[Newschool]

If I have a high output impeadance amp like from my reciever(about 100 ohms), plugging in my cousins 32 ohm dt880's doesnt sound too good.  Now when I plug in my 250 ohm dt990 with his 32 ohm dt880's it seems to degrade the sound of my dt990's compared to having just my 990's plugged in.
 
I always thought that headphones in parrallel didnt effect each other because they were basically seperate circuits.  Is this not true?  Because I could definitely tell that the sq got worse when my cousin plugged in his phones with mine.

 

[wes008]

The 32 Ohm DT 880s wouldn't sound too great because power is being lost from the low impedance load plugged into the high impedance output. Does your receiver have two outputs? If you're just using a splitter or the internal circuity is just set up like a splitter rather than two amp circuits, then when you plug them both in, the two loads are effectively reducing the total power, making your high impedance 990s not sound as good. 

 

[Newschool]

I understand that the power is less because power is lost inside the the amp but how does that effect sound quality? And I'm electrical engineering major so I was kinda looking for a technical response haha

And I'm using a splitter.

 

[wes008]

Quote:

I understand that the power is less because power is lost inside the the amp but how does that effect sound quality? And I'm electrical engineering major so I was kinda looking for a technical response haha

And I'm using a splitter.

Sorry I can't give the technical response 

 Here's a thread that might help: http://www.head-fi.org/t/607282/headphone-amp-impedance-matching-basics-you-need-to-know 
 
As to why the sound quality would be lower, it would be because the driver isn't sufficiently powered. That's why we don't drive our headphones out of our iPods/laptops. Not only is there an impedance mismatch, there just isn't enough voltage or current.