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HiFi Technical Terms - defined and explained in simple terms
Groan!! This section is written to explain in plain, simple, easy to understand terms, the complexities of technical terms used to specify and compare HiFi equipment. You DO need an appreciation of the terms and can stick to the top level explanations - however - for those wishing to go further and dig deeper, the second and sometimes third levels do some serious explaining that may help your understanding and appreciation of the complex subject of sound.
Common Terms..Choose a term and then click on it
- Balanced / Unbalanced / Single Ended - See.....Earthing and hum issues.
- Crossover (F) - A single loudspeaker cannot handle the full range of audio frequencies and so the workload is split two, three or more ways. As each speaker comes into use, the others are progressively turned off so that hopefully, you get a nice flat frequency response - NOT SO!! Each crossover frequency where one speaker switches off and the next turns on invariably produces a frequency anomaly. This can be reduced to very small proportions by good design but it is still present and will affect sound quality. Obviously a two driver speaker has only one crossover and produces the optimal response. Extra drivers introduce additional distortions.
Note that if you have a sub woofer fitted to your system, you have an additional crossover frequency where the sub woofer output drops and the main speakers take over. Careful matching of speaker volumes ie the ratio of sub woofer output to main speaker output can help mask this crossover. Ideally the sub woofer upper frequency response is just starting to trail off where the main speakers low frequency response is just picking up. Get the match just right and you will preserve a flat frequency response across the range of ALL the speakers ie 25Hz - 22KHz or wider. - Damping Factor - The ability of your power amplifier to control the speaker properly. Should be as high as possible. Is affected by the quality of speaker cable - go for as low resistance as possible.
- Dispersion (Angle) - Do you spend time positioning the speakers so that they precisely face the centre of the sofa? With Point Source speakers it doesn't matter! If a Point Source speaker has a dispersion angle of say 90 degrees conical, then in english, you can sit bang in front (0 degrees) or off to either side (45 degrees) and still hear all parts of the sound spectrum - impressive.
- Distortion (%THD) - A measure of the difference between output and input signals. In a perfect world, there would be no difference at all and distortion would be 0%. Distortion comes in different flavours - even harmonic (as produced by valve amplifiers) which sounds bad, and odd harmonic (as produced by semiconductors) which sounds absolutely awful. The aim is for the least amount possible. Levels of 1% are barely discernable by most, so 0.1% or lower is better. Critically, the loudspeaker is usually the major source of distortion, with levels so bad that most manufacturers do not publish them!! 2 - 5% is not uncommon and this is the number one area to tackle if upgrading or starting a new hifi system. The very best studio monitors (as highlighted elsewhere on this site) generate less than 0.4% THD over the range 50Hz - 20KHz which is absolutely brilliant for a speaker. MAKE SURE you check this parameter as it is the single most important quality measurement of your hifi! Top
- Dynamic Range (dB) - Simply a measurement of the difference in sound level (volume) between the very quietest sound and the very loudest. Expressed in dB (decibels). These extremes are limited in a hifi system and in general, the more expensive the system, the wider (better) the dynamic range. At one extreme, system noise and hiss limits the quietest sound coming from your loudspeaker, whilst at the other extreme, system power, distortion and speaker SPL (Sound Pressure Level) limits how loud your system can go.
- Earthing - Possibly the single biggest problem faced by hifi users is getting the system properly earthed. Suffice it to say that you can spend hours trying various combinations and still not get it right. A full technical description and suggestions to overcome this perennial problem can be found at.....Earthing and hum issues
- Frequency Response (x - y Hz +/- z dB) - A young pair of human ears may be able to hear sounds in the range 20Hz to 20KHz or even higher. As the years go by, your hearing deteriorates selectively, especially at high frequencies such that by middle age you might miss some sounds above 15KHz. Working in loud ambient surroundings, listening to extremely high sound levels especially where lots of distortion is present will, reduce your hearing either more quickly, or more extensively.
