Audio glossary
Plain-language definitions of the words used around headphones, hi-fi and audiophile listening, each with what the audiophila. catalog says about the term. Every definition is written to be read on its own; the catalog figures come from the products members have added and refresh daily.
111 terms shown
0–9
- 3.5mmConnections & formatsThe 3.5mm jack is the small round analog audio connector on phones, laptops and many portable players and headphones. It carries a stereo signal on a single plug.
- 4.4mm balancedConnections & formatsThe 4.4mm balanced plug is a five-contact headphone connector that carries separate positive and negative signals for each ear. It is the usual balanced output on portable players and desktop amplifiers.
- 6.35mmConnections & formatsThe 6.35mm jack, also called a quarter-inch plug, is the large headphone connector found on desktop amplifiers, receivers, mixers and musical instruments. As a headphone connector it is single-ended and carries the same stereo signal as a 3.5mm plug, on a sturdier body.
- 16-bit/44.1 kHzConnections & formats16-bit/44.1 kHz is the resolution of the compact disc: each sample has 16 bits of depth and there are 44,100 samples per second per channel. It is the baseline most streaming services call "lossless" or "CD quality".
- 24-bit/192 kHzConnections & formats24-bit/192 kHz describes audio sampled 192,000 times per second with 24 bits per sample. It is the highest of the common "hi-res" formats, with far more headroom than a CD, though whether that is audible is debated; 24-bit/96 kHz is more common.
A
- AACConnections & formatsAAC, Advanced Audio Coding, is the lossy compression format used by Apple Music and iTunes downloads, and the preferred Bluetooth codec on iPhones. At 256 kbps most listeners cannot tell it from lossless in blind tests.
- Active speakerGear & technologyAn active speaker has its amplifiers built into the cabinet, usually one per driver, with the crossover working on the signal before amplification. Studio monitors have been active for decades; hi-fi has followed as streaming made the all-in-one system appealing.
- AirSoundAir is the sense of openness and space at the very top of the treble, above about 10 kHz: the shimmer around cymbals, the breath in a voice, the feeling that there is room above the music. Products with little energy there sound closed-in.
- AmplifierGear & technologyAn amplifier takes a small audio signal from a source or DAC and makes it strong enough to drive headphones or speakers. Headphone amps deliver milliwatts into loads of roughly 16 to 600 ohms; power amps deliver tens or hundreds of watts into speakers.
- AnalyticalAudiophile slangAn analytical product presents detail first: every edge, breath and flaw in the recording is laid out plainly. Reviewers use the word for praise when they mean revealing and for criticism when they mean cold; it usually describes a neutral-to-bright tuning with low distortion.
- aptXConnections & formatsaptX is a family of Bluetooth audio codecs from Qualcomm, found on most Android phones and many headphones but not on iPhones. aptX HD and aptX Adaptive raise the bitrate and quality; aptX Lossless claims to deliver CD-quality audio bit for bit when conditions allow.
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- Balanced armatureGear & technologyA balanced armature is a tiny driver, long used in hearing aids, in which a pivoting metal reed moves a small diaphragm. Its size lets in-ear monitors pack several into one shell, each handling part of the frequency range.
- Balanced vs single-endedConnections & formatsA balanced connection carries the signal on two matched conductors and responds only to the difference between them, so noise picked up equally by both cancels. A single-ended connection uses one signal wire and a shared ground; it is simpler and fine for short cables.
- BassSoundBass is the low-frequency part of music, roughly 20 to 250 Hz: kick drums, bass guitar, the left hand of a piano and the weight of an orchestra. How much a product delivers, and how tightly, shapes its character more than any other region.
- Bass reflexGear & technologyA bass reflex speaker has a port, a tube or slot in the cabinet, tuned so the air inside resonates and reinforces the bass near the speaker’s low-frequency limit. It is the most common enclosure because it gets more bass from a given box.
- Belt driveGear & technologyA belt-drive turntable spins the platter with a rubber belt from a motor mounted off to the side, so the motor’s vibration is isolated from the record. It is the most common design in hi-fi turntables, favored for low noise.
