LETSHUOER R-Sonic Passive Filtering Module

A technological breakthrough

LETSHUOER's all-new proprietary technology is designed exclusively to
deliver listening experience that comfortable and natural.


LETSHUOER holds the opinion that excellent sound reproduction must be presented with the dual prerequisites of being non-fatiguing and pleasant, before showcasing even more details and technicalities in sound.

As such, we pursue this path with utmost persistence. Our engineers tirelessly iterate through designs to achieve the apex of this goal, and the result is the LETSHUOER R-Sonic Dynamic Harmonics, a passive filtering module, or PFM.


LETSHUOER R-Sonic PFM was inspired by passive radiator (PR) that is traditionally implemented in speakers.

As illustrated in this diagram, under normal operation of the speaker's passive radiator, it is evident that the PR and the speaker driver are situated in the same sealed space. The internal pressure generated by the speaker's operation pushes the passive radiator to increase the speaker's excursion, thereby enhancing the sense of low-frequency volume (as illustrated in the diagram, speaker A pushes PR B, with arrows indicating the pressure flow direction). Therefore, a prerequisite for using a passive radiator in the speakers is that it needs to share a common sealed enclosure within a closed box.

Please note that PFM is not the same as PR, and do not share the same technical definition and the application is different. LETSHUOER PFM is a reverse of the working principle of passive radiator. It has a vent hole within the IEM acoustic chamber.

LETSHUOER “R-Sonic Dynamic Harmonics” Passive Filtering Module

LETSHUOER R-Sonic PFM utilizes a membrane that acts as a filter that adjust the amount of pressure within the ear canal, which allows for adjustments to the earphone to achieve a more comfortable listening experience, especially during long listening sessions. Below are further elaborations on the R-Sonic technology:

1) R-Sonic is an adjustable module for tuning ear canal pressure.

2) The fundamental operational principle of R-Sonic is the adjustable characteristics of the surroundings of the membrane / passive driver.

In this illustration, LETSHUOER, after incorporating the R-Sonic passive filtering module (PFM), utilized a semi-open enclosure, retaining the exhaust ports of the passive filtering module and the shell, which in turn optimize the ear canal pressure.

R-Sonic Dynamic Harmonics Working Principle

While SPL is stronger, the PFM membrane is activated, pressure is transferred to the chassis of the earphone, and thus reducing the excursion of piston movement of the active driver. As such, listening fatigue is lowered.

This technology reaffirms LETSHUOER's dedication to refining acoustic techniques and prioritizing user experience. We strive to overcome every challenge, developing products that deliver superior sound. We will continue to explore and provide users with a high-quality listening experience.

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