It is therefore better to choose non-commensurate ratios for the walls where a home cinema is to be installed. Proper custom home cinema design and engineering will ensure that the modes are spread out as much as possible. Much work has been done on ideal home cinema room ratios. However, the various suggested dimensions are not necessarily the only optimum ones for all room sizes. It is also important to realise that room modes are inherent in any structure which encloses the sound sources. This means that changing the shape of the home cinema, for example by angling the walls, does not remove the resonances, it merely changes their frequencies from values which are easily calculated to ones that are not.

High end home cinema installations would deal with any modal issues by using custom resonant absorbers, offering an effective modal management system in their design.

Although for low frequencies air absorbs a minimal amount of sound energy, at high frequencies this is not the case. In particular humidity, smoke particles and other impurities will absorb high-frequency energy and so reduce the level of high frequencies in the sound. This is one of the reasons why people sound duller when they are speaking at a distance.

In terms of reverberation time and also the level of the reverberation field, the effect of this extra absorption is to reduce the reverberation time in the home cinema, and the level of the reverberant field, at high frequencies above 2 kHz. Unfortunately though it is dependent on the level of humidity and smoke in the home cinema room and so the high-frequency reverberation time, and the reverberant field level, will change as the audience stays in the space. Note this is an additional dynamic effect over and above the static absorption simply due to the presence of a clothed person in the home cinema seating area, and is due to the fact that people exhale water vapour and perspire. Clearly then the degree of change will be a function of both the physical exertions of the audience and the quality of the ventilation system!

As the effect of air absorption is determined by the distance the sound has travelled (relevant to the size of the dedicated home cinema), rather than its interaction with an acoustic panel, it is difficult to incorporate the effect into the reverberation time equations. An approximation that seems to work in home cinema design is to convert the effect of the air absorption into an equivalent absorption area by scaling an air absorption coefficient by the volume of the home cinema room. This is reasonable because as the volume of the home cinema increases the more is the air that the wave must travel through, and the longer the distance that it travels. 

For home cinema installations taking place in spaces smaller than 40 cubic meters, the effect can be ignored because the equivalent absorbing area is less than 1 cubic meter. However, the effect does become significant if one is designing a large high end home cinema, and air absorption would need to be considered.

It is important that these reflections be diffuse, as specular reflections in home cinema installations will result in disturbing comb filter effects, and distracting images of the sound sources in unwanted and unusual directions. Providing diffuse reflections in custom home cinema installations is thus important and this has been recognised for some time. Traditionally, the use of plaster mouldings, niches and other decorative surface irregularities have been used to provide diffusion in an ad hoc manner.

More recently diffusion structures based on patterns of wells whose depths are formally defined by an appropriate mathematical sequence have been proposed and used, in many high end home cinema designs. However, it is not just the provision of diffusion on the side walls that must be considered when designing a dedicated home cinema room.

Escient’s FP-1 can stream music from any Fireball music server and even a PC, without a docked iPod. Other Escient music servers that are part of the same network can access and play music stored on the iPod, including songs purchased from the iTunes store.

An IP and RS232 port offer wired control capabilities for other third party home automation control systems like AMX and Philips. The graphic user interface provided displays the artist, album, song title, and even the album’s cover. The Escient FP-1 supports and streams multiple audio formats, ensuring the highest quality possible from any audio system. 

Even in the quieter environment of a Victorian town in the days before road traffic, Sabine had to do measurements, using his ears, at night to avoid the results being affected by the level of background noise. Because we rarely hear a full reverberant decay, our ears and brains have adapted, quite logically, to focus on what can be heard. Thus we are more sensitive to the effects of the first 20 to 30 dB of the reverberant decay curve, the 60 dB reverberation is directly proportional to the earlier curves and so this should not cause any problems when measuring in custom dedicated home cinema installations.

However, if the curve of a home cinema room is of the double-slope form, then this simple relationship is broken. The net result is that, although the T60 reverberation time of the home cinema may be an appropriate value, because of the faster early decay to below 30 dB we perceive the cinema’s reverberation as being shorter than it really is. The psychoacoustic effect of this is that the dedicated home cinema sounds ‘drier’ than one would expect from a simple measurement of T60.