- Bit depthSpecs & measurementsBit depth is how many bits describe each audio sample: 16 bits for a CD, 24 bits for most hi-res files. More bits lower the noise floor of the digital format, giving a wider dynamic range, rather than adding detail to the music.
- Bit-perfectConnections & formatsBit-perfect playback means the audio data reaches the DAC exactly as stored in the file, with no resampling, mixing or volume processing by the computer along the way. It is the software side of keeping a lossless chain lossless.
- BluetoothConnections & formatsBluetooth is the short-range radio link that wireless headphones, earbuds and speakers use to receive audio from a phone or computer. The audio is compressed on the way by a codec, so Bluetooth is convenient rather than lossless.
- Bone conductionGear & technologyBone conduction headphones send vibration through the bones of the skull, usually from pads resting in front of the ears, so the ears stay open. They are built for runners and cyclists who need to hear traffic, not for sound quality.
- BrightSoundA bright product has more treble energy than neutral, so cymbals, consonants and string overtones stand out. It sounds detailed and lively to some listeners and harsh or fatiguing to others.
- Burn-inAudiophile slangBurn-in is the belief that gear sounds better after hours of use as its parts settle. Measurements show a small change in speaker suspensions and little or none in headphones and electronics; many owners still hear a difference, which sceptics put down to adaptation.
C
- Chi-FiAudiophile slangChi-Fi is the nickname for the wave of audio gear from Chinese brands that, since about 2015, has delivered in-ear monitors, DACs and amplifiers at prices that older brands could not match. It started as a dismissive term and is now mostly used with respect.
- Class AGear & technologyA Class A amplifier keeps its output transistors or tubes conducting all the time, so the signal never has to hand over between devices. It is the simplest and, in theory, cleanest output stage, and also the least efficient: most of the power becomes heat.
- Class ABGear & technologyA Class AB amplifier uses two output devices that each handle one half of the waveform, with a small overlap so neither switches fully off. It is the standard design for most solid-state and tube power amplifiers, balancing efficiency with low distortion.
- Class DGear & technologyA Class D amplifier switches its output devices fully on and off at a very high rate and filters the result back into an audio signal. It is over 90 percent efficient, which allows small, cool-running amplifiers with hundreds of watts.
- Closed-backGear & technologyClosed-back headphones have sealed earcups that keep sound in and much of the outside world out. They suit commuting, offices and recording, and usually give stronger bass than open designs, at some cost to spaciousness.
- Coaxial (S/PDIF)Connections & formatsCoaxial S/PDIF carries a digital audio signal on a single electrical cable with an RCA or BNC plug. It is the wired twin of the optical TOSLINK connection, with the same data format, slightly higher bandwidth and no immunity to ground hum.
- CrosstalkSpecs & measurementsCrosstalk is how much of one stereo channel leaks into the other inside a device, in decibels below the signal. Lower leakage keeps the stereo image stable; it is one of the measurable things a balanced connection improves.
D
- DACGear & technologyA DAC, or digital-to-analog converter, turns the numbers in a digital file or stream into the analog voltage an amplifier and headphones or speakers can use. Every phone and laptop has one built in; a separate DAC aims to do the job better.
- Damping factorSpecs & measurementsDamping factor is a speaker’s impedance divided by the amplifier’s output impedance, a measure of how firmly the amplifier controls the speaker cone’s movement. Values above about 20 are considered adequate; the very high figures on some spec sheets add little.
- DAPGear & technologyA DAP, or digital audio player, is a portable music player with its own DAC and headphone amplifier, built to drive headphones better than a phone. Most run Android, store lossless files and offer balanced output.
- DecaySoundDecay is how a sound fades after it is struck: the trail of a cymbal, the ring of a piano note, the reverb of a hall. Natural decay sounds spacious; cut short it sounds dry, and added ringing sounds muddy.
- Decibel (dB)Specs & measurementsThe decibel is the logarithmic unit audio uses for level and ratio. Each 10 dB is a tenfold change in power and sounds roughly twice as loud; about 1 dB is the smallest change most people notice. Almost every audio specification is written in it.
