Something I've investigated and wish to understand a little better in SoundID Reference.
Speakers are relatively simple in concept, flat is easy to quantify with a measurement microphone. I know there's a gradual high roll-off in SoundID which helps with translation to HiFi/Car/Consumer speakers which is standard practice.
Now headphones are very different, flat is not really flat due to the physics of people's ears and canals, accentuating high-mid frequencies and typically lowering bass. That is why Harman created their on-ear/over-ear and in-ear curves as it more closely matched peoples perception of what speakers sound like. There is a lot of information and articles online if anyone wants to research it further.
There are many other implementations of headphone EQ correction such as Oratory1990 and Crinacle who offer EQ filters to manually enter, based on the Harman 2018 on/over ear curve. However I have found the overall tone is quite different to speakers, Much of the mid-range is sucked out, the top is very bright and the bass can be fairly heavy.
I know Sonarworks have worked to make their headphone correction sound tonally the same as speakers with their correction applied, and I've spent hours testing it and comparing to other methods like mentioned above, and it does appear to be the case which is great.
I'm aware Sonarworks can't give away their IP, but having researched this myself and am very interested in what is implemented in Sonarworks speaker and headphones as a target curve? Or at least some clues to satisfy my curiosity ;-)
It is a really interesting area of research that I've spent a long time looking into, I am technical as been in IT all my life but also an amateur live and studio audio engineer, so the two things fuel my curiosity! It appears what on the surface is a simple topic, is complex, unclear and very nuanced, but very interesting!
Thanks
4 comments
If I can add a related question, Sonarworks headphone review's 'Adaptiveness Score' - to quote:
"Adaptiveness shows how capable these headphones are at delivering the same perceived frequency response to any listener. Headphones with high score will sound nearly identical to everyone."
My guess is Sonarworks have some clever secret magic whereby you test various different ear pinna and take an average for the overall measurement, that way the resulting EQ correction theoretically will work well with a wide variety of headphone users?
Hey Simon,
Thanks for your post and for showing your interest!
The Sonarworks SR (Studio Reference) standard sets the frequency response target to be neutral for speaker-based playback systems (a flat FR curve across all audible frequencies as perceived by the listener in the listening position). The headphone FR target is designed to emulate neutral-sounding speakers. The readily available average profiles in SoundID Reference are average summaries from several different units measured and tested (because even the same model headphones will differ pair to pair in frequency response). Due to that build inconsistency, there can be small anomalies to the flat target and therefore multiple units are measured.
More details about Sonarworks SR can be found here: What is SoundID SR?
Hi Simon,
Also, you can get some more context in this SonicScoop interview with one of our co-founders: https://youtu.be/hpfweXUjqa0?t=1560
At the 26:00 time stamp in the video, the speaker-to-headphone transfer curve is discussed in more detail. I highly recommend viewing the entire video for anyone who is interested in the psycho-acoustics subject, especially in the Sonarworks and room correction context in general - it is really good stuff!
There's some interesting hints in one of Sonarworks own blogs too, excerpts quoted below with links to the blog articles:
Successful Mixing with the Proper Frequency Response and a House Curve
"Your room’s acoustics will alter the sound of a perfectly flat monitor system and we know from extensive testing and interviews that many mastering and mix engineers prefer the monitors in their room to sound flat from 20Hz up to 1kHz and then smoothly roll off from 1kHz up to 20kHz, where the level is 3 dB to 5 dB down at 20kHz. The amount of high-frequency roll-off that sounds best will vary depending on the acoustic treatment of the room the reverb times at various frequencies, and the normal listening volume. Flat speakers in a well treated room will produce a curve like this."
and also:
Headphone Calibration: How It Works
"Sonarworks headphone measurement technology delivers Sonarworks PAPFR (Perceived acoustic power frequency response) technology on headphones. It is an innovative, patent pending measurement technology that measures headphone AFR as perceived by human ear rather than as measured by a measurement microphone.
.....The default flat frequency response reference target is made to match the frequency response of flat sounding speakers, ensuring smooth translation between working on studio monitors and headphones.
....The way how people perceive sound coming from speakers is different than sound coming from headphones. In addition to head related transfer effects, you will get ear canal resonances and the kinetic experience of bass. Our unique calibration process employs a transfer curve developed by experts that delivers sound signature as close as possible to what will be heard by human when listening to neutral speakers. This dramatically improves translation between headphones and speakers when creating records."