DIY Subwoofer

My friend wants to build a subwoofer for his new home theater set-up. Any good experiences/recommendations for kits or scratch-built bass blasters?
If he has any (reasonable) woodworking skills, then he can look into kits, one of the best being ACI Titan. You can find info at
Here is a comparison of several different drivers in different alignments.

When looking at any woofer spec's, ALWAYS take a look at the impedance at resonance. The higher the impedance, the more "out of control", "bloated" or "one-notey" it will sound. While this is not nearly as critical for HT use as it is for reproducing music, it is something to consider. If your interested as to why this occurs, let me know and i'll do my best to explain it in "English". Sean
I got excellent bass using the NHT 12" driver ($149)and madisound's 91 liter enclosure which I lined with a another 3/4" layer of MDF to make the walls 1.5 inches thick. Stuffed with fibreglass, it gives deep powerful bass. You need a solid 250 wpc to drive it though.