- Delta-sigma DACGear & technologyA delta-sigma DAC converts audio by resampling it to a very high rate with only a few bits, then filtering the result, rather than converting each sample directly. Almost every DAC chip made today works this way, because it achieves very low distortion cheaply.
- Diffuse-fieldSoundDiffuse-field is a headphone measurement target that describes how a flat sound source would measure at the eardrum if it arrived evenly from every direction. It is a reference for what "neutral" should look like on a headphone measurement rig.
- Direct driveGear & technologyA direct-drive turntable mounts the platter directly on the motor shaft, with no belt. It starts and stops instantly and holds speed precisely, which made it the standard for DJs and broadcast, and modern versions are quiet enough for serious listening.
- DSDConnections & formatsDSD, Direct Stream Digital, stores audio as a one-bit stream at a very high rate, 2.8 MHz for the DSD64 used on SACD, rather than as multi-bit PCM samples. It is a niche format for downloads and SACD discs, supported by many DACs.
- Dynamic driverGear & technologyA dynamic driver is the most common loudspeaker and headphone transducer: a coil of wire attached to a cone or dome, sitting in a magnetic field, that pushes the diaphragm back and forth when the music signal passes through it.
- Dynamic rangeSpecs & measurementsDynamic range is the span between the quietest and loudest sounds a system or recording can hold, in decibels. For equipment it is set by the noise floor; for a recording it depends on how much the mastering compressed it.
- DynamicsSoundDynamics is how convincingly a product moves between quiet and loud: the snap of a drum hit, the swell of an orchestra, the difference between a whisper and a shout. "Slam" and "punch" describe its low-frequency side.
E
- EfficiencySpecs & measurementsEfficiency is how much sound a transducer produces from the electrical power it is given. In everyday use it means the same as sensitivity: an efficient headphone or speaker plays loud from a small amplifier.
- ElectrostaticGear & technologyAn electrostatic driver moves an extremely thin, charged membrane between two perforated plates using high voltage rather than magnets. It needs a special energizer or amplifier, and is known for speed and delicacy in the treble.
- EndgameAudiophile slangEndgame is the product or system an audiophile says they could stop upgrading at: good enough that the search is over. It is used sincerely, hopefully and, very often, ironically, since most people’s endgame lasts until the next release.
F
- FLACConnections & formatsFLAC, the Free Lossless Audio Codec, compresses PCM audio to roughly half its size without losing anything: decoded, it is bit-for-bit the original. It is the standard format for lossless downloads, CD rips and most lossless streaming.
- FOTMAudiophile slangFOTM, flavor of the month, is the product everyone on the forums is excited about right now, before the next one arrives. The label is both a recommendation and a warning that the enthusiasm may not last.
- Frequency responseSpecs & measurementsFrequency response is how loudly a product reproduces each frequency from bass to treble, shown as a line on a graph. It is the measurement that best predicts how a headphone or speaker will sound, though it does not capture everything.
- Fun tuningAudiophile slangA fun tuning is a deliberately non-neutral sound, usually with boosted bass and lively treble, chosen to be exciting rather than accurate. It is the reviewer’s polite word for a V-shape that works.
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H
- Harman targetSoundThe Harman target is a headphone frequency response curve derived from listener preference research at Harman International, with a moderate bass shelf and slightly less treble than the diffuse-field curve. Many headphones and IEMs are tuned toward it, and many measurement sites compare against it.
- HDMI ARCConnections & formatsHDMI ARC, the Audio Return Channel, sends audio from a television back down the same HDMI cable that carries video to it, so a soundbar or receiver needs one cable instead of a separate optical link. eARC is the newer, higher-bandwidth version.
- HybridGear & technologyA hybrid in-ear monitor combines two or more driver types, most often a dynamic driver for bass and balanced armatures for the mids and treble. A tribrid adds a third type, usually electrostatic tweeters.
I
- I2SConnections & formatsI2S is the raw digital audio bus that chips inside a DAC or CD player use to talk to each other, carrying the data and its clocks on separate lines. A few boutique DACs expose it on an HDMI-style socket as an external connection.
