How to make subs in FL Studio
One of the best features of FL is the sampler...So what I do if I am using FL is use simple sampled waveforms from a good Hardware synth and layer them using the Sampler channels...The sampler has everything you need for Subtractive Synthisis (I really like their filters, a lot of people don't, but I like the character they add)...
On to the process...
A) Find any sample pack that contains basic sampled waveforms from Hardware synth.
B) Create a new project in FL.
C) Use 1 sampler channel for each Oscilator you are going to use (some people then use the Layer channelto tie the Osc's together, but I don't) and load up each waveform.
D) Create your bass sound (I don't know how much you know about synthisis, but a good understanding is needed. Same goes for FL)...Make sure that it just creates the mix of the Osc's, I wouldn't do any filter or dynamic modification of the sound at this point. Reason being that if you do it at this point, it may not fit in the tune your creating...Just create the raw sound filled with harmonics.*
E) Set up a Sustained note that plays for 2-4 bars at a tempo of 174 (or whatever your tempo is)...You can also set up any effects you need/want on the mixer. Bounce it down to a wav...I don't know your set-up, but what I do is send it to my outboard mixer and record the sound into Soundfordge from the mixer...It can add warmth and the all important "air".
F) Open up the song you what the bass sound in, create a sampler channel and load your new sound...Now, sequence your bass line and adjust your filters and envelopes at this point to fit with the needs of your tune.
*unless you want differnt effects/filters/modulation to effect the individuale waveforms before they are mixed.