By the way it's kinda different from RBass (quite a lot actually).
But like other said RBass is not a subharmonic generator, we can consider it a "bass enhancer" but what it does involves allowing bass frequencies to be heard on small speakers (wich is the opposite of a subharmonic generator).
But resonant HPF based enhancer can do a decent job on this purpose (since they resonate at higher frequencies), even all-pass based echancer can give something to a small speaker (mostly because of the dislocation of attack transient and mid portion of the envelope in response to the very low frequencies being stretched a bit).
In the meanwhile, just out of curiosity i tried to analyze RBass (i really never did before).
And i found there's no magic, it's really simple in reality.
If you want to recreate what RBass does just follow these steps (in this example i'll go with the 80hz default setting in Rbass):
- insert a clean digital EQ (ReaEQ is good for this), leave it alone for the time being.
- insert a multiband saturation tool with just TWO bands and set the crossover at EXACTLY 80hz.
Set the first band with a forgiving algorhythm (i use fabfilter Saturn on "gentle saturation" setting) and turn off saturation completely on the second band (the higher one).
You can also use the JS crossover and use wathever saturator you like.
From my analysis no need to search for even harmonics, rBass generate all the first three in the series in descending order of magnitude, so even a slight touch of any saturator capable of that should do the trick (MSaturator from Melda on soft2 setting should be good and free). Be sure to compensate the output level if gain increases
- Once saturation is set and ready to go just go to the EQ and put a PEAK band CENTERED at 80Hz,in ReaEQ give it a bandwidth of 1.3 and a gain of +2.5dB
- Add a second PEAK band and center the frequency at 40Hz (half the crossover frequency) and CUT -1dB
Done, this should null A LOT with the most beloved setting of RBass (80Hz, -24dB)
To boost the bass just add gain to the FIRST peak band anc CUT the second by the same amount (kinda...there's a relationship between, but since RBass bell shape and behaviour is a bit complex is hard to say without further investigation).
For the RBass 0dB setting things are a bit different just because of the bell shape that ReaEQ can't replicate very well.
That's the EQ setting for the default 0dB RBass:
1st band: 80hz, BW:1.5, gain +16dB (THAT'S A LOT!)
2nd band: 30hz, BW: 0.38, gain -11.5 (had to shift the frequency because of the bell shape)
To change the frequency just change the crossover frequency AND both the EQ bands frequency.
That's all, maybe some good JS programmer can come out with something useful and less messy than this plugin chain, but this is what i found and it sound very similiar to RBass.
Cheers and sorry for the loooong post