Review: IMR Acoustics R1 Zenith (The Chameleonic Beast)

If you haven’t heard of IMR Acoustics, you can still be forgiven. IMR Acoustics is relatively new to the audiophile market. The company’s owner Bob James or the “Filter Master” as I like to call him was previously employed at Trinity Audio which was quite a well-known brand. After the company went bankrupt, Bob started IMR Acoustics in 2017 and released his first pair of IEMs, i.e., the R1. Those IEMs were highly regarded in the audiophile industry as one of the best IEMs using filters at that time. Then later by the end of 2018, they have released the R1 v1.1 which is the R1 Zenith. It uses a newer version of the driver used in the original R1 and the vent port system (which is used to make its soundstage wider or intimate depending if the port is open or closed respectively) and this is the pair of IEMs that I will be reviewing today.

I’ve had the IMR Acoustics R1 Zenith for just over 2 weeks now and have listened to them for a total time of at least 60 hours and have burned them continuously for 50 hours. I’ve used them mostly daily during this time period to listen to all genres of songs (rock, EDM, pop, movie soundtracks, Western classics, etc.).

Don’t want to read the full review? Here’s your TL;DR :

The IMR Acoustics R1 Zenith is an excellent pair of IEMs that can be used by both bass heads and audio purists alike due to its excellent implementation of the tuning filters and I highly recommend buying these IEMs if you have the dosh to spare for them.

You can get the IMR Acoustics R1 Zenith here

But wait! Before you dive into the review, I have a quick disclaimer for you: I have received the R1 Zenith from IMR Acoustics directly for reviewing purposes. The IEMs are not meant to be returned to them but this doesn’t mean that I have been incentivised or pressurized by IMR Acoustics to write this review for them. All the words used in this review are my own and this review is written in the most unbiased way that I could have done.

Now, on to the unboxing of this IEMs.

Unboxing the IMR R1 Zenith

Priced at $649, these IEMs are not cheap and that shows during the unboxing of this product. The unboxing experience rivals that of even much more expensive IEMs than themselves. The R1 Zenith comes in a large book-like case which flips out from the top, exposing the IEMs themselves and a small card which show what the IEMs sound like when different filters are installed.

The box of the IMR Acoustics R1 Zenith

Upon removing the protective foam partition that the R1 Zenith is placed in, we will find a case and 3 stacks of foam partitions and an IMR branded hard carrying case. Underneath the case is a small product quick start guide.

The packaging of the R1 Zenith

Two of the partitions contain 6 pair of eartips including 1 dual-flange eartip, 3 single flange eartips (xl, l, s) and 2 foam eartips. There is already a single flange eartip (m) installed in the IEMs for a total of 7 pair of eartips included inside the box. The third partition contains the filter holder with a total of five filters (4 of them in the holder and the fifth is already preinstalled on the IEMs) and 3.5mm to 6.35mm adapter for amp uses.

Underneath the foam partition of the IEMs

Now, upon opening the case we find there is not one but two cables included inside the box. One is a standard 3.5mm TRS cable for smartphone or DAPs (Digital Audio Players) with single-ended connections. The other one included is a 2.5mm TRRS balanced cable which can be used in DAPs or DAC/Amps with balanced connections.

So, to summarize, when you receive the IMR R1 Zenith you’ll get:

  • The IEMs themselves.
  • 7 pairs of ear tips (3 pairs of large-bore single flange tips, 1 pairs of double flange tips and 2 pairs of foam tips)
  • 2 0.78mm cables (3.5mm and 2.5mm terminations)
  • Hard carrying case
  • 3.5mm to 6.35mm adapter
  • 5 Filters
  • Filter holder
All the accessories that comes with the R1 Zenith

So as far as accessories goes, the R1 Zenith comes with a ton of it and I really doubt that you need anything more for these pair of IEMs (except for probably a set of custom-built cable as the cables included in the box are a bit generic).

