[RaymondLeggs]

Does the felt on the back of the driver effect efficincy. I bought a pair of DJ headphones (doesnt matter which)(they are sort of fashion oriented), but to my surprise, the sound is actually balanced, and there is no boomy bass or recessed mids to be found. they sound nice but on my computer and Portable player they are not very loud. On my receiver they are much louder and more open sounding. there is only one vent hole open on the drivers the rest are covered with felt, I like the headphones, but i expected louder sound, or it could be that its a higher powers way of telling me to turn that racket down! 
 
 
I havent burned them in yet either

 

[cel4145]

The felt may effect frequency response some, but it will not change the driver efficiency to remove it.

A receiver will generally have a good bit more power than a computer or portable device. Get a portable headphone amp

 

[RaymondLeggs]

I found my Fiio E3 last night. it still works probably going to buy another headphone amp in a month or so
 
I think it may be the cups too. they dont provide a good seal, I am going to take some measurements and get another set the same size but with a smaller earhole. the headphones cups are about the same size as the sony MDR500DJ