64 Audio A12t

The U12t is considered to be at the pinnacle of IEMs. It has some of the best bass in an IEM I have ever heard, as well as some unique imaging abilities that are almost uncanny in its wide presentation. I had the U12t for about 6 months before buying my A12t. The A12t is advertised to be the custom version of the same IEM featuring the same driver count tuning and technical ability. I was not totally sure what to expect based on unit variation within the community, especially with CIEMs. Many say the tuning is darker while others say the build quality can be iffy at best. Personally, I think half of this is correct and I will delve into that now.

I have had my A12t for about a year now and I think it’s time for a review. I am by no means a professional, but I have learned a lot along the way and believe I can help someone on the edge of going to a CIEM, especially a 64audio.

I have now had 4 CIEMs: Ultimate Ears 4, Ultimate Ears 7, Ultimate Ears Reference Remastered and my trusty A12t. While Ultimate Ears is often recommended for their white glove service and excellent fit, the tone is dry, bleak and uninviting. I surmise this is because each is meant more for working than enjoying. My biggest issue with UE was surprisingly the fit. Using the same impressions, and the same 3d model, I got a different result from UE each time. I required each to be refit at least once and the UERR to be refit 4 times. This made me extremely nervous to dive into another CIEM, but using the same impressions and model 64audio nailed it on the first try!

64audio build quality is excellent. I cannot find any seams in the molding and the shells have no pressure points. I have worn these for over 8 hours with no pain or fatigue. If I had one complaint, the modules can be hard to remove, but I don't think many will module roll. So my first fear has been squashed as the build quality and fit are both stellar despite the rumors I had heard.

Unboxing: The unboxing experience is fairly bland, you get a box, a puck, your IEMs, 3 Apex modules and a rats nest of a cable. This is where the fun begins!


*You may notice my profile pic is all black (I had them reshelled for 2 pin, because IPX cables are both hard to find and mostly not great)*

I typically use the M20 module for a few reasons. The bass is the secret sauce of the IEM and the bass dips with each other module without affecting the treble. This can cause some gnarly sibilance, depending on your HTRF. I am not a cable person so all of my listening was done with a tripowin zonie 16, my Q5k, Quest style M15 or Inspire IHA1 tube amp (don’t recommend this, but I wanted to try out LID)

Let's get down to business. The first thing I noticed was this massive dip in the mid-upper treble region that drove me bonkers. I think it was done intentionally to make it a less fatiguing listen over time, but it wasn’t something I particularly enjoyed. Below are my measurements for the A12t using all Apex modules and one with no apex modules. Figured I’d get a measurement as long as I had the setup going. The setup is basically to wrap the nozzle in blue tack and shove it into a 711c Coupler! Not that the biggest deal in the world, but getting it consistent isn't the easiest. As you can see, the channel matching is excellent, but the dip I noticed is definitely right up front. Below are the images of how I measured them and below that is the results!




































Now we can talk to the nitty gritty. The best part of this IEM hands down is the bass and the imaging. When I wear IEMs, I want isolation and extreme detail retrieval. The A12t is the most detailed IEM I have ever heard, possibly to a fault. Live music can become distracting as the crowd becomes an instrument in the mix. I listen to mostly live music (Grateful Dead, Phish, Dave Matthews Band and old jazz) and this amount of detail can become infuriating on jazz tracks, where a pianist or player moans or does odd vocal cues or ticks while soloing (Keith Jarret, Brad Mehldau, Monty Alexander and Christian McBride all make odd noises while playing that can be picked up with A12t). This can be worse on classical tracks as clicking, bouncing, sheet turning or even emptying the valves can be heard. I think this level of detail is both unnecessary and harmful for my music. On studio tracks, it is a dream to hear a far off clap, chimes or even whistling come in at different volumes to create this wide stage unlike anything I have ever heard. Depending on your music of choice, this could be a real positive. I still haven't figured out how I feel here, but I would definitely believe it is polarizing.

Most IEMs fall within the category of in your head imaging: creating a strong center image with one on the left and one on the right. The A12t seems to work differently. It feels like the main goal is to keep the center image rather weak and then have equally strong left and right images. This creates the very large stage that many talk about. I think soundstage for an IEM is cool, it is not a deal breaker. Soundstage, the projection of a huge wide open area, is really reserved for speakers. The way the stage is presented saved some albums, but also ruined just as many. Some albums are mixed with the vocals leaning one channel. This creates a very odd experience based on the stage the A12t creates. I was so unnerved when I first got them I mistook it for channel imbalance. I did some channel flipping and then used DSP to institute the Jan Meyer crossfeed. This made them feel much more natural. Without the crossfeed, albums like City and Colour's "Little Hell" is unlistenable to me (one of my favorite albums of all time)

