I purchased the Shure Microphone 8900W at my local Apple computer store. I plugged it into my PowerBook G4 into the microphone plug. I tried a test recording. It seems to barely hear my voice. I went into the Sound interface of the computer and turned up my volume. It still sounds weak. The internal mic picks me up better than this one. Why?
The PowerBook G4 doesn't have a true mic input. It shows a little microphone on the 3.5mm jack but it's really more like a line input, which means it's expecting an audio device at a much higher level (line level). The microphone that Apple designed is proprietary and is essentially self powered outputting a higher level than a true microphone does. Our dynamic microphone needs to go into an input which is designed to amplify the signal with a pre amplifier.
What you can do if your interested in upgrading the audio quality is purchase a USB interface with a mic input. Most people are using these now for home recording. This is a device that you can connect a low impendence mic into and the USB will amplify the signal via the USB input on your computer. As an example, look at the Shure X2u or MVi.