(Last Updated On: August 31, 2020)

Sony dropped a bomb to their fans and audiophiles around the world in August 2018 by refreshing their previous in-ear monitor (IEM) series with the new in-ear reference (IER) series – filled by IER-M7 as the entry-level and IER-M9 for mid-range audiophiles.

Thank you, Sony Singapore, for loaning me the IER-M7 and IER-M9 IEMs. They were loaned to me in exchange for my honest review and opinion. The units will be returned after this review.
Sony's IER-M7 (left) vs IER-M9 (right)
Sony’s IER-M7 (left) vs IER-M9 (right)

Sony released a lot of remarkable models, such as MDR-EX1000,with excellent soundstage and astonishing capability in detail retrieval. After the XBA-Z5 – Sony’s previous flagship hybrid model which received tons of positive feedback – Sony took a step backward for a while and planned for their next flagship series. Without disappointment, Sony got back in the game in August 2018 with their brand new IER series which consists of IER-M7, IER-M9 and the flagship IER-Z1R

I have long-standing experience with Sony – my first pair of headphones and IEMs before I embarked on an audiophile journey are from Sony. I still remember how impressed I was when I first listened to them.

After a few years into this hobby, I am back to Sony again. The release of IER series surprised me and I anticipated auditioning them when they were first launched. How is Sony doing with their latest series of IEMs? Are they still maintaining the same characteristics? We shall take a look in this article!

IER-M7

Matte black faceplate of IER-M9
Matte black faceplate of IER-M7

Sony IER-M7

Rating: 3.5 / 5.0

“Both models have similar stages – IER-M7 is slightly wider due to the leaner sound signature. IER-M9 is deeper compared to IER-M7 – with a more three-dimensional headroom. “

Technical Specifications

  • Driver Configurations: Quad balanced armature (BA)
  • Impedance: 24 ohms @ 1 kHz
  • Frequency Response: 5Hz- 40000Hz
  • Sensitivity: 103dB / mW

Pros:

  • »Neutral and balanced sound signature
  • »Excellent build quality
  • »Lean and precise bass response
  • »High quality stock cable
  • »Airy and spacious highs
  • »Tons of useful accessories
  • »Wide soundstage
  • »Affordable pricing

Cons:

  • »Recessed in mids
  • »Analytical sounding
  • »Difficulty in driving
  • »Vacuum feel in the ear canal and ear drum flex

IER-M9

Carbon fibre faceplate of IER-M9
Carbon fibre faceplate of IER-M9

Sony IER-M9

Rating: 4.5 / 5.0

“I think that, after all, two of them are made for different groups of audiophiles – IER-M7 is more suitable for those who are after fast and more analytical sound signatures. While IER-M9 is for those who prefer overall smoothness and neutrality. “

Technical Specifications

Pros:

  • »Neutral and balanced sound signature
  • »Excellent build quality
  • »Sub-bass rumbles
  • »Uncolored and natural midrange for vocal monitoring
  • »High quality stock cable
  • »Smooth and well extended highs
  • »Tons of useful accessories
  • »Three dimensional soundstage

Cons:

  • »Bass might be too strong for reference IEM
  • »Vacuum feel in the ear canal and ear drum flex
  • »Steep price difference from IER-M7
  • »Difficulty in driving

Unboxing

The packaging for IER-M9 and IER-M7 are similar. The box is relatively larger compared to other models within a similar price range, such as Campfire Audio and Sennheiser. The internal black hard box is covered by a white sleeve. The image of the IEMs and Sony’s logo are printed on the sleeve.

The packaging of Sony's IER-M9
The packaging of Sony’s IER-M9
Packaging for Sony's IER-M7
Packaging for Sony’s IER-M7
Internal hard box after removing the outer sleeve. The internal is the same for both IER-M7 and IER-M9
Internal hard box after removing the outer sleeve. The internal is the same for both IER-M7 and IER-M9

The IEMs and its accessories occupy both sides of the box. On the left side of the box, users can find the IEMs, stock ear tips, and a 3.5mm stock cable. Sony is very generous in terms of providing accessories.

