WSS-6-BEU

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.

The nominal input power of a loudspeaker is the continuous power (Watt RMS) that can be absorbed by the speaker without it being damaged, and not a measurement of minimum amplifier power needed to drive it. Naturally the speakers can handle much higher power peaks for small periods of time (a few 1/100s of a second). If a speaker combines high nominal input power with a high sensitivity, then we can generate music and sound at realistic levels without compression or distortion.

No! The input power of a speaker by no means affects its performance. A high quality speaker in general must provide a smooth frequency response both on-axis (in front of the tweeter) and off-axis (at an angle from the tweeter axis), which is done through controlled dispersion, so that it doesn't induce any unwanted colorations in the sound. Furthermore, it must keep distortion at very low levels and at the same time be sensitive enough, without a very low impedance, so that almost all amplifiers can drive it successfully. Although it is a great asset to have high power speakers that can handle that extra boost we need to rock everyone from their seat during a party or movie viewing, the nominal input power is not at all related to the frequency response, dispersion and sensitivity of the speaker.

Every audio component in the world of Hi-Fi and Home Theater is usually accompanied with what is called a “break-in” period. This is usually a period of some days that the audio component is required to operate, before it can perform at its best. Like for ex. in power amplifiers or receivers where the power supply and capacitors “open up” after some hours of operation, the same goes for loudspeakers, where their woofer suspensions become “softer” and more accurate. After the break-in period is complete, the loudspeaker can perform as the manufacturer intended and is ready for critical listening sessions.

Crystal Acoustics loudspeakers will usually require about 100 hours in moderate playback levels before they can perform at their best, although the break-in period continues even after this time frame. It should also be considered that the absolute time of an actual break-in is affected by the speaker type, the amplifier that drives it. the playback level as well as whether the break-in period is performed through continuous or interrupted playback periods.

Tip: In order to perform a quick and effective break-in of your loudspeakers, you can follow this tip.

1. Place your loudspeakers face-to-face, in close distance.
2. Wire the first loudspeaker as indicated and reverse the +/- wiring of the second loudspeaker, thus reversing its phase.
3. Initialize the playback procedure, choosing some rich sounding, full band tracks that equally extend to all frequencies. Because of the out-of-phase setup of the loudspeakers, you will notice that the audio output of the loudspeakers is actually canceled by a great amount. As a result, you can leave your loudspeakers breaking-in without annoying your neighbors, even when you are away from home.

Sensitivity: Sensitivity is a measure of how loudly a speaker will play 2.83 volts, one metre in front of it. Since loudness is measured in decibels of Sound Pressure Level (dB SPL), the sensitivity rating is specified in dB SPL/2.83V/m. Note that 2.83 volts corresponds to one watt when applied to an 8 ohm speaker (P=V2/R, hence 1W=2.832/8). Since modern amplifiers are constant voltage sources across most of their working range, specifying the sensitivity at a specific voltage rather than the older standard of 1W (which translates as a different voltage for speakers that aren’t 8 ohm designs) provides for a much more consistent way of appreciating the sensitivity of speakers.

The sensitivity of a loudspeaker is a very important specification: the greater the sensitivity, the louder the speaker plays, and/or the smaller the amplifier it requires. As a rule, high sensitivity speakers decrease the cost of the required amplifier, offer lower distortion and a greater dynamic range.

Nominal Input Power: The nominal input power of a loudspeaker is the continuous power (Watt RMS) that can be absorbed by the speaker without it being damaged, and not a measurement of minimum amplifier power needed to drive it. Naturally the speakers can handle much higher power peaks for small periods of time (a few 1/100s of a second). If a speaker combines high nominal input power with a high sensitivity, then we can generate music and sound at realistic levels without compression or distortion.

Impedance: The impedance of a loudspeaker is a measure of how difficult a load it is on the amplifier it is connected to. The impedance of a loudspeaker varies significantly depending on the frequency. Most loudspeaker specification sheets provide the nominal impedance, which more-or-less is the average over the full frequency range. Because the impedance is an average, two speakers with the same nominal impedance may have vastly difference actual impedance at given frequencies. Keep in mind that a typical 8 ohm loudspeaker may vary from a minimum of 5 ohm to over 30 Ohm depending on the frequency. A lower loudspeaker impedance causes an amplifier to output more power and to reproduce higher volume levels and places a greater task on it.

Dispersion: How widely and evenly a speaker spreads its sound. A speaker with narrow dispersion beams its sound forward like the beam from a flashlight. A wide-dispersion speaker evenly covers the entire listening area with sound. Speakers must have a wide horizontal dispersion for two reasons. Reflections from sidewalls must have as close frequency content as the on axis radiated so that unwanted colorations are minimized. Secondly, wide horizontal dispersion permits all listeners to enjoy music and movies wherever they sit in the room.