So the conclusion is - Enjoy the best quality hifi from as young as you can and be careful only to listen at loud levels, to top quality (distortion free) music from good speakers. If just starting to collect your hifi system - start with a top quality pair of speakers first.So having achieved a wide frequency response of say 45Hz to 22KHz we now specify how "flat" that response is ie +/- 3dB. In simple terms a flat frequency response makes sure that a clarinet for example when played at the same volume by the musician over a wide range of notes - low to high - actually sounds identical in loudness through your speaker system. Not quiet in the low register but ear piercingly loud for high notes - but that it sounds natural, real. This needs to be true for all instruments be they high in tone like a piccolo or low in tone ie double bass. The better is the match between all notes, the tighter is the specification. So a speaker that achieves 45Hz-22KHz +/- 3dB gives a far better rendition of the original signal than one specified as 85Hz - 17KHz +/- 3dB. And both are much better than a speaker rated 50Hz - 20KHz +/- 6dB. Manufacturers sometimes publish frequency response graphs to try to prove how flat the frequency response is for their speakers - BEWARE. Compare apples with apples and take note of the scaling and actual values. Top
- Hum (dB) - A measure of the residual hum (faint buzzing noise) generated by your amplifier and heard through the speakers. There is absolutely no excuse for having ANY hum whatsoever - it should be inaudible at any listening level. Hum can also be symtomatic of Radio Frequency instability where your amplifier is generating large signals which fry the hearing of the local bat population.
- Nearfield - Refers to a speaker type where the listener is positioned physically close to the speaker as opposed to long throw type speakers that project sound over long distances.
- Phase - To do with the relationship between voltage and current when trying to get sound from your speakers. If two speakers are said to be "Out of phase" then when one speaker cone moves forwards, the other one moves back. This sounds odd (loss of bass frequencies) though hard to define. The solution is simple - reverse the wires to ONE speaker only. All speakers should be "In phase" ie all going in the same direction. Top
- Point Source - Sound eminating from a single location, a point source in space. Someone speaking to you is a good example of a Point Source sound.
- Signal to Noise Ratio (SNR) - A measure of the HISS and NOISE introduced by the equipment. Well designed equipment introduces no audible hiss at normal listening levels. Line inputs and amplifiers should have a specification of 90dB or higher. Higher = better.
- Sound Descriptions - Gritty, Coarse, Veiled, Thin, Harsh, Weak, Boomy, Tinny, Fogged, Abraisive, Punch (lack of)
Are all terms to describe Distortion especially in speakers. - Sound Pressure Level (SPL) - A measure of the loudness of the sound and is expressed as the number of decibels of sound produced by your loudspeaker when measured at a distance of 1m away from the speaker cone if driven by an amplifier producing exactly 1W of power. Top
- Speaker Sensitivity (dB/W) - A measure of how loud the speaker is with a given input signal (1Watt). Allows you to compare speaker sensitivities. In general, a more sensitive speaker (higher dB/W value) gives more sound output from any given amplifier and is therefore easier to drive. This translates to lower distortion = much better. Top
- Sub Bass Speaker - Seperate stand alone speaker optimised to produce very low frequencies. They can require the largest of amplifiers to drive them properly and drive size can be anything up to 18" (46cm). Can be capable of massive outputs and if over specified, can even damage your living space through the effects of vibration damage. Used sensibly, they are a must for all hifi systems. Top
- Tweeter - Small diameter drive unit to produce high frequencies.
- Woofer - Large diameter drive unit to produce low and mid range sounds.
- Wow and Flutter (%) - To do with cassette and tape machines where the tape speed varies over time. Has the effect of making instruments sound "wrong". A clarinet will sound as though it was immersed in a bucket of soap suds - odd. A specialty of cheaper cassette machines, pocket stereos and cheap tower systems. Top
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Balanced / Unbalanced... Basic Electrical Formulae... Crossover... Damping Factor... Digital Vs Analogue... Dispersion Angle... Distortion... Dynamic Range... Earthing... Frequency Response... Hum... Nearfield... Phase... Point Source... Signal to Noise Ratio... Sound Descriptions... Sound Pressure Level... Speaker Sensitivity... Sub Bass Speaker... Tweeter... Woofer... Wow and Flutter...