OK, I had posted this on the AKG K271 and super mini thread, it really deserves a post of its own, especially considering that it can be applied to ANY closed headphone. Most closed headphones have horrible damping/resonance control for the earcup chamber that the drivers sit in. That's why so many closed headphones sound bright, and bass is less than perfectly defined. So, below is my tweak, I've used it on the AKG K271 Studio's and the Sennheiser HD280 Pro's:
Here is a VERY cool tweak I did to the AKG K271's and also my Sennheiser HD280's. Tapping on the earcups of the 271's gave a very hollow, plinking type sound - obviously there is not much damping on the "cabinet" of the earcup. I opened up the headphones, and there's no damping material or acoustic material in there at all. This can't be allowed to continue! So, below is a copy of the tweak that I posted over on headfi:
OK, as many may know I've had a pair of AKG K271's for about a month now, after burn in I've been very happy with their overall sound, the frequencey response is very even for a closed headphone, and the dynamics are quite good, and thank god they are not so ridiculously bright like so many other closed headphones. But I've had a number of "small" complaints about their sound, nothing huge, just minor annoyances that would be nice to get rid of, namely the upper/mid bass is a little undefined and the really deep bass tends to come off sounding like midbass (ie the deep bass is not distinct from the midbass). 2nd, the midrange, while forward is a little occluded, not as transparent as I am used to from my Ety's and my HD600's. 3rd, there is a narrow band of brightness at about the 8-10khz range that (besides being slightly irritating) covered up the very high frequencies, causing a loss of ambiance and "space". Lucky for me these all can be fixed with a relatively simple and very cheap tweak.
THE TWEAK:
You will need 3 things to do this tweek - 1. a screwdriver, 2. a packet of BlueTak (the tacky putty used to hang up posters, available at all office supply stores), and 3. three cotton balls.
Step 1:
Remove the pleather earpads from the headphones, you will see 3 screws revealed on the exposed face of each cup.
Step 2:
Remote the screws and pull the cups off - do this VERY gently, the cups are soldered to some very short wires, they will not come off very far. Once you have the cups off and dangling from the wires, you can reach in and pull on the wires, there is a little bit of play in them, and once you pull them out a bit you will have a bit more room to work.
Step 3:
Take the package of BlueTak, and divide it in half. One half is enough to treat one earcup. Take the half and apply it to the interior of the earcup, making sure to keep it at about a 1 millimeter thickness. I found it easiest to pull the bluetak apart in to smaller pieces and apply those pieces one at a time to each part of the earcup in a clockwise pattern.
Step 4:
Take the 3 cotton balls and divide them each in half, giving you 6 pieces total when done pulling them apart. 3 will go in to one earcup, 3 in the other. They are too dense "as-is", so pull them a bit so that they "stretch" a bit, so they are not as dense and they can now cover a wider area. Place the cotton on top of the bluetak (but make sure it doesn't cover any of the screw holes, so you can get the screws in when you go re-attach the drivers).
Step 5:
Re-attach the drivers to the earcups and put the earpads back on. Repeat these steps for the other earcup.
That's it, simple, cheap and pretty easy.
HOW DOES IT SOUND?
Well, the bluetak and cotton soaks up that 8-10khz brighness so you get less brightness, plus the really high frequencies are now very clearly audible, the sense of space and soundstage are greatly enhanced. The midrange is cleaned up very nicely due to the more solid and less resonance earcups. The upper and midbass are still very good, but the deep bass is signifigantly better because the cotton "fools" the drivers in to thinking they are in a much bigger chamber than the earcups actually are, which gives a lower resonant frequency which really gives the low bass some power now.
Overall, this takes the K271's from the realm of "very good" to the realm of "greatness". Not too bad for a $2 tweak
Now, for the Sennheiser 280's:
The steps are exactly the same as above, but there is no room for any cotton, and you don't need it anyway, since the deep bass response on the 280's is crazy good anyway. But the BlueTak definitely smooths out the tipped up upper midrange, so that the mids and highs are now very much in balance with each other. Plus, the added bluetak takes away a bit of the air in the chamber of the earcups, which raises the FS of the bass a bit, so that the bass has more of a boost in the 60hz range, while still keeping its amazing deep bass response.
The net result on the 280's is that you get a very smooth and slightly resessed mids and highs which is VERY musical and very easy to listen to for long periods of time, but you also get a KABLAMO!!! bass response. Very nice, in fact the Senn's improve more than the 271's do, but the 271's are still a far better overall headphone due to their greater tranparency, more balanced sound, and better dynamics and ambiance retrieval after the tweak.
Anyway, let me know what you guys think. All I can say is that I finally found perfect sound with a closed headphone, which I never thought would happen after owning the HD600's. . .