Modern home cinema designers therefore worry much more about the early decay time (EDT) than they used to when designing dedicated home cinema systems.

This will subjectively alter the timbre of the sound in the home cinema due to both the effect on the level of the reverberant field, and the change in timbre as the sound in the room decays away. As an extreme example, if a particular frequency has a much slower rate of decay compared with other frequencies, then as the sound decays away this frequency will ultimately dominate and the room will ‘ring’ at that particular frequency.

The sound power for steady-state sounds will also have a strong peak at that frequency because of the effect on the reverberant field level. Materials used for constructing acoustic wall panels for all custom home cinema installations will always have some absorption coefficients, shown as a function of frequency. These are usually presented over octave bands. One could argue that third octave band measurements would be more appropriate psychoacoustically, as the octave measurement will tend to blur variations within the octave which might be perceptually noticeable.

In many cases, because the absorption coefficient of the acoustic treatment varies smoothly with frequency, octave measurements are sufficient. However, especially when considering resonant structures in dedicated home cinema installations, more resolution would be helpful. Note also that there are often no measurements of the absorption coefficient below 125 Hz, this is due to both the difficulty in making such measurements and the fact that below 125 Hz other factors in the home cinema room become more important.

You can simply record all CD’s to the Escient’s internal hard drive and let the music server automatically connect to the Internet to identify each CD. The Escient music servers provide the user with the artist and album name, genre, song list and cover art. Multiple touch panels can retrieve all information throughout the home, creating an easy to use multi room audio system. Escient music servers can integrate with various home automation products like AMX and Elan.

The Fireball SE music servers can be of course used as a stand-alone audio source and replace an existing CD player. Philips touch panels now offer great integration with their TSU9600 and TSU9800 control touch panels, allowing for absolute control and ease of use. Multiple Escient music servers can be used together, if extra storage and multiple streams are required. IP based multi room audio systems like Netstreams can distribute up to five simultaneous audio streams from a single music server.

The free Escient Fireball PC software shares all music stored on a PC with an SE music server. Anyway you look at it, the Escient SE music servers are the easiest and most affordable way to enjoy your music now and in the future.

For example, a home cinema room whose surface area is 75 sq. meters and whose volume is 42 cubic meters, would have a mean time between reflection of 6.51 ms. By applying a lot of absorption (let’s say that the average absorption coefficient is 0.9), the reverberation time can be calculated to be 0.43 s, and the average number of reflections that have occurred during the reverberation time can be calculated to be 6.45.

These are barely enough reflections to have hit each surface once. In such a home cinema installation, the reverberant field does not really exist; instead the decay of sound in the home cinema room is really a series of early reflection to which the concept of reverberant field or reverberation does not really apply. In order to have a reverberant field in dedicated home cinema installations there must be more than six reflections. A suitable number of reflections, in order to have a reverberant field, might be nearer 20, although this is clearly a hard boundary to accurately define.

Home cinema designs that are not properly engineered tend to be over-treated with absorptive acoustic panels so that they are very ‘dead’ and do not support a reverberant field.

Sleek and light-weight, the XP-8.4 wireless touch panel has an ultra bright LCD screen ensuring an easy, user-friendly graphical interface that matches every individual room decor inside the home. Screen layouts can be fully customised to perfectly suit one’s needs, offering complete control for multi room audio and video distribution, lighting, etc. The XP-8.4 wireless touch panel can display real-time feedback of temperature and security systems, plus instant “Now Playing” information from your favourite music sources.

Elan’s touch screen comes equipped with a built-in web browser for an easy connection to the internet, and also supports audio and video streaming due to its Flash player support.  

Conventional home cinema subwoofers that offer plain level and crossover frequency controls, usually fail to provide accurate deep bass response due to the interference with the home cinema room itself. Therefore, the Revel Performa 15a subwoofer is equipped with a parametric equaliser that allows a smooth low frequency response to be achieved in hi-end home cinema installations. 

This delivers tuneful and musical low bass reproduction without the boomy and irritating response of typical home cinema subwoofers. The Revel B15a subwoofer seamlessly integrates with the most demanding home cinema speakers and improves performance far above its frequency range, thus creating a holographic three-dimensional soundstage.