Crossover Frequency: The crossover frequency is the frequency at which the signal is split to the different drivers of a multi-way speaker system. In a typical two-way system, the crossover frequency between the woofer and the tweeter will be set around 2500Hz.

Cutoff frequency: The frequency at which the signal falls off by 3dB (the half power point) from its maximum value. Also referred to as the -3dB points, or the corner frequency. The lower it is, the more bass the speaker can reproduce.

An ohm is a measure of resistance (impedance) to the flow of electric current through a device. The impedance rating of a particular speaker varies depending on the frequency of the signal. Different speaker models have different impedance ratings. The nominal impedance that is usually specified for a speaker is an average rating of the impedance over the whole frequency band. Higher impedance speakers are an easier load on the amplifier since there is less current flowing into the speakers.

Therefore the amplifier’s operating temperature is cooler, since it is delivering less power. If a particular amp is designed correctly, as far as heat dissipation is concerned, then a lower impedance speaker can be used to get the most power out of it. Many stereo amps and receivers give a power rating for both 4 and 8 ohm speakers.

Some high-end amplifiers can drive speakers with one ohm impedance! On the other hand, many multi-channel receivers are designed to handle only 8 ohm speakers, since the heat generated by their multiple amplifiers is excessive. It is advised to choose an amplifier that can drive at least 6 ohm speakers. Therefore, you can connect the main speakers with an impedance down to 4 ohm provided that the surrounds are 8 ohm designs.

The sensitivity rating of a speaker is very valuable because indicates how efficient a speaker is. In other words, it tells us how loud the speaker will play when it is fed with a standardized signal.

Years ago, loudspeaker sensitivity was rated as the sound level at a distance of one metre for an input of one watt. Power input is voltage2/resistance. Because loudspeakers do not have the same impedance at all frequencies, a sensitivity rating would apply only at a single frequency (or in a confined frequency range at best). Obviously, rating sensitivity according to power input does not work well. The domination of solid-state amplifiers really provided the solution. These amplifiers are essentially constant-voltage sources, with power rated according to what they can deliver into an 8 ohm resistor. If the load impedance drops to 4 ohm, the power will double; at 2 ohm the power quadruples and so on, until the amplifier cannot deliver any more current or dissipate any more heat. This permits us to define an input voltage, not an input power, to rate the sensitivity.

The sensitivity rating is nowadays given (or should be given!) in number of dB SPL /2.83V /1 meter. For example, a particular speaker may have a sensitivity rating of 92dB SPL/2.83V/metre. This means that when a signal of 2.83V in amplitude is driven to the speaker, the generated sound is 92 decibels when measured at 1 metre from the speaker.

Sound Pressure Level: The three rules to calculation
The following rules are used to calculate the Sound pressure Level (SPL) in the room depending:

- On the distance of speakers and listener:
- Doubling the distance results in a 6dB reduction of the sound level
- At half the distance the sound level is increased by 6dB The sensitivity of our speakers:
- Two speakers deliver 3dB more than one speaker (stereo configuration)
- The power of our amplifier:
- Twice the power (watt) results in a 3dB increase of the SPL (under the assumption that the speakers can handle the extra power without distortion or damage) 

Sensitivity: The sensitivity of a speaker determines the generated Sound Pressure Level. The sensitivity is measured in dB SPL/2.83V/m, depending on the sound pressure level in dB that is generated at a distance of one metre and an input signal of 2.83V (which corresponds to one watt of power when applied to an 8 ohm speaker) from the amplifier. The greater the sensitivity:

- The louder it plays
- The smaller the power amplifier it requires

High sensitivity speakers decrease the cost of the required amplifier and offer low distortion and greater dynamic range.

But what is the real gain of 3dB? A speaker with 3dB higher sensitivity requires half the amplifier power to produce the same sound level. For example, a speaker with 94dB sensitivity requires half the wattage of a speaker rated at 91dB sensitivity to produce the same sound level. Thus, if the first speaker requires 100 watts to produce a certain sound level, a 91dB speaker will need 200 watts and a 88dB speaker 400 watts!

- How much more money do you need in order to buy a 400 watt amplifier and a speaker that can handle 400 watts?

