final A4000 measurement (frequency response graphs) and comparison with Etymotic ER2XR

Please disregard this post and see the latest final A4000 measurements (frequency response graphs) and comparisons with Etymotic ER2XR using v1.0 of my IEM Measurement Rig.

These measurements are made on my DIY IEM measurement rig and are not accurate, and don’t necessarily represent what you might hear, especially before 60 Hz (huge sub-base roll-off) and after 10 kHz (and maybe even after 3 kHz as my ER2XR graph is very different compared to Crinacle’s post that). You can use it just to get a comparative idea, hence the comparison with ER2XR to give you a point of reference. Improving the rig is an ongoing process.

Here is Crinacle’s ER2XR graph for reference

It looks like final went with the mids to bass rise like in the E series and the highs of the A8000 on A4000.

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.

final A4000 ❤ Love at first listen – Initial Impressions

To start with I had very high expectations from the final A4000 with some early reviews calling it a “baby A8000”, the A8000 being final’s flagship earphone that cost $2000. Given my experience with some earphones from final’s E-Series (E500 and E3000) that seemed very pleasant and maturely tuned but lacked both in quantity and quality in the highs for my preference and the fact that final is one of those few companies that seems to be very passionate about what they do, I was really hoping to find a final earphone that came close to my preference. So clearly I was going into this very biased.

Before I share my initial impressions it’s important to understand some context. At this point my reference earphone is the Etymotic ER2XR and I would classify myself as being a neutral-head. I listen to any and all types of music but I generally stay away from most forms of electronic music. I’m listening to music from Spotify (very high quality – downlaoded) on the Sony NW-A105. These impressions are OOTB (Out Of The Box) with no burn-in and I’ve listened to them for a couple of hours. final recommends 150 to 200 hours of normal-usage burn-in which according to them is primarily for the adhesive in the driver unit as it may affect the slight movement of the diaphragm and usage over time might allow it to move more freely.

With that out the way, here are my initial impressions:

  • The first thing I noticed is the bass. It is slightly more than on the ER2XR but the delta feels like it’s a lot more than it actually is because of the emphasis in the mid-bass on the A4000. This gives it more thump and makes it punchier compared to ER2XR (which has a sub-bass emphasis with a lot more rumble and comes across as cleaner and leaner).
  • Mids and vocals seem more forward on the A4000 and also very slightly cleaner.
  • The A4000 has a noticeable boost in the highs compared to the ER2XR but without sounding harsh to me. You can “hear the metal” of the instruments on the A4000 without any resonances that might make it sound metallic. This area might be problematic for some people as I’ve seen tolerances vary a lot when it comes to higher frequencies.
  • Imaging and separation seems to be slightly better on the A4000 while transient response is slightly slower compared to ER2XR.
  • Need to spend more time with them to say anything about resolution/detail retrieval as they seem very close.
  • These are power hunger with only 18 ohms of impedance but a sensitivity of 100 dB/mW and require similar power as the ER2XR which has an impedance of 15 Ohms and sensitivity of 96 dB at 0.1v (98 dB/mW [1][2])
  • The A4000 is super light, fits very well in my ears and is super comfortable for me, but the cable is very thin (above the y-split) and I feel like I’m going to break it every time I take them of while holding it just above the 2-pin connector.
  • If you prefer a dark and smooth sound, the A4000 might not be for you.
  • Overall I think it has a well balanced sound signature, sounds very coherent, has great timbre for most instruments and is more “fun” than the ER2XR on most tracks, which is not necessarily a good or bad thing, just different and I think they compliment each other well.

These are very early impressions so take them FWIW. My impressions might change after I spend more time with them and get some “brain burn-in”.

P.S. I haven’t heard the A8000 so can’t confirm the “baby A8000” claim.

That’s all for now. I’ll be doing a listening session post with these soon, so subscribe to the blog with your email to get notified as soon as I make future posts:



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