There are a total of 13 pairs of ear tips in the box! You are getting 6 pairs of Triple Comfort (foam) ear tips and another 7 pairs of hybrid silicone ear tips of different sizes (from SS to LL).

IER-M9, stock unbalanced cable and 13 pairs of ear tips
IER-M9, stock unbalanced cable and 13 pairs of ear tips

For those who are familiar with Sony’s ear tips’ price, you should be able to calculate how much “rebate” you are getting from these 12 pairs of ear tips from the box!

Moving to the right side of the box, you will find another cable. That’s right – another cable. This cable is terminated with Sony 4.4mm TRRRS balanced jack. For those who own digital audio players (DAPs) which utilize a 4.4mm balanced output, you’re going to enjoy this benefit.

Balanced terminated stock cable and hard storage case
Balanced terminated stock cable and hard storage case

Besides the cable, there is a hard storage case. The case is spacious and you can store your IER series IEMs in it without any issue. The hardness of the case is sufficient enough to provide adequate protection to your IEMs from falls and collision.

The storage case from Sony
The storage case from Sony
Internal of the storage case
Internal of the storage case

Technology

Audio Grade Film Capacitor

In designing IER series, Sony implemented their custom audio grade film capacitor in the crossover circuit. As reported by Sony, this implementation is able to deliver signals with lower distortion. In addition, audio grade solder is used, too, which helps to minimise loss in signal path. With the combination of these two implementations, IER-M7 and IER-M9 are capable of delivering a sonic presentation with minimum distortion.

Internal Design

The internal of IER-M7 and IER-M9 are specially designed, too. To hold the quad and penta drivers, a highly rigid housing was crafted to keep the BA drivers sturdy in place. This helps to eliminate undesired vibration from the drivers and hence keep the final sonic presentation clear and free from signal loss due to vibration.

The drivers used in these two models are Sony’s custom T-shaped BA drivers. As mentioned by Sony, this custom driver further aided IER-M7 and IER-M9 in achieving a clean and detailed presentation.

Build

Shell

Without reading the specifications, my first guess on the material of the shell was plastic because of its light weight. However, Sony is actually using magnesium to build the outer shell. This enhances the quality and durability of the build.

The size and shape of the shell are the same for both IER-M9 and IER-M7. There are some minor differences in the design between the two models – faceplate and nozzle. The faceplate of IER-M9 is with classy carbon fiber pattern, while IER-M7 has a more reserved, matte black faceplate. IER-M9 is more eye-catching in terms of the physical appearance.

Carbon fibre faceplate of IER-M9
Carbon fibre faceplate of IER-M9
Matte black faceplate of IER-M9
Matte black faceplate of IER-M9

Moving to the nozzle, IER-M9 has a magnesium nozzle, which is in one piece with the shell. IER-M7 has a more premium nozzle compared to IER-M9 – the nozzle is made of brass. Both models have the same nozzle length and design despite the differences in material. There are lips on the nozzle to provide a better catch on the ear tips.

Nozzle of IER-M9
Nozzle of IER-M9
Nozzle of IER-M7
Nozzle of IER-M7

On top of the shell, we can find the typical recessed MMCX port. You can still use the normal MMCX cable on both models, with some spaces left around the connector. This design reduces the rotatability of the MMCX and hence improves the durability.

MMCX connector of IER-M9
MMCX connector of IER-M9
MMCX connector of IER-M7
MMCX connector of IER-M7

Cable

According to Sony, the cables provided in the packaging are made of silver-plated, oxygen-free copper (SPOFC). Cable made with this material can minimise resistance and signal-transmission loss, eventually yielding in a less degraded sound quality with finer detail and smoother treble sounds.

