Hi Mazi, the approach is correct...
First of it's a little bit of a pain to do it 100% exact in Simpler, but never the less possible.
- Set snap on, if you have a 808 kick move your Start knob a little bit, probably about 1-2%, this is so you only start the sample where your bass sound starts.
Note: If you want a long fading 808 kick you can leave the start point right at the beginning for the punch and apply long release time.
- Put your Loop knob at 100% and disengage snap
- Zoom in to the loop start and adjust the Loop knob so it sits exactly on a zero crossing
Note: It's actually easy to spot when you're zoomed in it's the section where the line is the thinnest horizontal, hope this makes sense.
- Now that your Loop start is on a zero, zoom out and zoom back in to the loop end point, then do the same with the Length knob as you did with the loop knob, if you can't quite get it right "as it's a little rough in simpler" just look at the value you have on length, for example 0.79% and it's a little to the right of the zero crossing means you could get away simply by typing in 0.78%, anyway simply type in the value needed to get to your zero crossing, normally something close to what you have.
- Now you can check your sound already "careful with volume" now use the Fade knob to slightly adjust it so you don't or barely hear any clicks where the loop happens.
- Last things adjust your envelopes to your taste, attack for a slow rise, release for a long fade, and add additional effects to your sound, distortion, filters, whatever you are looking for.
I added a little screenshot to give you an example at what you should be looking at in terms of controls and waveform.
Hope this helps, happy editing!
This is just how to make a bass of a 808 kick not how to imitate the sound of anyone you mentioned, if you are talking about kick with long fade, which is often used in hip hop as well, just do the same with long release time and maybe you want to set the Start knob to the start of the sample, or you can use this with other kicks layered on top for the other elements of the kick drum that you want like transients and punch, also it's very important to tune your kick to your track, else it will just not sound right in the mix.