The test, first documented in March 2024 on the DIYAudio forum, evaluated nine dual op-amps through a Pearl 3 phono stage design. According to participants, the MC1458—originally introduced in the early 1970s—achieved the highest average listener score, despite specifications that are modest by current engineering standards.

Test Methodology

The evaluation was structured to minimize bias. Seven op-amps were anonymized by sanding off identifying marks and assigning color-coded labels, while two additional units were included as known references. The identity of each component was withheld until after scoring was completed.

The listening panel consisted of four individuals with varying levels of audio experience, including an enthusiast listener and a semi-professional musician. Playback was conducted using a vinyl-based system incorporating a Lenco L75 turntable, an Ortofon MC30 cartridge, and horn-loaded loudspeakers.

Participants assessed each op-amp across multiple criteria, including bass clarity, midrange presentation, treble response, transient speed, and overall musical engagement. Scores were recorded on a 10-point scale.

Results and Ranking

The final scores fell within a narrow range, from 7.0 to 8.2, indicating broadly similar performance across all tested components. The MC1458 achieved the highest average rating at 8.2.

Following the release of the anonymization key, the top-performing unit—previously labeled “A539”—was confirmed to be the MC1458, a dual operational amplifier derived from the earlier 741 architecture. Originally introduced with a unity-gain bandwidth of approximately 1 MHz, the device is often categorized as a general-purpose or “jelly bean” component in modern electronics.

Higher-cost alternatives included in the test, such as premium audio-grade op-amps, did not achieve top rankings.

Technical Observations

Subsequent discussion focused on possible explanations for the outcome. Measurement observations from the Pearl 3 design indicated that while most op-amps performed similarly on standard parameters—such as noise floor, bandwidth, and slew rate—differences emerged in harmonic distortion profiles.

The MC1458 was noted to exhibit relatively higher levels of second-order harmonic distortion compared to other tested units. Second-order harmonics occur at one octave above the fundamental frequency and are generally considered musically consonant.

In contrast, higher-order odd harmonics are more likely to be perceived as harsh or dissonant. The presence of stronger even-order harmonic content has historically been associated with tube amplifier designs, which are often described as producing a “warmer” sound despite higher total harmonic distortion (THD) measurements.

Interpretation and Limitations

The findings have not been presented as definitive. Participants acknowledged several constraints, including the small sample size, limited listening duration, and the use of a single playback system.

Short-term A/B listening tests may emphasize perceptible differences rather than long-term listening preference. Additionally, the Pearl 3 phono stage—like all analog circuits—is designed around specific component characteristics. Substituting different op-amps may alter circuit behavior in ways that extend beyond the component itself.

These factors complicate attempts to generalize the results across other systems or use cases.

Broader Industry Context

The outcome reflects a broader and ongoing discussion within the audio engineering and enthusiast communities: the extent to which objective measurements align with subjective listening experiences.

While modern op-amps typically deliver improved specifications—including lower noise, higher bandwidth, and reduced distortion—these metrics do not always predict listener preference in real-world playback conditions.

In particular, phono stages introduce additional complexity due to RIAA equalization, which shapes frequency response and may interact with component-level distortion characteristics in audible ways.

Follow-Up Community Response

In the months following the initial test, additional forum participants reported their own experiments. Some indicated a preference for lower-cost op-amps over premium alternatives, citing differences in tonal balance and perceived musicality.

However, these follow-up observations were similarly anecdotal and lacked standardized testing conditions.

Conclusion

The MC1458’s performance in this blind test does not overturn established engineering principles, but it highlights the limitations of relying solely on conventional specifications to predict listening outcomes.

The results suggest that, in certain circuit contexts, harmonic behavior and system interaction may play a more significant role in perceived sound quality than headline performance metrics.

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A bold new study is shaking up the world of headphone tuning — or at least trying to. Audio tech startup PEQdB claims it’s cracked the code on how headphones should sound, using machine learning and a mountain of data. But critics argue the research comes up short, lacks peer review, and reads more like a takedown than a breakthrough.

Let’s break down what this is all about — and why the headphone world is so divided.

PEQdB vs. Harman: The Big Audio Showdown

If you’ve ever adjusted your headphone EQ or read headphone reviews, chances are you’ve come across the Harman target curves. Developed by Dr. Sean Olive at Harman International, these curves — one for over-ear (2018) and one for in-ear headphones (2019) — are based on extensive listener research and have become something of a gold standard in audio.

