Bass (8.75/10): During my initial audition with the IER-M9, my expectations regarding the lower frequencies were not set very high – the M9, after all, sports solely Balanced Armature drivers which are often not considered optimal for the reproduction of bass notes compared to traditional Dynamic Drivers. Upon firing up my usual test tracks, however, it was quickly apparent that I had underestimated these little monitors.

The texture, decay and weight of the bass produced by the M9 is eerily similar to that of a DD, high praise for Sony’s in-house made balanced armature drivers. A general weakness of BA Bass is its propensity to sound thin and artificial, but the M9 reveals none of that. The slight bass boost in both the sub and midbass regions raises the “fun” factor, while still exercising excellent restraint. Bass is always exceptionally clean, tight and agile, highlighted by demanding drum-heavy tracks like Muse’s “Neutron Star Collision”.

Sub-bass extension is also fantastic, reaching all the way down to the lowest registers, considerably unique also in its ability to make it “felt” rather than “heard” compared to other BA setups. The rumble did, however, leave more to be desired, lacking the grunt and texture the Z1R can bring. All in all however, it’s stellar bass from the M9.

Midrange (9/10): One of the more frequently levied criticisms of the M9 is that it can sound “boring”, and this sentiment likely stems from the M9’s midrange presentation. It’s without significant peaks, neutral sounding and just ever slightly recessed in terms of stage presentation. The amalgamation of these factors ultimately contributes to bringing about the aforementioned impression many get with the M9.

The midrange however is still very much excellent, with the former mostly an issue regarding personal preferences. I do find myself clamouring for greater midrange presence at times, but objectively, the midrange of the M9 is supremely capable. It boasts fantastic clarity and detail, though perhaps just a fraction behind resolution kings like the 64Audio U12t or the Anole VX, given its greater emphasis on smoothness ahead of transparency, due to the slight touch of analogue warmth present.

Male vocals are some of the best I’ve heard on M9, perfectly conveying the velvety, rich texture of vocals such as Frank Sinatra’s and Andrea Bocelli’s like few monitors on the market can. While their female counterparts do still sound airy and natural, the M9 lacks the sparkle and brightness in the upper midrange register to really make singers like Adele stand out.