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  • LoudSpeakers

  • Want to get into the basic concepts of Sound, Hi-Fi and Home Theater?

    • What is sound and what are its basic characteristics?

      Sound propagates through the air in the form of an acoustic wave.

      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.

    • What is the purpose of each speaker in a home cinema system?

      The purpose varies according to the speaker placement and characteristics.

      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.

    • How many types of speakers are there based on their placement type?

      There are 3 types of speakers based on their placement type: Floorstanding, Bookshelf, Wall Mounted

      Τhere are three types:

      [image]

       

      Floorstanding

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      Bookshelf / Stand mounted

      [image]

       

      Wall mounted

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

    • Should I listen to my speakers with or without grille?

      Normally speakers are designed so that their performance is best with their grilles in place.

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      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.

    • If I already have a quality stereo system, do I still have to buy a complete new home cinema system?

      You should at least have a set of acoustically matched fronts and center.

      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.

    • Why do I need a subwoofer?

      To realistically reproduce low frequencies and feel what the director or musician intended.

      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.

      [image]

      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.

    • What are the benefits to using an active subwoofer?

      It will enhance all low frequency output, plus it will allow your amplifier to perform at its best.

      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.

    • How can my Home Theater elevate my gaming experience?

      Modern games have embraced surround sound, offering immersive, dynamic soundscapes.

      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!

    • How can I get the best out of an iPod/MP3 player using my hi-fi/home cinema speakers?

      Given the high quality of modern compression algorithms you can directly connect them to your system

      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.

       

    • What is a speaker's task and what determines its performance?

      It is to reproduce realistically every sound from a sound source

      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.

    • From hi-fi to 5.1 and 7.1 configurations. What to choose?

      Ιf you can afford it go for a 7.1 system and get the full experience of modern recordings and movies

      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.

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      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!

    • What are the Dipolar and Bipolar speakers? When are they used?

      Dipolar and Bipolar speakers are used as surround speakers in a Home Theater system.

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      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.

  • Can you explain what do all those speaker specifications really mean?

    • What is the nominal input power?

      The continuous power (RMS Watts) that a speaker can handle, without being damaged.

      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.

    • Is the nominal input power of a speaker a measure of quality audio reproduction?

      No, input power does not relate to performance in any way

      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.

    • What is the so called “break-in” period and what should I consider?

      It is a continuous playback period, after which, the speakers gain full performance capability.

      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.

    • What do all these speakers specifications mean?

      Specifications can be confusing and some are more important than others.

      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.

    • Why do different speakers have different impedance (ohm) ratings?

      Different speakers have different components which create variations in their total summed impedance

      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.

    • What does the sensitivity rating actually mean?

      It means how loud a speaker can play, when fed with a signal of given power.

      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.

    • How do you calculate the Sound Pressure Level in your Room?

      There are three rules you must follow. Learn more in the full answer of this question,

      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

    • What do speaker measurements reveal and how are useful?

      Read below to have a better understanding of speaker measurements.

      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.

  • Need a more detailed analysis on Speakers theory?

    • What are the different types of speaker design?

      There are two types, involving closed and open design principles.

      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.

    • How do speakers work?

      By converting electric signals into sound.

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      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.

    • What are the ideal properties of materials used to build speaker diaphragms?

      Rigid, yet low-mass materials are ideal for optimal control and sonic accuracy.

      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.

    • What is the role of the speaker cabinet?

      The cabinet amplifies the speaker’s output and optimizes specific frequency zones.

      [image]

      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.

    • What is 'speaker crossover'?

      The circuit which separates the range of frequencies by the speaker’s woofers and tweeters.

      [image]

      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.

       

  • Can Speakers be really… friendly?

    • Why do we need friendly speakers?

      Speaker characteristics directly affect the performance of your Hi-Fi system.

      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.

    • How friendly are your speakers to your Amplifier?

      Speakers must ideally match your amplifier, for maximum performance.

      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.

    • How friendly are your speakers to your Room's Decoration?

      Beautiful speakers can be placed freely, to achieve maximum sonic performance.

      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.

    • How friendly are your speakers to your lifestyle?

      The right speaker must perform equally well with soft music and bombastic action flicks.

      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.

    • What is magnetic shielding?

      Your speakers must not magnetically interfere with your sensitive electronic equipment.

      [image]

      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.

    • Why can selecting speakers be a challenge?

      Spending money on well known brands, does not guarantee sonic quality and high performance.

      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.

    • How should I compare speakers?

      Ideally, by following the “blind” test methodology, A-B switching and some reference recordings.

      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.

    • How should I evaluate speakers?

      By listening to them in an acoustically familiar room and focusing on the different sonic layers.

      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