STUNNING 2 K271 tweak (works w/HD280's too)
Sep 14, 2003 at 7:29 PM Thread Starter Post #1 of 64

Tyson

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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
smily_headphones1.gif


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. . .
 
Sep 14, 2003 at 10:17 PM Post #4 of 64

Tyson

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I really wanted to post pics, but don't have access to a digital camera
frown.gif


Regardless, this is a super simple tweak, just involves opening the earcup, applying the blutak and cotton, and putting the earcup back together. Took me about 15 minutes total. And like they say, if I can do it, anyone can
wink.gif
 
Sep 15, 2003 at 6:25 AM Post #6 of 64

Tyson

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The main thing is space - there will almost always be space for the bluetak, but there may not be space for cotton. With the cotton, you want it to stay in a fluffy state, and not get compressed. If it gets compressed, it's density increases and it will act in a manner that will decrease "perceived" volume in the earcup, which is the opposite of what you want, which is a perceived increase.
 
Sep 16, 2003 at 3:08 AM Post #7 of 64

Tyson

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Took my modded 280's in to work today to compare them to my co-workers unmodded 280's, just to make sure I wasn't imagining the improvements the bluetak tweak gave. In direct a-b comparison, it was immediately obvious the modded 280's sounded far better than the unmodded ones. The unmodded ones sounded weak in the bass and papery/opaque in the mids and highs, in contrast to the strong/percussive bass on the modded pair, and the mids were more pleasant, while sibilance (and snare drums) no longer have a tendency to dominate the mix. Overall, for $2 total, I'm very happy indeed with this tweak.
 
Sep 16, 2003 at 7:55 AM Post #9 of 64

Xplo

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So I tried this mod on my 280, since I've got some of this tacky putty stuff lying around anyway. There really isn't a lot of room in the cups, especially behind the driver, but I did my best to smoosh the stuff around and make it thin and even. (No pics here either.. no camera.)

One unfortunate side effect of doing this mod: the threading inside the "post" that the bottom left screw screws into seems to have been weak or stripped or something. When I removed the screw, bits of the plastic were clinging to the screw threads.. and now the screw won't grip the threading on the inside of the post. So the little "cap" on the left cup that hides the wiring and holds the cup onto the band tends to come loose.
frown.gif


I'll probably fix this more permanently later.. if I can figure out how. Some kind of epoxy filler or something would probably do the trick.. and also make it impossible to remove the screw again without major surgery! Any suggestions?

As for the sound of the mod itself... it seems to perform as advertised! I honestly couldn't say how much of the change is just my imagination and how much is real, but I did test the cups against each other after modding one and there seemed to be a difference between them. Now that both cups are done, I'd say that the 280 sounds warmer, smoother, less distant, and possibly even a little more detailed. Bass on some tracks does seem a little punchier. If it's just my imagination, then ignorance is bliss; either way, this is just the "between a 280 and a V6" sound I hoped the 280 would have for me when I ordered it.

It's enough to make me wonder if Sennheiser wouldn't look into selling some 280-based cans with some rubbery material like this built in.. if there's a significant acoustic difference to account for what I'm hearing, I'd recommend the hypothetical new phone over the V6 to people in a heartbeat (assuming it was at or very near the 280's price).
 
Sep 16, 2003 at 8:13 AM Post #10 of 64

hero zero

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hmmm...I blue-tacked the inner circle of my HD280s quite some time ago in the inner cirrcle of the right earcup, but it didn't seem to do much, if I could tell, so i removed it in the end...I guess I should try blue-tacking the entire thing and put cotton over it...but yeah....there's not much space to work with...

I don't know about the enclosures of the K271S's, but the K171S seem to have a lot of space in them for this mod [unfortunately, I returned them due to comfort issues]

my interest would be to mod the Sony V6 this way [to reduce what could be harsh treble]...I don't know how much space there is in the enclosure as I don't have them yet...but if the design is anything like the A-T ATH-M30, there might enough space for the mod to work....

....as for the M30's themselves, I'm not sure if there's much of a need to do this mod as the high's are already kind of recessed....
 
Sep 16, 2003 at 3:13 PM Post #11 of 64

Tyson

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Yes, there is not much room in the 280's, so when you are done, you have to press down on the driver to compress it back in to place in the cup before re-applying the screws. If you stripped the plastic, the next size up of screw will probably work so you don't have to use epoxy or anything drastic like that.
 
Sep 18, 2003 at 7:59 AM Post #12 of 64

Tyson

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Been experimenting with the ammount of cotton I use on the K271's, and I've come to favor a bit more in there than I initially advised. I put in about 2.5 cotton balls worth in to each earcup, so that the bluetak is completely covered and cannot be seen at all through the cotton. There is a bit of compression to the cotton when I reapply the driver to the earcup. The net result is the bass does not resonate quite as deep (it still goes deep, just not as loud as before), but you get a big payoff w/the upper bass being more precise and tuneful, and the highs much better. It just gives the whole can a much more coherent, pleasing, natural, and precise sound.
 
Sep 18, 2003 at 8:29 AM Post #13 of 64

Tyson

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Also, on the 271's, if you take off the foam over the drivers you will notice that there is a series of holes where the sound comes through. These holes are in a circle around the center of the earcup. Positioning the headphones so that the bottom of this circle lines up with your ear canal, and the upper part of the circle lines up with the top of your ears results in stronger/better bass, and a reduction of the prominent sibilance on sss and sshhh sounds. At least on my head that's how it works
smily_headphones1.gif
 
Sep 19, 2003 at 6:28 AM Post #14 of 64

pbirkett

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Another little tweak for the K271 (I didnt think it warranted a new thread) is if you have one of the Corda range of amps (or others with varying output impedance sockets) is to run the K271S from the 120-ohm socket. This increases the bass and makes it sound smoother and warmer, and with no drawbacks that I can detect (other than the headphone needing more gain to reach the same volume).
 
Sep 22, 2003 at 11:03 PM Post #15 of 64

Tyson

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OK, went back and doubled the ammount of bluetak I use on the 271's earcups, it's now about 2mm thick all the way around the entire inside of the cup, plus I increase the ammount of cotton stuffing to about 2.5 cotton balls, there is not any room left in the cup for any more material at all.

The extra bluetak and cotton does make a nice improvement in the sound. The last little bit of plasticky coloration is removed and the bass is more tuneful, and even better integrated in to the overall sound. They are starting to sound a lot like my Ety 4P's at this point and I'm pretty happy with the 271's for my closed headphone of choice.

With this config, the 271's are very accurate, and will reveal a bright or lean source pretty ruthlessly, so my advise is to use a neutral or mellow amp with them. And they do require an amp, as they do not sound very dynamic out of a portable devices headphone out.
 

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