Look at the 2.5mm jack on the headphones.
How many black, or coloured bands or rings does it have on the jack two, or three ?
Now look at the jack end of the audio splitter you bought, how many rings does it have two or three ?
If it goes from three rings to two rings or bands located on the 2.5mm jack end of the headphones and the splitter cable it is why your Audio does not sound right.
If the Siberia headphones plug into the splitter with two female ends on where you fit the jack into it.
Pull the jack out by a small amount so one of the three rings can be seen.
And the audio through the headphone left and right will sound sharper and not faded or washed out like it is distant Helloder.
An don`t forget that if you have the headset set up as the default communications device that you need to configure the output depending on if the headphones are 2.1, 5.1 or 7.1 capable.
Right click on the windows speaker icon at desktop.
Go to playback devices.
Right click on the headphones.
Select configure speakers.
Set to 2.1 stereo head set. or 5.1- 7.1 Surround sound .
Click ok or apply.