Bass: Contrary to what I was expecting, the bass is actually full and warm. Now this is a pleasant surprise for me as I generally like a warmer bass presentation anyways. Bass notes have good impact and have a certain thickness to it. Despite the thicker note presentation, the bass is still very nicely textured. The level of detail is high and the bass exerts great control, keeping everything tight and in control. There is a nice attack and decay speed, but I find the reverb (persistence of sound in a space after the original sound has been removed) to be lacking for bass and drums. This can cause it to sound not as natural, especially when compared to dynamic driver based earphones that usually have better timbre. The bass can also give off impressions that it is slower than it actually is as a result of the thick and full notes, but it is relatively quick and can handle busy passages with ease. The bass quantity of the HF-2 is close to neutral and is only missing some extension at the very bottom. The lower frequencies can still provide a nice rumble and hit with authority, often making me wonder if the sound is really coming out of a TWFK dual driver configuration. Don't mistaken that statement as if these are a basshead's wet dream come true though, because they are not. I think the HF-2 has just the "right" amount of bass to not offend for being excessive, or disappoint from a lack of bass.
Midrange: The HF-2 has a smooth and liquid presentation that is neither forward nor recessed. The clarity is very good but the HF-2 is not the most transparent in its price range. While I would not call the midrange as analytical, detail retrieval in the midrange is above average and presented in a nonaggressive manner. With the dual drivers, there is no dedicated midrange driver but Starkey did a good job in the overall coherency when transitioning between the bass, mids and highs. As for vocals, they are not recessed but rather quite well balanced with the other frequencies. They are also not thin-sounding and have just a bit of warmth along with a softer note presentation. I do find myself yearning for more edge and bite for certains genres, but that would be my only caveat with the mids.
Treble: The treble region has good extension that is free of sibilance and harshness. It does not have a splashy, hot treble with many spikes, but instead a smooth and non-fatiguing top end. As a result, it does not sound nearly as effortless and endless as treble happy IEMs. Despite this, the treble does not lack energy and like the bass, is inoffensive. The top end is resolving and nicely detailed, resulting in an involving sound. The HF-2's treble does not have enough to please fans of analytical sound signatures, but it is neutral and accurate which helps with the overall realism.
Soundstage / Presentation: In terms of the presentation, the HF-2 is fairly neutral sounding and a very balanced in-ear. There is a very slight elevation in the bass and it does add some warmth, but the HF-2 stays true to the recording. The soundstage is just average, with good depth and okay width, but for the most part stays concentrated in the center. It doesn't sound as airy as the competition, but it does have accurate positioning.