| I just got a firewire hard drive for my laptop. My laptop (as most/all pc laptops) doesn't have a 6-pin connections. I think mac laptops are the only ones that have the luxury of 6-pin connections. But my new drive works excellent with the 4-pin connection.
But as far as I understand/know, the only difference is power supply. 6-pin supplies (sufficient?) power, while 4-pin doesn't.
An example would be how the f/w works with an iPod. If you use a 4 pin, the iPod won't get charged, but a 6-pin charges the iPod. So if I'm not wrong, the two extra pins doesn't have anything with data transfer, but are only for extra power.
So, the 6-pin connection will be needed if you want to plug in a device to your computer and not have any power cords connected to it. I think a lot of soundcards works that way. (You have to use external power if you use a 4-pin connector, and not if you have a 6-pin connector.)
Bottom line:
I'm almost certain that using a 4-pin connection with the mackie won't affect the data transfer. A big device like that is (probably) externally powered, and should not require the power that a 6-pin connection delivers. You shouldn't need an adapter either. All you need is a f/w cable with a 4-pin in one end and a 6-pin in the other end. They shouldn't be too expensive or hard to find.
Alternatively, if things turn out that I'm completely wrong and that you need a 6-pin port, you could buy (for laptop) a PCMCIA card with 6-pin firewire connections. | 
