64Audio A4s

Disclaimer:
A4s is personal unit and I bought it for myself.

Background:
My last IEM (before the A4s) is JH Audio JH5. Two BA drivers with also custom-fit. I purchase it around 2015-2016. It was a good pair IEM for me personally. The sound is laid back mid area with smooth treble and enough bass.

After 7 years, I thought it’s time to upgrade. Since I’m in Indonesia, we don’t have any freedom for CIEM brands. Local retailer only have 64audio and local CIEM builder.

Why CIEM?:
Personally, I don’t want to spend big money on common stuffs. I want my things to be as personalized for me. Custom IEM is perfectly matched for me. Also I don’t have any issues when using my JH5.

In the local retailer, I tried U4s (with M12 Apex Module) and I love it. I like the midrange, the enough bass (but bigger and better than my previous JH5) and also the sparkly treble. order A4s and I wait 3+ months to arrived. Spoiler alert: I need to wait 2 months extra to become satisfied.

Review:

Packaging:
The packaging is simpler than the universal version. It only comes with IEM unit itself, a CIEM cable (that different with universal one), M20 Apex module (-20db isolation), candy case from aluminium, silica gel, and IEM cleaner.

Build Quality:
To be honest, I disappointed with the build quality. The resin is so thin, and the IEM itself feels so lightweight. Maybe related with the APEX module so it needs chambers in there (?), I don’t know. But my cheaper JH Audio JH5 feels sturdier than pricier A4s (JH Audio resin is very good and very solid).

Sound:

Bass:
A4s comes with M20 Apex Module that have HUGEEE bass. Sub bass is slamming hard, the body is fat, and also bass decay is very good and very rich, thanks to the dynamic driver. It is not typical fast bass.

Midrange:
It is not the lushest vocal that I have ever tried in IEM. It feels right. It is not laidback, and never sibilance. It just right amount with right intensity.

Treble:
U4s in universal form is very energetic IEM. The treble sparks. A4s is smoother than U4s. It’s not as energetic as in universal form, but still extended.

Upper treble:
I feel in the upper treble is emphasized, maybe because of the tia driver. In the first try, it feels weird. After some times, the upper region feels so open.

Imaging:
One thing that I love with A4s is very good handling complex percussion. Tracks like Polyphia in Remember You Will Die handled very well. I can easily pinpoint any instruments that coming from the drivers.

Summary:
A4s is a good basshead CIEM. But (personally) I feel disappointed. I am not basshead. I do love bass, but not over-bass. AI tried U4s with M12 module and I like it (because the amount of the bass is very appropriate for me personally) and the A4s sounded so bassy.

After I got the A4s, immediately I tried the M12 module. The bass tamed down, midrange and treble more open than before. So I ordered another M12 module, and need to wait 2 months to wait. A4s with M12 is a killer IEM for me personally.

Disclaimer: I was able to enjoy these in-ear monitors as loaners directly from 64Audio. Since the pair I got were loaners they were provided with universal fit shells (seems obvious, no?). There has been ample discussion about the differences in sound between 64Audio universal and custom shells. If you're interested, search out the 64Audio thread.

Introduction: I’ve been a happy listener to 64Audio’s Trio for three years now. I really love their sound. I was surprised when I looked back to find I haven’t posted a review of the Trio yet. I suppose I should correct that. I’ve been poking at 64Audio in their Head-fi forum to produce a Trio with a custom shell. I’d be on-board immediately. They’ve politely ignored me (well, OK, not exactly ignored, they’ve told me, “no” and then refused to continue playing). I was excited to hear about the A4s: four drivers, dynamic-driver bass and tia tweeter. Quite close, at least in driver compliment, to Trio. I asked for a demo pair to see if I’d like them.

This is a bit of a mini-review as I had only one goal: comparing the A4s to Trio. Even so, I can't believe, looking back, I didn't take even one photo!

Packaging: My loaner pair arrived in a plain brown wrapper. Just the new 64Audio aluminum case with the screw-on top.

