64 Audio Aspire 4 Vs U4s Comparison Review

There’s a new IEM from 64 Audio has been released, and it’s bound to be compared with a ton of other products from their library. I chose to compare the Aspire 4 to the U4s, as it’s the closest upgrade in price. Is the Aspire 4 the most economical option, or is the U4s worth spending more money on?

What You Get

Aspire 4 U4s
  • Carry Case
  • Foam + Silicone Ear Tips
  • IPX Cable
  • Cleaning Tool
  • 1/4″ Adapter
  • Shirt Clip
  • 64 Audio U4s IEM’s
  • 2 pin .78mm to 3.5mm Unbalanced Cable
  • Hard Leather Case
  • 3 Pairs of Silicone Ear Tips
  • 3 Pairs of SpinFit Silicone Ear Tips
  • 3 Pairs of True Fidelity Foam Ear Tips
  • Apex Modules: m20, m15, mX, m12
  • Cable Clip
  • Cleaning Tool
  • Sticker

Look & Feel

The biggest difference these two IEMs have in design is the presence of the APEX modules on the U4s. You get a much plainer look on the Aspire 4 in comparison, which is also a downgrade when it comes to aesthetics. The U4s are more flashy with their aluminum shell finish and faceplate. In terms of fit, the Aspire 4 feels lighter but the seal isn’t as strong as the U4s. Both IEMs are still pretty comfortable to wear though, especially with foam tips.


Both IEMs feature hybrid driver configurations comprised of dynamic and balanced armature units. The main difference between the two is the U4s’ tia driver, which relegates high frequencies. They can both be driven be any headphone output, but the Aspire doesn’t use he same cable as the U4s. It’s a proprietary cable that you can’t upgrade yet.


Both of these IEMs present different types of soundstages. In terms of pure stereo ability, the U4s are superior to the Aspire 4. It’s much wider and communicates more definitive movement from the left and right channels. The advantage of the Aspire 4 is its depth, stacking sound elements in a more holographic stereo environment. It displays sounds with a similar amount of dimension compared to the U4s, but the Aspire’s more enclosed space makes this more apparent. I prefer the way the U4s present their sound due to their better communication of height and height, but the Aspire has more articulate layering, with instruments appearing forward and backward around your head.

Low End

The bass is one of the best features of both of these IEMs. They have different styles of tone that complement their sound signature, especially the U4s which has more customizability with its APEX modules. The Aspire 4 doesn’t have that luxury but still comes across as smooth and detailed. You’re going to get a more accentuated mid-bass with the U4s, but the sub-bass takes more of a backseat no matter which module you have in. The Aspire 4 is more balanced and gives its bass frequencies more even gain. If you prefer warmth though, the U4s will supply that timbre, and the Aspire 4 will sound tighter in comparison.


With the Aspire 4, the mids act as a critical reference to use as monitors, but the U4s come off more naturally than them. It puts more emphasis on notes and overall appears more musical than what the Aspire has to offer. The Aspire 4, despite being mostly flat, has more noticeable dips and peaks than the U4s. This makes the dynamics of the mids a lot more wild on the Aspire 4, but there’s still roominess and detail spread out across its response. I much prefer the delicateness of the midrange with the U4s.


The Aspire 4 and U4s are very similar in how they color the high frequencies. They both feature a similar transparency and sharpness, but the U4s handle it much more elegantly. With the Aspire 4, the highs are very bright and can be a bit peaky compared to the lighter U4s. More texture and flavor are gathered from the U4s, while the Aspire 4 just seems more resonant and clicky.


After this comparison, I much prefer the U4s over the Aspire 4. Even though I appreciate its depth and bass clarity, the Aspire 4 is way more limited in its sonic capabilities compared to the U4s. Its price and professional focus might be what will sell you more on them though, which is completely reasonable. However, I don’t think you can beat 64 Audio’s premium line of IEMs. From its sound to its build, these are still the ideal line of audiophile IEMs, and the Aspire 4 doesn’t exactly fit with them.

The 64 Audio Aspire 4 and U4s are available at Audio46.

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Alex S. is a sound designer and voice-over artist who has worked in film, commercials, and podcasts. He loves horror movies and emo music.