Are you sure? 
This was definitely intriguing. I definitely hear a difference between my iPad Pro and Oppo HA2se (both 1 Vrms, though latter puts at 30mW into 300 ohm). Bass is noticeably less prominent and treble thinner with the former. I'm surprised as I always was of the belief that amp-ing was primarily for loudness. Kudos to baskingshark for emphasizing how a big of a difference amp made. It really makes these come alive.I keep forgetting to ask did we ever get a final confirmation on the correct specs for ST-10S Black-Gold? I am very curious about this.
I remember there was quite a confusing period there where the advertised specs were saying either 120Ω or 150Ω and then if I recall correctly @DBaldock9 after testing discovered that his pair had an impedance of 300Ω or higher. I too have seriously questioned and doubt the given 150Ω impedance and 110 dB/mW sensitivity rating and do believe that mine are closer to 300Ω with a sensitivity maybe in the mid to high 90s only.
If they are indeed 150Ω / 110 dB/mW it doesn't explain at all why they sound better (less anemic) when amp'd as 110 dB SPL can be easily reached with only 0.39 volts; a current of only 2.58 mA; and require power of only 1 mW which is available from nearly all mobile sources that I can think of.
But if the impedance is indeed much higher and the sensitivity much lower this would then explain the need for them to be amp'd... I created this scenario as follows:
It's a bit strange. First of all these buds are assembled from DIY parts that can be found in few stores on Ali. This version of OPENHEART is exactly the same as this DIY bud on CKLewis Audio Store. They make a typo for sensitivity. It's 105dB and not 99dB.
@buzzyman Thank you for sharing that. I have a feeling that there may have been a huge variance with driver impedance on the initial run as I finally found @DBaldock9 's post stating that his were testing @ 300 ohms. Do you have any thoughts regarding the sensitivity rating being much lower than the stated 110 dB/mW? Cheers.
It seems to me that the sensitivity of my 150 ohms drivers is slightly lower than 110 db. Because I listen to them on a portable dac Topping nx4 dsd using hi gain. I think the sensitivity is closer to 96 db / mw.
Yep, new. Looks like BGVP DX5
I intentionally left those 2 first questions out as I wanted to receive every possible recommendation. But I forgot about drivability - I prefer those that can be driven by a phone. Thanks.
