The NT6 PRO packaging box is a small black metal box, and other accessories include a cleaning rod, a cleaning cloth, an instruction manual, and a frequency response chart. The isolation of the NT-6 PRO is better than general custom isolations due to the silicone resin material filler inside, reaching a good level. Before conducting the sound evaluation, I ran my NT-6 PRO for approximately 100 hours. During the evaluation process, I compared it with other customs, including Hidition NT-6, Heir Audio 8.A, JH Audio JH16, Rooth LS8, SpiralEar SE 5-way Reference, ACS T1 Live!, Ultimate Ears In-Ear Reference Monitor (IERM), Starkey SA-43, and Earsonics EM4. Low frequency: The NT6P's low frequency can be described as stunning, with a considerable deep bass extension and lean neutral mid-bass. This reminds me of the NT6 and ER4, especially in the performance of acoustic instruments and some electronic and pop music with heavy bass. The low frequency of the NT6P is not warm, but rather smooth. Compared to the NT6, its low frequency is more prominent and full, but not as heavy as some customs like the 8.A. It sounds relatively lean yet has a good bass extension. It has excellent control, power, and a punchy feeling. Compared to the 5-way, the low frequency of the 6P falls slightly behind in depth and dynamic range. Compared to the JH16, the 6P has more detail in the low end, more precise positioning, and even surpasses the JH16 in terms of speed. In comparison, the JH16's low frequency is warmer, while the 6P's low frequency is more composed. Mid frequency: The mid frequency of the 6P is not as prominent as the high and low frequencies, but the positioning is very accurate. The mid frequency of the 6P is clear, accurate, and has astonishing resolution. Not only does it have a strong sense of overall space, but its separation and localization are also impressive. The 6P does not have the "organic" sound like the 5WAY or T1 LIVE, which gives them a richer and more imposing midrange. Instead, it appears somewhat lean. The midrange of the 6P highlights clarity, accuracy, and high transient response, with powerful analytical capabilities and good musicality.
   High frequency: The 6P is definitely the brightest-sounding IEM I own, without a doubt, while still ensuring extremely high-quality high frequencies. Its high frequency is not like the JH16 and LS8, which give a sense of hitting the ceiling. Its extension is incredibly impressive, at least in my opinion. Unless there are issues in the recording process, the 6P does not have severe sibilance, but it still exists. The extent of the high frequency extension of the 6P makes its sound feel somewhat unnatural to me, but its high quality makes it highly listenable. Overall performance: The 6P has a surprising soundstage, slightly smaller than the SA-43 and on par with the SE 5WAY. It has distinct layers and high instrument separation. Unlike the organic sound of the 5WAY, the 6P presents a large amount of precise information with extremely high transient performance. The sound is not as scattered as the SA-43. The presentation of the soundstage for acoustic instruments may not be as good as the SA-43, but the 6P excels in the performance of electronic instruments. The sound of the 6P is extremely transparent, combined with the high frequency extension, making the overall sound very bright. Perhaps the biggest drawback of the 6P is its tonality, which may sound somewhat unnatural, but as mentioned earlier, it still maintains high listenability. In terms of source matching, compared to the Clip+ (rockboxed), iPhone 4S, RoCooBA, and HF801 (with GAME card), the DX100 is the best choice for the source. This combination effectively showcases the sound characteristics of the 6P and reduces any harshness. The best pairing with an amp is the DX100+627, providing better spatial and layering sense, as well as control. The high frequency part becomes smoother, smoother, and more musical, making it an ideal match.

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