Cable of IER-M7
Cable of IER-M7
Cable of IER-M9
Cable of IER-M9

Two cables are provided for each model – 3.5mm unbalanced and 4.4 balanced terminated. Both cables have the same physical appearance, except for the jack. The stock cables come with pre-formed ear guides for easy positioning. This is extremely useful especially for those who are working onstage or in the studio. The cable stays nicely behind your ears without need of additional adjustments.

MMCX stock cable
MMCX stock cable
Unbalanced (3.5mm) jack of stock cable
Unbalanced (3.5mm) jack of stock cable
Balanced (4.4mm) jack of stock cable
Balanced (4.4mm) jack of stock cable

The cables are soft and supple. It can be coiled and stored neatly in the storage case provided. According to Sony, the cable in IER-M9 uses silk braid as a cable insulator. The insulator has the capability to absorb vibration and prevents rustling or bumping noises when you touch the cord. This silk braid insulator is not used on the IER-M7 – the internal braid of cable can be seen through from the transparent plastic insulator.

IER-M9 uses silk braid as a cable insulator
IER-M9 uses silk braid as a cable insulator
Cable of IER-M7 - there is no fabric insulator like IER-M9's cable
Cable of IER-M7 – there is no fabric insulator like IER-M9’s cable

Fitting and Isolation

The form factor of the shell for both models is moderately large. I don’t experience any difficulties in inserting them into my large ears. However, for those having smaller ears, Sony’s IER series might not be a good choice.

Using the large hybrid ear tips provided in the case, I can get excellent isolation. The passive noise cancellation is good and I can enjoy the music. However, I faced a dilemma here – the isolation is good to the extent that it creates a vacuum-like condition in my ear canal. Whenever I push the IEMs into my ears, my ear drums actually experience some flexes, which is uncomfortable for me. Same thing goes with removing the IEMs.

Sony IER-M7
Sony IER-M7

Sound Analysis

To analyze the sonic quality for both models, I paired them with my reference DAP – Lotoo Paw 6000 and reference digital analogue converter (DAC)Lotoo Paw S1. Both DAP and DAC come with 4.4mm balanced output and I’m able to use the stock balanced cable from the packaging to maximize the performance.

Despite having relatively low impedance and high sensitivity, IER-M7 and IER-M9 are actually challenging to drive well. I need to toggle both Paw 6000 and S1 to high gain to get a good audible volume. So for those who do not have a powerful source, you might need to reconsider before getting these two models.

This can be caused by the custom BA driver designed by Sony – which requires more energy and power to move the diaphragm. A wild guess here.

IER-M9 with Lotoo Paw 6000
IER-M9 with Lotoo Paw 6000
IER-M9 with Lotoo Paw S1
IER-M9 with Lotoo Paw S1

Sound Signature

Different from previous hybrid series, the new IER series now has a more balanced and neutral tuning to achieve the referencing characteristic. However, you can still “feel” the characteristics from old Sony’s IEMs.

Both IER-M7 and IER-M9 have a neutral and well-balanced sound signature. This sound signature suits their series well. Similar to previous IEMs from Sony, which I owned, they are considered “dark” – the presentations are more reserved and polite.

Understanding that there are actually some models from Sony which have more engaging and energetic sound signature, I shouldn’t call the dark sound signature Sony’s “house sound,” but it is one of the characteristics for some of Sony’s IEMs.

The dark sound signature actually suits the referencing purpose well. The musical notes are delivered parallel, without any bias and coloration to the audience. With my Lotoo Paw 6000, which is slightly dark in nature, this combination can be a studio reference setup – a lot of details with the lowest level of coloration.

Lotoo Paw 6000 paired with IER-M7
Lotoo Paw 6000 paired with IER-M7

Soundstage

Both models have similar stages – IER-M7 is slightly wider due to the leaner sound signature. IER-M9 is deeper compared to IER-M7 – with a more three-dimensional headroom. Within the period of reviewing, I didn’t experience any congestion, even with complicated tracks like rock bands.

