Colored earphones and headphones are destructive for certain types of music

To understand this, we need to first understand how records are mixed and mastered.


Mixing is the process of taking raw recorded tracks and using tools like compression, EQ and reverb along with adjusting levels and panning to create a finished stereo mix.


Mastering is the final step in the production process that takes the finished stereo mix and optimizes it for playback on a variety of devices.

EQing individual instruments

Mix engineers first work on the individual tracks to make them sound right and then put them together to make a record. For acoustic music, the mix engineers (especially when they are also the producers or have access) sometimes go into the recording booth to hear what an instrument actually sounds like and then try to replicate that while mixing with the instruments raw tracks using EQ (among other things) before putting all the tracks together to create the final record. The important thing to note here is that the EQ is done for each individual instrument.

Earphones and Headphones as EQ

One way to think about the things in your chain when listening to music, is to think of them as EQ devices (among other things). A colored earphone/headphone in that sense is the same as applying EQ but this EQ is done on the final record (similar to mastering) and there’s a reason the first rule of mastering is “do no harm” and why mastering is all about making subtle changes. An EQ applied to the final record is destructive, especially for well recorded acoustic music where authentic replay matters, because it changes the sound of the individual instruments in different ways and an EQ that works for one instrument might not work for another.


This is also the reason why most earphones and headphones (since they are all colored in some way, some more than others) can’t do justice to all instruments and can at best be good for certain instruments on certain records, and why neutrally-tuned earphones and headphones might be better for well-recorded acoustic music where authentic replay matters (for some definition of neutral, which is a post for another day 🙂).

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Notes from InnerFidelity Podcast No. 10 with Dave Friesema, Lead Engineer at Etymotic

InnerFidelity Podcast No. 10 With Dave Friesema

In addition to its extensive hearing and testing products, Illinois-based Etymotic has won over the hearts of many audiophiles with their ER line of earphones. Lead Engineer Dave Friesema chats with us to discuss the company’s design approach to balanced armature headphones, consumer research and what’s next for the future of headphones.

Here are my notes on the stuff I found interesting in InnerFidelity’s Podcast no. 10 (May 1st 2019) with Dave Friesema, Lead Engineer at Etymotic:

  • About Dave
    • He has worked on the ER MMCX series (ER4, ER3, ER2), the first Bluetooth series, HF series and the MC series.
    • He is the project manager for the ER MMCX series.
    • He was a fan of the original ER4 before working at Etymotic.
  • About Etymotic
    • It’s a company of engineers.
    • They have always been a measurement heavy company and use KEMAR mannequins and lots of (single cavity) ear simulators (while at the desk).
    • They have their target for what they consider accurate.
    • Those who have been at the company for a long time know what the ear canal resonance is and they know what the right answer is at this point i.e., 15dB resonance between 2.6 – 2.8khz for insert earphones since the ear-canal is not flat and has this resonance built in. When sound hits your eardrums this resonance is built in so for insert earphones you have shifted that resonance so you have to put it back.
    • Etymotic has always been about hitting targets and is mathematical about it but they give importance to listening because you can’t hear with your eyes.
    • Lots of people in the company have good ears and their inputs are taken.
    • Etymotic traditionally moves very slowly.
  • On Keeping Things Simple
    • Etymotic has always been a single driver (no crossover) earphone company but it’s not to say they would never do multi-drivers. Dave can’t imagine doing something with 10 drivers but if he had to go down that path he would just use 2,3 or 4 drivers.
    • If you’re just putting in redundancy by taking the same driver and using two of them to cover the same frequency range, all you are doing is adding sensitivity and you’re not driving that large of a volume into the ear canal.
    • You don’t really need something that is a 120 dB sensitive with a 100 mW drive. You’ll just blow your ears out.
  • On Accuracy
    • If you have an accurate earphone then everything sounds the way it’s supposed to sound. As a guitar player you want your guitar to sound the way you are used to hearing them. You don’t want the frequency response massively changed to emphasize the frequencies of the guitar, you want it to sit in the mix the way you’re used to hearing it.
    • Years ago they used to go to trade shows and take the KEMAR mannequins with them. Somebody could bring their own earphone and they could play their own music that they would record through the KEMAR and then they would take the recording and play it again and repeat the process 3 times (like taking a photocopy of a photocopy of a photocopy). At the end of 3 loops the Etymotics would sound more or less the same (not perfect though) but with the colored earphones it would make a huge difference after just 3 loops. Either it would sound like it’s totally under water or thin and bright. Every coloration was emphasized with each replication.
  • On The New ER4 MMCX Series
    • Dave wanted to improve a few things with the original 4:
      • 4S was fairly inefficient (100 ohms).
      • 4P was more efficient and had lower impedance. When impedance goes down it tilts the frequency response so the 4P was considered a bass-boosted version but it wasn’t really. It just had a tilted frequency response where the bass and lower mid-range tiled up a little bit and the peak and higher frequencies tilted down a little bit. It was warmer and wasn’t as detailed as the 4S.
    • With the new ER4SR they tweaked it to bring the accuracy where they wanted, making it more accurate than the original 4S and they were able to drop the impedance to 45ohms.
    • For the ER4XR they went with a different driver to hit the same mid-range and high frequency and get an actual bass-boost (instead of just tilting the frequency response) without compromising the mid-range and treble for it.
  • Studio (Reference|Edition) Series Vs. Extended Response Series
    • The Studio series (SR/SE) is accurate throughout and is flat in the bass
    • The Extended Response (XR) series is about making it as accurate as they could in the mid-range and higher frequencies with a little bit of low-end boost.
  • On Bass-Boost
    • In the ER4 and ER3 there were excursion limits to the BA driver and it wasn’t easy to add 10 dB of bass boost (it was more closer to 4 dB).
    • With ER2 which is a moving coil driver they could have added more bass but they kept it modest which is also a big change for them.
  • On Why Insertion Depth Is Important
    • Makes big difference to higher frequencies.
    • You avoid the occlusion effect with deep insertion.
  • On BAs
    • They source BA drivers from different people and they are all slightly customized but he won’t say if they are Knowles drives.
    • There are very few companies that manufacturer BA drivers and do it well because setting up the tooling for it is not an inconsequential thing (high-precision assembly and expensive).
    • BA drivers come in standard sizes and there’s customization that can be done within it.
  • On Future Plans
    • There might not be more earphone in the ER MMCX series. They went with a good (ER2), better (ER3), best (ER4) family in the series.
    • They might look at adding a higher end earphone as part of a different series.
    • No plans for circumaural and supra aural headphones.
  • Miscellaneous Stuff
    • Bluetooth stuff is disposable electronics. Etymotic users are about buying a few earphones and keeping it for years.
    • MC and MK series are the other moving coil driver earphone along with ER2.

