DIY PVC Pipe Dream
In recent years, I'm been impressed by individuals who have the capability of constructing their own audio products.  In examples that I have personally auditioned, quite a few of these projects sound better than comparably priced commercial equivalents.  In a few instances, however, there are no comparable commercial equivalents.

Let me first say that I am not the kind of individual who has talents in constructing things.  I'm pretty good at assembling kits, such as the inexpensive furniture that you assemble, but I have no wood working skills. 

I first got the inspiration from Kurt Chang who I met through the Chicago Horn Club.  Kurt had constructed a pair of dipole speakers using the Fostex FE103 driver and cardboard.  When I listened to these speakers, I broke into a wide grin.  High end audio speakers from a 3" driver and two pieces of cardboard.  Anyhow, Kurt extended an invitation to his home to audition some of his other audio creations.  When I was leaving Kurt's home, he showed me a box filled with a variety of Radio Shack full range drivers.  "Take a pair with you" Kurt offered me.  I picked Radio Shack's copy of the Fostex FE103.

I decided to do a little more research on the internet about full range driver speakers and came across the Periscope constructed by Guiseppe Pipitone.  This discovery led to Rob Sampson's "Laying Pipe with Audio Lego".  The things that struck me about these speakers was the way they were constructed from PVC pipes and fittings.  This is what gave me the inspiration for my version.  Let me say that I have not applied the theory and formulas for a TQWT (tapered quarter wave tube) or transmission line designs.  I determined the dimensions based on how high I wanted the driver to be mounted.  The tube is not tapered, but the 90 degree elbow is completely filled with fibrous material that is used to stuff pillows.

Internal wiring is plenum CAT5 wires and the binding posts are from Radio Shack.  The PVC parts are from Menards as was the 12" round pine board and the thin oak I used to make the speaker flange (this was the most difficult part for me - to cut circles without a Norm Abrams workshop).  Paint for this project was from Rust-oleum.  I mention this because I tried some "house brand" paints and had problems getting a nice looking finish.
October 19, 2002
Today I took these speakers over to Kurt Chang's home to compare these against speakers that he had built. Kurt had built a pair of speakers based on the Fostex FE103 design that was a traditional bookshelf with a front port.  When we compared the two speakers, I told Kurt that I liked the sound of his speakers better.  He then told me that the drivers were not identical to mine because his had be treated with Dammar.  What is Dammar you ask, it is a varnish that is used for oil painting and can be found in art supply stores.  For this application, the Dammar must be diluted with lacquer thinner in a 1:5 ratio (it does not have to be exact).  What Kurt did was to use a Q tip and the diluted Dammar and applied three thin coats on the cone of the speaker.  BE SURE that you do not apply any to the surround of the speaker.  What this did was eliminate a brightness that I heard through the speaker without eliminating any high frequencies.  If you are familiar with the audio term "smoothness", that would be how I would describe the change. 

Another important thing that I learned from Kurt was that my design did not compensate for baffle-step-loss.  In fact, with the circular baffle with the speaker mounted in the center, was the worst design choice as far as baffle-step-loss is concern.  I am going to change this to a rectangular baffle and will post my results when I am done.

Update February 18, 2003
I changed the design to a rectangular baffle utilizing Golden Ratios.  Unfortunately, I did not have the tools to accurately cut the mounting hole for the driver so that I would conform to Golden Rations.  Listened to the speakers after this change, I did not detect a significant difference.  I also took this speaker to a friends home who has a fairly sophisticated SET based system.  My friend was quite impressed with this speaker and I mentioned that this was the best that I had heard from this speakers with his electronics.

I have decided not to compensate for the baffle-step-loss of this design, but rather to use this speaker in conjuction with a sub woofer. 
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