Design and Build Quality

Now I will be honest with you. When I initially saw the R1 Zenith, I thought that it was actually a new variant of the Acoustune HS1551Cu because of its venting screw (more on that later) jutting out from the body just like the latter IEM. Anyways, the overall build quality of the IEMs is top-notch. Since it is made of metal (probably aluminium), it feels substantial on the hands but is still lighter than quite a few IEMs I have tried (RHA I am looking at you). The body is made using two separate pieces and then the pieces are screwed together. Also, the R1 Zenith has a 2-pin detachable cable system with gold plated connectors. In the previous model, i.e. the R1, there was an issue where the polarity of the 2-pin connection was reversed which rendered it unusable with other third-party aftermarket cables. But it was finally fixed with this iteration of the R1 Zenith. I have personally tested them and they seemed to work just fine with other 2-pin cables.

The IMR R1 Zenith themselves

Now coming to the cable, IMR Acoustics has used a basic 2-pin connector rubber-coated OFC cable. This cable looks very generic for a $650 pair of IEMs but that doesn’t mean it is bad. The cable is quite thick and feels soft and solid in the hands. Also, the cable is resistant to tangle so that is a plus if you keep your expensive IEMs in your pockets (like me).

The cable used in the IMR R1 Zenith

But overall the cable is perfectly fine and for the price, the overall build quality of both the IEMs and the cables is simply excellent.

Ergonomics and Fit

Now this a place where your mileage may vary a lot. The R1 Zenith like most other IEMs at this price uses an over-the-ear fit. Now my ear canals are small so I used the small tips included in the box. Now, there is something to note here. The cable also doesn’t help with the fit. I have the tendency to listen to my IEMs when I go to sleep, but whenever I lie down, the cable often moves out of my ear and dangles beside it. This is really annoying for me at least and I hope that IMR Acoustics implement some kind of an ear guide in the next iteration of its IEMs. I have also noticed that when using two of the included filters, i.e., the black and the gold filter, they introduce driver flex into these IEMs. This is because there is no venting on the side of those filters to remove the air which is present in the other filters. So that is something to keep in mind. But overall, the fit was fine although it a tad bit on the looser side.

Driver flex is an issue where you will hear a sound like crushing paper whenever you put the IEMs inside your ears.

As far as ergonomics go, even though they are made of metal, they weigh only 6g and thus, it feels really comfortable and light on the ears. I have worn them continuously for 3 hours without feeling the need to remove them from my ears. Sometimes I have literally forgotten that they were in my ears. So, ergonomics is also great in these IEMs and there is honestly nothing to complain about in here.

The fit of the IEMs in my ear is just right, nothing to complain about here

Noise Isolation

Now coming to noise isolation, since the seal was quite good on these IEMs (at least for me), basically most of the ambient noise was cut out. Only the horns of the vehicles and the rumbling of my bus (I usually test noise isolation inside public transportation as it gives a very nice idea of what to expect). So, although it won’t be able to cancel out high frequency and/or loud noises like the metro or an airplane (at low volumes at least), you can except a decent amount of noise isolation with the R1 Zenith. But enough about this, let’s start with the main factor which is the make-or-break property of any audio gear, i.e., its sound.

Sound Quality

Now, on to the most subjective part of the review: sound quality. Also, I won’t be posting any graphs in this review (or any review for that matter), as I don’t believe in graphs as much as I believe in my ears!

This time, I’ll be listening to the earbuds via 3 sources:

  1. PC -> Fiio Q1 (Mark-1) -> R1 Zenith
  2. Asus Zenfone 5Z -> Fiio Q1 (Mk.1) -> R1 Zenith
  3. Hiby R3 -> R1 Zenith

If you plan on purchasing these headphones or any other high-end headphones for that matter, I suggest you get a good DAC/Amp to go with it. It will go a long way to make your listening experience much better and enjoyable.

I will also list the soundtracks that I’ve used for each section of my sound test. (Note: All my tracks are either 44 kHz / 24-bits – 192 kHz / 24-bit FLAC or DSD64/DSD128.) Also, the filter I have used for this test is the Blue Filter as it is the most balanced out of them all and the port was also set to open. I will also elaborate on each of the other filters provided inside the box below.


Now if you are opting for the blue filter as your daily driver like me, do not expect heart-thumping bass here. If you want that, then I would suggest you to switch to the black or gold filters. Anyways, although the bass is somewhat light in here, it is well textured and very detailed and surprisingly airy. But the sub bass rumble is a bit on the thinner side here. But as I said, the blue filter was not meant for bass and more for a balanced and airy sound signature.