But PEQdB, a Stanford-based company, says it’s time for a new standard. In a self-published white paper, the company argues that Harman’s approach is outdated, overly simplistic, and doesn’t reflect how people really hear.

Their answer? An algorithm-driven tuning model based on 266 headphone models, built using a wider dataset and modern machine learning techniques. They claim it solves the flaws in Harman’s system — and gives listeners more accurate sound.

Competing Methods, Conflicting Results

So how exactly does PEQdB’s method differ?

• Measurement Devices: PEQdB rejects Harman’s use of the GRAS 45CA flat-plate fixture, saying it lacks realistic human anatomy. Instead, they use a diffuse-field head-related transfer function (HRTF) modeled on the eardrum responses of 47 real people.
• Testing Conditions: Their trials involved A/B tests using the song “Inner Cell” by King Gizzard & the Lizard Wizard — chosen for its complex, high-resolution sound.
• Adjustment Options: PEQdB let users adjust nine parameters across three EQ filters. Harman’s method? Just two filters for bass and treble.

The underlying idea is that PEQdB’s more flexible and data-rich approach better matches human hearing — especially in an age where machine learning can dig through piles of data in ways traditional studies couldn’t.

But What Does the Data Actually Say?

PEQdB’s central claim is that its curve works equally well for both over-ear and in-ear headphones — challenging Harman’s belief that each type needs its own tuning. They also say their curve addresses common complaints about Harman’s sound: “shouty” mids, “veiled” highs, and “thin” bass.

But not everyone agrees. In fact, Harman’s own recent study from 2024 showed that 72% of listeners still preferred the Harman in-ear curve (or something very close to it). Even among those who didn’t, preferences still fell within familiar boundaries:

• Most preferred fuller bass with balanced highs
• A minority (often older listeners) liked less bass and more treble

So PEQdB may be trying to fix something that isn’t broken — or at least not broken for most people.

Critics Raise Red Flags

While PEQdB’s research makes bold claims, it’s sparked plenty of skepticism for a few key reasons:

1. No Peer Review

Their white paper is self-published and not peer-reviewed. That alone doesn’t disqualify it, but it does raise questions — especially when paired with a lack of statistical analysis (no error bars, confidence intervals, or in-depth comparisons).

2. Uncontrolled Testing

Anyone can use the PEQdB tool from home, which makes it accessible — but also problematic. Listening conditions vary wildly, and the tool doesn’t account for things like mismatched headphone pairs or IEM eartips, which can greatly alter sound perception.

3. Short Listening Clips

Tests use 20-second A/B comparisons. That might be enough for first impressions, but not for judging long-term listening comfort or fatigue — a major factor in real-world preference.

4. Aggressive Tone

Instead of positioning its work as a complement or evolution of existing research, PEQdB takes a combative stance — dismissing Harman’s work with statements like “the most statistically optimal headphone target curves ever created.” Critics see that as arrogant and unscientific.

The Community Reacts: Mixed at Best

The headphone community’s response has been split. Some early adopters say PEQdB’s tool helped improve their listening experience. But many others find the results either underwhelming or too similar to Harman’s curve to justify the hype.

A common complaint: too much ear gain around 3kHz, which can make music sound harsh or fatiguing. Others say the tuning is too safe — lacking enough bass or sparkle to be truly exciting.

More broadly, some listeners suspect this is less about advancing audio science and more about grabbing attention. That skepticism only grows when you consider the figure behind the research.

The “Sharur” Factor

The lead author of the PEQdB paper goes by “Sharur” online — a polarizing personality known for stirring up debates in audio forums. While past controversies shouldn’t discredit research on their own, they certainly haven’t helped PEQdB’s case.

Some users worry that the research is more about disrupting the status quo than building a better standard.

Final Thoughts

PEQdB’s challenge to Harman’s headphone tuning legacy is bold, ambitious, and rooted in some compelling ideas. More data? More flexibility? Machine learning? It all sounds promising on paper.

But without peer review, detailed analysis, or real-world validation across controlled environments, it’s hard to take the conclusions at face value — especially when delivered with such heavy-handed criticism of long-established science.

For now, the Harman curve still holds up — not because it’s perfect, but because it’s been tested, retested, and refined through rigorous research and listener feedback. PEQdB might be onto something — but it’ll take more than a flashy dataset and a bold tone to convince the audiophile world.

Source: Headphonesty – This New Research Claims Headphones Have Been Tuned Wrong for Decades, but Critics Aren’t Buying It

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