| Low-Impedance Range | Under 50 ohms (Commonly cited industry threshold) |
| High-Impedance Threshold | 150 ohms and above (General audio engineering convention) |
| Human Hearing Range | Approx. 20 Hz – 20,000 Hz (Established audiological standard) |
| Acceptable THD Level | Below 1% (Widely referenced audio engineering benchmark) |
| Typical Driver Types | Dynamic, Balanced Armature, Planar Magnetic |
Why Headphone Specs Feel Like a Foreign Language
Headphone listings throw around terms like impedance, THD, and soundstage as if every shopper has an engineering degree. Most of us don't — and manufacturers rarely explain what these numbers actually mean for how something sounds in your ears. This reference guide cuts through that noise.
Whether you're scanning a product page or trying to understand why one pair costs three times another, the glossary and quick facts below give you a reliable foundation. For a broader look at reading spec sheets across any product category, see our plain-language spec sheet walkthrough.
Impedance
The electrical resistance a headphone places on an audio signal, measured in ohms. Lower impedance headphones work directly with phones and laptops; higher impedance models typically need an amplifier.
Sensitivity
How efficiently a headphone converts electrical power into sound, expressed in decibels per milliwatt (dB/mW). Higher sensitivity generally means louder output from a given source.
Frequency Response
The range of audio frequencies a headphone can reproduce, measured in hertz (Hz). Human hearing spans roughly 20 Hz to 20,000 Hz; the shape of the response curve matters more than the stated range alone.
Soundstage
A subjective description of how wide or three-dimensional recorded audio sounds when listened through headphones. Open-back designs tend to produce a broader soundstage than closed-back designs.
Driver
The transducer inside a headphone that converts electrical signals into sound waves. Common driver types include dynamic (moving coil), balanced armature, and planar magnetic.
THD (Total Harmonic Distortion)
A measure of unwanted harmonic frequencies added by the driver during playback, expressed as a percentage. Lower THD indicates more accurate sound reproduction.
Closed-Back vs. Open-Back
Closed-back headphones seal the ear cup to isolate sound, reducing leakage in and out. Open-back headphones have perforated cups that allow airflow, often producing a more natural soundstage but less isolation.
Codec
A compression algorithm used to transmit audio wirelessly over Bluetooth (e.g., SBC, AAC, aptX, LDAC). The codec used affects the quality ceiling of wireless audio transmission.
The Core Specs You'll See on Every Listing
A few numbers appear on virtually every headphone spec sheet. Here's what they describe — and how much weight to give them.
| Low-Impedance Range | Under 50 ohms (Commonly cited industry threshold) |
| High-Impedance Threshold | 150 ohms and above (General audio engineering convention) |
| Human Hearing Range | Approx. 20 Hz – 20,000 Hz (Established audiological standard) |
| Acceptable THD Level | Below 1% (Widely referenced audio engineering benchmark) |
| Typical Driver Types | Dynamic, Balanced Armature, Planar Magnetic |
Impedance (measured in ohms) describes how much electrical resistance a headphone presents to the audio source. Low-impedance headphones (under 50 ohms) work well with smartphones and laptops. High-impedance models (150 ohms and above) typically require a dedicated headphone amplifier to reach their full potential. Running a high-impedance headphone from a phone won't damage it, but the volume and dynamics will often feel constrained.
Sensitivity tells you how loud a headphone gets per milliwatt of power — expressed in dB/mW or dB/Vrms. A higher sensitivity number means the headphone gets louder from the same source output. This pairs closely with impedance when assessing whether a headphone needs amplification.
Frequency response is usually stated as a range, such as 20 Hz–20,000 Hz (the approximate boundaries of human hearing). A wider stated range doesn't automatically mean better sound; what matters more is how flat or consistent the response is across that range, which a simple frequency-range figure won't tell you. For a comparison of how these specs play out differently between headphones and portable speakers, the Bluetooth speaker spec breakdown is a useful counterpoint.
Subjective Terms Worth Understanding
Not every important audio concept shows up as a number. These descriptive terms appear in reviews and marketing copy — knowing what they actually mean helps you evaluate whether a claim is meaningful.
Soundstage describes the perceived spatial width of audio — how much a pair of headphones makes music feel like it's coming from a space around you rather than just inside your head. Wider soundstage is often associated with open-back headphone designs. For a deeper look at how physical design shapes this experience, our headphone form factor comparison explains how housing type affects sound characteristics.
Imaging is related but distinct: it refers to how precisely a headphone places individual instruments or sounds within that soundstage. A headphone can have a wide soundstage but poor imaging, and vice versa.
THD (Total Harmonic Distortion) measures how much unwanted harmonic content a driver adds to the original signal, expressed as a percentage. Lower THD generally indicates a cleaner, more accurate reproduction. Anything below 1% is considered acceptable; audiophile-grade headphones often measure well below 0.1%.
Spec Numbers Have Limits
Manufacturer-published specs are measured under controlled lab conditions that don't always reflect real-world listening. Two headphones with identical frequency response ranges can sound dramatically different due to driver tuning, ear cup shape, and materials. Use specs as a starting framework, not a final verdict. Whenever possible, cross-reference with independent measurements and structured listening tests.
Be cautious when evaluating terms that sound impressive but carry little technical weight. Our marketing language decoder covers phrases like "studio-quality" and "Hi-Res Audio certified" that appear frequently in headphone listings without universal standards behind them.