Mic-In and Speaker option while using headset

Hi,

I have a Sony MDR ZX310AP headset. I would like to use it only as microphone input, for output I'm using a separate speaker.

My PC has a 3.5mm jack hole (one with headset symbol) at the front.

In Realtek Audio Console, when I choose "Headset", it works very well: my voice input is clear, and the sound I hear from Sony headset is clear.

When I choose Mic-In option however: the sound I hear from my separate speaker is very clear, but my voice input is very small, I have to speak really loud for it to pick up my voice.

Is there any options I'm missing ?