The baffle is the part of the box that the driver mounts to.

I think you should do some research on porting boxes so that you learn what drives the tuning. There's a few great articles over at www.jlaudio.com under the tutorials section that should get you started. I highly recommend you read those....that's how I learned to build ported boxes.

It will show you why in fact you can't just cut that port into four pieces and divide. Tuning frequency is driven not only by the size of the box, but also the length of the port(s) and the cross-sectional area of the port(s) - notice I didn't say volume of the ports!!!