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In the Forum: Horn-Loaded Speakers
In the Thread: The tapped horns: cons, pros and Sound
Post Subject: Non-linear problems with single woofer tapped horns. Push-pull is the answerPosted by JLH on: 5/5/2009
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Take a look at the below Dumax Report on the Dayton Titanic Mk III subwoofer.
http://www.parts-express.com/pdf/295-404dumax.pdf
Of course this is not the woofer I used, but the asymmetry seen in this report is very illustrative of most woofers on the market. Even the best pro sound woofers have a degree of asymmetry. Since the motor’s ability to control the cone is not symmetrical, this leads to even order distortion. However, when you use woofers in push-pull with a common chamber; the chamber acts as an acoustical summation device. The suspension non-linearity and the asymmetrical drive get canceled. Where the two woofer’s motor strength differs, the net result is an average of the strengths (Green line). See below graphics.
From original report
Superimposed and flipped to show non-linearity – Green line shows result of summation
Notice how the Bl non-linearity begins at only 3mm of cone travel. Notice how Kms non-linearity begins at only 7mm of cone travel.
This is the best I can explain this from a technical stand. Subjectively, I would not consider using anything but push-pull for “subwoofer” applications. However, I am willing to use single woofers for mid-bass and higher frequencies where dual woofers are not practical. But never use a tapped horn above 150Hz, its not good up there. It all depends on your application. Everyone’s situation is different.
Rgs, JLH
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