Package
The overall package of the U4s is very nice.
You get a neat round leather box, a set of silicone and foam ear-tips as well as four Apex modules. Namely the M20, M15, MX and the all-new M12 (golden) module. The U4s comes with a standard 3.5mm single ended plug. No, there is no other option available.
Build Quality
When it comes to build quality, I have to admit, that 64 Audio is doing a perfect job. There is not a single spot on these IEMs and the finishing of the shells is just right out masterclass. They sure have come a long way since their first set of universals.
The shells are held in a wonderful matte blue with absolutely no signs of the CNC machine or from the coloring process. They are 100% smooth and exemplary. The face plate has a meteor design of a dark pattern, on top of which their logo sits.
Personally I don’t think anyone could complain about the build quality. I certainly won’t.
The metal shells also can take a beating – not that you should do that, but once I dropped my U4s on a stone floor, and there’s not a single ding in it. And the U4s kept on working as usual.
Sound
For this section I have used my Lotoo PAW Gold Touch, PAW6000, Sony WM-1A (first Gen) as well as my Chord Hugo2 and Hugo TT2. I used the M15 module for most of the time, as it is the U4s’ standard module.
The U4s can be narrowed down to an energetic low end, smooth lower mids and fast and sharp treble. It has good values in terms of technicalities (resolution, layering, staging).
Let’s dig a bit deeper into the U4s’ sound now.
The first thing that struck me was the forward and energetic bass. You can definitely tell this is a dynamic driver pushing the lows here. The physicality and impact is very addictive. Some might find the bass to be overpowering, but then you can just swap out the M15 module for one of the other two with lower isolation values. Problem solved.
The bass has excellent body and weight. If you are listening to a variety of electronic genres you will definitely enjoy the U4s’ impact, speed and thunder. The texture and resolution of the U4s is another section where I found myself amazed when listening.
The U4s reaches deep into sub-bass, but you can easily tell, that the prime focus of the dynamic driver is pointed towards mid and upper bass. This also gives the lower midrange a certain boost, making deep male vocals more visceral and thicker.
However, this is a very sensitive and critical area for other frequencies. With the M15 module installed, the U4s has a slight masking problem, where the rest of the midrange spectrum seems a bit smudged. Again, you can solve that by switching to the M12 or MX module. Especially the M12 is a good choice in my opinion, as you still get great bass, but you push the mids more forward.
Instruments and vocals have a slightly darker sound to it, which also gives them a thicker presence. The U4s oozes of smoothness, where you could easily enjoy heavier and faster tunes. I found myself listening to many rock albums with the U4s, but also gave them proper listening time for Hip Hop or electronic music.
Mids are pushed more back of the scene and take a backseat in comparison to the prominent bass. This also means that the mids are more closed in and that there is not a lot of air around the musicians. The U4s creates a smaller room where depth and width could be better. With the black MX module the U4s creates the widest image, and puts the mids more in front.
Imaging and instrumental separation are two sections that depend strongly on the module. Both of them vary between lower (M20) to higher values (MX). The lesser the isolation, the wider the image and more room between the instruments.
With the M15 loaded U4s instruments have a good cut between them, but they sound closer standing to each other. The MX is your weapon of choice if you want to breathe in a fresh breeze into the stage.
The treble of the U4s is very detailed, sharp and direct. Personally, I am missing a touch of smoothness or silk on the top of the U4s’ frequency spectrum. Some higher notes, especially hard and fast hitting cymbals, can come across as thin. The U4s has a lot of energy in its highs and delivers wide extension into the upper treble.
The part on sound continues on the next page with Comparisons and Final Verdict!
Page 1: 64 Audio, U4s
Page 2: Package, Build Quality, Sound
Page 3: Comparisons, Verdict