What’s in the box? Inside were the demo U4s, some Comply foamies, a few different pair of silicone tips, Apex modules and a cleaning brush.

Physicals:

• Head phones: The U4s have 64Audio’s familiar universal shell, very similar to the U12t. Unlike my Trio, the Apex modules are interchangeable. The U4s fit well enough, the sound pipe even seems smaller than those of my Trio. Pretty familiar stuff for those acquainted with 64Audio.
• Cable: The cable seems like 64Audio’s stock black cable. Some folks hate this cable, vocally. I don’t hate it, but I think the cable contributes the least to the overall sound of an IEM. So there.

Fit, Comfort, Isolation: The U4s fit just like my Trio. I initially thought the sound pipes were smaller (turns out: 5.3mm for U4s, 5.3mm for Trio, shoot), so I got excited and tried all kinds of different tips: Comply small (muffled the treble), some of the supplied bullet silicone (didn’t “hold” securely), and my stand-by SpinFit dual flange (also muted the treble, but to a lesser extent than the Comply). I ended up using a pair of bullet silicone, but I can’t for the life of me tell you which brand. I’ll have to post photos and ask… These are the most tip-dependent IEMs I’ve tried. The U4s stayed put and I got a good seal until I had to talk, or chew, or move my head more than once or twice. Of course, why should I care about any of that? The models for sale are custom.

What I Listened to: I would use a pair of A4s for mobile listening, and I like the sound of 64Audio IEMs with my Astell&Kern AK70 Mk II, so that’s what I listened to.

Soundstage: Even though I’m not particularly concerned with soundstage when I listen to head phones, I wish I’d taken more time to evaluate the sound stage of the U4s. But I listened to mostly electric and electronic music: rock and electric jazz/ fusion, so I didn’t get a good sampling of the U4s sound stage capabilities with real instruments in a real space.

First impressions: I didn’t make extensive notes about my first impressions of the U4s. I was actually fairly prepared for what I heard, having had a pair of U4t demo IEMs briefly. The U4s, with its dynamic bass driver, is rounder than the older U4t, and the sound is more coherent, more whole. I think 64Audio have been busy with their cross-over designs. When I had the U4t demo, I remember thinking, “that’s the low driver, oh there’s the tweeter”; it was fairly easy to hear when one driver was rolling off and another picking up. Not so with U4s.

Highs: U4s treble is extended, delicate, and articulate. I think I’ve used the same adjectives I used when I describe Trio treble. However, U4s treble and Trio treble are not the same. The best word I have to describe Trio treble is “sweet”. Some find Trio’s highs tizzy or strident; I do not. Ever. I love Trio treble. U4s treble is drier, more analytic. I might even say “brittle”, but perhaps “brassy” is a better word. A couple of my favorite audition songs are from Stevie Ray Vaughn: “Chitlins Con Carne” and “Riviera Paradise”. The instrumentation in both songs is simple: bass, drums and guitar (OK, “Riviera Paradise” adds a piano). Since there’s really only one instrument in each of the major frequency ranges it’s easy to listen for details, and both songs are pretty well recorded. The cymbals in both are bright and crisply defined. Frequency extension is good: I don’t get the feeling there is air I’m missing. Leading edges are emphasized more than the decay of each note and this gave me the impression Trio had better high frequency detail retrieval. I’m not sure that’s really what’s going on, though. In any event, Trio’s softer top end made the cymbals in these songs softer, yes, but at the same time fuller and more fleshed out. U4s, though, provided more space around each note and made sure you notice cymbals are percussion instruments. Cymbals are kind of a litmus test for me, other high frequency instruments like flutes and violins had the same characteristics as cymbals: more space between notes and a bit dryer through the U4s, fuller and more fleshed out through Trio. I didn’t notice any troublesome sibilance with the U4s.

I can’t help but think U4s treble is similar to the treble I heard from the FiR M4. Pretty high praise, actually. When it came time to scratch the IEM itch I nearly resorted to flipping a coin to choose between Trio and M4. Different sounds, but both satisfying.

