I really needed a new set of speakers. My musical tastes are for acoustic music; classical, jazz, blue grass. This means that I needed an F3 of 42hz (bottom string on the double bass). I also wanted to do this on the cheap. I had the further requirement that since I did not have access to a proper shop, I was going to have to build the things with hand tools.
From all that I had read, is sounded like my best bet would be a Weems pipe. I call this layout a Weems pipe because it is described by David Weems in Speaker Builder Magazine and in some of his books. It is a very specific subset of TQWT, which is a subset of Voigt pipe, which is a subset of TL, yada, yada, yada.
For a driver, I chose the Radio Shack 40-1354a, now unfortunately out of print. This is a 5 1/4" wide range, whizzer cone driver. It's real specs are Fs 58-60, Qts ~ .47 and Vas 10.5-11 liters. Plugging the numbers into Weems' formulas gave me this cabinet:
In order to build this with only hand tools, I used white pine lumber. Note that the inside width is 5 1/2", the width of a nominal 6" board. Therefore, I did not have to finish the edges of the partition and back. The edges that did need finishing are on the outside and were done with a plane after gluing. The back of the partition, the top and the back of the cabinet was lined with fiberglass ceiling tile (the plastic cover removed). Here is the measured result:
Here is the lowest 1k hz, combined output in black, driver in red, terminus in blue:
For those interested, here is what Martin King's Mathcad worksheet predicts:
These speaker sound better than they measure. The 500hz hole is not very noticeable, psychoacoustic masking, I presume. They are smooth and detailed, and while the bass is by no means thunderous, it is there all the way to F10~40hz.
So, you really want to do a folded pipe. OK. Try this. It should perform exactly like my straight pipe, however, be aware that I have not built or tested this design. Yow may have to adjust the port length, depending on the driver you actually use. Start out with a length of 2" and increase it as necessary to get the results you want.
