I am looking to create Dubstep Whomp's on logic epress 9! anyone know of a good and easy to understand tutorial?
I believe what you're talking about is often referred to as a "wobble bass" and can be made in a variety of ways, for a variety of textures.
Choose a synthesizer plugin to start with - you don't need any particular one, but just needs to have a nice lowpass filter, and a low-frequency oscillator ("LFO") that can modulate the filter cutoff frequency.
The basic idea is:
After that, it's all about customizing the sound to your taste. Try different waveforms, filters, LFO settings, whatever. Try changing the LFO rate as it's playing. Try adding vibrato if your synth does that. Make sure your filter is filtering the whole sound, and not letting any of the oscillators get through unfiltered.
The key element in the dubstep / drum and bass wobble is the moving filter cutoff. You can do this many ways, but the one I wrote up here is the one I've used. You could also, for example, change the cutoff rate by hand, if you want a particular pattern of filter movement.
If the terms here don't make sense, by all means look them up. They're fairly straightforward synthesizer terminology and apply to most synthesizers. Your plugin probably has a manual that describes how to use them.
One more thing - and I know it sounds silly - but search YouTube for "dubstep wobble bass". There are lots of tutorials out there, however I don't know of any for Logic in particular.