden and others has made this a fairly simple process. The application of various acoustic treatments such as absorbent panels, diffusers and bass traps can then be used to bring the rooms acoustics up to an optimal level of performance.

This photo was taken during the day with lights on, the blinds open and has been further processed to increase the brightness. The room is a tad dark at the best of times and dominated by audio/video equipment. A lot of people, especially non audio/video enlightened ones when seeing the room for the first time are a bit lost for words.

Drawing of the room showing the positions of the video (pink), speakers (orange), subs (purple) and acoustic treatments (grey), mainly 500mm and 250mm cylindrical bass traps but also including flat panel diffusers. Some of the vertical bass traps run floor to ceiling for room mode control whilst others are purely to control reflections. The physical acoustic centre of the room, an equal distance from each of the five main speakers, in this case 3000mm, is in the middle of the seating area. Whilst you can correct electronically for speakers that are closer to you than they perhaps should be, there's nothing like having them all as far away as possible as it increases the size of the sweet spot so more people get good quality surround audio.

Walls are double solid brick, except the front and stub wall which are stud but filled with Rockwool and lined with 16mm FyreCheck plaster. In order to dampen the room somewhat and avoid a hard concrete box one entire brick wall (the left side one) is covered with a stud wall using 10mm Gyprock. The vertical studs are metal and only fixed top and bottom so the entire wall can flex. Floor is solid timber over concrete slab, windows are double glazed laminated glass.

It's a pretty big room at 6800mm x 5000mm (22.3ft x 16.4ft) and with a average ceiling height of 3100mm (10.2ft) that works out to be a tad over 100 m3 (3700 ft3) and that's before it opens out onto a 1600mm wide passageway. A good size for decent audio for reverberation, standing wave reduction (1.0 : 1.6 : 2.2 ratios) and such but it does require a lot of power to achieve realistic sound levels. With seating starting just in front of the projector (30 degree viewing angle) the sweet spot for good surround audio is fairly large. Despite it's size though it's still surprising how quickly you run out of spots to put seats when a few friends come around to watch a movie.