The details of each track are managed well by both models – deliver smoothly to the users. Expect a more distanced presentation from IER-M7, with greater space and air. IER-M9 has a fuller body and richer presentation. The gaps between each note in the track are filled more compactly in IER-M9.

IER-M7 with Opus #3 and ALO Audio RX Nickel version
IER-M7 with Opus #3 and ALO Audio RX Nickel version

Lows

The bass for IER-M9 has a greater impact compared to IER-M7. This is one of the reasons why IER-M9 has a deeper soundstage.

Despite it being powered by a BA driver, the bass body for IER-M9 is full and can be competed with some dynamic drivers powered IEMs. On the other hand, the bass response on IER-M7 is more reserved – leaner and faster. It has a typical bass response of BA driver-powered IEMs.

The sub-bass on the IER-M9 is extended deeply and has sufficient rumbles. Pair it with a powerful source like my Lotoo Paw 6000, the quantity and quality of the bass can probably fulfill the needs of a basshead audiophile. IER-M7 has a shyer sub-bass. I can feel the sub-bass presence after listening to the IER-M9 – the difference is drastic.

I think IER-M9 would be a better choice because the rumbles in the sub-bass actually brings in some liveliness to the presentation. The fast bass in the IER-M7 might make it a little “dry” or analytical.

Sony IER-M7
Sony IER-M7

Mids

Moving to the mids, IER-M9 mids also has a richer and fuller body compared to the IER-M7. The mids of IER-M9 have equal emphasis at the sub-bass, pushing it more forward and nearer to the audiences. This made IER-M9 to be more engaging. The slightly recessed mid-bass in the IER-M9 makes a good space for full-bodied mids to flex its muscles.

I think the bass of the IER-M7 is tuned to be more reserved and to cater to the lean mids here. IER-M7 cannot afford to have a bass which is as prominent as IER-M9 because the mids are weaker. The overly prominent bass will cause IER-M7 to have a “V-shape” sound signature. Hence, the fast bass is paired well with the lean mids here, making overall signature to be balanced.

IER-M9 has more ups and downs in the presentation – from the punchy sub-bass to the slightly recessed mid-bass and finally a full bodied mids. IER-M7 is more linear here, everything from the bass to the mids are almost in a straight line, the mids is still slightly recessed compared to the bass.

Sony IER-M9
Sony IER-M9

Highs

The performance in the highs are equally good on both models – well extended but not piercing. Because of the slightly darker sound signature, the treble is forgiving, even for those who are having low treble tolerance, like my fiancée. She can listen to IER-M9 for hours without complaining that the treble is being too bright.

For those who are a fan of the Westone UM Pro series, IER series from Sony perhaps can be your next upgrade. I see some similarities between them.

Because of the lean presentation in bass and mids of IER-M7, the space and air in the highs are more prominent, making it more sparkly compared to IER-M9. The treble on IER-M9 has a smoother and more comfortable characteristic.

I think that, after all, two of them are made for different groups of audiophiles – IER-M7 is more suitable for those who are after fast and more analytical sound signatures. While IER-M9 is for those who prefer overall smoothness and neutrality.

Sony IER-M7
Sony IER-M7

Verdict

The IER series is, indeed, an excellent series from Sony to re-enter the IEM battle arena. The detail retrieval capability and reference sound signature will definitely win a lot of audiophiles’ hearts, including mine. The different tuning approach in IER-M7 and IER-M9 is a wise move, to address different needs from different groups of audiophiles.

No matter which is your preference, Sony’s got your back with their new IER series.

Sony IER-M7 and IER-M9 are retailing at USD$499 and USD$999 respectively. You can purchase them from Sony’s official website.

With the launch of IER series, Sony once again proves to the world that the matured state of their tuning and desire can cater to the different needs in the audiophile community.