Headphones
Psychoacoustic Calibration
in Headphones
Reference-class sound reproduction for mixing, mastering, and audiophile listening
Accuracy in sound reproduction is an important and often overlooked factor in the world of audio. Whether listening for personal enjoyment or working in a studio, anomalies in the sound you hear from a playback system can greatly disrupt your enjoyment of the music. This is especially true for audio engineers who endeavor to bring the best sound they can to the stage. Inaccurate monitoring in studio environments is a major contributing factor to poor mix translation. Most studio speakers, and even headphones, do not exhibit an acoustically neutral reference response. This makes it nearly impossible to make mix decisions with any degree of confidence. All critical choices are made based on what our monitoring system tells us, and unless it is calibrated, we won't be hearing the truth in what it is saying. All we hear in raw, uncalibrated listening environments, including headphones, is a distorted version of reality. The true form of the music is lost to the influence of the anomalies imparted on the sound by the monitoring system and the listening environment that contains it.
All of this is to say that your headphones are probably not as accurate as you may think they are. Sure, they might sound good, but can you trust them to tell you the truth about your audio? Are they giving you the most accurate sonic image possible? It's not likely. What measures are there to ensure sonic truth?
Equalization vs Convolution
We use high-resolution stereo FIR convolution filters to reproduce the most accurate representation of the source material possible from your headphones. Equalization of a headphone unit cannot reproduce the same resolution. Not only is EQ limited in its number of adjustment bands, but many equalizers are also limited in their capacity to equalize both the left and right channels independently of one another. This is important because the two drivers of a headphone typically resolve slightly different variations of the main tone of the unit, up to 4 or 5 decibels at varying frequency zones. Stereo convolution filters are easily able to address this issue, providing frequency response in each individual ear that is resolved to within ~1dB (+/- 0.5dB) of the psychoacoustic target. Our filters are generated with 65,536 taps at 48kHz, which allows for a resolution equivalent to 32,768 bands of phase-optimized equalization.
The following images show the left and right measured responses of several different pairs of headphones. Take particular note of how the two cups in each image do not resolve the same frequency response. Although each L/R pair is close, and some are closer than others, none are close enough to reveal full potential in perceived depth. The audible effect of these differences is such that the soundstage, or imaging, can often be skewed either to the left or right ear by up to five or six decibels at random frequencies throughout the spectrum. This imbalance is simply due to the fact that many headphone manufacturers have hardware tolerance levels that aren't up to reference class listening standards.
Additionally, equalization does not account for phase. Our convolution filters optimize headphones to the ideal minimum phase response in each ear individually, thereby revealing the highest levels of fidelity.
Truth in the Making
The goal with calibration is to even out the left and right responses by matching them to a psychoacoustic target that is optimized to the way our ears hear the frequency spectrum in headphones. At Meridian Soundworks, we do that by designing a set of unit-specific targets for each headphone that infuse a linear slope with varying degrees of the Harman curve to generate ideal filtered responses in which the lows and highs are balanced to yield a response optimal for the widest range of HRTF tolerance. Each target is used to generate a left/right pair of inverted responses. These L/R pairs are then exported as stereo FIR filters that are auditioned by ear and checked to ensure soundstage accuracy and truthfulness to a neutral and unbiased reference tone. This process is carried out for each individual pair of headphones. Users can then determine which of the filters they prefer, or customize their own filters based on personal target preference.
At Meridian Soundworks, we calibrate circumaural (around-the-ear) headphones with a personal and professional touch. Every pair is meticulously measured, analyzed, and calibrated manually to within ~1dB tolerance from the targets. Once calibrated and optimized, the resulting correction delivers a heightened awareness of detail in the audio where nothing is masked and everything is revealed. You'll immediately notice evenness of bass frequencies, fullness of the midrange, a balanced and focused center image, and the clarity and separation of every element within the soundstage.
