Making a volume controller

[Brawler]

I want to create a volume controller to put between my DT880 (250 ohms) and soundblaster Z card. I want this volume controller because right now I have to use windows volume control which I find unhandy. I prefer a volume knob and now I have few steps to control the volume. When I reach 10% volume in windows things are getting pretty loud already.
 
I've been doing some searching and I figured using a stereo potentiometer can be a good option. I can get my hands on an Alps blue velvet potiometer (10kohms) if that does any good.
 
I found this picture:


 But I don't know if this is legit. I mean, is it this easy? You just hook up the left/right/ground channels to the propriate pins and thats it? Don't I need some additional resistors anywhere?
 
Also I'm not sure how this actually works. I figure you put resistance in the lines to reduce volume, but to add just resistance you need only 2 pins per channel on the potentiometer. I read something about the potentiometer in this case being a 'potential divider' but that is going over my head for a bit.
 
 
So basically the questions are;
is the picture legit and can I hook it up like that without frying my soundcard? If its legit, how does it actually work (what are the ground pins doing?)?

 

[MisterX]

Yes, it's that easy
 
https://en.wikipedia.org/wiki/Voltage_divider

 

[NiHaoMike]

You'll want to use a lower resistance potentiometer. If you used 10k, you'll find very little volume over most of the range and a very steep transition to full volume near the top.
 
Additionally, common "log" potentiometers are not very log. You'll do better with a linear potentiometer and a simple trick to make them more log.
http://sound.westhost.com/project01.htm
For your headphones, a 2.2k will do the trick. Like this one:
http://smile.amazon.com/WTH118-Linear-Potentiometer-Shaft-Diameter/dp/B00PZT2X0Q/

 

[Brawler]

Thanks for the replies, the linear/log pot trick with a resistor to short the out and ground lines sounds like a good idea.
About the 10k ohms value, I have used a 1k ohm controller before and it leaves a lot of volume to play with. I also understood that this value is less critical because the potentiometer is a voltage divider and not a simple resistor in the line. Combine this with easy availability of good quality 10k potentiometers I wanted to give this a try.