Foreword: The Plus is Massdrop's first fully in-house developed IEM, sporting three BA drivers. This sample was kindly provided by @CEE TEE. Frequency Response Rescaled Impulse CSD THD Impedance response Analysis The 8k resonant peak on the Plus is highly affected by insert depth. It essentially flattens out the closer it is to the reference plane (for reference, most IEMs with the same peak simply have the peak shifted down rather than flattening out). It can be inferred that a deeper insert is optimal for the Plus. (The same characteristics can be seen in Etymotic IEMs) Channel matching is good. No qualms. The Plus follows Etymotic's Diffuse Field tuning but with a 5dBish boost in the bass. In theory, this should make for a more "musical" signature. Being a full BA setup, D3 distortion is expectedly high. In this case, it is slightly higher than the other BA IEMs that I've measured (UERM, Atlantis etc.). D2 distortion is also comparatively higher. Extremely reactive with impedance. Source rolling and matching highly recommended. Incredibly textured and clear notes, too much for my tastes. I'd prefer to smooth it out slightly with higher OI devices, but your mileage may vary. I follow @Hands' opinion of the Plus' timbre; a little thin and almost "crinkly" sounding. Timbre is much better with a better fit, but still leaning more towards thinness in terms of note weight. Great for picking out details, but admittedly not as good for a more "natural" sound a la Andromeda or UE18+. Overall the MD+ is a very technically proficient IEM and works well for reference and critical listening, easily on the level of the ER4 veterans, perhaps higher depending on your uses. A great take on the "slightly fun reference" signature whilst sacrificing none of the performance.