Bass: This is the best bass I have heard in an IEM. I played bass throughout high shool and college so I consider myself a bass head. I like it to punch and feel gritty. BA bass memes need not apply as this is the best bass I have heard in an IEM. I am not enough of an expert to tell you what driver type is being used by ear. My ears and listening abilities are average at best, but I do have a lot of experience hearing IEMs and this one is just so special. Stand up bass with bows in classical and jazz creates an emotion. The texture comes through so smooth without interrupting the mix. The strings vibration can be felt where most IEMs turn this into mud. The A12t has such a natural timbre, I almost though I was listening to my HD600s. Something like this is typically reserved for headphones, but 64audio figured it out

Mids: I struggled with the upper mids lower treble, but it’s mostly good. Male vocals come through (mostly) and guitars and most instruments are presented naturally. The ear gain is turned down a bit, but I found myself happy, but I think fixing the dip should be a point that 64audio should aim for as this is just an odd tuning that is very difficult to fix with EQ as it is a large peak and requires multiple filters. Despite the odd tuning, the more relaxed tuning means a less fatiguing session so this can be a pro or a con. Personally, I would rather them be a bit more aggressive, but with EQ they can be made a tad more energetic without destroying other amazing features of the IEM.

Treble: The TIA driver sits right on the tube and creates a very forward treble experience. To my ears I like the mid and upper treble with a big if. I struggle with high treble like cymbals, rides, high hats, flutes or anything sibilant. This creates some oddball situations where one song can be dark and the next song is unbearably sibilant. It’s probably the way the upper treble peaks and dips are hit by my HTRF, but I think the treble is the biggest weak point here. When the song works with the tuning, the texture and air are very natural. Over time it can become fatiguing, especially with cymbals and woodwinds. Female vocals in Kpop or soprano vocalists in Opera are also a struggle as well. I would avoid this IEM if either of these genres are important to you.

If I had to define the tuning I think I would call it U- Shaped? It has beautiful bass recessed mids, but the high treble adds a ton of air. I do not like the amount of air presented, but some people may enjoy it. I EQed this with my graph, measured the IEMs with the applied EQ rinse and repeat until I found a decent target for this IEMs. This leads to my last test

Could I fix the tuning reasonably? My goal: 10 filters, with no more than 8db of gain on any filter. The use of high quality drivers would prevent most distortion, but I need to be able to use this with my Q5k or other gear on the go. I think that it succeeds on a high level to become the best all rounder IEM with a bit of work.

I decided to measure my EQ results to see if it was being applied correctly. For the most part, it is!



I am still working on my target as I love bass extending a bit further into the mids at around 250 hz, but the main dip has been fixed. That dip at 10k is also real after running sine sweeps, but I still need to figure out if I care to fix it.

As I have now tried all of 64audios UIEM lineup and the A12t, I would recommend the A12t if you are ok using DSP and EQ. However, my issues with it may not be an issue for you. The 64audio Nio with the MX module creates my ideal sense of stage, detail and bass, while also clocking in a tad cheaper. The N8 appears to be a Nio in disguise for CIEMs, but I didn't want to risk it. Personally, the pros out weight the cons and I would highly recommend the A12t as the CIEM market under $2000 is slim pickings. The fit is outstanding, the bass is top notch, the customer service impeccable and the quirkiness of this IEM makes it an exciting piece to own that I reach for many time over my other headphones.

Disclaimers:
- My own pair was an original A12t from before they apparently changed their design. It has also been reshelled by a third party. I'm not sure how much the sound has changed, though I have compared it to the U12t, and other people's description of the difference between the two is somewhat similar.
- I have a rather limited selection of genres I listen to regularly: jazz, electronic, some pop, and a crap ton of lofi-hiphop beats to study/chill to (oh baby).
- This is an iem I have spent a lot of time with. I haven't had a chance to own other iems of its caliber for any long length of time and hence cannot make really detailed comparisons.

The 64 Audio A12t is a strange ciem. It's fraternal twin brother, the U12t, is touted as a neutral monitor with excellent resolution. To me, the two are quite different; the A12t is a darker sounding beast with a truly monstrous subbass.

My personal unit pre-reshell


Overall Signature and other features (TLDR)
To my ears, the A12t has deep, well-extended bass, neutral lower mids, slightly thin upper mids, and a slightly dark and relaxed treble. Overall, it has excellent dynamics and clarity. Soundstage is larger than average, depending on your setup (more on this later), with a pitch black background. It is probably best suited to smaller bands like some jazz, rock, and Lofi-hiphop and chill (oh baby).

