K3003 "front vent mod":
Introduction
The AKG K3003 are among my favorite IEMs, but recent listening comparisons with the DUNU 2000J have made me realize that the latter's bass is not only a bit tighter, but also more tastefully integrated with the rest of the sound signature. While I still ended up preferring the K3003 overall (by a slight margin) due to more refined sounding mids and treble, I also caught myself wishing the AKGs had a little less bass emphasis. Or, in other words: the DUNUs have spoiled me in that regard...
As shown in
Rin's frequency response graph, the K3003 with reference filters are actually noticeably bassier than "reference". Now, the obvious remedy for this coloration would simply be to EQ the mid/upper bass a bit down, and there are no objections to that. But being the curious mind that I am, I kept wondering whether a similar effect could be achieved with a simple and reversible modification of the IEM itself.
Instructions
The only things required for this mod are a spare Sony hybrid tip and a small cutter knife.
Cut two 1mm slices off the hybrid's tip stem.
Stretch one slice over each nozzle. They will serve to seal the pressure equalization vents (see arrow).
Align the slice with the nozzle base, so that the vent is fully sealed. Now put the tips on and listen to one of your favorite test tracks.
Your test track should sound noticeably bassier than before. If you don't hear a difference, check whether the vents are fully sealed.
If you hear a bass increase in both earpieces, you're good to proceed. Cut two 1 x 8mm stripes off the hybrid's tip cap.
Now, this is the tricky part: take the K3003 tips off and place a stripe alongside the nozzle, so that it protrudes about 1mm at the front end.
Hold it carefully in place with your fingertip as you put the tip back on.
Check the result: you should see the stripe from outside, but it must not protrude further than shown in the picture.
Congrats, you're done!
How it works (I think...)
To be completely honest, I didn't think this mod would work at all. By blocking the pressure equalization vent and introducing air leakage with help of tiny stripes, I'm actually only trading the stock front vent for a DIY one. However, it seems that slightly more air is able to escape alongside the stripes than through the stock vent, and that results in slightly less bass energy reaching the ear drum. As far as I can tell, the rest of the frequency spectrum remains widely unaffected.
How it sounds (imo)
Better! (or else I would have kept this to myself
No day and night difference to stock sound, but perceived bass is more linear down to 40Hz, after which it gently starts to roll off. Overall bass levels are a few dBs lower than before, making the K3003 even a smidgen less bassy than the 2000J. Personally, I'm going to stick with the mod.
(Disclaimer: I've found this mod to be safe and completely reversible. Even so: try at your own risk.)