The bass in these IEMs with the blue filter is enough to satisfy most, if not all, audiophiles but those who want more bass just needs to change the filter to a black or gold one.

The separation between the lows and the mids is simply extraordinary. They are really nicely separated from each other. The mid-bass of these IEMs with the blue filter is surprisingly good. It has a nice body and has a bit of impact unlike the sub bass in the track Indica Badu by Logic. And there is a surprising amount of micro detail even in the bass region. Bass guitars have a nice texture and airiness to them and you can literally feel every plucking of the strings on the guitar.

So overall, for a pair of IEMs targeted for audio purist at this price, I would say that the bass response is simply excellent and as I said, changing the filters from blue to black or gold increases the bass dramatically (will elaborate more on this in the Filter section).

  • Axel Thesleff – “Reincarnation”
  • Martin Garrix – “Animals”
  • Martin Garrix, Tiesto – “The Only Way is Up”
  • Alessia Cara – “Here”
  • Zara Larsson – So Good (album)
  • Jordan Comolli – “Alone”
  • Marshmello – “Alone”
  • Axel Thesleff – “Done”
  • J Balvin, Willy William – “Mi Gente”
  • Logic – Indica Badu (ft. Wiz Khalifa)


The mids is the strongest suit in its versatile armoury. The vocals are more forward than the other frequencies but as the soundstage is wide on these IEMs (more on that later), the vocals tend to sound a bit laid back and relaxed in here. Vocals sound airy, wide and extremely detailed. Male vocals have a really nice warmth in them and female vocals sound energetic and feels really airy without sounding overly tinny. There isn’t a hint of sibilance even in the most sibilant which is a great thing as well. And the separation between the vocals and the other instruments is simply phenomenal. Even in low volumes, it reveals so much detail and clarity in each and every song that I listen to that it really doesn’t surprise me anymore that these IEMs cost $650.

These IEMs bring out an extraordinary amount of micro details in vocal tracks which is simply not present in other cheaper IEMs.

Drums also sound really detailed and clear in these IEMs. In tracks like “Back in Black” or “Thunderstruck” by AC/DC, the drums sounded nicely layered and the separation between them and the vocals were simply astounding with excellent amount of soundstage. It felt as if AC/DC was literally giving you a personal live performance to you for free! In the song “The Reason” by Hoobastank, Doug Robb’s voice (the lead singer of Hoobastank) sounded really airy and the drums had a nice impact, detail and energy to them.

So, IMR R1 Zenith really killed it in the mids department and believe me when I say this, the mids of the R1 Zenith make them worth the asking price of these IEMs.

Tracks used:

  • Adele – 25 (album)
  • Charlie Puth – Nine Track Mind (album)
  • Ed Sheeran – X / Divide (album)
  • Amber Rubarth – Sessions from the 17th Ward (album)
  • AC/DC – Razor’s Edge
  • John Newman – “Love Me Again”
  • Elvis Presley – “Can’t Help Falling in Love with You”
  • Sigrid – “Everybody Knows”
  • Hoobastank – The Reason


Now onto treble. Let’s start with those cymbals and hi-hats. They sound really crisp and energetic with a huge dollop of detail in them. Especially its rendition of guitar is extremely good. They sound clear, well textured and detailed, the guitar takes its time to decay and it decays with a certain smoothness which I really like here and has excellent separation as well from the other instruments in any given soundtrack. In tracks like “Numb” by Linkin Park, even though they are not the best recorded amongst tracks, the R1 Zenith does a splendid job separating the electric guitar from the piano that is played at the part “I’ve become so numb…” which simply cannot be heard properly in other cheap IEMs.

Now coming to pianos, their rendition is simply superb and is quite detailed and have really nice extension in them. In the track “Rhapsody in Blue” by George Gershwin, the piano is handled really delicately and has a lot of detail in it. Church organs in this track never sounded harsh in the R1 Zenith which is really good as I had found it harsh in some other IEMs at exactly the same volume. Now, bells sound controlled and energetic in the R1 Zenith without a hint of boominess in them. Trumpets also sounded clear and natural and is full of detail in here.