- IEMGear & technologyAn IEM, or in-ear monitor, is an earphone that seals in the ear canal with a silicone or foam tip. Born as stage monitoring for musicians, IEMs, especially at the budget end, are among the most competitive parts of the headphone market.
- ImagingSoundImaging is how precisely a product places each sound within the stereo picture: whether a voice sits in a clear spot between the speakers or smears across them. Good imaging lets you point at where each instrument is.
- ImpedanceSpecs & measurementsImpedance, given in ohms (Ω), is how much a headphone or speaker resists the current an amplifier sends it. High-impedance headphones need more voltage to play loud; low-impedance ones draw more current and are easier for phones to drive.
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- LayeringSoundLayering is the sense of depth in a presentation: the impression that some instruments sit in front of others rather than all on one flat plane. It is the front-to-back part of soundstage.
- LDACConnections & formatsLDAC is Sony’s high-bitrate Bluetooth codec, sending up to 990 kilobits per second, about three times what standard codecs manage. At its top setting it carries close to CD-quality audio, though it is still lossy and drops to lower rates when the connection is poor.
- LosslessConnections & formatsLossless audio is a file or stream that reproduces the original digital recording exactly, with no data discarded, unlike lossy formats such as MP3 and AAC. Any PCM audio stored in FLAC, ALAC or WAV without data removed is lossless, whatever its resolution.
M
- MC cartridgeGear & technologyA moving coil cartridge puts tiny coils on the stylus cantilever and fixes the magnets, the reverse of a moving magnet design. The lower moving mass is prized for detail, but the output is far smaller and needs a phono stage with extra gain.
- MidsSoundThe mids, or midrange, are the frequencies from roughly 250 Hz to 4 kHz where voices, guitars, pianos and most of the melody live. Because the ear is most sensitive here, small changes in the mids are easy to hear.
- MM cartridgeGear & technologyA moving magnet cartridge generates its signal with a tiny magnet on the end of the stylus cantilever that moves between fixed coils. It outputs a few millivolts, works with any standard phono stage and usually has a replaceable stylus.
- MusicalAudiophile slangMusical is the word reviewers use for gear that makes them enjoy the music rather than notice the equipment. It usually means a slightly warm, forgiving tuning with good dynamics, and it is as much a mood as a description.
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- NeutralSoundA neutral product adds as little of its own color as possible, so recordings sound the way they were mixed. In practice it means a frequency response close to an accepted target, with no obvious bass or treble emphasis.
- Noise floorSpecs & measurementsThe noise floor is the faint hiss or hum a system produces with nothing playing. A low noise floor, sometimes praised as a "black background", lets quiet passages and reverb tails emerge from silence instead of from hiss.
O
- ObjectivistAudiophile slangAn objectivist is an audiophile who trusts measurements and blind listening tests over sighted impressions, and holds that gear which measures transparent sounds the same. The opposing camp, subjectivists, trust what they hear in normal listening. The argument between them is the hobby’s oldest.
- Open-backGear & technologyOpen-back headphones have earcups that let sound pass through the outside, usually through a grille. They leak sound both ways, so they are for quiet rooms, and they are widely preferred for a spacious, natural presentation.
- Optical (TOSLINK)Connections & formatsTOSLINK is the optical version of the S/PDIF digital audio connection: a plastic fiber carrying the signal as pulses of red light. It is found on televisions, game consoles, CD players and most DACs, and it is immune to electrical hum and ground loops.
- Output impedanceSpecs & measurementsOutput impedance is the resistance an amplifier presents to the headphone or speaker it drives, in ohms. A low value, ideally under an eighth of the load’s impedance, keeps the tonal balance and bass control the designer intended.
P
- Passive radiatorGear & technologyA passive radiator is a driver with no motor, just a cone and suspension, mounted in a speaker cabinet to do the job of a port. Air pressure from the active driver moves it, adding bass without the noise of a port tube.
- PCMConnections & formatsPCM, pulse-code modulation, is the standard way of representing digital audio: the waveform is measured many thousand times a second and each measurement stored as a number. CDs, WAV and FLAC files and nearly all streams are PCM.
