Technical

Surround Sound

5.1 surround sound

surround-sound5.1 surround sound is the most common format. It includes a total of six channels – five full-bandwidth channels with 3-20,000 Hz frequency range for front left and right, centre, and left and right surrounds, plus one “low frequency effects” (LFE) subwoofer channel for frequencies from 3-120 Hz.

As we stated above, 5.1-channel surround sound is the most common home theater configuration today. And there are two main formats that deliver surround sound for 5.1-channel systems.

Dolby Digital

Dolby Digital quickly established itself as a reigning surround format, largely thanks to DVDs. These days, it’s also used in video games and HDTV programming. Although Dolby Digital, strictly speaking, is simply a method of encoding audio information digitally, the term is often used to refer to 5.1-channel audio – its most popular form. In discussing Dolby Digital surround sound, we’ll be focusing on this multichannel format.

Unlike earlier forms of surround sound, Dolby Digital 5.1-channel audio is a “discrete” multichannel surround sound system. With six discrete channels, sounds can be placed very precisely, for improved dialogue clarity, imaging, spaciousness, and realism. You also get a dedicated subwoofer channel, for plenty of deep bass.

DTS

Like Dolby Digital, DTS provides 5.1 channels of digital audio. However, DTS uses less compression than Dolby Digital. As a result, some say that the sound produced by DTS is slightly more accurate than the sound produced by Dolby Digital. While most audio/video receivers will have both Dolby Digital and DTS, fewer DVDs and video games are encoded with DTS, compared to the number encoded with Dolby Digital.

7.1 surround sound

surround-sound-27.1 surround sound systems are also available, and simply add another full-bandwidth channel to the mix.
In addition to HD video, today’s high-def disc formats can also support more detailed audio. Most Blu-ray Disc players support 7.1 audio formats, and some even offer high-quality, lossless surround sound.
While your high-def disc player and receiver may be able to decode these new surround sound formats, it’s important to note that not all discs you play will take advantage of them. Be sure to check out the details on the high-def discs you watch to see which audio format they use. You’ll also want to connect your player to a compatible receiver using your disc player’s compatible HDMI output (version 1.3 or above).

Lossless surround sound formats

The newest high-resolution surround formats, Dolby TrueHD and DTS-HD Master Audio, offer up to 7.1 discrete channels of lossless audio. Along with adding two extra rear channels to the standard Dolby Digital and DTS formats, Dolby TrueHD and DTS-HD Master Audio discs are encoded with more audio information per channel. In fact, it’s identical to the movie studio’s original master. That means the improved directionality and more precise effects make it even closer to the experience of being in a movie theater.

Additional discrete 7.1-channel surround formats

You may find that some Blu-ray discs are also encoded with other discrete 7.1-channel surround formats. Dolby Laboratories and DTS developed Dolby Digital Plus and DTS-HD (High Resolution), respectively. These formats deliver 7.1 independent channels of sound. They provide more detailed surround effects than 5.1 Dolby Digital and DTS, though they aren’t lossless like Dolby TrueHD and DTS-HD Master Audio. Receivers that support lossless 7.1-channel formats will also support Dolby Digital Plus and DTS-HD (High Resolution).

HDMI

Because there are many different types of HDMI cables with many different purposes and functions, it is important to know the differences between them when making choices about your HD setup.

What is HDMI 1.3

  • HDMI 1.3 allows the availability of a new mini connector for devices such as camcorders
  • The availability of HDMI 1.3 depends on your specific equipment.
  • All HDMI cables should be made using the largest gauge (AWG) wire with individually shielded pairs possible with top quality workmanship. This protects your signal from Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI).
  • Increases single-link bandwidth to 340 MHz (10.2 Gbit/s)
  • Optionally supports 30-bit, 36-bit, and 48-bit xvYCC with Deep Color or over one billion colors, up from 24-bit sRGB or YCbCr in previous versions.
  • Incorporates automatic audio syncing (Audio video sync) capability.
  • Optionally supports output of Dolby TrueHD and DTS-HD Master Audio streams for external decoding by AV receivers.[8] TrueHD and DTS-HD are lossless audio codec formats used on Blu-ray Discs and HD DVDs. If the disc player can decode these streams into uncompressed audio, then HDMI 1.3 is not necessary, as all versions of HDMI can transport uncompressed audio.

What is HDMI 1.4

  • HDMI 1.4 increases the maximum resolution to 4K x 2K (3840x2160p at 24Hz/25Hz/30Hz and 4096x2160p at 24Hz, which is a resolution used with digital theatres);
  • HDMI 1.4 includes an HDMI Ethernet Channel, which allows for a 100 Mb/s Ethernet connection between the two HDMI connected devices;
  • HDMI 1.4 also introduces
    • an Audio Return Channel
    • 3D Over HDMI (HDMI 1.3 devices will only support this for 1080i)
    • a new Micro HDMI Connector, expanded support for colour spaces
    • an Automotive Connection System.
  • HDMI 1.4 supports several stereoscopic 3D formats including field alternative (interlaced), frame alternative, frame packing, line alternative, side-by-side half, side-by-side full, 2D + depth, and 2D + depth + graphics + graphics depth, with top/bottom half and full formats to be added in January 2010.
  • HDMI 1.4 requires that 3D displays support the frame packing 3D formats at either 720p50 and 1080p24 or 720p60 and 1080p24.
  • High Speed HDMI 1.3 cables can support all HDMI 1.4 features except for the HDMI Ethernet Channel.