So overall, I am really impressed with the treble that the R1 Zenith has offered me.

Tracks used:

  • Led Zeppelin – IV (album)
  • Ed Sheeran – X / Divide (album)
  • Linkin Park – Meteora
  • Amber Rubarth – Sessions from the 17th Ward (album)
  • Pink Floyd – Dark of The Moon (album)
  • John McLaughlin, Al Di Meola, and Paco De Lucía – Friday Night In San Francisco (album)
  • Ludovico Einaudi – Islands: Essential Einaudi (album)
  • Axel Thesleff – “Reincarnation”
  • George Gershwin – “Rhapsody in Blue”

Soundstage, Positioning and Separation

(a) Soundstage and Positioning

Now, there are 2 ways to accurately measure a IEMs’ soundstage and positioning. First, is to use well-recorded binaural tracks (see track list below for more info). The second method (which I personally prefer more) is gaming. I have used two games specifically for this purpose. One is the well-known CS:GO and the other is Hellblade: Senua’s Sacrifice (the latter is a much more immersive experience).

Now, soundstage. For a pair of IEMs, they have a soundstage that rivals even that of my own Sennheiser HD58X which is an open-back pair of headphones. The soundstage in the R1 Zenith is really wide and expansive here and this is all due to the venting system implemented by IMR Acoustics on these IEMs. This venting system is basically a small plate over the driver which can be opened or closed by turning the screw on the back of the IEMs. When the back-plate is open, the soundstage is really wide (just like my HD58X like I said previously and I am not making this up) and when the back-plate is closed, the overall soundstage gets just a bit more intimate, but it is still very wide and I would say that it is about as wide as my Moonbuds Crescent in its closed state which is simply spectacular for a pair of IEMs. But at this price, I simply did not expect anything less than this to be honest.

Now coming to its positioning, I felt that it is really accurate in here. To test it out, I fired up CS:GO and I could easily pinpoint the source of the gunshot. Furthermore, in Hellblade: Senua’s Sacrifice, I could feel the voices whispering in my ears. Even in orchestral soundtracks like in Symphony No.5 by Beethoven, the overall layering and positioning of the instruments is really striking to say the least. So overall, I am pretty impressed with the soundstage and positioning that the R1 Zenith provides, even with respect to its price.

(b) Separation

The separation of the instruments should be, to be honest, one of the highlights of these IEMs. Again, coming back to orchestral music, the separation between the different instruments in, say “Symphony No. 5 in C minor” by Beethoven, is honestly remarkable. You can literally distinguish all the instruments that are being played in the track. Also, the layering of the different instrument in different spaces is also something that I have noticed it doing remarkably well in. So overall, I was really impressed with the separation of instruments it provides.

Tracks used:

  • Amber Rubarth – Sessions from the 17th Ward (album)
  • Yosi Horikawa – Vapor (album)
  • Led Zeppelin – IV (album)
  • John McLaughlin, Al Di Meola, and Paco De Lucía – Friday Night In San Francisco (album)
  • Beethoven – Symphony No.5 (album)


Since this is a very essential part of the functioning of the R1 Zenith, I thought that I would make a separate segment where I would describe each of the Filter’s functions. I will be comparing all the other filters with the blue filter as it was the main filter which I have used here. So, let’s get started!

All the filters included with the R1 Zenith

(a) Black Filter

First, let’s start with the black filter. Before starting with the song aspect, I would like to say that this filter introduces driver flex in the R1 Zenith as the filter is not vented to produce more bass. Anyways, upon putting on the IEMs with the black filter and playing an EDM, the first thought that came to my mind was that the bass is humongous with these filters! It felt as if there was an 8-9dB increase in the low-end frequency. But the major downfall of this filter is that it makes the bass a bit loose and boomy which will put off most audio purists away from this filter (and the gold filter as well). But even though the bass is increased in such an exponential rate, it really didn’t affect the mids much although it did push it back a little. Male vocal sounds a bit deeper and female vocal gain a bit of warmth as well. Even the soundstage of the IEMs surprisingly was not compromised with the black filter. Treble is also controlled and sounded a bit laid back with the black filter. But I would say that the separation between the instruments suffer a bit. Overall, it sounds really good with EDMs and pop songs in general but I wouldn’t listen to anything else with these filters on.

