Hey I just got my TRN ST-1 with mic cables. First impression that I got it is comfortable to wear and the looks are not that cheap because it's shiny metallic , isolation is quite great at the price of 14$ I got. So now we are talking about the sound quality and I am owning trn ba5 and trn st 1 :
1. Low : rumble type of bass for bass heads acceptable
2. MID : Vocal is clear at this price surprisingly I was entertained
3. High : it is not as loud as kz zsn pro series , hmmm it is more comfortable to hear , not harsh
To increase the sound quality you can use cables of any since it's hybrid iem , I use KZ Bluetooth module aptx , and it is really good , mid is getting better and bass slightly reduce , and treble raise .