I read somewhere here that somebody suggest to use that.
It's a bit more complicated than that. According to Rin Choi's measurements, the ER4B's impedance is fairly flat until 3 kHz where it decreases. Therefore adding a serial resistor will decrease the treble above 3 kHz, in other words, relatively increase everything below 3 kHz.
The 4B has a capacitive component that throws off the resistance curve. That said, it also boosts treble with more impedance. In fact it is the most treble heavy of the line. For all that Rin talks about the Ety line, the pages for them are pretty sparse. Anyway here are the three in line. Keeping mind the only difference is inline resistance and in the case of the B a cap.
There are people who make P/S/B adapters but they won't be cheap.
Alternatively you can use EQ to tweak the bass to whatever you want.
They are not at all like the er4`s, they have a bassy signature somewhat like the gr07. Notably, there is more roll off in the highs, yet they are smoother, and more emphasis on the bass and mids giving a thicker, more lush sound, soundstage and intrument seperation is about the same and isolation is also great. They are more compact than the er4`s and the cable is much thinner without the large cable divider that houses the resistors.They are a tad less microphonic due to the shorter stem length of the earpieces.