Below you will find a basic explanation of a few terms you will come across when looking to purchase your new Hi-Fi or Home Cinema. We will continue to expand upon this and offer walk throughs and how-to guides as well. Please email us firstname.lastname@example.org if you there is a subject you would like us to address.
Active / Passive Speakers
Passive speakers require some form of amplification to work and active speakers have built in amplification.
This is the lower end of the frequency range and is reproduced by dedicated Subwoofers or/and woofers in loudspeakers. Bass is fundamentally about moving air.It is non-directional and radiates all-round.The larger the drive unit the easier it is to reach the same frequency. This allows for less excursion to be used making it easier for tighter speedier bass. This however, does also depend upon the drive unit quality as the more the drive unit bends and succumbs to it's fast movements the more the signal it's producing is distorted.
The majority of speakers use their woofers to replicate frequencies between 30Hz and 500Hz , most bookshelf speakers however will be starting from 60Hz. Subwoofers are tailored to support the lower end of the frequency spectrum and some even reach a single figure level. It is interesting to note though, at 20Hz and below this is felt rather than heard.
This all equates to the fact a subwoofer if often a good addition to a system to help replicate the bass of a track that your speakers may struggle to produce. We will be adding an article on the art of subwoofers at a later point!
Bi-wiring / Bi-amping
Different brands take different views on the pros and cons of bi-wiring / bi-amping with some believing it leads to a cleaner signal, better power balance and reduction in clipping and others believing it can lead to a less coherent sound.
Bi-wiring uses a single amplification output source and connects separately to the low frequency driver and to the midrange/tweeter.
Bi-amping is similar to bi-wiring, but involves separate amplifiers, one for the woofer and one for the midrange/tweeter. The most common type of this is passive bi-amping which uses separate crossovers within the speaker which filter down the bass and midrange amplification.
Active bi-amping is where you have an electronic crossover between the preamp and power amps (the passive crossovers must be eliminated in order to achieve the advantages of active bi-amping).
Clipping is a form of distortion caused that cuts off the peaks of audio signals. It usually occurs in an amplifier when the input signal is too large or when the voltage rails of the power supply can’t deliver the necessary voltage to the amp. If a clipped wave is viewed on a waveform monitor, the tops are flattened, or squared off, rather than rounded; because of this, the higher frequencies are lost.
A clipping amplifier can damage speakers as it causes unnatural movement from the speaker cones.
Crossovers split the audio signal into separate frequency bands to be delivered to the correct driver for the frequency. You will see crossover ranges quoted in Hertz on a spec sheet and this indicates at which frequencies sound will be reproduced.
Nearly all crossovers are passive circuits, designed to match the characteristics of the drivers and their mounting, and are built of capacitors, inductors, and resistors. Active or 'electronic' crossovers are used in some high performance hi-fi speakers. These have the advantage of not being powered off the incoming signal and allow for amplification after this stage.
DAB(Digital Audio Broadcasting), was developed to solve the problem of the reduction in available bandwidth for radio stations. This was leading to a lower quality of sound which a digital signal improves upon as well asallowing for station information and EPG (Electronics programme guide). DAB+ was introduced in February 2007 and introduced AAC+ audio codec which is a more efficient compression leading to superior sound.
DAC stands for Digital to Analogue Converter. It is used to change digitized information (zeros and ones) back into an analogue waveform that an amplifier and speakers can process. As digital formats have gained in popularity and more music is stored on hard drives or streamed the popularity for standalone DACs has grown dramatically.
Frequency is the property of sound that determines pitch. The audible frequency range for humans is roughly about 20 Hz to 20,000 Hz (20 kHz). When you are looking at frequency response specs you will also need to make note of the +/-dB value which expresses the potential deviation from intended volume within that frequency range. A high value will lead to an inconsistent volume of sound.
Measured in Ohms, impedance is the level to which an electrical circuit restricts current flow. Expressed on spec sheets as nominal impedance, the majority of speakers are usually either 4 or 8ohms. This is important specification for two reasons; firstly connecting your amplifier to the wrong speaker impedance can lead to damaging or blowing your amp. Too low impedance when connected to class solid state amplifiers will cause overheating, so if you have 4 ohm speakers check to see if your amplifier will be capable of driving this load.
Ohm's Law states: In an electrical circuit, current flow is directly proportional to voltage and inversely proportional to impedance.
Current = Voltage .