In addition, the distortion of a speaker with a 400 watt input is greater than a 94dB sensitivity speaker with only a 100 watt input

Since the very first days of speaker design and evaluation there has been a big debate on what measurements tell us about the speaker: how they correlate with our listening experience; to what extent the designer can rely on them; and how accurate and repeatable they are. Of course, these are questions that are the subject of specific fields of acoustics, such as psychoacoustics, and it would be impossible to cover everything here. However, we can give some useful insights to the user that wants to know more about the scientific aspect of acoustics as opposed to the hocus pocus that often surrounds speakers!

The main measurement a designer cares for is the frequency response of the speaker as measured at a specific distance (one or two metres from the speaker) from the driver and exactly on the axis of it (on-axis). This shows the response of the speaker for all frequencies of the audible band. Whatever you may hear and read about, 'flat' is unquestionably the best response. It is the only reference one can rely on, and it is what designers should thrive for. A flat response means that the speaker reproduces all sounds without emphasizing or reducing specific frequencies that would result in a sonic coloration.

Now watch out because there is a big problem here. Room acoustics truly define the lower frequency response of a speaker. In order to have accurate and repeatable measurement in many places for bass, we either must have a huge room, so that sound reflections don't influence the measurement, or we must employ a technique called Near-Field measurement. In this technique, the low frequency response of the speaker (and port(s) if any) is measured with the measurement microphone almost touching the cone, thus eliminating the contribution of all reflections whose magnitude is much smaller than the original signal. This measurement is then spliced with the on-axis measurement at a certain frequency, to give a very good approximation of the speaker’s response in an open space, with no physical boundaries nearby.

The interesting point of the accurate near-field response is the frequency where the Sound Pressure Level of the speaker falls by 3dB compared to its average value. This is referred to as the f3 and is a measure of the ability of the speaker to reproduce low frequencies. Of course when evaluated in a realistic room the speaker's bass will be quite different due to the standing waves (room modes). However, the flatter the response up to the f3 frequency means the easier it will be to find an optimum place for it in the room that gives a smooth result.

Then we have the frequency measurements performed at angles off-axis. These depict phenomena as the summation issues introduced by the phase shifts of crossover networks, etc. Again here we want to be as close to the on-axis response (which should be the flattest it gets!) as possible. In this way we are pretty sure that the reflected sound from the ceiling, floor and sidewalls will have the same sonic character as the direct signal. We need to confirm as well that the crossover network used does not cause a big response deviation off-axis.

Another important measurement is the impedance versus frequency graph. This depicts the overall impedance of the speaker (including the resistance of the coil, its inductance along with the effect of the air and the enclosure interacting with the driver) from 20Hz to 20kHz and shows where the minimum impedance occurs and what is its value. Normally we want the minimum impedance to be higher than 3-4 ohm, so that pretty much any amplifier can drive the speaker. In high-end speakers however values of minimum impedance down to even one ohm are not unusual. The frequency at which the lowest impedance is observed is also important. If the frequency of lowest impedance is high, the load is easier on the amplifier, because in this area the power of audio information is small. If the lowest impedance frequency is in the mid or low range, then the speaker is considered a difficult load, since there is a great percentage of the audio power in this range.

Based on the enclosure (cabinet) construction, speaker designs include the following:

Acoustic suspension enclosures (closed-box) are air-tight, since they use the enclosed air to dampen the behavior of the woofer. When the woofer moves forward a vacuum is created behind the woofer that sucks the woofer back to its resting position. When the woofer moves backward there is an internal air pressure increase, which pushes the woofer to its resting place. A properly designed acoustic suspension loudspeaker has tight and deep bass with a gradual roll off below its cut-off frequency.

However, acoustic suspension loudspeakers tend to be inefficient since the acoustic energy generated by the back of the woofer is not used. A ported enclosure is another way to use the energy that is wasted by an acoustic suspension loudspeaker. By opening an appropriately sized hole (bass reflex) in the enclosure and attaching a pipe of specific length to it, the low frequencies generated in the enclosure come out in phase with the bass generated by the front of the woofer. Varying the size of the hole and the length of the pipe varies the low frequency extension. Ported enclosures are much more efficient than closed-box designs, resulting in much smaller enclosures for the same cut-off frequency. As for the bass response below the cut-off frequency, this rolls off more steeply than in the closed-box configuration.

A loudspeaker (or ‘speaker’) is an electro-acoustic device that converts electrical signals into sound. Speakers pulse in accordance with the variations of an electrical signal and sound waves propagate through air.

We will give a brief description of how electrodynamic speakers (the most commonly used type of speaker) work to reproduce as faithfully as possible the various sounds that nature and musical instruments produce.

Electrodynamic speakers are the most popular speakers. They come in various shapes, sizes and price brackets. Our familiar cones and domes characterize electrodynamic speakers. They are the diaphragms that generate the sound and usually the only visible parts of a loudspeaker. The electrodynamic speakers’ operation is based on the principles of electromagnetic induction. That is, when a conductor moves in a magnetic field it experiences forces that result in the generation of an internal electric field and potential differences at its ends.

