Amplifier and loudspeaker power ratings are specified differently. For amplifiers, the output power is specified on the basis of an undistorted continuous sine signal; for loudspeakers, the (long-term) power handling is specified on the basis of a noise signal shaped in accordance with the standard frequency distribution of a music signal. The respective peak values are twice as high with sine signals, but at least four times as high with noise signals. Over a short period of time Crystal Audio loudspeakers can handle levels distinctly above the norm power specification. Amplifiers, however, can supply only a little more than their nominal power even over a fairly short period of time, after which clipping will set in. Amplifier power and loudspeaker power handling thus cannot be related exactly. To define a reasonable speaker/amplifier combination, all Crystal Audio loudspeakers are specified with a "recommended amplifier power". The lower value marks the minimum amplifier power for achieving slightly more than moderate volume levels under typical listening conditions. The upper value guarantees that even at the highest volume levels that are suitable for the loudspeaker, the amplifier signal will be clipped only rarely. However, due to the varying nature of audio signals, these are only general suggestions to be adjusted according to your system.

Crystal Audio does not recommend any particular brand of amplifiers. The choice of an amplifier is a personal matter dependent on taste, power handling, how many speakers are being used, what type of features you need and of course what your budget is.

However, we can give a few hints on what to look for when selecting your Amplifier/Receiver. Speaker Amplifier requirement figures (Watts) are intended only as a guide.

As a rule, buy the most powerful amplifier that you can afford within the specified range and use it with great care. It is easier to damage the loudspeaker with a small amplifier driven into distortion using too much volume with bass and treble boost, than with a large amplifier, which has plenty of power in reserve.

In addition, check whether the receiver offers Auto-Calibration (it is strongly suggested for inexperienced Home Theatre users). In addition, can it decode today's high definition audio formats (Dolby TrueHD, DTS-HD Master Audio, etc.), and does it support HDMI connectivity and offer upscaling for video signals?

We recommend that you discuss with your local specialist hi-fi dealer what they would recommend as they have firsthand knowledge of what systems work best with room layouts, sizes and shapes.

If the amplifier’s power rating is below that of the speaker, the amplifier will try too hard to keep up with the speaker, which means that here is danger that the amplifier will "clip" which could possibly cause damage to the tweeters or destroy the speakers.

Yes it is! If you use modern, stylish and compact speakers for the Left and Right channels, then you most probably need a Subwoofer to add the bass frequency extension needed to get a realistic music reproduction. Classic stereo amplifiers do not support the connection of a subwoofer, while modern receivers offer a subwoofer output, plus electronic crossovers for the proper bass management. Set the crossover frequency to 80Hz (if your main speakers are able to reproduce those frequencies) and set the levels of main speakers and sub, so that the result is balanced.

However, note that it is not only about having small speakers. Even if your speakers can reproduce low frequencies, the bass management can only be optimum if you can isolate them and place the speaker reproducing them (here comes the Sub!) in the best position according to room acoustics (where the standing waves are less prominent so that the low frequencies sound field is smooth). Otherwise, you will be obliged to keep the low frequencies tied to the main speakers, whose position is strictly specified and not flexible like the subwoofer's.

Apart from that, you get a mult-ichannel receiver and have the added bonus of being able to upgrade to a 5.1 or 7.1 system at any time you wish.

The letters DSP stand for Digital Signal Processing. The signal is the information that is picked up from the Blu-ray, DVD or CD, flows through the system, and eventually emerges as music or movie soundtrack.

Signal processing refers to just about everything your sound system does to your signal -- anything from raising it from a preamp to an audible level, to boosting or cutting bass and treble, all the way to making your living room sound like a stadium or a movie theatre. Digital Signal Processing performs that type of signal manipulation in the digital domain.

