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REVIEW: 643ears LOAK

I would like to extend my sincere thanks to Musashi Saita, founder, owner and, as far as I know, sole proprietor of 634ears. His passion for the project is something rare to see in the hobby nowadays, although from what I hear, there’s a vibrant, active DIY audio community in Japan that’s little known in the west. In any case, this review would not have been possible without Musashi’s generosity of spirit, and dedication to his craft.


634EARS (pronounced “rokusan-yon-ears”) in Japanese, is the brainchild of Musashi Saita, a Japanese DIY earphone enthusiast. 634 is the numeric reading of Musashi’s name, so 634EARS is literally ‘Musashi’s ears’. The brand was, until recently, virtually unknown outside of Japan, and even now seems to flying under the radar compared to some of the crowd favourites. 

I first heard about the company through an obscure Head-Fi post about Musashi’s newly-released entry-level single dynamic driver IEM, 9iNE. One thing lead to another, and soon enough I had a two 9iNE versions on hand, along with three versions of the current flagship model, LOAK. 

That’s right, versions. These are not your typical IEMs; each IEM family is based on a similar foundation – in LOAK’s case, an upgraded 10mm dynamic driver encased in a metal cylinder shell – but the IEMs themselves are essentially modular. Some use different metals for the back and front sections, typically stainless steel and/or titanium, and each are made with a different backplate, either an exotic wood variety, a metal compound, or an open grille. 

As such, while the components are similar, the sound and tuning differ between models, sometimes to the point where they’re entirely different-sounding IEMs. This is very much the case with the LOAK models in this review. Moreover, since every IEM is made and tuned by hand, buyers can also select different tuning profiles, with more or less emphasis on bass, midrange or treble. 

This level of modularity is unusual in the hobby, and if nothing else makes 634ears a very interesting and unique project. There are other things that sets it apart too, like real value pricing, attention to detail, and build quality, and I’ll cover all of these on the following pages. But first, let’s discuss the usual tangibles, and we’ll get to the various differences between the models in the sound analysis.   

Packaging and accessories

It’s difficult to say how the retail versions of the 643ears LOAKs are shipped, though anecdotally I’ve seen them arrive in well-made, branded carboard boxes with smaller hard-shelled carry cases that fit both earpieces and their included accessories. 

In my case I received a selection of samples in nondescript bubble wrap packets, but what stood out was a neatly handwritten note from Musashi thanking me for taking the time to test and review his craftwork. I believe he includes personal notes with each of his shipments, and that’s exactly the type of person I believe he is, something that I truly value in this often-impersonal hobby. 

The accessories are spartan; there’s no flash here, only high-quality minimalism. Each set comes with two sets of tips, both silicone, one soft black, the other clear with black cores and slightly more rigid. A cleaning tool is also included. 

The stock cable seems very well made, non-braided with no zero microphonics and a smooth sheathing material, but is sadly 3.5mm by default. I asked for a 4.4mm cable and was supplied with an excellent looking and sounding 8-braid black cable, which is available as an upgrade option on request. 

Unfortunately, neither stock or upgraded balanced cable have pre-moulded ear guides, mainly because LOAK can be worn both downward and over-ear. Since over-ear is my preference, I found both cables a little unwieldly, so would recommend a switch to a cable with ear guides if you intend to wear your LOAKs over ear. 

Continue to design and fit…



Picture of Guy Lerner

Guy Lerner

An avid photographer and writer 'in real life', Guy's passion for music and technology created the perfect storm for his love of portable audio. When he's not playing with the latest and greatest head-fi gear, he prefers to spend time away from the hobby with his two (almost) grown kids and wife in the breathtaking city of Cape Town, and traveling around his native South Africa.


One Response

  1. Brilliant review, Guy. A very beautiful and detailed insight to the LOAK family of 634EARS, and frankly it has made me wonder should I go for an Open model next, as I refrained from getting one in fear of having the bass losing its physicality and outside noise interference.

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