Sound is a form of energy. It is generated by an audio source and is detected by human hearing. A loudspeaker converts the electric energy from the amplifier into acoustic energy we hear by moving air. Sound propagates through the air in the form of an acoustic wave. This acoustic wave carries the audio information of the initial disturbance of the air caused by the loudspeaker, according to the rules of wave propagation.

A wave is a disturbance or variation that transfers energy progressively from one point to another. It may take the form of an elastic deformation or of a variation of pressure. According to the rules of physics, a wave is described by its wavelength, its period, its frequency and its speed.

Wavelength is the distance the audio wave travels until it completes a full cycle and it starts repeating itself. In physics the wavelength is symbolized by the Greek letter λ and is measured in metres.

Period is the time required by the audio wave to complete a full cycle, or to cover a distance equal to its wavelength. It is symbolized by the letter T and is measured in seconds (sec) or milliseconds (msec).

The frequency of an audio wave indicates the number of cycles generated in one second, which is how many times the audio wave repeats itself in one second. It is symbolized by the letter f and is computed in Hertz (Hz) or kilohertz (kHz). One Hz means one cycle per second. One kHz is one thousand cycles per second. Humans can hear sounds with a frequency between 20Hz and 20,000Hz (20kHz). Age and long-term exposure to loud environments reduce this range.

The speed of a wave indicates how fast it travels through the medium it propagates. The speed of sound is measured in metres per second (m/sec) and is symbolized by the letter c. The speed of sound through air is influenced by the temperature of the air, which affects air density. At 21 degrees centigrade the speed of sound in air is equal to 344 m/sec.

The front speakers (left/right) reproduce the main musical soundtrack, off-screen dialogue, and transition sound effects.

The centre speaker reproduces on-screen dialogue, the central images of the musical soundtrack, and transition sound effects.

The surround speakers provide sound effects and ambience, while the subwoofers provide dynamic low frequency information.

Τhere are three types:

	Floorstanding
	Bookshelf / Stand mounted
	Wall mounted

You can choose any type for hi-fi or home cinema use.

Normally speaker manufacturers design their speakers so that their performance is often best with the grilles in place. Removing them could cause an over-brightening of the sound (richer treble content) which, although initially impressive at first audition, doesn't necesserily translate to more accurate reproduction.

Crystal Audio speakers on the other hand are designed using minimalist frame grilles that are 'sonically transparent' eliminating unwanted sound absorption and diffraction. You can enjoy the full sonic experience of the Crystal Audio speakers with or without their grille. It all goes down to taste.

Of course, if you have children or pets we would strongly suggest keeping them on, or you risk damaging the speaker.

Not necessarily. Ideally you should have at least all three main speakers (front and centre) acoustically matched. If your stereo speakers are quality performers, however, you just have to ensure that the centre speaker you buy also performs up to their standards.

Using the calibration features of modern day home cinema receivers you can alter some of the sonic characteristics of the main speakers so that they more closely match.

Bass reproduction places great strain on speakers. Speaker manufacturers therefore resorted to producing an independent unit called a subwoofer. Its task is to exclusively reproduce the lowest octave of the audible frequencies (20Hz to 80Hz according to the THX specifications, or up to 120Hz maximum for smaller main speakers). Thus the main speakers are released from the work of recreating low frequencies. As a result they behave more linearly, are more efficient, while at the same time are much smaller in size and of course less expensive. Since low frequencies are largely non-directional, the subwoofer reproducing them can be placed far from the main speakers and still sound as if they were emanating from them.

Furthermore, if you have all the low frequencies coming from one speaker (the subwoofer) it can be placed in the most suitable part of the room to minimizes standing waves, thus giving a more uniform bass reproduction. Get more information on standing modes.

There are many good reasons to add one and ideally two subwoofers to your system. The first reason is to add bass to a system whose main speakers lack good bass response

Another reason is to remove the bass reproduction requirement from your other speakers, which improves their performance by minimizing inter-modulation - that is the non-linear mixing of sound with different frequencies.

In addition if you use an active subwoofer, you will free up your amplifier’s power reserves, improving overall performance. Adding a subwoofer to your system must be done carefully. The subwoofer must be matched to the other speakers.

You must select the correct cut-off point for the low frequencies produced by the subwoofer. You must match the level of the subwoofer to the other speakers, so that the bass is not over emphasized.

Finally you must position your subwoofer in the correct place. It is true that our ears cannot easily tell where the bass comes from. As a result we can get by with using only one subwoofer for bass reproduction. However we must make sure that its position does not create standing waves.

Using four subwoofers is preferable as you will get a better bass performance and will have less of a problem with standing waves, since the bass will originate from many locations in the room. The much more smooth bass performance across many different positions in your room will justify the extra cost of them.

Let’s face it; we are not back in the 90's when gaming was just kids' entertainment, enjoyed through a PC with cheesy speakers, or the, small by that time, TV and its integrated speakers. Games are now designed using the most state of the art visual techniques and the most elaborate sound effects. A whole team of experts are working on the scenario, the direction, the lighting (just like a movie) and professional studios are used to produce and mix the sound effects. Games that are mostly enjoyed by the 29 years old fan (in average) and which absolutely require a modern, high performance multichannel Home Theater system to immerse the gamer into the realistic action it is designed to offer.

Now that the connection with the Home Theater system is as easy as to say HDMI, your gaming experience can take a whole new dimension, heard and viewed through your quality system. Enjoy a bright and real-life size image together with thrilling bass frequencies from your subwoofer and immersing rear effects from your surrounds now!

