Target curves: Harman, diffuse-field, and a house curve
A target curve is the reference shape a headphone is measured against — because, as any frequency-response graph shows, a flat line does not sound neutral. Diffuse-field, Harman, and ahouse curve are three different answers to “what should neutral sound like.” None is objectively correct; they are reference points, and your own preferred target is personal.
Why a target exists at all
A headphone that sounds perfectly neutral does not measure as a flat horizontal line. The measurement includes the response of the artificial ear and the rig, and your own ear adds its own shape — so “flat” on the graph would actually sound thin and harsh. Instead of comparing a curve to a ruler, we compare it to atarget: a shape that has been found to sound neutral or preferred. How far a headphone deviates from the target is what you actually hear. (If that is new, start withhow to read a graph.)
Diffuse-field: the neutral reference
The diffuse-field target is the older, more academic reference: roughly how a flat, neutral sound source measures at your eardrum in a space full of reflections coming from all directions. It is a principled anchor — but on a headphone it tends to read bass-light and a little bright to most listeners, because real music and real preference are not the same as an idealized acoustic average. Useful as a baseline; rarely anyone’s favorite as-is.
Harman: the preference target
The Harman target came from a different question: not “what is acoustically neutral,” but “what do listeners actually prefer?” Through blind, level-matched studies, Harman’s research (led by Sean Olive) landed on a shape that starts diffuse-field-ish and then adds a deliberate bass shelfand a defined presence/treble region. It is now the most-cited “preferred” target, and for good reason — it is grounded in real data.
Two honest caveats. First, it is average preference: a lot of people cluster near it, plenty sit to one side (more or less bass, gentler treble). Second, the Harman target is Harman International’s research and IP — we reference it because you should understand it, but we do not ship it as our default.
House curves: a brand’s chosen default
A house curve is simply the target a brand, reviewer, or tuning tool picks as its own reference — usually a preference-style curve with small deliberate choices baked in (a touch more sub-bass, a slightly gentler top). It is not a claim of universal truth; it is a considered default. Attune ships a diffuse-field reference and a Warren Labs house curve — neutral with a little more bass, built cleanly from public research — as honest starting points, not commandments.
The part everyone forgets: the target is a reference, not a rule
Because Harman is so widely cited, it is easy to treat “closer to Harman” as “better.” It is not. A target tells you what a tuning is relative to a reference many people like — which is genuinely useful for comparison. But the right target for you is the one you would pick by ear, and it may sit a few dB off any published curve. When someone calls a headphone “neutral,” the honest question is always: neutral against which target?
This is exactly what Attune is built around. Instead of chasing someone else’s target, you take a blind, loudness-matched ear exam on your own music and let your preferred curve build itself — then you can see how it compares to diffuse-field or a house curve, rather than assuming one is right.
Find your own target in AttuneThe honest bottom line
Diffuse-field is the neutral anchor, Harman is the data-backed preference average, and a house curve is a considered default. They are reference points for reading a graph and comparing headphones — not a ranking. Learn what each represents, then trust your own ears over any one line.
Common questions
What is a target curve?
A target curve is a reference frequency-response shape that a headphone’s measurement is compared against. Because the ear and the measurement rig add their own response, a headphone that sounds neutral does not measure flat — so we judge it against a target instead of a ruler.
What is the Harman target curve?
It is a target derived from listener preference studies (led by Sean Olive at Harman): a diffuse-field-like shape with a deliberate bass boost and a defined treble. It has become the most-cited “preferred” target, but it represents average preference, not a law.
What’s the difference between Harman and diffuse-field?
Diffuse-field is a neutral acoustic reference — how a flat source measures at the ear in a reflective space — and tends to read bass-light and a touch bright to many listeners. Harman starts from that idea but adds bass and reshapes the treble based on what people actually preferred.
Should a headphone follow a target curve exactly?
No. A good target is a starting reference, not a rule. Close tracking usually sounds balanced, but small deliberate deviations are how headphones get their character — and your own preferred target is personal.
What target curve does Sonic Temple use?
Attune ships a diffuse-field reference and a Warren Labs house curve (neutral with a little more bass), both built from public research. We do not default to Harman, which is Harman International’s IP — we reference it honestly rather than ship it.