Is this normal? (Lower 29 Hz frequency actually gives more bass)

How does the bass sound with no equalization?  Did you lower it from say +10dB to +5dB when you noticed the increase?  This could be due to clipping or severe distortion.  As an equalizer tries to exhibit more control over a signal, especially digitally, the circuit will introduce a ton of noise due to trying to amplify just one band, but in fact grabs a bunch of other bands.  Who knows how it is handling the signal either, it could be rounding it off and flattening the peaks.  I am going say that the problem is most likely digital processing.  I cannot imagine this happening with an analog EQ.

Looks like your EQ preset just overpower the sub bass around 30 Hz and choke the sound, you should let the other frequencies of your music to breath by boosting the 30Hz just by 3 to 7 dB (you need to be gentle in the sub area, the sound can get very messy before you notice). The other option is to not use EQ on the sound at all, and if you don't like the sound of your hps buy one that you like without the need for EQ.
 

 By reducing a frequency that the headphone can't really accurately reproduce with any kind of volume anyway, you've allowed the nearby lower bass/mid bass regions to be free of the overhang created by the driver trying to do something it can't, in your case resulting a cleaner, tighter sound.

Having tuned car systems for forever and a day, the general idea is to cut frequencies whenever possible if needed, not boost them.

EDIT: Acix beat me to it....but you get the idea. ;) 

Within your question lie the answer, your bass is in the 59 - 119 Hz area and not in the 30Hz.

Very little  musical energy resides at 30Hz with the exception of large pipe organs and a bit of electronica.  As an example, the *lowest* note of an electric bass guitar is a bit over 40 Hz.  The greatest bass energy, such as the bumps in rap, are at roughly 100-120Hz.

In addition to the fact that the typical equalizer built in to a computer playback program or portable player does much more harm than good, there is no reason to boost these low frequencies.