The close mic will give a more direct sound with an accentuated attack, and the distant mic will give you more of the low end (it takes several feet of "air" for a bass wave to develop).

By using various combinations of the two mics, I'm able to get a great sound that often just can't come out of one mic. While two mics can often spell trouble because of phase anomalies, this is a case where those same problems can work to your advantage. By balancing the signals different ways, you are affecting the phase relationship between the two mics and altering the EQ curve, hopefully for the better. The faders on the respective channels of the console of course control the amount you vary the signal. The amount you move the faders to change the sound can often be measured by hair widths. A little dab will do ya!

Miking a good bass amp isn't a problem providing you're working in an environment where you can play the thing loud enough, and of course you need a decent mic. Though you could use a general-purpose dynamic vocal mic to capture the bass guitar, you'll find that most of these have a deliberate low-frequency roll off to compensate for the proximity effect when used up close. Because of this, unless these are placed right up against the speaker grille, you could find the bottom end tends to lose power.

A better bet is to use either a non-vocal dynamic mic that has a reasonably flat low-end response or to try one of the dedicated bass/kick drum mics, placing it around six to 12 inches in front of the best-sounding speaker in the cab. If you look at the frequency plot of a kick drum mic, you'll find the frequency response looks like the back leg of a donkey that's just been hit by a truck, but the results are often flattering and powerful, which is far more important than any misplaced notions about accuracy!

If you're using a valve amp, you may find you don't need to add further compression, or at least not much, but if the amp is solid-state and doesn't have a compressor of its own, then it's probably a good idea to at least try adding compression to see what can be achieved. The safest approach here is to leave the compression until you mix unless the levels are so erratic that clipping might be a problem.

Tonal changes can be made by moving the microphone -- the brightest sound is found by pointing the mic at the center of the speaker, while moving it to one side will produce a warmer, less in-your-face result. It's also worth varying the distance to see what result that has.

Try adjusting the mic position for the best results before adding any EQ at all, and if you can save the EQ until you mix, you'll keep your options open. After all, what may sound great in isolation may not sound so right when the rest of the mix is up and running.

Tricky this one but generally many engineers use large diaphragm mics for bass sounds. The ElectroVoice RE20 is a good one as can be the Sennhesier 541 and AKG D112. It sound obvious but you need to think about the frequency response of the microphone. If you use an SM58 to "mic-up" the amplifier you just wont get all the rich low-end tonality that is needed for a cool sound.

Placement is subjective and there is no right way or wrong way but to use your ears. You want to be in the control room listening to the bass player play the bass while your helper moves the mic in front of the amp to find the "sweet spot". In fact use that technique for all your mic techniques; just moving a mic a couple of inches will radically change the sound you get.

The basic miking techniques for the speaker itself are the same as with a guitar as far as placement is concerned.
The classic "Dead Center" miking position, this is the most obvious and most common positioning. Sometimes, with certain mics this may want to be avoided because it does put a huge amount of pressure on the mic because the sound is coming from right in the center of the cone. It does give a clean, pure representation of the speaker, but is sometimes prone to overdrive the mic.

Placing the mic on the center of the cone. I have seen many live sound engineers use this method, I don't use it myself, but it is a nice sound, with, some say, less pressure put on the mic. Still, it is a nice, close-proximity option for you to try with you amplifier.

Putting the mic at a 45-degree angle with the cone centered on the cap. I have seen this method used more for the second mic on a cabinet rather than the first, but none-the-less, it is an option. Used further back from the amp it can be good for grabbing extra bass. Theoretically, the highs will just shoot right past it and the booming bass will the picked up more with this position.

Putting the mic perpendicular with the speaker. This is even a more radical approach to getting more bass in your sound. Same theory as above, just a greater angle to let more highs zip past.

Though the direct method is probably the most common, as stated above, but a miked speaker can add some very big fullness to the sound. And the bass, more than the guitar, uses much of the body of the instrument to create some of the tones that they produce. This is why miking the body itself can be so effective in getting some great bass sounds.

If you are of the style that uses a lot of slap & pop-style bass, miking the body, especially at the neck-meeting-the-body position, will help pick up those sharp pops against the frets that give that style it's unique sound.

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