I don’t use Android or Samsung phones but it’s possible they have some DSP audio enhancements turned on that you like the sound of? iOS doesn’t really do anything like that.

If the Samsung’s headphone jack has high output impedance, it’ll give the Sennheisers a bit of a bass bump, which many people like. EQ (unfortunately not many options for that on iOS, besides an outboard device like the Qudelix5K) or an impedance adapter between the dongle and headphones can produce the same effect.

Each audio capable device has its own Digital to Analog chip to convert digital audio signals to analog signals that your headphones need. Each DAC chip has its own unique sound signature hence the change in sounds quality

If you wanted to make the sound quality even better, you could consider purchasing a separate DAC for higher quality. As Otherwise-Rope8961 correctly said, different devices have different Digital to Analogue chips, which do affect sound conversion. I’ve tried plugging in my Hifiman Sundara directly into my old Samsung S7, and I got a sound output only in the right ear, weirdly. Probably dust and stuff in the aux in connection.

You might have a low quality lightning to 3.5mm adapter though, and Apple can be quite pesky with sound and outputs. My headphones have just randomly stopped playing when I’ve got them connected to my iPhone 14 even with a DAC.

What are you playing the music out of, apple music, youtube, spotify?

You probably have some audio enhancements on in the background within Android. I noticed the same thing using a passthrough vs using a cheap crappy dac and it was because there were some android audio enhancements checked on by default.