Review of Acoustune HS1551CU – Dynamic Goodness

Review by our guest reviewer, Rizjan Java Fantillan

The Company

Acoustune is a company based in Japan which started in 2013. One of their goals is to design and manufacture the most dynamic high resolution earphones in the market. Perhaps their best innovation on their iteration of the single dynamic driver is the use of the medical grade material called Myrinx. This allows the driver to produce better resolution as well as improve the staging capability.

The Acoustune HS1551CU




Acoustune truly delivers a very unique unboxing experience. You’ll be greeted by a metal hardcase with the HS1551CU sitting inside a perfectly molded foam to ensure that it’s safe from any bumps or falls. Wrapped around the foam is the MMCX 4 Core Pure Copper Cable while it also comes with a leather pouch. Inside the pouch is a leather, and velcro cable organizer. Lastly, there are 4 types of Eartips in different sizes namely: AET02 (Foam), AET06 (M+), AET07 (S/M/L), AET08 (S/M/L).

Design and Comfort

Judging from its design, the HS1551CU looks like a complicated mechanism emphasized by the bolt in the middle of the IEM. This however, is what Acoustune calls as the damper rod which intends to eliminate the resonance. Despite its complicated design, however, I was surpisingly pleased by how it fits in my ears. It’s not cumbersome on the ears yet it I still had to find that specific angle to get a decent seal. For me, the shallow fit worked well though I can still hear some background noise bleeding in. On the good side, however, it doesn’t have that vacuum feel in my ears which most IEMS have and this allows me to have longer periods of listening.


Acoustune HS1551CU is one of the very unique looking IEMs that I’ve seen. The chamber is made up of 100% Brass and the housing is 100% aluminum, giving it a very tough and industrial looking build. The IEM is a bit weighty when you hold it but in my surprise it doesn’t compromise the comfort. The Stock cables are thick and very high quality not the most flexible but it sure compliments the overall look of the IEM.




The HS1551CU is said to be less bassy than the AL version. But don’t underestimate the Bass of the HS1551CU. I am very much satisfied with how it produces an organic timbre. Decay is not too fast nor too long which suits well to my liking. Sub-bass is presented neatly and not overpowering. However it lacks that rumble that bassheads crave for. What I like about the Lows is that it never bleeds in with the other frequencies, its just very neatly presented, very smooth and weighty giving the HS1551CU that rich-warm signature.


This section is one of the things why I was so surpised when I got to hear the HS1551CU first hand. The tuning of the mids fits well with the low end, the mids are not recessed. Very musical and smooth sounding, vocals really pops out and it is again, neatly presented. Though at some genres it may sound laid back giving it a relaxing and soothing sound signature.


On the Treble side of things, this IEM didn’t fail to amuse me. It has that decent decay over the high frequencies but the decay doesn’t stay long either. It’s not the best but it gets the job done. I can hardly hear any sibilance, which is the thing that puts a nice grin in my face whenever the vocals hit the high notes. Somehow it has that slight airyness to it giving it a nice delicate extension on the upper end. Given a smoothed top end, I found that microdetail retrieval on the HS1551CU takes a backseat.

Soundstage & Separation

Soundstage is where the Acoustune’s Dynamic Driver pops out, the HS1551CU has that wide stage presence which doesn’t sound artificial. Instruments, meanwhile, are placed well giving it a very nice imaging. Separation, however, is not the best but I am amazed on how the HS1551CU puts out a clean presentation with one single driver.




Acoustune HS1551CU has that warm and smooth sound signature that may be perfect for you. It may not have the bass quantity that you’re looking for. But if you’re seeking an IEM that is built like a tank, looks unique, sounds clean across all frequencies and boasts an impressive soundstage, then the Acoustune HS1551CU might be for you.


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