At the heart of the electrodynamic speakers there is a strong permanent magnet, cylindrical in shape, with a cylindrical shaft (the pole) at its centre. Between the pole and the magnet there is a space of a few millimeters, in which a very strong and homogeneous magnetic field exists. The space between the magnet and the pole holds the voice coil. The voice coil is free to move in the magnetic field and supported by an elastic suspension, which makes sure that the coil does not touch the pole, and behaves as if it is floating. When the audio signal in the form of alternating current is conducted through the coil, forces are generated that cause it to move back and forth. On the outside of the coil a diaphragm is attached, the size of which determines the lowest frequency that can be reproduced. The diaphragm moves and sound is generated.

Larger diameter cones require larger voice coils and magnets. This creates speaker drives with large mass and inertia, which require more power to drive. In an effort to minimize the mass of the diaphragm while keeping the required rigidity, synthetic and sometimes exotic materials are used, such as polypropylene, Kevlar, titanium etc.

When the cone of a loudspeaker moves forward to impart pressure on the air layers in front of it, then an equal and opposite-directed decompression is created behind it. The low frequencies generated in front of the cone are non-directional and move to cover the area in front and behind the cone. This causes their cancellation, since they interfere destructively with the equal, yet out of phase, low frequencies generated behind the cone.

The ideal way to avoid this phenomenon is to place the speaker in the middle of a large surface. This is known as an ‘infinite baffle’. Of course, this solution is totally impractical so manufacturers resort to surrounding the speaker with a cabinet. Cabinets are therefore used to support the speaker drives and nullify unwanted cancellations.

The cabinet design contributes greatly to the response of the loudspeaker and either mimics the free loudspeaker behavior (infinite diaphragm design) or uses the enclosed air to improve performance (bass reflex and acoustic suspension design). The ideal speaker cabinet is rigid so that it does not vibrate from the internal air pressure variations. In addition the cabinet must have significant damping behavior to minimize unwanted sound radiation.

Speaker manufacturers face many challenges in designing speakers. High-frequency reproduction requires fast and accurate diaphragm movements. These diaphragms must have low weight to minimize heat generation and increase speed and control.

Tweeters, reproducing high frequencies, have low-weight diaphragms and powerful magnets, such as those manufactured from high-density neodymium. Many other materials are used for tweeter diaphragm manufacturing, with aluminum being particularly well suited for this task. They are rigid and low mass, and reproduce fast transients with high speed, accuracy and distortion-free sound. Nomex and silk also make excellent diaphragms.

Yet low frequencies require large diaphragms that are capable of moving the required volume of air to generate low-frequency sound waves. Large diaphragms weigh more, have greater inertia and decreased sensitivity, while also requiring more power to be set in motion.

Woofers, reproducing mid and low frequencies, require drivers with larger diaphragms. Kevlar cones are an industry favorite due to their natural mid-range response. Another excellent choice for middle frequency speakers are Alucone® speakers, which have a rigid low-mass aluminum sandwich alloy cone for fast transients, accuracy and distortion-free sound.

As for the dedicated low-frequency subwoofers, excellent choices for the diaphragm materials are carbon fiber, polypropylene and light but rigid specially-treated paper cones.

When the cone of a loudspeaker moves forward to impart pressure on the air layers in front of it, then an equal and opposite directed decompression is created behind it. The low frequencies generated in front of the cone are non-directional and move to cover the area in front and behind the cone. This causes their cancellation, since they interfere destructively with the equal yet out-of-phase low frequencies generated behind the cone.

The ideal way to avoid this phenomenon is to place the speaker in the middle of a large surface – known as an ‘infinite baffle’. Of course, this solution is totally impractical so manufacturers surround the speaker with a cabinet. Cabinets are therefore used to support the speaker drives and nullify unwanted cancellations

The cabinet design contributes greatly to the response of the loudspeaker. It either mimics the free loudspeaker behavior or uses the enclosed air to improve performance (bass reflex and acoustic suspension design). The ideal speaker cabinet is rigid so that it does not vibrate from the internal air pressure variations. In addition the cabinet must have a significant damping effect to minimize unwanted sound radiation.

High-frequency reproduction requires fast and accurate diaphragm movements. To increase speed and control, and minimise heat generation, diaphragms must be low weight. Likewise, low frequencies require larger diaphragms, which are capable of moving the required volume of air to generate low-frequency sound waves.

