I decided to make Pair Up section a little different in this review. For every pair of earphones or headphones I compared the sound performance between SP2k and SPK and indicated the volume level in ().
Beyerdynamic T5p 2nd (Tesla, full size, BAL)
SP2k (70) vs SPK (76) – in both pair ups the sound has a balanced sig with a smoother, warmer, more natural tonality. With SP2k the soundstage is wider, bass is tighter and punchier, and I hear a little more clarity in mids/vocals, especially upper mids. Treble is the same. Except for a noticeable difference in soundstage and bass, the rest is just finetuning.
Audio-Technica ATH-R70x (470 ohm, open back, SE)
SP2k (110) vs SPK (115) – in both pair ups the sound has a balanced sig with a more neutral smoother tonality. With SP2k the soundstage expansion is wider, bass is punchier and faster, mids and treble sounds nearly identical in tonality, but overall SP2k has a tighter sound with a blacker background where details popping up faster and with a little more clarity. Again, a lot of this is finetuning, while soundstage and bass difference are more noticeable.
MEZE Empyrean (planar magnetic, BAL)
SP2k (83) vs SPK (90) – in both pair ups the sound has a balanced sig with a more natural organic tonality. With SP2k the soundstage is wider and more holographic, and the bass is faster as well. Not necessary with more punch, but the speed is faster due to faster attack and shorter decay. Also, I noticed more clarity in vocals when paired up with SP2k, which makes SPK sound a bit congested in comparison, especially when it comes to vocals.
VE Zen ZOE (320 ohm, earbuds, BAL)
SP2k (85) vs SPK (90) – balanced signature, and thicker sound with a warm smooth tonality. With SP2k the soundstage is just a little bit wider, while bass and treble are nearly the same as with SPK. The biggest difference here is in mids, where paired up with SP2k I hear ZOE mids/vocals having more clarity and better retrieval of details.
64 Audio U18t (18BA, BAL)
SP2k (51) vs SPK (60) – a balanced signature with a slightly more forward mids presentation, more revealing natural tonality. I do hear soundstage to be wider with SP2k, and also bass being just a little tighter, faster, and more articulate. Also, mids have a little more clarity, and faster and tighter, I can actually hear a blacker background with SP2k. With U18t the difference is more subtle, where SP2k finetunes rather than drastically changes the sound.
64 Audio Fourte Noir (DD/3BA, BAL)
SP2k (55) vs SPK (61) – a balanced signature with a little extra emphasis on lows and overall more natural revealing tonality. The sound difference here is less drastic as well, similar to U18t. The soundstage is wider with SP2k, and the sound is a little tighter, sharper, and I can hear blacker background with SP2k, but it’s a subtle change with a more noticeable difference in soundstage and detail retrieval which are improved with SP2k.
FIR Audio M5 (DD/3BA/ESTAT, BAL)
SP2k (54) vs SPK (61) – a balanced signature with a little extra emphasis on lows, and more natural revealing tonality. The difference here is more noticeable between SP2k where the soundstage is wider, bass is tighter and faster, and retrieval of details and separation of sounds is noticeably better, making pair up with SPK sound more congested in comparison. Especially the difference in mids is quite noticeable.
Campfire Audio Andromeda (5BA, BAL)
SP2k (37) vs SPK (44) – interestingly enough, with SPK the sound sig is leaning more toward being slightly v-shaped, while with SP2k the sounds sig is more balanced where mids/vocals being more forward relative to SPK. Soundstage is a little bit wider with SP2k, and also bass has more rumble and a little faster/tighter with SP2k. Mids/vocals clarify is improved, and I hear blacker background. I was a little surprised here since the difference was more noticeable. Also, a slight waterfall hissing when idling with both DAPs.
Campfire Audio Solaris (DD/3BA, BAL)
SP2k (36) vs SPK (43) – in this comparison with Solaris, both DAPs have a balanced signature with a more vibrant natural revealing tonality. The soundstage width difference is more noticeable here, with SP2k being wider. I also can hear more sub-bass rumble and overall bass being tighter and faster with SP2k, but it’s not a night and day difference. SP2k mids have a slightly more forward mids/vocals and I hear slight improvement in retrieval of details. But overall, the differences are more subtle in this comparison. And also, I can hear waterfall hissing when idling.
Empire Ears Wraith (7BA/4ESTAT, BAL)
SP2k (37) vs SPK (46) – the sound signature here is more balanced with a neutral natural tonality. The difference in soundstage width is quite noticeable with SP2k being wider and more holographic. Also, SP2k has more sub-bass rumble and slightly more punch in mid-bass. Mids have more clarity in SP2k as well, but still the tuning of Wraith calls for a smoother, more natural tonality. Both have a similar slightly rolled of treble. And in both cases, Wraith has a noticeable hissing which you can hear not only when idling but also during lower volume listening.
Empire Ears Legend X (2DD/5BA, BAL)
SP2k (59) vs SPK (67) – in this comparison the sound sig is not exactly the same. While the bass is lifted in both pair ups, the sound sig with SPK is more L-shaped with duller upper mids/treble while with SP2k the sound sig is closer to being balanced with more bass emphasis, more clarity in mids, and a touch more sparkle in treble. The changes in mids/treble with SP2k is most likely due to bass being slightly less overwhelming which gives mids/vocals and treble some room to breathe. No hissing with this pair up.