Bass
The bass response of the A12t is its strongest asset. Both quantity and quality are the best I've ever heard out of a balanced armature setup, easily besting even some dynamic drivers. The extreme subbass extension, combined with the higher isolation offered by the custom format, allows the A12t to do some interesting things with bass. There's a particular quality to acoustic recordings involving bass and subbass, where instruments and voices close to a microphone cause the diaphragm of a microphone to move more quickly as a result of the mechanical movement of air. Even with pop filters, the A12t can pick up on very subtle yet sudden movement of air, producing low level subbass that you feel more than you hear. What results is an intimate presentation of voices and instruments that feels like you are sitting right in front of/beside the singer/performer. (This isn't to say that the A12t is a purely intimate sounding ciem, more on this later)

With balanced armature bass, most people would describe the sound as having little decay and attack that is too fast. They have high detail and an etched texture but lack oomph and juice. Many people prefer a more subwoofer-like bass with dynamic drivers that can "move" more air. The bass that the A12t puts out is something like a halfway house between balanced armature bass timbre and dynamic driver bass timbre. The ported balanced armatures in the A12t, combined with whatever magic 64 Audio has added with tubes and filters, creates a slower decay with decent attack. It has just the right amount of bass detail and texture without sacrificing decay completely.

I think with bass quantities like this, it'd be a sin not to mention bass-filled electronic music. The A12t shines in this department. Bass slams are huge and powerful, sometimes even fatiguing to listen to. Spaces from Yosi Horikawa is glorious to listen to on the A12t, surpassing both headphone and speaker setups I have tried. The sound is so guttural and goes so low that you can feel the power of the bass in your neck.

For some pop tracks, bass is a little more on the edges of the soundstage. Here, the A12t shines as well. Tracks like What's up Danger and Sunflower from the Spider-verse soundtrack have bass swells that feel like waves in the background. The bass sounds properly large without ever being overbearing.

Mids
The mids on the A12t measures relatively neutral. In my experience, the mids on the A12t changes depending on the setup you pair it with, so I'll give give a couple of sources for comparison. I haven't tried/don't own the popular daps of today, namely the Cayin N6ii, Sony WM1A, and the Lotoo Paw 6000, so I can't comment on those sources.

Out of my Hifiman R2R2K Red, the A12t is neutral in the mids with less presence in the upper mids. Here, lower mids and upper mids have great textural detail. Instruments are well defined while lower voices and instruments have a tad more body (due to the bass). Upper voices sound a little less substantial, so in less well-recorded female vocals or songs featuring female vocals with busy track mix (basically anime music and kpop), female voices will sometimes drown out in the mix and sound hollow compared to iems like the Fibae 7, VE Elysium, and perhaps some Harman tuned iems. That isn't to say that the upper-mids are outright bad. With well recorded violins, trumpets, and vocalists like Billie Eilish or IU, the A12t doesn't disappoint. In particular, Billie Eilish's voice still has the right amount of body and density. I think this is the way the A12t should sound in most scenarios, relatively neutral with slightly less forgiving upper mids in terms of body.

Out of a warmer source like the iBasso DX150 (amp8), the A12t sounds warmer and darker. In this case, the A12t male vocals and lower registered instruments are more prominent in the mix. Bass guitars sound big and gritty, and male vocals have more gravity to them. This setup is less versatile compared to the previous setup, but I think can convey more emotion with rock music, R&B, and some jazz. Well recorded female vocals are still good, but I prefer other setups for that.

Treble
My hearing for treble isn't particularly good; I can barely hear past 16khz, though I'm told treble extension past that doesn't really change much of the sound. From what I can hear, the A12t has good extension above 10k but overall is a hair darker than neutral. Based on crinacle's measurements, playing around with equalizers, and listening to iems with different treble peaks, I find that the A12t darkness stems from a dip around 6-9k. The A12t still maintains a treble peak at 5k and a mild peak at 8k, giving it an accurate treble timbre. The dips and peaks give the A12t a smooth yet realistic sounding treble and very good noise control. With a good source, the A12t's background is pitch black; instruments are well delineated in a sea of silence and sound very effortless. The darkness does have its downsides though; cymbals and snare hits don't sound quite correct in my opinion. Compared to my favorite trebles, the VE5 and the Fibae 7, the A12t is definitely darker and more subdued. The VE5 has a prominent and bright treble, but timbraly, the A12t is similar, likely due to the VE5's massive 6k dip. The Fibae 7 has a similarly dark treble from 6-9k but also has a more prominent lower treble, giving it a more forward treble delivery as well. In this case though, the A12t begins to sound significantly less wide and airy by comparison.

My personal unit post-reshell, pictured here with the Hifiman R2R2K Red


Comparisons

I haven't compared all of these iems back to back so they may be inaccurate.

M15 vs M20: With the M15, the A12t tends closer towards neutral. Soundstage is wider, but there is also a hint of a little smearing around the edges of instruments. The M20 is more bass heavy and has a sharper picture overall, but it is more intimate sounding.