However, large diaphragms weigh more, have greater inertia and decreased sensitivity, while also requiring more power to be set in motion.

To overcome the conflicting drive requirements for low and high frequencies, speaker manufacturers resort to two or more designs where dedicated drivers reproduce specific frequencies. This technique requires the use of a crossover circuit, which separates the frequencies and routes them to the appropriate drivers.

Speakers are the most critical link between the amplifier, the room and your ears in the music reproduction chain. They carry music from the amplifier to your room and interact with both. Speaker quality and build characteristics directly affect the performance you will get out of your home cinema/Hi-Fi system.

It is widely known that matching speakers with amplifiers is very important if you want to achieve the sound quality that you paid for.

Even with large and expensive high-end amplifiers, you need sensitive, easily-driven speakers. High-sensitivity speakers reproduce music realistically, without compression or distortions.

Most people usually try to hide their speakers, even when these are crafted like expensive furniture that serve our music enjoyment. However, speakers that match your interior décor can be placed according to the laws of electro-acoustics without compromising your style.

Sound quality is greatly influenced by the position of the speakers in the room. Less expensive speakers correctly placed according to the rules of acoustics will play better than more expensive speakers placed in the wrong position, for example hidden in the corners.

Sometimes all we ask for is background music to a friendly dinner. At other times we are asking for the thrill of a demanding soundtrack or the recreation of a concert in our living room. Our demands from a quality speaker system change depending on our mood, the needs of our busy, varied lifestyles and on the diversity and increasing sophistication of home entertainment technology, like home cinema and games consoles. Crystal Audio speakers are built to satisfy all these needs and more.

The magnetic fields generated by the powerful magnets of speaker drivers mean that magnetic shielding is necessary to protect TVs and susceptible magnetic storage media. Speaker magnets are therefore housed in a steal enclosure or a second magnet with reverse polarity is placed behind the speaker to cancel the stray magnetic field.

One of the main challenges in setting up a home theatre is choosing loudspeakers. This task is complicated by the incredible variety of loudspeaker brands, models, designs and prices. Spending more money or buying well-known brand speakers does not guarantee that you will purchase the right model. After all, audio experts agree that only a small percentage of loudspeakers are worth buying, and there is often little relationship between performance, brand and price. Within a price range the majority of loudspeakers are underachievers. The rest are good performers and only a select few are star performers.

Comparing speakers can be a fairly complicated procedure. Even a small difference on the sound level can make one speaker sound better than another.

Do not be fooled into thinking that if you use the same amplifier and keep the volume level constant, the speakers will play at the same level. This is due to the fact that different speakers have different sensitivities to the input signal. Level-matching can only be done with the use of a sound pressure level meter, known as a decibel meter, available from an electronics store.

It is possible to feed the speakers with white noise, which is included in tracks of special speaker evaluation CDs and DVDs, and match the sound level of the speakers. In an ideal situation the different speakers would be hooked up to an A-B switch that allows the listener to instantly go back and forth between the different models.

Once the levels are matched it is possible to go on to the next stage of a listening evaluation.

The tone settings of the pre-amplifier should be set to flat, as we do not want equalization interfering with our evaluation.

Then, pay attention to how natural the music sounds. Concentrate on the voice of the singer and evaluate how real it sounds. Do the same with musical instruments. Do they sound true? Is the sound balanced, with no artificial emphasis on the bass, midrange or highs? Can you separate the instruments playing? Is the sound focused and the sound image correct? Do the speakers perform well at high and low volume settings? Does the sound stir you emotionally and do you have the feeling of listening to a live performance?

Once you answer the above questions you will have an excellent picture of the performance of the speakers you are comparing.

Evaluating speakers is really much more difficult than it might initially sound. A whole field of acoustics, namely psychoacoustics, studies the way we perceive sound, decode it in our brain, compare it to realistic sounds and how our auditory perception gets fooled or misled – and not strictly in a bad way! Virtual surround technology is wholly based on the fooling of our auditory perception for a good reason.

Without getting or even attempting to go really deep into the theory, here are a few general rules:

- Don't let your other senses, and mainly your sight, intervene in your judgment. Big or good-looking speakers by no means necessarily translate into good sound
- Consider the room in which you are auditioning the speaker. It is almost impossible to evaluate a speaker in a room you haven't heard music in before
- Especially in non-acoustically correct rooms the evaluation of speakers is totally unfair
- The best place to evaluate speakers in is your own listening room. That's why Crystal Audio offers a 60-day trial period during which you can fully evaluate the speakers, trying your favorite music and movies and asking the opinion of your friends and family members
- Choose reference material (music or movies) and not some average recording. Consult our great Reference Recordings tool and find the best recording of the genre you prefer
- Try to listen closely to each different layer of sound. Listen to the acoustic instruments, the voice of the singer and evaluate their closeness to reality

Consider the spaciousness of the sounds, the wideness of the stereo image, the bass quality (tight, bringing music to life or muddy) and the overall experience you get. Close your eyes, immerse yourself in the music and sounds, and feel the emotions triggered from science meeting art

THX, the trademark of THX Ltd., is the ultimate set of standards for home theatre sound. It incorporates a series of patented electronic and loudspeaker specifications designed to bring the big theatre experience right into your home.

