64 Audio U4-SE

On a “budget” and still sounds great!

PROS: nice bass impact, balanced tuning, great retrieval of details, original shell design compatible with apex modules, custom storage case.

CONS: more eartips wouldn’t hurt.

The product was provided to me free of charge for the review purpose in exchange for my honest opinion.

Manufacturer website: 64 Audio, On Summer Clearance Sale – HERE.


Feel free to call me spoiled, but it’s not easy to go back to the “lower end” IEMs after being exposed to different flagships. A lot of work goes into the design and the development of flagship models where manufacturers are trying to set the new high bar. Though, sometimes stepping down in driver count of lower model doesn’t necessary mean a water-down design but rather a different signature with some performance compromises. For example, when I reviewed U12, my readers asked me about U6 which many consider to be a scaled down version of U12. Not everybody can afford the flagship, thus a lower driver count model could be a nice alternative. Similarly, U8 is known for its powerful bass impact which you can still get in a scaled down and more affordable U4 version.

The fascination with bass impact has been slowly spreading across audiophile community, and I’m sure 64 Audio received a lot of feedback about it. As a result, they came out with a Special Edition U4-SE model, retuned to give the new audiophile flavor to an old basshead classic. When I received U4-SE, the original intent was to take a listen, provide feedback, and maybe write a short impression, but a few paragraphs I started with turned into a full review. I actually learned this Special Edition version laid down some ground work for 64 Audio U18/Fourte flagships. Despite U4 four-driver arrangement, it shares some drivers with the current TIA flagships, including how Apex bore blends with the sound at the back of the stem, resulting in Apex module being even closer to the speaker while relieving the air pressure and fine-tuning the sound.

Of course, you have to be realistic, no manufacturer is going to create a giant-killer lower-end model to compete and to challenge their own flagships, but 64 Audio certainly did create a Special Edition model at a more affordable price (relative to their other higher end models) and with a very impressive sound performance I would like to discuss here in my review.


The unboxing experience of U4-SE is common with other 64 Audio A/U models, from 2 to 12 driver ones. The packaging box itself is very compact – a dead giveaway that you are dealing with a custom case and not a typical Pelican case. The cover of the packaging sleeve features a company logo with a picture of monitors corresponding to either Universal or Custom shell design. With an outer sleeve off, you will see a cover flap with a picture of a performer and “hear everything” printed underneath, very appropriate for this Special Edition model since it has great retrieval of details. Once you lift the cover flap up, on the other side of it you will find a Quick Start Guide with info about headphone listening safety, volume advisory, and pointers about putting these monitors in your ears – all useful info, especially for beginners.

Also, inside you will find a custom travel case, 64 Audio stickers, and a plastic bag with eartips. Overall, a very compact packaging, unlike U18/Fourte which intentionally had a large packaging box with enough room to list all the special design features of those latest 64 Audio flagships.


Since this is a universal version, it arrived with a handful of eartips. Here you will find a genuine Comply set with 3 pairs (S/M/L) of foam eartips, and a pair of double-flange silicone tips. Choosing the right eartip is a matter of a personal preference which going to affect not only the fit and the comfort, but also the sound. As I mentioned in all my previous 64 Audio reviews, I usually don’t find the included tips to work well with my ears, and I end up using a pair from my private stash. I do wish 64 Audio would include a better selection of eartips, maybe another set with hybrid tips that have a firmer cap and a longer stem.

Other included accessories were a custom storage case which I’m going to talk about next, and 64 Audio round stickers. Inside the storage case you will find a small dehumidifier, cleaning tool, and a shirt clip.

The storage case.

In all my previous 64 Audio reviews, I called their new case a “VIP case”. Everything from an easy to handle wide latch and air valve eliminating build-up of inner case pressure when you close it, to individual earpiece storage sections with a removable rubber lining and a custom built-in cable winder, a spot to plug right angled headphone connector and to place the included round dehumidifier container, as well as a built in organizer to hold securely a shirt clip (included), a cleaning tool (included), and 2 sets of Apex modules (M20 included) – all this was custom tailored and well thought of. There is even enough room if you decide to use a thicker replacement cable.

When you place the order, you can also specify if you want your name to be etched on the top of the storage box to personalize it. While many companies use off-the-shelf Pelican or Otterbox storage cases with a pre-cut foam inserts, 64 Audio went one step further with their own custom designed case which protects your investment and keeps everything organized inside. It also great to know that regardless of 64 Audio model, 2 driver or 18 drivers, you are still getting this custom storage case with every order.


