I went through the listings of woofers that are available from the numerous suppliers and figured that if I used a JL Audio 10" sub, I could get down to about 26hz and it didn't require a huge box. The vents were going to be a little long, but I figured out how to make due. I created my design on Pro-Engineer software at work and made all the drawings. I got all the wood and started cutting and assembling the cabinet. I was almost done with the cabinet and decided to re-check my calculations. Now, this is something that I should have done way before I even bought the wood, but hey, I made a mistake. During my re-calculation, I remembered something I had read or heard from somebody on a newsgroup, so I got the Loudspeaker Design Cookbook out and started reading again. If you make a design that is ported and isobaric, you have to double the length of the port. This meant that my two ports had to be something like 35" long each! There is no way to do that and still have a small box.
The result of this calculation was that I returned one of the drivers and use only a single one in the cabinet. I still used the two ports and I made them as long as I could by adding 3" 90 degree ABS elbows from the hardware store, but I know that the sub does not do what I intended it to, at least not cleanly. I still have great sound, and it does help to strengthen the low end of the sound spectrum, but not with the cleanest sound reproduction. I have since plugged one of the ports with an ABS plumbing test cap that I spray painted black. This will get the box volume closer to the correct numbers since I can now count the volume inside the plugged port along with the rest of the cabinet. This also helps get the correct length for the ports more in tune with the speadsheet that I used to double check my numbers.
Pictures of my current sub: pic1, pic2
I have decided that the easiest coarse of action for my home theater
is to purchase two Parts Express Titanic 1000 subwoofer kits. More information
can be seen at www.partsexpress.com
or on my equipment page
