This Instructable will show you how to build a loudspeaker that can mount in most standard interior doorways, using the room as the enclosure. The system is easily removable, though quite heavy. The system shown here is not a high-fidelity system, but it is very efficient (i.e. LOUD) and can reproduce very low frequencies. Based on the parameters of the woofer, this system should easily reach below 30Hz (-3dB) without including the natural boost obtained from room reflections. With this boost included, the system should reach 20Hz - the lower limit of human hearing. All of this bass extension comes at a very respectable 96dB with a 2.83V input (4 ohms).
It consists of (8) 12' woofers, (8) 5' midranges, (4) 2' x 5' tweeters, a simple crossover and (4) easy to use mounting brackets. The size and number of speakers can be just about anything you want, but this combination utilizes the available space in a doorway quite well.
Step 1: Get Stuff
- 12" woofers qty 8
- 5" midranges qty 8
- 2"x5" tweeter qty 4
- input terminal qty 2
- 10W resistors qty 2
- 3.3uF non-polarized capacitors qty 2
- 16uF non-polarized capacitors qty 2
- 0.7mH inductors qty 2
- 0.4mH inductors qty 2
- 18 or 16 awg wire qty 50 ft
- 4' x 8' plywood qty 1
- 2 x 4 studs 96" qty 5
- L-brackets qty 4
- 1.25" weather strip qty 17 ft
- 3/8" carriage bolts qty 4
- 3/8" nuts qty 4
- 3/8" wing nuts qty 4
- 3/8" fender washers qty 4
- 3/8" T-nuts qty 4
The midrange and tweeter units were chosen based solely on price. These can be replaced with any midrange and tweeter of your choosing as long as they are wired properly and the sensitivities are matched to each other and the woofers. This can be done in the crossover and will be partially explained later.
The woofer was chosen based on price and a parameter called Qts. This parameter should be available from the speaker retailer and should be between 0.65 and 0.95 for best results. The woofers I'm using have a published Qts of 1.17 which is a little high, but as I said, this particular system is not designed for high-fidelity. The picture below is from the Parts Express website and it has the same specs as the woofers I'm using.
All of these drivers were purchased from the PartsExpress factory buyout section of their website (www.partsexpress.com) for less than $120 total. Better divers would make for a better system, but things get really expensive when you have to buy 8 of each component.
EDIT - 11/23/2010 This (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=292-422) is an excellent woofer to use in the Homewrecker as well. They are only $13.76 each if you buy 4 or more. They are less efficient than the original woofers used and you will have to account for this in the mid and tweeter level, but they are 8 ohms which will be easier on your amp. Plus, I think they look better without the ribs on the cone.