yes, I use it all the time when tracking drums.
In order for MS to work, you need two mics, not just one. A figure 8 (the "side") and a mid mic (generally in cardioid, but will work with omni or figure 8 for different levels of room sounds). If you just use the figure 8, you might think that you are hearing stereo if you set if up manually, but in fact you are just hearing mono twice. The decoder is expecting to hear two sources, so it's probably just spitting out one side.
The mid mic points directly at your sound source (in my case with drums, about 3 ft off the ground pointing directly at the snare/kick from anywhere between 4-12 feet away from the kit depending on how big the room is and how much of it I want to hear in the mics). The side mic is 90 degrees off axis, ie points directly to the left and right as compared to the mid mic. You want the caspsules of both mics to be as close together as possible without the mics bumping or rubbing.
To use the MS Decoder in Logic, you need to set up a stereo channel/input. If you are inputing on 1-2, the mid mic has to be in input 1 (or the "left" input) and the side mic in input 2 (or the "right" input). It won't work if the side mic is on input 1. As long as it's set up properly, it's actually quite painless to use. I have an engineer friend who hates MS because it really a pain to set up using a mixing board. The MS Decoder makes it a breeze, so I use MS quite a lot.
There are some great advantages to using MS stereo....
1) you can change the width at any point in time after you've tracked.
2) you don't need to have a matched pair of mics (you can get all sort of different sounds by combining different mics)
3) since the mid mic is pointing directly at your sound source, you don't have any off-axis coloration happening at the mic. The side mic is null in middle which is pointing at your source, so in fact, really mostly picks up the reflections of the room. It's like getting a great mono source recording and a great picture of the room and mixing them together.
4) you can choose to cancel the side out altogether and just use the mid mic.
Some disadvantages......
1) you don't get as "deep" a stereo image as you would with a spaced pair or decca tree.
2) on a mixing board without an outboard decoder, it requires three channels to set up for tracking and monitoring instead of two (however, in Logic this a moot point, since the decoder does the work that the three channel would accomplish)
Well, hope this helps. Let me know if you are still having problems setting it up, or if you want any recommends in terms of choosing mics for either the mid or the side. I've tried a lot of different combos and can steer you in the right direction depending on what you are going for.......
