Hi Friends,
I'm happy to share my findings after experimenting with stacking magnets on Sennheiser HD202-ii.
To quote our guru:
I agree, and measurements indicate this to be true.
Bass: Smoother bass in the 20-40Hz region. I'm not sure if the drivers are playing those notes, not cleanly anyway, so perhaps this shows that stronger magnet gives
better control. 50-300Hz is identical to the stock unit.
Midrange: 300-3000Hz is identical to the stock unit.
Treble: Now this is where it gets interesting. Using a
ring magnet, 20x2mm with 5mm hole, there is a massive dip between 7and 9kHz. This magnet is wider than the stock magnet, maybe it's messing the magnetic field of the original magnet? Around 10-13kHz, this combo is about 2dB hotter than stock. Not happy with the dip, I then
stacked two of 10x2mm coin magnet. Compared to stock, this results in 2dB cut around 6-7kHz
and 2dB boost around 10-13kHz. To me, this means less sibilance and better shimmer. Tambourine sounds with realism I've never heard before with this pair. Not only more presence, but more accurate timbre, in my subjective opinion.
Perhaps this is also a good time to mention that the stock magnet on the HD202-ii is a strong one. 15mm in diameter, and looks like a neodymium magnet. It is very decisive on pulling/pushing so it's very easy to determine the polarity.
I measured using REW and Dayton Audio UMM-6 mic, calibrated. I will not show my measurements because I am not confident of their accuracy. I just use it for my own learning, such as in this case, telling me if my mods are doing anything, or if my ears are fooling me. I took 3 measurements each side, and averaged them. Then I averaged the left and right for each setup. That means, the above conclusion is reached after 18 measurements. Not bragging, just wanted to share my method. Hope this is of some use to all of us.
20mm ring magnet is bigger than the stock magnet. Will update this post with the final setup soon.