Random materials I have stuffed into the M20 module:
Cotton strands: It's a very subtle change, but I think this is the best material for the treble performance. Treble is a tiny hair more prominent.
Earplug foam: Earplug foam increases the isolation and pressurizes the A12t. This loses the comfort of the normal apex modules. It also increases the bass more and gives the A12t tack sharp imaging, but the stage is much more intimate and can be congested with busier tracks.
Comply tips foam: Similar to Earplug foam but to a lesser degree.
Comply tips ear wax protector: Almost no change at all.

U12t: Overall the U12t is more neutral than the darker A12t. Firstly, the treble of the U12t is more prominent, giving it the better apparent detail retrieval. The increased excitement makes the U12t well suited to all genres of music including both older music and modern pop. In terms of bass, the A12t is the clear winner. The improved isolation seals the deal (pun intended) and gives the A12t more body to the bass and lower mids. The U12t should be the better all-rounder of the two, but the A12t has the advantage in smoothness and a more relaxed listening experience, making it better suited to jazz and Lofi-hiphop and chill (oh baby).

A6t (universal demo): Oddly enough, the A6t is also tuned with a more prominent treble at 6-9k. On first listen, the A6t is more exciting sounding with similar subbass performance. I think most people would probably go for the A6t instead of the A12t. However, I think more seasoned listeners would probably choose the A12t; the treble on the A12t makes it more relaxed sounding. It also has superior dynamics and a blacker background, making it more refined and better for long term listening.

N8 (universal demo): The A12t and N8 have similar signatures, though the dynamic driver in the N8 gives it a slower, larger bass. Quantity wise, they are similar, but because the dynamic driver has a much longer decay with less defined attack, the N8 sounds boomier and warmer than the A12t. I think choosing between the two is mostly a matter of preference.

U18t: The U18t and the A12t aren't particularly similar in my opinion. The U18t is a mildly V shaped iem with an exciting sound an large sounding instruments. Details are extremely clear, and it is easy to follow every single thing that happens in the music. It is huge fun to listen to. The A12t has more prominent bass and is less detailed overall. If the A18s is the halfway house between these two iems, I would probably pounce on it immediately if I had the finances.

You can ask for other comparisons, though I probably won't get back to you
I may try to compare with the Z1R, which I heard separately once before.

Sources and cables

Source wise, I think it is probably hard to go wrong with any source above $1k these days. I don't really recommend pairing the A12t with any mid-tier daps though, as I find the usual signatures in that price range to not be particularly suited to this particular iem.

Hifiman R2R2K Red: I'm only gonna write about this dap because it's my only dap of this tier. The R2R2K Red has a neutral sound with prominent and fast subbass. The subbass enhances the A12t's more intimate staging qualities, but the fast lower midrange prevents the subbass from drowning out the stage. Treble is a tad dark with this pairing, but I think it's a worthy match considering how good the bass is here.

ALO Gold 16: This cable really unlocked the A12t for me. I have a review of the cable elsewhere with a more detailed description, but overall, this cable increases the depth of the soundstage and speeds up the bass and lower mids, all while improving the black background of the A12t.

Hansound Agni ii: The Hansound Agni sounds fast, so fast that some music sounds like it's pitch shifted. There is a wall of sound kind of quality to the Agni, but it isn't unpleasant. Music is very exciting to listen to, with a particularly sharp upper mids and treble. Subbass is even faster on this cable than on the Gold 16, giving bass a powerful attack, but taking the A12t's bass timbre closer towards BA bass territory.

OC Studio AuX: Contrasting the Agni, the OC Studio AuX is a slow, bloomy, and warm sounding cable. The AuX makes the A12t sound closer to dynamic driver territory though it is still nowhere near N8 territory. The bloomier subbass may sound initially like a higher quantity of bass, but it's attack and impact are less than the Agni.

OC Studio Montana: A bit of a halfway house between the Agni and the AuX. Nothing much else to be said here, but good detail retrieval and good bass. Meh ergonomics.

EA Cleopatra: The EA Cleopatra gives the A12t melodic and musical yet transparent mids. Details are very there, but the melodies and fundamentals sound with a bell-like clarity. The subbass is more subdued here, with less sub bass. Treble is more refined and natural, with a very wide sounding soundstage.

EA Leonidas ii: Wide soundstage, but it sounds a little too smooth in my opinion. The Cleopatra is a better pairing in this case.

Conclusion
At $2000, the A12t sits in kind of a weird place. It's not the most famous of the 64 Audio lineup, the U12t can be had for the same price, and below its price is the arguably more interesting N8. However, the A12t still carves out a space for itself as a more relaxed darker iem with a big and powerful subbass. As Theodore Roosevelt put it, "speak softly and carry a big stick; and you will go far."