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Benchtester's projects and tips

Pictures and Graphs

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Here is a picture of the speaker. I am describing their current condition as "breadboard prototypes" although they are now "daily drivers" (please excuse the pun).

The outer curve of the waveguide was routed with a large table edge profile bit. Unfortunately this left a 3" I.D. hole. I blended the curve to the tweeter surround with black modeling clay.

The first graph shows the on-axis speaker response in magenta, the midrange in brown, the tweeter in green and the reverse null in blue. The phase plots all line up closely at the crossover point. Ignore the spikey phase curve; that is for the reverse null.

The second graph shows the FR at O,30,45 and 60 degrees. I wanted to set-up the speakers in the traditional equilateral triangle, without toe in. So the 30 degree curve is the actual listening angle. These speakers have pretty good tonal dispersion. There is a drop in SPL with the off-set angle. If you move around the room the SPL directionality is noticable. (Maybe room for improvement of the waveguide geometry.)

Some people have asked why all the fuss over time alignment. Here is a previous graph of the speaker with a front surface mounted tweeter. While the conditions and crossover are not identical, it does give a good idea of the affects on the FR. The magenta FR curve picked up a 5 dB dip between 3 and 4 khz. The blue reverse null is only a bit over 10 dB.

Most importantly it sounds clean through the crossover frequency.

Lastly, is a picture of the speakers at Burning Amp '08. They are at the corners of the demo table with the blue table cloth.
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Updated 01-18-2009 at 04:29 AM by benchtester (learning how to attach graphs)

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