THX Certified Home Theatre products deliver cinema-quality picture and Hi-end sound to home environments. Through optimized audio-visual technology and speaker placement, you get a movie experience at home that's as faithful as possible to what the director intended.

Products certified by THX assure the best possible quality in music and sound reproduction.

THX Certification is the “seal of approval” for speaker quality. It is the absolute assurance that your loudspeakers will reproduce all music and film material in the way that the composer and film director respectively intended.

THX Ltd. is the founder of quality assurance programs for superior cinema presentation and the leading provider of product certification and venue design for the entertainment and consumer electronics industries.

To ensure accurate playback as the director or the producer intented.

The digital sound formats were developed for movie presentation in cinema settings. Because home environments are different to cinemas, the same THX audio standards that ensure accurate playback in theatres have been adapted for viewing movies in Blu-ray, DVD and broadcast formats at home.

Incorporating a variety of digital encoding technologies like Dolby Digital, DTS and PCM, THX Certified Home Theater products offer the most consistently accurate, trouble-free reproduction of sound. THX certified equipment offer comprehensive solutions to multichannel audio formats based on their end to end home entertainment expertise. THX certified equipment ensure:

- Very clear dialogue
- Sharply positioned sounds
- Enveloping surround sound that puts the audience inside a movie
- Thunderous bass and crystal clear highs
- Maximum contrast between quiet and loud sounds
- Smooth and continuous sound movement

THX Certification has nothing to do with the type or format of the sound information stored in the CD, Blu-ray or DVD. The high standards of a THX certified speaker determine its capability of reproducing crystal clear sound and music. In this way a THX certified loudspeaker has the same perfect behavior in any input signal.

Each THX home cinema component - processor, centre speaker, surround speaker, subwoofer, amplifier, Blu-ray player, interconnect, speaker wire, and acoustically transparent screen - solves specific problems in home cinema sound reproduction. You can use any THX home cinema product in any home cinema system. When used all together, these components work synergistically to produce an ultimate surround sound experience.

The driving force behind the establishment of THX certification was the observation that conventional audio components could not accurately reproduce film soundtracks in the home environment.

A need to correct the audible tonal and spatial errors caused by the playback of soundtracks designed in and for large cinema in the smaller environment of a home. A need to more accurately reproduce the complex and competing sound fields present in multi-channel sound playback.

Movie cinema THX certification was introduced in 1983. THX certification was developed by director George Lucas, who was dismayed with the sound quality of most cinemas. He felt that all of the directors’ efforts to stir the emotions of the audience with the use of sound and music were undermined by poorly equipped cinemas that reproduced highly distorted sound. George Lucas tasked Tomlinson Holman (then his corporate Technical Director) to develop a set of criteria that cinemas had to meet to guarantee that the soundtrack was played back just as the director intended. These criteria were named Tomlinson Holman eXperiment, or THX for short.

The home version of THX was introduced to the public in 1990. Home THX certification aims to duplicate the THX cinema sound in a home environment. The THX home cinema standard has a firm foundation in the production processes associated with all feature film material.

The THX standards are a set of minimum criteria that audio components must meet. In addition, there are many different types and levels of THX certification that components can obtain. Manufacturers of home cinema components can differentiate their products by outperforming the minimum standards specified by each certification level and therefore produce components that do not sound alike.

Many consumers erroneously consider THX a multi-channel sound format, similar to Dolby and DTS. THX is a certification program which assures the finest picture and sound quality for cinemas, mixing studios, home cinemas, Blu-rays, multimedia products, and luxury automotive vehicles.

Absolutely! The goal of THX home cinema is to accurately recreate the experience of the film mixing studio. All mixing studios are capable of creating both 4 and 5.1 channel mixes. The acoustics, equalization curves, and loudspeaker arrays used in a mixing studio remain the same for a digital 5.1-channel soundtrack as they do for a 4-channel Dolby Surround soundtrack. THX home cinema technologies are needed to reproduce these movie soundtracks accurately.

