How to design a waveguide for Tweeer, and driver testing questions (1 Viewer)

[chung_sotheby]

I am currently working on the design of my diy designed speaker, and I an looking to use a waveguide for my tweeter (scanspeak d2905-9500). Is there any way to determine the paramerters of the waveguide, like the optimal shape and what the measureable effects of the waveguide will be? I have heard that a waveguide, when designed propertly, hwlps increase power handling, increase off-axis response, and helps time align a tweeter to the woofer? Are any of these statements unture, and are there any other positive/negative effects of a waveguide? And finally, to test drivers, exactly what do I need. I know that I need a sealed testing box and microphones, but what kind of equipment is best suited for quick and reliable testing of drivers' parameters. Thanks

 

[Greg Monfort]

>I am currently working on the design of my diy designed speaker, and I an looking to use a waveguide for my tweeter (scanspeak d2905-9500).
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Technically, a waveguide is a constant cross sectional area tube, though I assume you mean either a horn or diffusor.
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> Is there any way to determine the paramerters of the waveguide, like the optimal shape and what the measureable effects of the waveguide will be?
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Yes, for an in-depth look, study horn design. I'm not familiar with this tweeter, but WRT to tweeters in general, they can't handle any compression without increasing their distortion too much so a conical horn is best. Here the angle of the walls sets the dispersion angle and the depth sets the 1/4WL cutoff. 60 x 60deg is good for most HIFI/HT applications. I recommend some felt or similar around the perimeter of the mouth to attenuate mouth reflections.
Since there's no real compression, there's very little increase in efficiency down low, so don't expect to use it much closer to its Fs than normal.
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> I have heard that a waveguide, when designed propertly, hwlps increase power handling, increase off-axis response, and helps time align a tweeter to the woofer?
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True. WRT time alignment, use this technique: http://www.soundpractices.com/images/phase.pdf This will also tell you how long the horn needs to be and its Fc if a flat baffle is used. From there, an XO point can be derived.
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> Are any of these statements unture, and are there any other positive/negative effects of a waveguide?
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Well, they do all this by decreasing the polar response in the BW where the driver is a point source, so depending on the application/your preferences, it could be considered a negative.
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> And finally, to test drivers, exactly what do I need. I know that I need a sealed testing box and microphones, but what kind of equipment is best suited for quick and reliable testing of drivers' parameters. Thanks
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It depends, as there's different ways and $$ requirements. Search the net, there's tons of info out there.
GM