While U18/Fourte flagship now feature 64 Audio new SPL cable, U2-U12 models still come bundled with their original OFC cable, but it’s an updated version which has a more durable 2pin connector housing and a softer cable sleeve.

As far as the cable goes, it feels durable and still flexible without springy memory effect. It has 4 separate conductors, braided from the connector to y-splitter, a tight rubbery black shielding, and no microphonics effect. The headphones plug is a right-angled 3.5mm TRS gold plated connector. The y-splitter is a common heat-shrink tube, nothing fancy, and the chin-slider is a clear short tube piece with enough friction to keep it from sliding freely. After the y-splitter, cables are twisted, and toward the earpiece connector have a memory wire which you pre-shape for comfort. I’m not a big fan of memory wires, but this one works fine, keeping the fit secure. The 2pin connector is universal which can be used in both surface and recessed 2pin shell sockets, and it’s conveniently color-coded with a Red dot for the Right side and a Blue dot for the Left side which you have to make sure to attach with both dots pointing the same way to avoid phasing effect.

Aftermarket cables.

Though I have tried different aftermarket cables with U4-SE, I ended up coming back to the original OFC because U4-SE tuning has a little peak around 9k, and most of the SPC, Silver, Copper, and other exotic cables seems to add a little more brightness and air to the treble, making the sound a little piercing to my ears. With OFC cable, you still get a well-defined bass, but upper mids and treble have a bit smoother tonality, just enough to take an edge off the treble. This is a purely subjective opinion because I’m sensitive to high frequencies. But feel free to experiment with other cables if you want to push the retrieval of details and the resolution further.

Out of the box, I actually preferred 64 Audio new SPC cable, but after 24 hours of burn in, I reverted back to the original OFC cable. I know some people don’t believe in burn in, even with dynamic drivers, but I’m describing what I hear. You have to take into consideration that crossover components and solder joints can go through a very small change which could have a subtle effect on FR, just enough to be noticed.


U4-SE Special Edition comes only in universal-fit design, using hypoallergenic acrylic shells in translucent charcoal color. I will talk more about modules later, where M20 Apex module was included by default. Inside this very compact shell, you have 4 balanced armature drivers, which include 2 low, 1 mid, 1 high, and a large vent cavity to accommodate the Apex modules. With this 3-way partitioning, you also have a corresponding 3-way passive crossover.

Unlike the original 4-bore U4 design (one bore per each driver group and Apex module), here you have a new 2 bore design with 2 visible sound tubes. As I mentioned in my Intro, U4-SE shares some drivers with the TIA flagships, and Apex bore blends with the sound at the back of the stem. The Apex module shares the same bore as low and mid drivers, while the high drivers use an independent sound bore. Because most of the air pressure is created by the low drivers, this setup allows the Apex module to vent the air pressure before it even enters the ear canal. Of course, both U18 and TIA Fourte flagships are based on tubeless design, using sound chambers to blend the sound.

The shell itself is compact, doesn’t stick out of my ears too much, though don’t expect to put your head with your ear down on the pillow while wearing U4-SE. You also get access to easy removal and replacement of Apex module, and my favorite – long enough nozzle for a comfortable fit, depending on the eartip selection. The nozzle has a thicker part in the middle which keeps eartips from sliding off when removing the shell from your ears. The faceplate is flat and comes with a default 64 Audio logo print. The inner part of the shell has rounded edges and sits comfortably inside the ear. The overall size of the shell is on par with U6, maybe even a touch smaller.

The fit.


Page 2: Sound analysis, Pair up, Comparison, and Conclusion.

35 thoughts on “64 Audio U4-SE

    1. I never heard the original u4, but others mentioned it has a rather basshead oriented tuning – more emphasis on low end and rolled off upper frequencies. Again, never heard these so can’t say for sure, but sounds like a different tuning in comparison to SE version.


  1. My question is not directly related to U4SE. I saw you mentioned UM Pro 50. Can you please briefly compare UM Pro 50 to iBasso IT03? Are they similar or completely different in sound signature? I own UM Pro 50 (upgraded from UM3X) and planning to get iBasso DX200 soon. What, in your opinion, would be a step up from UM Pro 50 to pair with iBasso DX200, considering that I like UM Pro 50 signature? Thank you!


    1. Something like it03 or u4se will be a side grade rather than upgrade from umpro50. Westone has this unique signature where the sound is less aggressive, more laid back. Going to it03 will make sound more v-shaped, where stepping up to u4se will be an upgrade from it03. U6 has a similar less aggressive tonality, but going from umpro50 to u6 will mean sacrificing bass and smoothing out top end. Look into mine w80 review, in my comparison between w60, w80,es60, umpro50 – it can give you a good idea of how these Westone iems stack up against each other. Also, keep in mind, it04 is around the corner.