In the beginning there was only one set of THX criteria for home cinema audio systems, simply known as THX. However Lucasfilm THX realized that its standards had to be differentiated for different size home cinema rooms. THX Select is the THX reference standard for smaller rooms. THX Select criteria are specifically calibrated to define reference level performance in room volumes of about 2000 cubic feet.

During the CES (Consumer Electronics Show) of 2007, THX announced the THX Select2 certification as an upgrade to the company's THX Select specification for home entertainment products. The new THX Select2 certification provides additional THX listening modes for enhancing playback of a variety of entertainment content, including movies and video games. It specifically addresses receivers, incorporating new features and improved noise floor performance. Based on the same values and principles of THX Ultra2, THX Select2 certified receivers deliver higher quality to smaller home cinema environments.

THX Ultra is the original THX home cinema standard. THX Ultra applies more rigorous standards to home cinema components, so that they provide the reference level performance for viewing rooms up to 3000 cubic feet.

THX Ultra2 requires amplification for seven channels and stricter requirements for amplifiers and speakers than THX Ultra (Ultra2 specification calls for a subwoofer flat to 20Hz, down from THX Ultra’s 12dB roll-off below 35Hz). The specification also features switchable Boundary Gain Compensation (BGC) that alleviates boomy bass as a result of near-wall listening positions (or, for that matter, subwoofer placement). The Ultra2 processor accommodates both 5.1 EX/ES soundtracks, as well as multi-channel audio recordings by directing ambient sounds to the dipole speakers and discrete effects/sounds to the back channels.

The THX certification for multimedia products aims at delivering cinema-quality picture and sound to the desktop by ensuring that multimedia products comply with THX’s rigorous standards. In other words, the THX certified multimedia stamp is a guarantee that your computer setup is capable of delivering the highest possible fidelity for your MP3s, CDs, DVDs, games, and other digital audio sources, through cinema-quality audio and visual experience.

Note that THX certified multimedia speakers are not to be confused with THX Select certified speakers, which offer the best quality in a home cinema setup as opposed to more modest computer designs.

Yes. The speakers in a THX home cinema system (both Ultra2 and Select) are optimized for multi-channel sound (4 or 5.1 channels), so you get better imaging and clarity from the front speakers, and more envelopment from the surround speakers. Both of these benefits are ideal for music reproduction.

The difficulty exists because dialogue in a film competes with music and sound effects. In addition, all of the sounds are coming at the listener from many different directions. Clearly, the best way to hear clean dialogue is to reproduce it with as little coloration as possible. This means you need to hear flat frequency response all across the listening area and have controlled speaker/room interaction.

THX home cinema 5.1 systems include three front speakers (left, centre and right), two surround speakers and one or more subwoofers. Many systems also include one (6.1) or two (7.1) more surround back speakers. Each speaker has its own specifications and characteristics although a flat frequency response in the range each speaker is called to perform, is a prerequisite.

The final requirement for accurate multi-channel sound reproduction is accurate deep bass response. All THX subwoofers are designed to precisely match left, centre, and right (LCR) speakers through the electronic crossover in a home THX processor or receiver. THX subwoofers must have an accurate in-room response from 35Hz to 200Hz so that the crossover at 80Hz results in a smooth transition. Approved systems must be able to generate 102dB sound pressure level or louder without distortion in a listening room of 2000 cubic feet (roughly equivalent to a 20 square metre room).

Conventional two-channel speaker designs are constructed to present a good solid image over a 45 to 60 degree angle. If you spread the speakers too far apart, you get a hole in the centre image. Place them too close together, and the soundstage collapses into a fuzzy mono sound. In a multi-channel sound system, sound images are formed between left and centre and right and centre speakers. This means that speakers must be more precise in their imaging characteristics.

Front channel imaging is extremely important in producing accurate sound. For films, the sound has to match the picture perfectly. Home THX front channel speakers improve dialogue intelligibility and imaging in two ways. First, they provide wide horizontal dispersion. This allows for people sitting off-axis to hear full and flat frequency response. The second technique is to control the speakers' vertical dispersion. Audio engineers have found that the ceiling and floor reflections deteriorate a speaker's ability to image. In addition, the coloration from these vertical reflections cloud intelligibility.

Few enthusiasts realize that the centre speaker handles almost 40% of the dialogue in a typical surround presentation! Our ‘Free Air’ spherical rotating tweeters and THX certified dispersion characteristics ensures you'll never miss a word of dialogue.

THX recommends that the surround speakers are dipolar, which are designed to provide a "movie without walls" experience. A dipolar speaker does this by painting the walls and the ceiling with sound. It sends very little sound towards the listener. The sound reflecting off the room’s walls and ceiling provides an enveloping soundfield, immersing the listener in the movie experience.