I found the U4s treble muffled or muted when I tried foam tips, and even so when I used my SpinFit dual flange but to a lesser extent. I like the treble best with wide-bore bullet shaped tips. Unfortunately, that proved problematic with the bass due to an inconsistent seal.

Mids: Margot Timmins’ voice when singing “I Don’t Get It” from The Cowboy Junkies’ Trinity Sessions was thin and pure and whisper-y. Very intimate. The harmonica was presented up-front with the reverb from the church space clearly audible. Michael Timmins’ guitar was clear and bell-like, uncluttered with reverb or distortion. Emmylou Harris’ voice singing “Deeper Well” from Wrecking Ball is a little more forward of the instruments than I’m used to, a touch less weary and worn sounding. That’s a shame as part of the brilliance of this song to me is how well Mrs. Harris’ voice supports her character’s story. I enjoy the vibraphone solo in Roy Ayers’ “Evolution”. The U4s emphasized the leading transient of each mallet strike, sacrificing somewhat the bloom of each note. Decay was very rapid and that made the solo sound quite fast.

One of the coolest jazz records I’ve heard in the past year is the soundtrack for Ascenseur pour l’echafaud recorded by Miles Davis (OK, he had some help…). Wonderfully noir, Miles’ trumpet manages to sound distant and intimate at the same time, breathy more than biting, plaintive. The U4s does this well. And back to “Chitlins Con Carne” and “Riviera Paradise”: Stevie Ray Vaughn’s guitar was rendered richly and with warmth through both the U4s and Trio. Probably not the same presentation, but both sounded so good I didn’t spend any time picking either presentation apart.

Lows: Sorting out Neal Peart’s kick drums from Geddy Lee’s bass in “Limelight” is mildly difficult: they run together in my Mobile Fidelity edition of Moving Pictures. Bass from the U4s is even enough, and articulate enough, to separate the two fairly well. In addition, the electronic bass notes in “Time” from Pink Floyd’s Dark Side of the Moon are full and enveloping; though a bit dry for me to get that “hug from Mom” feeling I often get when listening to Pink Floyd. Pity, that’s one of my favorite musical experiences.

Can’t discuss 64Audio IEMs and bass without mentioning Apex modules. I spent a lot of time with the M20 modules installed. It took me forever to decide, to my surprise, I didn’t really like the sound with the M20. I found it boomy and disconnected from the rest of the music. It’s not that bass bled into or covered up the midrange, more that it sounded like it was being played back from a different room, and was mismatched in level. I swapped in the M15 modules and the balance was better for almost everything. I missed the head-filling, ear drum rattling bass contained by the M20 modules I enjoy with some of my earthquake tracks (like the Blade Runner: 2049 soundtrack) but it’s a good trade for the improvement in the sound of much of the other music I like. A couple of examples: Dunn’s electric bass in “B Movie Boxcar Blues” (Blues Brothers, A Briefcase Full of Blues) had more personality when I used the M15 than the M20 but less weight. The bass line in Billie Eilish’s “Tough Guy” doesn’t lose anything when I substitute the M15 for the M20 and that’s important: the bass is the most important part of that song to me, that and the rhythm of Billie Eilish’s vocals. Contrast that with “Deeper Well” which loses its menace and some of its grounding compared to the M20. That is a loss to me. Overall, Trio bass suits my taste better. It’s just as deep and powerful as U4s/ M20 bass with all the balance and cohesiveness of U4s/ M15 bass. It’s also lusher and more detailed. Note that some listeners might find that wetness a disadvantage. One of my friends much prefers drier, faster, leaner bass than I do so he can follow what’s going on in the metal he listens to.