Calibration fixes inter-channel volume imbalances and reshapes the frequency response to a precise psychoacoustic target that sounds natural, open, and clear. Psychoacoustic filtering and frequency-dependent windowing of the raw data allow the ideal correction of headphones, providing coherent and accurate sound reproduction across the entire frequency range that allows your monitoring quality to rival that of the most accurate studios in the world.
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The benefits of MSC headphone calibration include:
• Accuracy of sound reproduction
• Flat and true reference class frequency response for studio engineers
• Optimized phase response
• Complete confidence in mixing and mastering decisions
• Mix translation across the widest range of playback systems possible
• Less hearing fatigue over longer casual listening sessions
• User customization of calibration profiles
Our filters are highly precise finite impulse response (FIR) wav files, which can be loaded into any convolution reverb plugin or dedicated DRC convolution engine, such as Hang Loose Convolver. Additionally, MSC Certified correction is easily integrated into the signal path alongside binaural room emulators such as:
• Waves NX series
• dSONIQ Realphones
• Acustica Sienna & Sienna Sphere
Simply load your filter plugin into the signal path in series with the room simulation. Specific instructions are provided with the purchase of any pre-calibrated headphone or calibration service.
Individually calibrated headphone units are available directly from us. You can choose from the available models on this page, or we can order anything you want and ship it to you once it has been calibrated. You can even send your personal headphones in for calibration. We'll get them sounding great, and then send them right back you.
All headphone units currently in stock are listed in the shop section below. To purchase any of the headphone models in the shop, send an inquiry to meridiansoundinfo@gmail.com with a descriptive subject line. All sales are handled personally. Reach out to us! We'd love to get to know you and answer any questions you have.
Each of our headphones units has been individually measured and calibrated, and is sold along with the following:
• A download link to the unit's calibration files, provided at 44.1kHz, 48kHz, 88.2kHz, and 96kHz sample rates
• Instructions for calibration filter implementation
The service fee for calibration of "sent-in" headphones is $120 per unit, which includes:
• Measurement and analysis of the unit
• Calibration files provided at 44.1kHz, 48kHz, 88.2kHz, and 96kHz sample rates
• Instructions for calibration filter implementation
Finally, we understand that everyone's anatomy is different and each individual needs varying degrees of accommodation with regard to HRTF. Furthermore, we also understand how important it is to provide flexibility in order to accommodate personal preference. This means it is essential that we provide a means for you to further optimize your target, allowing the perfect sounding filters to be dialed in for your ears. Also included in the price, either with a set of our pre-calibrated headphones or a pair that you send to us, is the added benefit and power to have customized calibration filter profiles generated specifically for you and your headset. We can even take custom EQ curves that you send us and fuse them together with your headset's profile. We're always available to help if you need advice as well. We want to provide the most optimized service possible, so don't hesitate to contact us if you have questions.
Send all inquiries to: meridiansoundinfo@gmail.com
Individually calibrated headphones for precision monitoring
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Questions before you go? Check out this last-minute FAQ:
How do I use my calibration filters with my headphones?
Using our FIR filters requires a combination of hardware and software. Correction is processed via impulse response convolution, which needs to be run from a computer. A convolver of some kind is needed to process the signal. We'll have more information available here soon. In the meantime, feel free to ask for specific information via email.
What do I need to process my calibration filters?
There are three essential requirements. First without a doubt is a desktop or laptop computer. It doesn't have to be fancy, but it does need a reasonably good quality audio card or external interface to power your headphones. Second is a VST plugin host, such as a Digital Audio Workstation or a desktop systemwide configuration. The processors required for the filters are all available in VST3 format. Next is the processor itself, which is known as a convolver. Convolution is the key technology involved that provides the sound quality of our filters.
Are the headphones featured on this page new?
They are not still factory-sealed, but they are in new condition. They are carefully handled during the calibration process, which is necessary to measure them and verify filter integrity. All units come with their original packaging, which is in the same condition as it arrived here.