(b) Pink Filter

Now with the pink filters on these IEMs, there is no issue of driver flex as the filter is properly vented. Anyways, the bass on these filters is quite a bit less than that in the black filter but comparatively more than the blue filter. Its bass is much more controlled than that of the black filter and is as airy as the blue filter. The amount of sub bass is also increased in the pink filter without sounding boomy like the black filter. The vocals sound a bit thicker in the pink filters which I really like about this filter. The instruments sounded a bit relaxed and laid back with this filter. But the sound stage is as wide as the blue filter as well as the separation between the instruments. Audiophiles who are not satisfied with the bass of the blue filter and wants a relaxed presentation will really like this filter. So overall, this filter sounds really good with any kind of music thrown at it.

(c) Gold Filter

Now coming to the gold filter, the driver flex is back again with this filter. The only thing going for this filter is its bass and nothing else to be honest. The bass here is even bigger than the already huge bass of the black filter. Due to this, the mids suffer as the bass often mixes with the low-mid frequencies and thereby reducing detail and clarity, making it sound somewhat congested. Soundstage also takes a hit with this filter as it becomes more intimate. The vocals sound really lush, thick and intimate with this filter and the treble is somewhat rolled off and pushed back than the other frequencies. This filter is for hardcore bass heads who listen to nothing except for EDMs. So overall, this filter is meant only for listening to EDMs and nothing else will sound very good on it.

(c) Orange Filter

Now finally coming to the last filter in this stack, that is the orange filter, there is no driver flex with this filter as well. This filter provides an overall laid-back presentation of the sound. The bass is light with this filter just like the blue filter but the vocals and instruments sound really relaxed and bit distant here. But there is no reduction in detail at all and the soundstage is just as wide as the blue filter. Also, I felt that the instruments tend to roll off with this filter just like the gold filter to really take out the harshness of edgy instruments. This filter goes really well with jazz music. So overall, this filter will be appreciated by people who wants a laid-back presentation of his music without the bass of pink filter.


You should be able to easily drive them out of a smartphone but to really get the full out of this beast, you should definitely get a nice set of DAP or DAC/Amp. They have an impedance rating of 32Ω and a sensitivity of 108 dB +/- 3dB so you shouldn’t face any difficulty while driving them out of your smartphones even though I wouldn’t recommend doing such injustice to a high end TOTL pair of IEMs like this one.

Technical Specifications

  • Brand: IMR Acoustics
  • Model: R1 Zenith
  • Type: In-Ear Monitors
  • Driver: Hybrid Driver (Piezoelectric Ceramic Driver with a Beryllium diaphragm)
  • Impedance: 32 Ω
  • Headphone sensitivity: 108 dB +/- 3dB (1 kHz/1 Vrms)
  • Frequency range: 14–40000 Hz
  • Plug: 3.5 mm/2.5mm
  • Interface: 2-pin (0.78mm)
  • Cable: Two 1m OFC Cable (One balanced and other unbalanced)
  • Weight: 26 g (including cable) / 6g (for each earpiece)


In conclusion, you are getting a well-built pair of IEMs which looks, feels and sounds simply astounding to say the least. It comes with a ton of accessories to get you started and to top it all off, the filter implementation is the best I have seen in all the filter style IEMs that I have tested in my reviewing period. Like such a drastic change in the overall sound signature of a pair of IEMs is rarely seen, even at this price. But the biggest caveat of these IEMs is its price. At $650, you have far left the budget IEMs and have reached the hi-fi category of IEMs where there is a lot of competition and you simply cannot make an impulse buy as it IS quite an amount to pay and invest for a pair of IEMs. But even at that high price, I can say that the IMR R1 Zenith is worth paying for. The sound quality, soundstage and the separation that it delivers is simply remarkable for a pair of IEMs. Plus, not everybody’s sound signature preference is the same. One person might like a balanced sound signature, another person might like a laid-back presentation and another person might like a lot of bass and that is R1 Zenith’s biggest strength. It is suitable for every kind of listener due to its well implemented filter system and I will easily recommend these IEMs to anyone who have the budget of over $500.

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