That is, it deals with your signal not as a continuous stream but as a series of "zeros and ones". DSP’s most common applications used to be the re-creation of various acoustic environments in our living room, so we can listen to Miles Davis play in a "jazz club" and the Benedictine Monks chant in a "cathedral". Nowadays, more sophisticated DSPs decode the multichannel high definition formats and calibrate automatically your speakers' response so that their in-room performance is balanced.

Because the speakers in a home theatre system are all at a different distance to the viewers, multi-channel playback requires a delay of the signal reaching them, in order to virtually align the speakers, so that they are equidistant to the listener. This delay is inserted to the receiver via the distance of each speaker from the main listening position. Note that this is mostly done automatically in modern Auto-Calibration receivers, using their calibration microphone. By inserting the correct delay times needed, the carefully created sound stage is accurately rendered.

Most modern receivers feature an Auto-Calibration function (be it Audyssey technology on Denon and Onkyo designs, Sony's Digital Cinema Auto Calibration, Pioneer's Multi Channel Acoustic Calibration or Yamaha's Parametric Room Acoustic Optimizer). Basically you set a microphone (provided with the receiver) where one of the ears of the main listener would be and the receiver outputs a series of signals (mostly noise bursts) to all of your speakers, setting their levels, distance from listener, confirms their correct phase and finally tries to correct through equalization either the non-flat response of speakers themselves or the combined effect of room acoustics with your speakers that results in uneven response. The series of tests from the receiver may be repeated for more microphone positions, depending on the Auto-Calibration algorithm implementation, resulting in more uniform reproduction across a wider area as opposed to a confined sweet spot.

Most probably, the levels and distances of speakers are spot-on after the Auto-Calibration is finished. However, check to see that the figures seem reasonable. As for the frequency correction performed through EQ, do not always assume that it gives a better result. Be sure to listen your system using your favourite music and movies and turn the Auto-Calibration EQ on and off periodically to see what sounds best to your ears. If on the other hand you are an experienced Home Theatre user, really striving for the best result, you can fine tune the EQ settings using your ears (NOT advised!) or a SPL-meter together with a DVD that provides band filtered noise, enabling you to measure the SPL produced by your speakers for some split bands of the 20Hz-20kHz spectrum.

The size of the capacitors and the transformer utilized in the power supply section and the implementation of the amplified stages determines the capability of the amplifier to drive low impedance speakers.

The most critical factor is the amplifier capability to increase the output current that it can supply to the speakers. Amplifiers with carefully implemented power supplies, large transformers and capacitors, do not run out of the power required to deliver the sound accurately.

If the amplifier cannot supply the required current, then the sound of the system will be inferior and could even damage the speakers.

Weak bass, reduced dynamics and harsh highs characterize the sound of a system whose amplifier is not up to the task. Especially dangerous for the speakers is the occurrence of "clipping". In general, all semiconductor amplifiers can drive any speaker as long as it is not clipping.

Today's receivers, on the other hand, offer protection so that they don't result in clipping even if the connected speakers have quite a low impedance.

The audio sources of home entertainment systems are becoming increasingly digitally based. This has increased the popularity of digital power amplifiers. There are two methods for engineering a digital amplifier: true digital power amplifiers and power amplifiers which incorporate digital technology. The latter type accepts a digital signal at its input which is then converted to an analogue signal by its integrated Digital to Analogue (D/A) converters, and is amplified in the traditional analogue way. As for the first type (a true digital amplifier or class D design), they transform the incoming PCM (pulse code modulation) audio signal, into another digital format called PWM (Pulse Width Modulation), which is then amplified in the digital domain. The PWM amplification stage is a type of switching circuit, and is therefore not influenced by nonlinearity and transistor noise. The PWM data switches conventional transistors on and off depending on the length of the data pulse. The signal amplitude depends on how long the transistors are on or off. The on/off output of the transistors represents the audio wave. At the final stage, the PWM amplified signal is lowpass filtered (using a high quality coil-capacitor network), so that only audible frequencies pass through while all the high frequency content is rejected.