So in short lower impedances mean relatively more current is needed. This combined with the speaker sensitivity will give an indication of how easy/hard a speaker is to drive.
The part of the frequency range that sits between the bass and treble. The midrange handles most instruments and vocals, so is of particular importance to music reproduction. You usually see the lower end cross over around 400-500hz and the upper end at 3-5khz, in between these frequencies are what is handled by a midrange driver.
This refers to a speaker’s efficiency IE how easy a job the amplifier will have driving it and should be used to determine the amount of power necessary to operate your speakers. It is a measurement of sound output derived from a speaker with one Watt of power from an amplifier and usually measured with a sound level meter placed one meter in from of the speakers. Therefore the result is expressed in dBs and you should see next to Sensitivity in brackets (1w/1m) or it maybe (2.83v/1m). 2.83Volts is equivalent to 1Watt at 8 Ohms.
Most AV/HiFi speakers designed for the home are very inefficient converting about only 1% of electrical energy to acoustic energy. The remainder will be lost to heat conversion mainly in the voice coil and magnet assembly.
Typically a speaker of 89dB is easy to drive but just a few dB lower and your speakers will require a lot more current to start singing.Small satellite speakers due to their size it is assumed they are easily driven, but rated at 87dB they require a fair amount of current to get singing. If you are looking to achieve reference levels of pressurisation for your home cinema then you will generally be aiming for speakers 90dB+ or you will need a big amplifier and speakers with high power handling to make up for this.
When setup correctly a pair of speakers should paint a larger picture than just seeming to emanate from two audio points.Instead speakers will layout the whole stage and allow for picking out different instruments and vocals. This is achieved by slightly tricking the brain, when sound is received from both speakers simultaneously it will appear as though it has come from directly in front of you. Michael Jackson’s Thriller is a good one to test this with as the door creeks open at the start and the footsteps walk down the corridor it should actually seem like they are walking from right to left. Some speakers do this better than others so you are looking for a wide sound stage and good imaging meaning that you can hear the separation of the instruments.
Total Harmonic Distortion (THD)
Harmonic distortion is unwanted noise added. Total Harmonic Distortion, abbreviated THD, is a specification that identifies the amount of unwanted harmonic frequencies generated when a signal passes through an audio component, most commonly an amplifier. All amplifiers and signal processors add distortion to the signal, minimising this can be one of the keys to a great sounding unit
This is the unit which handles the high frequencies in sound reproduction usually 2kHz – 20kHz which is the upper end of our hearing. Some tweeters do extend beyond this point and there are super tweeters on the market going way beyond our audible hearing. The most common type for home cinema and Hi-Fi is a Dome tweeter but you also find Ribbon tweeters which generally come at a higher price point. The perfect material for a tweeter needs to have low mass, high stiffness and good dampening, and each manufacturer take their own approach to achieving this. Two examples would be Wilson Audio’s Alexandria XLF speakers (£200,000 a pair) use a soft silk dome tweeter and Focal Grande Utopia Speakers (£121,000 a pair) which use a metal Beryllium Inverted Dome. Even at the reference end of the market there is no one standard for tweeter manufacturing and one is not necessarily better than the other so it is always worth getting in some listening time to see what’s right for you.
Are a unit of power indicating how much your amplifier can supply or what power your speakers can handle. A lot of attention is paid to this statistic but it is not the magic number IE more watts does not mean better quality or even a louder sound. Pay particular attention to the parameters of how the stat is quoted… Sometimes, for example, an amp manufacturer will quote an output value of watts that is based off driving one sound channel when in actuality the amp will need to drive two channels or more in the case of surround sound systems. Check to see if it is it quoted as RMS (root mean square) which is the correct way or Peak power which does not give you a real indication of its true output. Additionally when looking at a wattage value bare in mind at this value other unwanted effects may be being maximised like the percentage THD (Total Harmonic Distortion).
Another fact to note here is that to get a +3dB gain in volume you will need to double the power of your amplifier regardless of your speakers sensitivity, so high Watts quoted is far from the end story, look further into it and do not take some numbers at face value!
This is the driver which handles the lower frequencies but most commonly is a mid/bass driver in a two way speaker design. The ideal material has to tick the box of all three key parameters: damping, lightness, and rigidity to try and give perfect frequency curve. The most standard and cheapest drive units are made from polypropylene, but they can range from Kevlar to ceramic-coated drive units. Each manufacturer again has its own take on what makes the best woofer.