Dynamics, transients and articulation: The U4s are articulate. Pizzicato strings, cymbal strikes, drum rolls, the initial pluck of a guitar string are all presented clearly. The Rognir I recently had are faster than the U4s, but that’s not really playing fair, the Rognir have the best transient response of any head phone I’ve heard so far except for my Stax (maybe). The U4s do prioritize the leading edge of notes more than Trio. Perhaps I’m simply accustomed to Trio’s sound, but they have a balance between the attack and decay of notes which pleases me. The U4s emphasis of notes’ leading edges over their decay makes music sound fast and sometimes dry, but it does bring out detail and make the sound stage sound spacious. Hearing the audience chatter and clink their glasses in “Gloria’s Step” from Bill Evans Sunday at the Village Vanguard made it apparent the U4s could provide big bombastic sound as well as small, quiet details.

Comparison: I have another bit of disclaimer. I asked for a demo pair of U4s specifically to see if these could be a replacement for my Trio. I’ve wanted to try custom IEMs, love the sound of my Trio but can’t get them with custom shells. Would the A4s check enough boxes to be a successor to Trio? Since that’s the question I wanted answered, I didn’t do any further comparisons with the U4s while I had them. Only the Trio. For these A/B comparisons I used my Audition Songs playlist. I’ve included impressions gained from the most notable tracks below.

Unlike Trio, U4s does not have “sweet” treble. Some of the best-recorded cymbals I know of are on Doc Powell’s The Doctor. I listened to “All Right Now”. While Trio emphasized the decay of each cymbal strike, the U4s put the initial strike of the stick front and center. Trio had more bloom, U4s had more air.

The piano in “All Right Now” had more life when played through Trio than when I listened to the same song with the U4s. But my goodness, the U4s provided wonderful dynamics, action, and pace. Wonderfully lively and engaging. Female vocals, like Margot Timmins singing “I Don’t Get It” were more up-front in the sound stage when listening to Trio than the U4s. Margot’s voice had a little more dimensionality as well. I made similar notes when listening to Emmylou Harris singing “Deeper Well”. The gravel from the roads her character had traveled was back, making the story more complete. While I was fiddling with tips for the U4s, I was shocked to find Frank Sinatra’s voice robbed of all its chestiness on “One for My Baby” (Sings for Only the Lonely). Once I got the tips sorted out, the lower midrange followed. Here as well, Trio provides more “chest”.

When listening to “All Right Now” from The Doctor, I was frustrated by the level of the electric bass: with both IEMs I wish it was a bit higher in level. That said, U4s bass was drier with perhaps a bit less body. I guess I’ll have to look to other songs to decide which bass presentation I like better. I also had “Sea Wall” from the Blade Runner: 2049 soundtrack on tap. Bass is not shy in this recording, especially not in this track. After “All Right Now” I had to turn the volume down to keep my ear drums intact. U4s bass can be thunderous and head-filling. I like that. Even when the music calms down somewhat after the initial assault (say at 2:30), there is that throbbing undertone of bass. Driver flex? How about ear drum flex? I had to turn the volume up a bit to make “Sea Wall” as thunderous with Trio as with the U4s (104 dB/mW vs. 107 dB/mW). Even so, Trio was less head-filling. Even that thrumming/ throbbing beginning at 2:30 is less pronounced than with the U4s. After a few minutes, though, I got reacquainted with Trio bass, and didn’t miss the U4s thunder. When I switched back, though, I was glad to have it back. Different, but compelling.

Conclusion: The short version of all of this is: U4s treble is more analytical than Trio treble. Both are extended and detailed, but where I find Trio “sweet” I hear U4s as “brassy”. The midrange of Trio has more details. The tonality of both IEMs is very pleasing, but there’s more to hear in Trio’s presentation. In an e-mail from 64Audio I was told Trio has a tia mid-range driver, which surprised me. Both because it’s not mentioned on the 64Audio webpage, and because I thought that was one of the things you got by paying up to get a Fourte. Perhaps a tia midrange explains the differences I hear between the U4s and Trio here. At the bottom, Trio extends lower, but U4s has more bass volume (at least with the M20 module). Articulation and transient response are at a high level with the U4s. It lends a nimbleness, speed and energy to the music. In comparison, Trio is slightly behind here but oddly doesn’t sacrifice detail retrieval while sounding more relaxed and musical at the same time.