I wrote an Excel sheet that allows the calculation of TQWT enclosures similar as the Needle.
The calculation is completely parameterized, therefore it can be used for any driver. It is meant to exchange data between the MathCad scripts of Martin J. King.
Compared to the Needle there are following differences:
1. The tube-diameter increases linear. As the Intercept theorem is used, the upper end of the divider is not at the center of the box but slightly moved towards the baffle.
2. The baffle can be removed.
The internal port and the internal top allows additional fixation. As the dimensions of both internal parts are used for the calculation of the length of the middle line it is not possible to omit those.
The external top and the external bottom are optional, but these two parts simplify the assembly of the box. Furthermore they represent extra material in the main direction of the standing waves.
3. The thickness of the baffle can differ from other components.
4.The Excel sheet contains a Helmholtz calculator for the slot.
The Helmholtz frequency of the port must be adapted to Fs of the driver (or the tuning frequency). The hight of the slot has to be chosen accordingly. The width of the slot is determined by the diameter of the driver and two bars.
The diameter and the length of the equivalent tube can be used in MJKs MathCad scrits for further optimizations.
I used the Huebscher formular to convert the dimensions of the slot into an equivalent tube.
5. In the list of parts there are some components (marked light/dark blue) that contain an allowance of 1mm or 2mm. That additional material can be sandpapered off after the assembly of the box.
Note that there is no real correlation between the CSA of a conical horn & the driver Sd.
I have downloaded this and hopefully will get around to experimenting with it next week while on vacation.
I have built a 3 pairs of TQWT pipes.
The 1st was a 4 foot tall 4x6 box that I stuck a pair of Audio Vox 5 inch full rang speakers in.
Sounded good enough I built another pair this time out of 3/4 inch plywood 48" tall using 8" radio shack full range drivers with a whizzer
something like a 1334 speaker?? Can't remember, blew them up. Just managed to get a pair of 8" pioneers to try in them.
I then built a pair using "weems spreadsheet" using Parts Express 69 cent 4" full range driver. They sound really good.
My kids grab them every time I make a pair for their surround systems (they have great hearing and use low volumes)
I am presently working on a design using a 4" full range speaker that was found in the Bose 901's series I & 2's and some other speakers like Fraziers. Plan on using these as my rear speakers on my 5.1 system that has 901 series II's for mains.
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