ISN Audio D02 Review: Greatness With An Achilles Heel?

Pros: Well-tuned, Balanced V-shaped with no honky mids, Good soundstage, Fit, Switches give more flexibility with the upper mid-range and treble

Cons: Serious Driver Flex, Peaky upper mid-range and lower treble.

Driver Setup: 1 Dynamic Driver

Price: US$80


Disclaimer: This review set was graciously lent to me by a friend and the review is written of my own accord.

ISN had been around for quite some time with its acclaimed hybrid model – H40 which impressed many and managed to attract numerous followers. Today we will be taking a closer look at its cheaper offering the ISN D02 which is a single dynamic driver IEM which we will see if they are able to re-create their success with the D02!

Accessories (Score: 7.0/10)

The package itself is small and compact, with just a carrying case with the IEM itself, tips and cable all packed into the carrying case. Of course, I don’t expect it to be as “grand” and fancy as compared to the likes of Moondrop’s idea of package and accessories but I guess these will suffice as they covered all the important accessories that I feel any IEM should have.

Build Quality and Fit (Score: 6.5/10)

The shell feels good in the hand and the fit is above average as it has a relatively longer nozzle (deeper fit) as well as a very ergonomic design. Isolation (no leakages post insertion however it is vented so isolation takes a hit) is good with the right tips and the cable quality looks well built and rather fancy in my opinion. All is well here except the driver flex issue.

I understand that there are some units that do not experience this issue but unfortunately this is just my experience with the unit. To overcome that, there are many solutions posted elsewhere on the web, but the general rule of thumb would be slow insertion and slow removal to minimise “pops” from the driver.

Sound (Overall Score: 7.5/10)

This unit sounds like a borderline V/U shaped IEM to me, but it manages to steer clear of that honky mid-range trait which many other V-shaped IEMs suffer from. In general, I enjoyed the sound of the ISN D02 and it being one of the few V-shaped IEMs that I consider to be “unique” due to its vented design. This review was done with the switches being set “up” which is its default setting, flipping the switches reduces its high frequencies which may serve you well if you want something less aggressive.

Frequency Response of the ISN D02

Frequency Response of the 2 switch configurations

Sources used

  • Ibasso DX120
  • IPhone XR
  • Atom DAC and AMP

Music/Albums/Artists, I listened to

  • Alan Walker
  • Billie Eilish – When we all fall asleep, where do we go?
  • Tchaikovsky 1812 Overture
  • Cigarettes After Sex
  • One Republic – Dreaming Out Loud
  • Kodaline
  • Keane – Fears and Hopes
  • Nino Rota – The Godfather OST
  • Fedde Le Grand – Cinematic
  • ARTY – Rebound
  • Halo 2 OST
  • Halo 1 OST
  • Czardas
  • Lauv
  • Aladdin OST

Bass (Score: 8.0/10)

Bass is tasteful here as it does have that rumble as well as an impactful punch. For example, when listening to the Halo 2 OSTs, bass drums, as well as bass guitars, sound deep and huge which really helps to translate that “epic-warzone” vibes. Its sub-bass is relatively less emphasised here than mid-bass, but it does not overshadow them. the decay might be a tad too long which makes the presentation slightly sluggish or muddy when moving through fast passages but in general still an acceptable trade-off between impact/presence and agility.

I would say that the bass on the ISN D02 can satisfy most casual and semi-critical listeners although bass heads should take note that although the frequency response graph measured in this review shows an emphasised sub-bass response, I do suggest otherwise based on my experiences with this unit.

Mids (Score: 7.0/10)

Mid-range sounds less emphasised but not too much such that it feels honky or absent. Male vocals still manage to shine through the accompanying tracks in Keane’s “Everybody Changing” however I do sometimes feel that the keyboard tracks and bass lines are constantly competing against the main vocalists for the spotlight.

I do pick up some glaring midrange spikes that made the keyboards, pads and synthesisers sounding relatively much more forward than the rest. I would say that male vocals on the ISN D02 sounds more laid back/less intimate as compared to female voices. I do find the upper mid-range peaks and low treble to be peaky which I find myself toning down the volume as it can get slightly tiring to listen to.

Treble (Score: 7.0/10)

The treble doesn’t sound splashy nor sibilant, but there are some spikes in this region as OSTs with violins and synths sounds relatively way too forward and present as compared to other parts of the track. For most of the time, it sounds balanced or relatively on par with other emphasised frequency bands and occasionally giving that sparkle to spice things up. For example, when listening to “I will survive” cover by Scary Pockets, the combination between its bass guitar line, cymbals and high hats shimmer made it super lively and chill at the same time.

The ISN D02’s treble really brings some energy to the table but on the flip side, it might induce fatigue as time passes. For sure, there are going to be tracks that expose its uneven/peaky treble but for most tracks, you can expect that airy but non-sibilant energy that you soak your ears in.


On top all the frequency response and how it is tuned throughout, the soundstage is one of its unique points and one of the first quality that I noticed when I plugged in and play. Its vented design seems to be giving it that technical edge in this area and I am just very pleased with what ISN had done here. Imaging is decent/above average from binaural recordings and tonalit wise I would prefer a more present lower-mids to keep things more balanced.


QoA Vesper (Review here)

I think it is a pretty close match up here but I will lean towards the QoA vesper partly due to its completeness as a package, build quality (no driver flexes picked up) as well as sonic performance. The vesper’s upper-midrange and lower treble has more control and does not have that uneven peaks as per the D02. Although the ISN has a better soundstage, the Vesper compensates with its overall presentation and the ability to suit more genres!

The D02 is no slouch either but it innately possesses more quirks that appear right in my face which cannot be avoided


In conclusion, I felt that for 80 USD the ISN D02 checks most boxes that I look out for when looking for a sub 100 pick. It was tuned well, along with that awesome soundstage that is tough to see in sub 100 choices. Although, driver flex was a huge issue that I encountered with this unit which I felt is one of the greatest weaknesses that it has. Other than that, I am fully confident of its sonic performance at this price range, a fearsome contender to all the other sub 100USD V/U shaped IEMs out there.

Overall Grade: C+


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