When compressed audio, mostly in the form of MP3 files, hit the market, it was initially questionable whether there was any point in using quality speakers to reproduce such compressed music content.

Today sophisticated compression algorithms, along with the 'luxury' of working with higher bit rates thanks to cheaper disk space and faster network connections, MP3 songs can deliver extraordinary quality.

Now you have your iPod and MP3 player stuffed with hundreds or even thousands of your beloved songs, arranged in playlists or by genre or by artist. Why not hook it up to your hi-fi/home cinema system and enjoy all your music at top-notch quality?

Just use a mini jack to RCA cable, connect this from the iPod/MP3 player to the ‘analogue audio in’ of your amplifier and turn your player into a powerful and flexible music system.

Of all the components of an entertainment system, none has a task as difficult as a loudspeaker. This box is called upon to reproduce the sound of everything from a human voice, to drums, to a cello, and much more. It must do this in a realistic way that convinces us that what we are hearing is live.

There are many desired aspects of a loudspeaker’s performance, including:

- Flat and wide frequency response
- Low distortion over a wide range of levels
- Good transient response
- Appropriate dispersion
- High sensitivity
- Low impedance

The first ingredient that determines a loudspeaker’s performance are the drivers (speakers) themselves. They convert electricity to sound, by driving the air in front of them. Their construction (intensity of magnet, size and type of diaphragm, voice coil used, overall geometry) is crucial, in conjuction with the enclosure employed, to the speaker’s the performance.

Most speakers’ enclosures are boxes or cabinets of various designs. The quality and type of enclosure (open box or closed box) is a basic ingredient of the speaker’s performance as well.

The drivers are fed signals that are filtered from the crossover of the loudspeaker so that music is split into smaller ranges of frequencies, for specialized drivers (woofers and tweeters) that cover these ranges. Crossover network quality is therefore a basic ingredient of the speaker performance.

Finally, and most importantly, the room where the speaker performs is a crucial ingredient of the performance. Speakers will sound drastically different in different rooms.

5.1 channel home cinema receivers have been the standard for over a decade. They provide an impressive surround sound experience, especially in small to average-sized rooms. A 5.1 channel system comprises:

1. A centre channel to carry a significant portion of the soundtrack and most of the dialogue, keeping the voices centered when they need to be
2. Left and right front channels to create the soundstage for the movie soundtrack, reproducing much of the music and special effects, and helping the sound follow the action that is moving across the screen
3. Left and right surround sound channels to create a lifelike sense of spaciousness, providing the ambient sounds for a movie or audience reactions in a concert video
4. The subwoofer, which provides the low frequency effects (sometimes referred to as an LFE), giving weight and impact to movie soundtracks, particularly in action features

A 7.1 channel system incorporates all of the above elements, but adds an extra two surround effects channels. Side sound effects and ambience are directed to left and right surround channels, and the rear sound effects and ambience are directed to two rear or back channels. In this set-up the surround speakers are set to the side of the listening postion and the rear or back channels are placed behind the listener. Here the additional channels (sixth and seventh) provide a more intense surround experience by enabling enhanced localization of sound effects.

There are an increasing amount of Blu-ray soundtracks that contain 7.1 channel information - whether it be 7.1 channel uncompressed PCM, Dolby TrueHD, or DTS-HD Master Audio. If you have a 7.1 channel receiver with audio input and processing capability via HDMI connections (not pass-through only connections), you can take advantage of some, or all, of these audio capabilities.

Also, even with playback of standard DVDs, if your DVD soundtrack only contains Dolby Digital or DTS 5.1 or, in some cases, DTS-ES 6.1 or Dolby Surround EX 6.1 soundtracks, by using the Dolby Pro Logic IIx extension or other available 7.1 DSP surround modes that may be available on your receiver, you can still extract a 7.1 channel surround field from both two or 5.1 channel source material.

To cut a long story short, if you can afford it go for a 7.1 system and get the full experience of modern recordings and movies!

Both Dipolar and Bipolar speakers are used as surround speakers in a Home Theater system. They have two or more speakers that output sound from opposing sides of the cabinet, that is towards the front and the rear of the listening room if they are used as side surrounds in which case they are mounted on the side walls. While the Bipolar speakers however have the speakers on the opposing cabinet sides emitting sound in-phase (speaker diaphragms move in and out simultaneously), the Dipolar speakers emit sound out-of-phase (when one speaker's diaphragm moves out, the other is moving in and vice-versa).

This results in the Dipolar speakers producing a more diffuse sound field, with little direct sound reaching the listener, but instead with relfections that encircle him. However the null that is produced towards the direction of the listener (because of the cancelation of out-of-phase waves) results in a loss of acoustic energy and a strong colouration of the reproduced sound. The ambience may be created but more direct auditory cues cannot be faithfully reproduced. For this reason Crystal Audio has designed a Surround speaker (THX-D) that preserves all the advantages of monopoles (direct firing speakers) and bipoles/dipoles while at the same time being elegant and friendly for wall mounting installation.

The THX-D speakers use a 6.5'' woofer pointing to the user that provides all the information up to the mid-highs, thus giving all the basic sonic cues. The mid-highs to high frequencies are reproduced by a pair of tweeters mounted on angled sides of the cabinet facing towards the front and rear walls of the listening room and connected in phase. Thus they reach the listeners via reflections from the wall, giving a unique spaciousness and envelopping feeling. The highs are not coloured by the destructive interference of the out-of-phase waves but instead reach the listener without any spectral distortion. Furthermore, both the power (averaged) and on-axis response are smooth for the best surround reproduction anywhere in the room.