      Liked by 1 person

    1. I have been told it could go on sale toward the end of this week. This is a limited special edition. They don’t sell it regularly. Yeah, curious how it04 will sound as well.


  2. I purchased these recently as B-stock, right before the summer sale (doh!). Although sometimes the bass is strong, with most music I can’t hear it very well. Sometimes certain notes seem to be quieter than others to the point of not being able to discern the pitch of the note or that there’s a note played at all. This is compared with any other headphones I own (Q701, ATH-M50, ATH-IM70, MDR-7506). I prefer to listen on any of these, due to oI don’t have extensive experience with any other higher-end IEMs. Based on your experience, does this sound like an issue with the tips and the fit in my ear, a RMA issue or just a mismatched expectation for what IEMs can do? Most friends who have listened to these, though not all, have complained about bass response. Unfortunately I can’t return them in any case, as I purchased B-stock.

    Thanks much


    1. I think it’s a combination of both, perhaps not a good match with a current set of eartips where you are not getting a good seal, and also a different expectation and sound preference where you comparing it to heavier bass full size headphones. The original U4 as well as higher end U8 are for basshead lover, that’s probably where you threshold of bass preference is. U4-SE is a totally different beast, re-tuned and redesigned for audiophiles, different grouping of drivers going to the nozzle bores, different tuning, etc. These are going to be bass-light and intentionally tuned for that purpose because audiophiles want a more balanced sound. For me personally, they have plenty of bass, but it will vary from person to person, due to our sound preference. The supplied eartips are not that great, you need something firmer.


  3. Trying to decide between these or CA Lyra II. Both used. This being a bit cheaper. Used with Opus #1. Current top IEM is the AKG N40. Haven’t heard a BA only IEM.

    I like a present top end but am sensitive to sibilance and too much in your face treble


    1. Sorry, not familiar with Lyra II or N40. U4-SE shouldn’t have too much “in-your-face” upper mids/lower treble. It’s not exactly laidback/smooth, but I don’t consider it to be fatigue.


  4. Thanks for this review man
    I’ve searching for a good mid-tier IEM for my AK70 (very difficult to match DAP) , i tried the Dunu DN-2002 wich are very good match, but are very uncomfortable too…
    i sell my Westone W40 because his laid back signature does not match with the warm coloration of the AK70
    Then i read this review, and i want to try the apex modules in a mid-tier iem without lose too much money…
    Well i don’t lose my money, this IEMs have all the advantages of the W40s, same retrieval of details, a bit more bass tuned and less laid back signature, very balanced IEMs perfect for warm sources, very comfortable to wear and don’t cause fatigue…
    Very good review, this IEMs are exactly as you described it


  5. Nice review. Interesting because of the massdrop 😉
    how would you compare the u4-se with the flc8 or custom art ei.xxx ?


    1. well, FLC8 gives you a lot of flexibility to fine tune the sound because of all the filters, but it can’t match the impact and articulation of U4-SE bass, and also FLC8 doesn’t have the same level of transparency and detail retrieval… Ei.xx is ok, but too smooth and laidback in comparison, not anywhere close when it comes t layering/separaiton/transparency and detail retrieval of U4-SE. It has been awhile since a sub $1k iem impressed me that much, though I also like IT03 3way hybrid, but when it’s paired up with their CB13 cable, which both cost as much as U4-SE.


  6. Nice review. Trying to decide between the u6 and u8
    My current iem is um pro 50,and I love rock n’ roll so I prefer bass.
    But I kinda feel like pro50 sound really thick ,warm and the bass just overpower the mid and high.
    Ive demoed the A3 once only remember is clear and tight.
    Looking for smooth, neutral, clear , detail, fast and crisp bass sound.
    Need some advices ty.


    1. U6 might be too neutral for your taste. I didn’t hear U8 but it’s considered to be the basshead of the family 🙂 It probably will satisfy your bass needs but I’m not sure if it will overpower mids/highs. U4SE will give you a good doze of bass and crisp mids/treble for the guitar crunch. I have umpro50 and u6, but personally will choose u4se over them.


      1. Thanks dude. after I demoed some high end IEMs
        I prolly will get U12 over s-em9,Andromeda,JH13,Katana
        Should I get the old ADEL model or the new APEX?
        The 64 Audio ADEL model is on sale on my local store.