Racking

While audio visual equipment can be placed almost anywhere, it is recommended that it be installed and maintained in a fixed enclosure or equipment rack. To the technology enthusiast, an audio visual equipment rack is much more than a place to store equipment; it is a system unto itself.

By keeping equipment in an equipment rack you help to ensure the safety of your equipment, deter the theft of valuable hardware, and make the system easy to access for service and future growth. In addition equipment racks can be supplied with accessories for power management, thermal protection, and cable management.

Thermal Management

Thermal control and management is very important when thinking about putting a lot of audio visual devices in a single room or cupboard. Thermal control can extend equipment life, minimize noise and reduce breakdown or service of your devices.

Amplifiers, Game Consoles and Sky Boxes can be the worse for create heat inside a rack or cupboard and if this heat is not managed it can cause major problems including complete failure of the products.

Dimmable Lighting and Lighting Scenes

Dimmable lighting is not a new technology; it has just been refined and now gives us a reliable and a ‘green’ solution to lighting. Not all lights are dimmable a lot of lighting companies are trying to make most lights work but some light and light bulbs just cannot be used in a dimmable circuit like certain LED and fluorescent fittings. The thing to make sure of is the dimmable ballast of the light fitting.

Media Servers

Media storage devices or servers usually in keep all of your media in the form of magnetic media, servers often use several sets of hard drives that have duplicates of the same data to prevent loss in the case of a hard drive crash or other physical damage. This duplication is often referred to as Redundant Array of Independent Disks (RAID). There are many different levels of raid storage the basic RAID 1 just mirrors your data across the disks where as the Imerge XivaSafe will use RAID 6 that splits your data across many discs duplicating it so that a loss of even two hard drives will not let you loose any of your media.

Acoustics

surround-sound-3There’s much more to the sound we hear than just what comes out of our speakers, you hear reflected sound from your room’s four walls. Your room’s ceiling and floor contribute reflected sound, as well.
The sound that you hear in any room is a combination of the direct sound that travels straight from your speakers to your ears, and the indirect reflected sound – the sound from your speakers that bounces off the walls, floor, ceiling or furniture before it reaches your ears.

Reflected sounds can be both good and bad. The good part is that they make music and speech (like movie dialogue) sound much fuller and louder than they would otherwise. (If you’ve ever played your speakers outdoors where there are no walls to add reflections, you’ve probably noticed that they don’t sound very good – thin and dull, with very little bass.) Reflected sound can also add a pleasant spaciousness.

The bad part is that these reflections distort sound in a room by making certain notes sound louder while canceling out others. The result may be midrange and treble that’s too bright and harsh or echoey, or bass notes that are boomy, with a muddy “one-note” quality that drowns out deep bass.

Using sound-proof panels and linings is a great solution to stop reflected sound and keep your room neutral to get the best out of your sound system but also just adding rugs or curtains to your room can reduce the reflective effects of a room.

Viewing Distance

As a rule of thumb with 720p resolution projectors, a viewing distance of less than 1.5 times the screen width will cause pixilation and artefacts to become more visible and intrusive. While it is true you have a very BIG image in front of you, these distractions can compromise viewing satisfaction. On the other hand, high definition 1080p resolution projectors, allow you to sit a bit closer, say at 1.2x the screen width, without worrying about pixilation or artefacts. That still might be too close for comfort from an aesthetic point of view, but some people like to have that very large image in front of them.

The maximum distance is the distance at which all the projected information can still be understood. In the case of home cinema this distance is normally up to 6 times the screen’s height.

The bottom line is that two issues need to be considered in your ultimate decision on screen size. One is your personal aesthetic preference, and the other is the technical limitations of your projector to produce a fully resolved image at any given viewing distance.

Choosing the right screen size and the right aspect ratio will have a huge impact on your long term enjoyment of your theatre. So give these matters serious thought. When it comes to a successful home theatre design, these factors are much more important than the projector you choose.

ANSI Lumens (Projector Brightness)

There are two major considerations when looking at the brightness of a projector (measured in ANSI lumens).

  • The ambient light inside your room. This should be as dark as possible. Artificial light is always less invasive than natural light so you’re better off having shutters or curtains/blinds that close out all light and having a dimmable lighting circuit to reduce to ambient light to view your projection or switching the lights off if possible.
  • Throw distance. This is the distance from the centre of the projector lens to the screen. The further away the projector, the larger the image and the more the set amount of light emitting from the projector is dispersed. If you double the projectors distance from the screen, you get an image four times bigger (twice as wide and twice as high) and only 1 quarter the brightness. As a guide, projectors of around 500 ANSI lumens are good for small screens in small rooms, 700 for a small screen in a medium room and 1000 upwards for larger screens and rooms. Remember, the larger the room, the larger the screen and so the further away and brighter the projector will need to be.

What next?

Got a project, need advice or just want to say hello? Get in touch