Stock
The stock Letshuoer S12 iem is bass light, and thin with an upward tilting frequency response and exaggerated treble. But beyond this, I heard great potential in the driver in its timbre, transient response and resolution.

The Mod
I deconstruct the driver of the S-12 and put in place a whole new damping scheme based on my years of experience modifying full size planar magnetic headphones. These modifications change the way the diaphragm moves, the resonance characteristics, the frequency response and thus changes every aspect of the sound including resolution, openness, transparency, speed, dynamics and tonality. After countless experiments and prototypes I have come up with a modification that completely transforms them from stock and makes them near perfect iems.

The Sound
The result is an absolutely neutral iem, no bumps or peaks from bass to treble. They have endless extension on both ends of the spectrum, tight, thunderous, punchy, layered bass, a gorgeous, upfront vocal range that is never recessed but also never forward or harsh, and clear, airy, peak free treble.

They have extremely fast transients and great resolving ability unlike any iem I have heard. My modified acoustic environment and new driver damping not only fixes the frequency response but also allows the diaphragm to move more freely and faster which gives them more air, openness, resolves more detail and allows the driver more excursion for much better bass response than stock which confines the driver into a higher pressure more closed enclosure.

Accessories
All of my modded iems include a beautiful sounding OCC copper cable with great ergonomics and flexibility in either 3.5mm or 4.4mm connection, a set of 3 kinds of premium tips - a full set of every size of Azla Crystal tips, some flexible silicone wide bore tips, and the best foam tips I have found which sound identical to the Azla tips to me (a first, usually foam tips are highly congested), and your choice between 2 premium leather iem cases (see pictures).

Gear Synergy
My RD-m12 scales really well but also sound great out of an iPod. But the better amp and DAC you put behind them the better they will sound up to the best amps and DACs on the market. They are capable of sounding like TOTL headphones only held back by the form factor of being in your ears. In my system, they are great out of an iPod even with compressed music, better out of my Yggdrasil and Pietus Maxiumus, and even better out of quiet desktop tube amps like the Eddie Current Aficianado, Studio B, Aegis, Drop TA-84 and more. Out of these amps they sound like TOTL full size orthos inside your ears.

The only area where I feel other iems can be better is in soundstage size, where some BA iems have bigger soundstage but at the cost of coherency, correct timbre, and resolution.