I have 2 question. How different would the sound be between a small sealed enclosure and a medium sealed enclosure? 2nd question: A lot of manufactures lists a range of airspace for sealed enclosure, for example .35-1.0 how would you know how big to build the box?

 

Sub values are usually measured in air volume in which the speaker occupies space and area where it operates. This is usually measured in cu.ft. This value is determined by L (length) X W (width) X H (height) inches (INSIDE DIMENSIONS) of your sub box. Once you get this value, divide by 1,728. This will give you the cu.ft. volume. You must try different values of your box to get to the manufacturer's recommended volume. If you get somewhere in the middle of their values, your sub will sound best. To determine your outside dimensions, just add/take in consideration of the thickness of your wood (3/4" or thicker) MDF--medium density. Adding bandpass ports to sealed encosures even makes your subs sound even better, but requires much more formula in designing the correct box dimension. You may want to visit a local car stereo dealer for this type of install, and tell them what size you want to work with, and they will design a box for you.

 

like he said, a correctly built bandpass or ported can make some great sound, if built correctly. Also, a bandpass sounds really nice for rap and hip hop; very boomy bass. A draw back to bandpass is that they are generally huge boxes, so if you drive a civic hatchback prepare yourself for a lot less room. I saw a bandpass box made by JL audio and it was huge...and there was only one 10.

Sound wise, back to your question of small versus medium, small sealed boxes sound tighter compared to medium or large sealed boxes. But you generally need more power to drive a woofer in a small sealed box. But remember, the most important thing is that your box matches the recommended air volume. Good luck on building your box, i had hella fun building my first one! 2 12" shared chambered 3.5 cubic feet of air: one big box! 3 feet long, 14 inches tall, 12 inches deep: but fits nicely in my trunk =)

 

Small, Medium, Large are all relative to the sub and the enclosure type. Small for one sub might be 4.3 cubic feet. For another it might be 0.2 cubic feet. Size affects efficiency, low end extension and roll-off.