- Phono stageGear & technologyA phono stage boosts the tiny signal from a turntable cartridge to line level and applies the RIAA equalization that undoes the bass cut and treble boost applied when the record was cut. Without one, a turntable sounds faint and thin.
- Planar magneticGear & technologyA planar magnetic driver is a thin, flat diaphragm with a printed conductive trace, suspended between magnets. The whole diaphragm is driven at once, instead of from a single voice coil as in a dynamic driver.
- Power outputSpecs & measurementsPower output is how much an amplifier can deliver into a given load, in watts for speakers or milliwatts for headphones. The figure only means something with the load stated, since the same amplifier delivers different power into 32 Ω and 300 Ω.
- PreampGear & technologyA preamp, or preamplifier, selects between sources, controls the volume and passes a line-level signal on to a power amplifier. In a separates system it is the control center; an integrated amplifier builds one in.
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- R2R/ladder DACGear & technologyAn R2R, or resistor ladder, DAC converts each sample directly through a network of precisely matched resistors, one step per bit. It was the original way to build a DAC and has returned as a boutique alternative to delta-sigma chips.
- RCAConnections & formatsRCA is the round, single-pin analog connector used in pairs, one red and one white, to carry a stereo line-level signal between hi-fi components. It is unbalanced, cheap and everywhere, and the same plug carries a coaxial digital signal.
- ReceiverGear & technologyA receiver is an amplifier with extra functions built in: a radio tuner in a classic stereo receiver, or surround-sound decoding, video switching and room correction in an AV receiver. One box replaces a preamp, power amp and several sources.
- ResolutionSoundResolution is how much fine detail a product lets you hear: the breath before a note, the texture of a bow on a string, the room around a singer. High-resolution gear reveals small sounds without making them louder.
- Room treatmentGear & technologyRoom treatment is anything added to a listening room to control reflections and resonances: absorbing panels, bass traps in the corners and diffusers on the back wall. In a speaker system the room changes the sound more than most equipment does.
S
- Sample rateSpecs & measurementsSample rate is how many times per second a digital system measures the audio waveform: 44,100 for a CD, 48,000 for video, 96,000 or 192,000 for hi-res files. It sets the highest frequency the format can carry, at just under half the rate.
- Sealed enclosureGear & technologyA sealed enclosure is a speaker cabinet with no port, so the trapped air acts as a spring behind the driver. It gives tighter, more gradual bass than a ported box and sits happily near walls, but produces less deep bass for its size.
- SensitivitySpecs & measurementsSensitivity says how loud a headphone or speaker plays for a given input: so many decibels per milliwatt or per volt for headphones, per watt at one meter for speakers. Higher numbers play louder from less power.
- SeparationSoundSeparation is how clearly individual instruments and voices stay distinct when they play at once. Poor separation turns a busy chorus into a wall of sound; good separation lets you follow one part through it.
- SibilanceSoundSibilance is an exaggerated, hissy edge on "s", "sh" and "t" sounds in a voice. It comes from a treble peak somewhere between about 5 and 10 kHz, on the product or in the recording.
- SidegradeAudiophile slangA sidegrade is a purchase that changes the sound without improving it: a different flavor at the same level. The word is a gentle self-criticism from people who bought something new and got something different.
- SINADSpecs & measurementsSINAD is signal-to-noise-and-distortion ratio: how much louder a test tone is than everything the device adds to it, noise and distortion combined, in decibels. Higher is cleaner. It is the headline number on many DAC and amplifier measurements.
- SNRSpecs & measurementsSNR, signal-to-noise ratio, is how much louder the signal is than the background noise a device produces on its own, in decibels. Higher is better; above about 100 dB, noise is usually inaudible at normal listening levels.
- Solid-stateGear & technologySolid-state means an amplifier or other circuit built with transistors and integrated circuits rather than vacuum tubes. Nearly all modern audio electronics are solid-state; the term mostly comes up in contrast to tube designs.
- SoundstageSoundSoundstage is the sense of space in a recording: how wide, deep and tall the music seems, and how far outside your head the instruments appear to sit.