The total energy radiated by a speaker in all directions is called its "Power Response". The THX dipolar surround speaker is required to have a flat power response. This means that the total energy radiated by the speaker (in front, above, below, behind, and to the sides) must together average a flat frequency response. With the total speaker energy being flat, a listener anywhere within the surround speaker's firing area will hear flat frequency response.

In a cinema, the surround speakers and the front speakers are different because they do different jobs. The front speakers deliver clear dialogue and localized sound that matches the picture. The surround speakers create diffuse and enveloping surround ambiences with occasional effects like pans or "fly-overs." If you build a 5.1 channel home cinema system using conventional loudspeakers, you’ll need a minimum of five matched speakers plus a subwoofer for accurate sound reproduction. By contrast, THX home cinema speakers have multi-channel sound capabilities built in. THX LCR speakers and THX dipole surround designs psycho-acoustically match the best surround sound performance of a cinema or mixing stage. The THX subwoofer keeps the size of all of the speakers small while allowing for peak dynamic range and bass performance.

THX recommends the use of main L/R front speakers that handle bass frequencies down to 80Hz, with one or more subwoofers for frequencies below. When using smaller loudspeakers we can cut off the bass at 120Hz instead of the optimum 80Hz crossover point. The associated subwoofer crossover frequency must also be adjusted to handle frequencies up to 120Hz. And we make that easy because all our THX Select certified subwoofers faithfully reproduce the bass up to 200Hz! Crystal has you covered!

The Re-Equalization circuit found in THX processors, corrects the over-bright sound of movie soundtracks. Movies are mixed in cinemas with a controlled high frequency roll-off, called the "X-Curve". This curve, an international standard, is part of every mixing and cinema's playback system because high frequency roll-off is appropriate for sound sources that are not close. But since home listening distances are shorter, audio mixed under the "X-Curve" sounds too bright when played back through flat response speakers. To match sound for smaller spaces and distances, THX uses a special Re-Equalization Curve, designed for home environments, to restore the correct tonal balance of a movie soundtrack.

* Image explaining this THX technology belongs to THX Ltd

Adaptive Decorrelation compensates for monophonic surround channels in Dolby Pro Logic. In the cinema, this goes unnoticed since the sound is mixed up by the large number of surround speakers and by small room reflections. Your left ear and right ear never get identical sounds, so you never identify the surround sounds as mono. (Even with Dolby Digital and DTS sound and "split" left/right surround channels, mixers use a lot of mono surround sound effects.)

In a home environment, you’d detect the mono "feel" of the surround channels. In response, the THX Decorrelation Circuit subtly adjusts the time and phase of one surround channel against the other. This constantly changing time and phase differences means that your left ear and right ear never hear identical signals. The sound is never identified as mono and remains spacious, just like in the cinema. For Dolby Digital and DTS split surround signals, an intelligent Adaptive De-correlation circuit de-correlates the surround channels only when it senses mono surround signals.

* Image explaining this THX technology belongs to THX Ltd

THX Loudness Plus is a new volume control technology with which home cinema audiences can now experience the rich details and ambient sound in a surround mix at any volume level. THX Loudness Plus incorporates two new THX technologies. As you change the volume, THX Multi-channel Spectral Balancingâ„¢ and THX Dynamic Ambience Preservationâ„¢ automatically and seamlessly apply the appropriate compensation. This delivers a more accurate listening experience at any volume level.

Basically, what it does is to automatically adjust the front-to-back speaker level relationship as you turn the volume level down so that the perceived sounds match as closely as possible the original mix as played back at the reference level (as was recorded and mixed in the studio).

THX Advanced Speaker Array (ASA) recreates the 5.1 studio surround sound field in your home by digitally reconfiguring the surround channels for the type of media you are enjoying. Featured on all Certified Receivers, THX ASA establishes THX Listening Modes, making it convenient to have one speaker set up for movies, music and games. 

	THX Cinema Mode Recreates the ambiance of the movie theater by positioning the 5.1 mix to immerse you in the movie’s soundtrack.
	THX Games Mode Distributes the sound effects and dialogue generated by the game engine, placing the audio from a 5.1 mix source to the appropriate “action” location – creating 360-degree gaming experience.
	THX Music Mode Emulates the original studio environment by repositioning the 5.1 surround sound mix further behind you for an accurate and increased sense of spaciousness and localization – placing you directly in the recording session.

THX Surround EX

Decodes the third surround channel from the traditional two surround channels, creating a more immersive entertainment experience. 

* Images explaining these THX technologies belong to THX Ltd