Then people think about Realphones, the first things that come to mind are usually room emulation or binaural sound source positioning. But there's another critically important component: headphone correction profiles.

Correction profiles determine how accurately your headphones reproduce tonal balance, and how reliable your mixing decisions will actually be. This isn't just EQ applied to a pretty curve. It's the result of a complex measurement process that accounts for real-world usage conditions.

Why is creating accurate profiles so difficult? To understand this, it helps to compare the process of measuring speakers versus headphones.

Speaker manufacturers have it relatively easy. A typical measurement procedure looks straightforward: the speaker is placed in an anechoic chamber, a measurement microphone is positioned at a set distance, and when the measurement is conducted correctly, you get an objective frequency response. The results are repeatable and reproducible: any qualified lab with equivalent equipment will get nearly identical data.

With headphones, the situation is fundamentally different.

Headphones work in direct interaction with the listener's head, and a person's individual anatomy has a significant effect on perceived sound. This is a fairly serious influence, capable of shifting the frequency response by tens of decibels.

Factors that affect headphone sound include:

• The size and shape of the head, which determine clamping force and the position of the acoustic drivers relative to the ears.
• The geometry of the outer ear changes the pattern of sound wave reflections and resonance characteristics.
• The shape of the ear canal directly affects high-frequency transmission.
• The density and elasticity of skin tissue influence the degree of acoustic isolation.
• Glasses and hairstyle affect how well the earpads seal.
• The temperature and moisture of skin change the mechanical properties of earpad materials over time.

Of course, headphones can be placed in an anechoic chamber and measured. But the data obtained this way doesn't reflect how the headphones will actually sound on a real user's head.

What's more, many of the factors listed above change over time: earpad wear, temperature-related material changes, variability in fit. All of this makes static correction without the ability to fine-tune somewhat imprecise.

There are many approaches to measuring headphone frequency response. Relatively affordable tools priced under $300 have appeared on the market, marketed as instruments for "professional measurements."

The core problem with budget measurement systems is their use of a simplified ear canal simulator: a straight cylindrical tube instead of the complex anatomical structure of a real ear. Our tests have shown significant deviations from professional measurements, including extra peaks, elevated high frequencies, and boosted low-frequency response. These devices do not comply with the international standard IEC 60268-7, and the results of such measurements are not comparable to those from a proper headphone measurement rig. Their accuracy is insufficient for creating high-quality correction profiles.

There's another important nuance. Even expensive industrial measurement rigs have their own resonances. These resonances are calculated and accounted for so that the rig shows headphone frequency response in terms of what actually occurs during real-world use. These resonances cannot be equalized out: they are too individual. That's why the measurement methodology for correction purposes differs from the standardized industrial methodology used to obtain technical specifications.

At dSONIQ, we've developed our own headphone measurement methodology for creating accurate correction profiles. The result of years of work is the list of supported models in Realphones.

Our standard correction profiles for the most popular headphone models are based on measurements of dozens of individual units. Variation between samples from different production batches can reach plus or minus 3 dB or more. That's why measuring a single pair of headphones isn't enough: statistical analysis across many units is required to arrive at a reliable averaged profile.

Measurement accuracy is ensured through strict control of conditions. The position of the reference monitoring system is fixed to within 0.5 cm, and more than 18 measurement points around the listener's head position are used for its calibration. The engineer's position is controlled by a microphone stand calibrated daily with a laser rangefinder. The chair is bolted to the floor and the monitors are mounted on stands, which guarantees repeatable acoustic conditions for every measurement session.

Our reference monitoring system reproduces frequencies starting from 14 Hz, which is critical for accurate assessment of the low-frequency range. MIDI controllers are used for quick switching between listening modes, allowing the engineer to focus on the sound rather than technical operations.

The goal of this development is to achieve a level of monitoring accuracy comparable to working on speakers in a professional control room. The objective is not to match theoretical target curves or produce visually appealing graphs, but to create conditions for accurate, neutral, and trustworthy monitoring on whatever headphones you have.

Standard correction profiles are the core value of Realphones. Without them, the rest of the plugin's functionality loses its precision and practical usefulness.

Creating correction profiles is a complex process that requires a great deal of expert hands-on work and time. This is why we don't yet have standard correction profiles for some popular models.

There are many third-party headphone measurements available online, and the desire to rely on them is understandable. Realphones allows you to create custom correction profiles based on such data, which can serve as a useful interim solution while we work on official standard profiles. But it's important to understand that Realphones is not simply an EQ. It's a comprehensive monitoring setup system: correction, studio environment emulation, and acoustic system emulation working together. Frequency response correction is just one component. The reliable monitoring that helps you make mixes that translate is achieved through the combined operation of all Realphones modules.

Over the years, we've developed our own quality standards for measurements. They ensure a predictable result when using the full capabilities of Realphones. We can't guarantee that third-party measurements made using a different methodology will produce the correct result. For monitoring you can trust, we recommend using standard profiles from the list of supported models in Realphones.

We aim to make working in Realphones comfortable with whatever headphones and earpads you have. In some cases, we create separate profiles for different earpad options, which is an aspect that doesn't get enough attention. Our baseline measurements are conducted with the stock earpads included by the manufacturer. But we sometimes add additional profiles: for third-party earpads that many users find more comfortable, and for common replacements when the original earpads wear out and become difficult to purchase.

A good example is the Gewa HP NINE-X. This model ships with two sets of stock ear pads: velour and leather. The differences in sound between them are significant enough that each option requires its own correction profile.

When earpads are swapped out, the following parameters change:

• The distance from the driver to the eardrum shifts: changes in the thickness and density of the padding affect phase characteristics and frequency balance.
• The angle of the acoustic driver changes as well, since different mounting geometries alter the direction of radiation.
• Acoustic damping is affected because materials with different porosity and density absorb energy differently across the frequency range.
• The seal of the earpad fit directly influences low-frequency performance and the level of external isolation.
• The volume of the cavity between the driver and the ear changes, shifting the resonant frequencies of the system.
• The character of reflections from the surface varies, since the texture and acoustic properties of the material affect high-frequency behavior.

Swapping earpads can result in changes that exceed the differences between entirely different headphone models.

Work is currently underway to optimize the headphone measurement process. This development will allow us to reduce the time required to create correction profiles and continue expanding the list of supported headphone models.

We continue to develop Realphones and improve our correction profile technology. Every update to the supported headphone list is the result of careful work by our team. There are many exciting updates ahead, and we'll be sure to share them when the time comes.

Thank you for being with us. Your support is what keeps us moving forward.