  7. Great review! Of particular interest is your comparison between the U4SE and U6. I listen to mostly indie rock with predominantly male vocals and prefer a fuller vocal rather than one that can be described as thin or noticeably recessed in the mix. Could you please elaborate on your statement “U6 lower mids are warmer and with a little more body, while U4-SE lower mids are leaner and cleaner”? If I am not mistaken, male vocals typically fall within the lower mids so I am slightly concerned about the U4SE’s presentation in this area. I typically listen at lower volumes as well, so don’t want to find myself listening too loud to bring the vocals up. I am just trying to determine if the extra cost for U6 is warranted. Thanks for your time!


    1. Based on your requirements with emphasis on vocals, i do believe you will benefit more from U6 tuning. U4SE is for more revealing, maybe even closer to analytical audiophile listening, for sure the sound is crisper and more revealing when compared to U6. Especially for a fuller vocal range, U6 will suite you better.


      1. Thanks for the quick response! Your thoughts confirmed my suspicions. What do you make of the impedance adapter talk regarding the U6 and U12’s? I read that a 20 ohm or even 75 ohm adapter is needed for the U6 to sound its best due to it being mixed for pro audio use? I’ve also heard that these adapters actually degrade the sound quality? I’m a bit confused about this and honestly one of the reasons why I was thinking about just getting the U4SE.

        I forgot to mention I am also sensitive to peaky treble and sibilance. I assume the U6 would be better as far as that goes and be less fatiguing?

        Thanks so much!


      2. Yes, U6 will be less fatigue. With U6, according to 64 Audio rep in head-fi thread, those were tuned for performing musicians who use wireless packs that have higher output impedance. U4-SE was tuned for a typical DAP/smartphone application with a lower output impedance, the same as their flagship U18/Fourte. Don’t use impedance adapters, instead try it with UE Buffer Jack (only $10), imho works better 😉


  8. Thanks! I think I’ve decided on the U6. However, I was planning to use them balanced and can’t seem to find anyone selling a buffer jack or impedance adapter for use with 2.5 mm balanced cables. So it looks like my options are to run single ended with the buffer jack OR go balanced and live with the lower output impedance of my xdp-300r. I could even run balanced and apply a bit of EQ to boost the upper mids slightly as recommended by Brooko. Have you tried any of the 64 Audio iem’s balanced?


    1. I use U18 and TIA Fourte balanced only because those are resolving iems that benefit from high end sources that have balanced outputs with a black background. Don’t think U6 will benefit from balanced of 300r, cause i was under impression these onkyo/pioneer daps only boost the power in balanced, not the actual audio performance. Either way, don’t get too overwhelmed with bal vs se. Since i assume you have 2.5mm terminated 2pin, just try it to see if you even hear any difference. Listen to your ears 😉


      1. Listen to my ears… why didn’t I think of that! I’ll just wait and see how I like them first and go from there. Thanks again for your insight!


    1. They are on a thinner side, but still build tough. Plus, if anything, 64audio will replace it under warranty. If you are on a budget, you can get pure copper cable from Penon, check out my review from a month or two ago. Effect Audio makes very good cables, but pure copper will run you $150. Still a bargain in comparison to some of the $1.5k-$2k cables i’m using lol!


  9. Hi, I have U4SE in my possesion and I’m in the market for Android DAP. I’m new to this DAP thing with my most recent experience is with fiio X3iii. Do you think HiBy R6 will be a good match to U4SE? I’m a little bit worry of the high OI of R6, maybe you can test them out? I also consider Cayin N5ii if R6 just alters the sound signature of U4SE too much.
    Also I’m thinking about purchasing Focal Clear soon so I need a DAP that can handle both U4SE and Clear.
    Thank you for your thought.


    1. I haven’t ried U4SE with R6, but I’m pretty sure it will change the sound, but not a problem if you use iEMatch from iFi, it will “restore” it back. Are you in a market for Android dap to run apps and streaming and bluetooth headphones? If you want the best Android experience, get R6 with iEMatch impedance adapter. Otherwise, if you want a good audio “budget” player and just occassional streaming (like Spotify or Tidal) N5ii is really good actually. In theory N5ii and R6 sound very close, just with multi-BAs that use crossover, you will need iEMatch or Earbuddy from iFi when using R6. Focal Clear should sound the same with both N5ii and R6… Btw, I will be working on N5ii review next and then R6.


      1. cool. could you please use U4SE or other multi-BAs IEMs in your R6 review later so we can see how big the impact? looking forward to read your review! *and then I’ll decide


      2. output impedance of R6 has zero effect on U4SE, it sounds identical with and without iEMatch. U4SE was tuned and designed for higher impedance output sources.


      3. thank you! I’m glad to hear that U4SE sound is not changed by R6 despite having impedance as low as 12 ohm. now I can back the R6 campaign with confidence.


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