- StreamerGear & technologyA streamer is a network audio player that pulls music from streaming services or a home server and sends it to a DAC, over a wire or through a DAC built in. It replaces a laptop or phone as the source in a hi-fi system.
- Sub-bassSoundSub-bass is the lowest audible region, roughly 20 to 60 Hz: the rumble under a film score, an 808 kick or a pipe organ’s longest pipes. It is felt in the chest as much as heard.
- SubwooferGear & technologyA subwoofer is a speaker dedicated to the lowest octaves, typically below 80 to 120 Hz, with a large driver and usually its own amplifier. It lets the main speakers hand off the bass they cannot reproduce and fills in the bottom of the room.
- SynergyAudiophile slangSynergy is the claim that certain combinations of gear sound better together than their parts suggest: one amplifier with one headphone, say. Some of it is real electrical interaction, some is taste, and some is a way of justifying a purchase.
T
- THDSpecs & measurementsTHD, total harmonic distortion, is how much a device adds overtones that were not in the signal, given as a percentage or in decibels. Lower is cleaner; below about 0.1 percent it is generally inaudible on most music, though listeners argue about the exact threshold.
- THD+NSpecs & measurementsTHD+N is total harmonic distortion plus noise: everything a device adds to a test tone, distortion and background noise together, as a percentage of the signal. It is the figure most spec sheets quote and the inverse of SINAD.
- TimbreSoundTimbre is the character that makes a violin sound different from a flute playing the same note: the mix of overtones and the way a note starts and ends. A product with accurate timbre makes instruments sound like themselves.
- TonalitySoundTonality is the overall balance between bass, mids and treble: whether a product sounds warm, bright, neutral or scooped. It is the first thing most people notice and the main thing a frequency response measurement describes.
- TonearmGear & technologyThe tonearm holds the cartridge and lets it track the record groove from edge to center while applying a small, set downward force. Its geometry, bearings and rigidity decide how accurately the stylus follows the groove.
- Transient responseSoundTransient response is how quickly and cleanly a product reproduces the start of a sound: a drum stick on a rim, a plucked string, a consonant. Fast transients sound crisp; slow ones sound soft or smeared.
- TrebleSoundTreble is the high-frequency region above about 4 kHz: cymbals, the edge of a voice, string overtones and the sense of "air" in a recording. Too little sounds dull; too much sounds harsh or sibilant.
- Tube amplifierGear & technologyA tube amplifier uses vacuum tubes, also called valves, instead of transistors to amplify the signal. Tube amps measure worse than solid-state designs but are loved for a sound many describe as warm and full, and for the glow.
U
- U-shapedSoundA U-shaped tuning lifts the bass and treble a little and leaves the midrange only slightly recessed, so it keeps the energy of a V-shape without pushing voices as far back. Many well-regarded consumer tunings are U-shaped.
- UpgraditisAudiophile slangUpgraditis is the compulsion to keep buying new gear in search of an improvement, whether or not one is needed or audible. It is diagnosed with affection on forums and is the main reason the used market is so well stocked.
- USB audioConnections & formatsUSB audio sends digital audio from a computer, phone or streamer to a DAC over an ordinary USB cable. It is the most common input on modern DACs, carries the highest sample rates and DSD, and needs no driver on most operating systems.
V
- V-shapedSoundA V-shaped tuning boosts both the bass and the treble and pulls the midrange back, so the frequency response looks like a V. It sounds exciting and impactful, at the cost of voices sitting behind the drums and cymbals.
- VeiledAudiophile slangVeiled describes a sound that seems to come through a thin curtain: the detail is there but softened, as if the upper midrange and treble were turned down a notch. It is the standard complaint about relaxed or dark tunings.
W
- WarmSoundA warm product has a little extra bass and lower midrange and a little less treble, which makes voices full and the sound relaxed. Taken further it becomes dark or muddy; its opposite is bright.
- WirelessGear & technologyWireless headphones and speakers receive audio over Bluetooth or Wi-Fi instead of a cable, with a battery, DAC and amplifier built in. They trade some fidelity and the ability to upgrade parts for convenience and features such as noise cancelling.