The story behind Sony MDR-CD900ST and it’s unique design and tuning choices

As an owner of the Sony CD900ST and someone that absolutely loves it, I was very curious about the story behind this cult Japanese headphone and the reasons behind some of it’s design choices. So I did some digging and this is what I found.

What the CD for Digital?

The first Sony CD headphone was released in 1982 to faithfully reproduce the wide frequency band and dynamic range of Compact Disc (CD) sound sources in the “digital age” [1] that was ushered by the release of the Philips and Sony co-developed Compact disc (CD) format that same year [2].

So, if you’ve always wondered what the ‘CD’ in CD900ST signified and why the headphone has that famous “For Digital” sticker, now you know.

P.S. Someone please tell Zeos so this doesn’t haunt him forever.

The Driver-on-Ear Headphone

The MDR-CD900ST was jointly developed by Sony and Sony Music Studios originally for use at CBS/Sony Shinanomachi Studios. According to Koji Nageno the engineer behind the MDR-CD900ST, he worked together with the engineering team of Sony Shinanomachi Studio and it took him 3 years to tune it to the satisfaction of Sony Music who had very specific requirements around sound localization and sibilant sounds [3]:

It was very important that they (Sony Music) wanted the sound to come from the front. For example, when a singer sings 10 cm away from the mic, the sound coming out of the headphones must also be able to tell this 10 cm distance. While most headphones tend to have wide dimensions and sound distant. Which is quite different So I tried to get the sound from the driver to be as direct as possible to my ear.

To be able to do that I had to reduce the space between the headphones and the ears. Using a 40 mm driver and a not very thick headphone pad to reduce this area. I also put a small seal around the driver to direct the sound from the driver to the ear. When wearing headphones, the ears will be close to the driver, similar to wearing headphones over the ear half-ear. Which will make the sound from the driver go directly to the ear.

In addition, they also have very complex requirements, such as the style of the sound emanating from the teeth, such as the S, that must be tuned to the manner they want. Which I have to put in a lot of effort in tuning until the success of Sony Music.

Koji Nageno in this interview (translated using Google Translate)

A lot of people think the thin earpads on the CD900ST and the driver touching your ears are just bad design or some Japanese quirk but it was in fact a design choice to achieve a very specific sound goal: localization.

Built to last

The MDR-CD900ST is known as the de-facto standard for monitor headphones in Japan [4] for more than 30 years for good reason.

Sony thoroughly pursued the qualities (maximum input of 1,000 mW, replacement parts system [5], etc.) and durability required in the professional world to withstand the grueling requirements of regular use in recording studios and broadcasting stations [6].

Open to All

Since it’s launch, it’s durability along with the emphasis on sound quality required for monitoring ensured it gained the trust of not only studio personnel but also by artists, and had been featured on TV, radio, magazines, etc. This resulted in a flood of purchase requests from the general public so in 1995 it was made available to consumers.


After reading this article If you’re thinking about buying the MDR-CD900ST you should know the following caveats:

  • The MDR-CD900ST is officially available only in Japan [7].
  • Since it’s a professional headphone intended for business use by recording studios, it doesn’t come with any warranty [6].


That’s all for now. I really enjoyed researching and writing this post and found lots of other interesting information on the MDR-CD900ST that I’ll write about soon in future posts so subscribe to the blog with your email to get notified as soon as I make future posts:

See Also