Basically what you're talking about is adding more absorption/damping to the cups, it's called the markl mod now. You can even pay markl (Lawton Audio) to do it for you. Basically put dynamat on the inside of the cups and back of the driver housing and add some polyfil in place of the fibreglass pad they include.
Open-back D2000s are something I have more experience with, personally (I was doing it before it was cool
), and it changes the sound pretty dramatically. You lose some bottom-end impact, but retain the top-end harshness. They're less boomy, but that's about it. It's not bad, but it's not the same as a designed open-back headphone (like say, the K701). General thinking is that with most headphones they're designed a certain way for a reason, and trying to change them is probably not going to result in a good product unless you've got measurement equipment to set-out with. Of course you can just tinker around and if you like the result's thats great, but usually the tinkering doesn't produce instantly good results.
Regarding the whole reflected sound inside the cups, this will probably be interesting to you:
http://www.silcom.com/~aludwig/Loudspeaker_construction.html
Same principles apply for sealed/closed headphones.
With a sealed headphone the goal is not to "kill" the cups entirely, it's to use the sealed enclosure for acoustic effect and "kill" resonance. If you had more information about the drivers you could model them and sim the enclosure to figure out Q; perfect-world is .707, my guess is that most (modern and consumer-oriented) closed headphones run somewhere closer to .850 or higher. Means more mid-bass (which sells) at the cost of absolute extension (.707 will get you the flattest response possible for a given driver). Also keep Hoffman's Iron Law in mind here.
Anechoic chambers are used for a variety of research purposes - like measuring what a speaker driver sounds like "out in a field" (but without environmental noise). They're very eerie to stand in and make a lot of noise. You would not want one for your stereo listening. What you would want, instead, is a properly trapped-and-treated and reflection-controlled room. Look at a cinema or concert hall as an example; reflected sound is controlled and low frequencies are managed. You get a room that has a fairly flat FR, and lets whatever you're playing back handle its business (be it a piano, a singer, or PA loudspeakers). Sound still bounces around, but it isn't completely random. This means less filtering. This means better sound. This is entirely relative to the polar dispersion of your speakers - for example a parabolic speaker (which would be VERY directional) will behave much differently than an omni-radial speaker (which is completely non-directional and emits equal amplitude and phase sound in a 360* pattern). Even in the same room.
With headphones though, there is no room to contend with. There's only the coupling with your head. And you really can't change the shape of your head. The most you can do is screw with the earpads and headband to change how the headphones sit and seal (and maybe cut your hair out of the way), and that can influence sound. But back to the original question, with a sealed headphone, adding or removing damping to/from the earcup can entirely change the sound. You may or may not like the results (there's nothing that says perfect phase and impulse magnitude response sounds the best, it's just the mathematically most ideal).
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From what I've heard, the reflected sound from the cups of sealed cans can interfere with the true sound quality of the sound driver, and that soundscape can be extended quite a lot by venting sealed cans. Seeing that there are some obvious advantages to eliminating the sound reflection of sealed cans, has anyone tried an anechoic mod to their cups?
While it's definitely not the same as drilling holes into the cans, does anyone know if lining the insides of, say a denon d2000, with non-reflective foam wedges would improve soundscape the same way? I know that anechoic chambers are used in the sound industry to create a environment of "infinite acoustic depth" by eliminating reflection.
Seeing that there are probably some sound engineers on head-fi, I was wondering if there was a certain way these wedges should be arranged. Due to the space limitations of a set of cans (however big my d2000's may be), would it be have a real effect? If so, is there a critical size, angle, or arrangement that I would need to take into account for the maximum effect?
I have no issues with my d2000's right now; theyre awesome cans. But I need something to occupy myself, and I think this would be a fun project, so any input is appreciated.
