# Tapered/flared enclosure ports



## Guest (Sep 18, 2007)

Hi, would anyone be able to explain to me the rationale behind tapered ports, as seen in transmission line speakers or e.g. the B&W Nautilus?

I have seen styles that taper down to a small outlet, and also 'horn' style flares from within the enclosure.

Which is preferable, and do they offer significant advantages over a straight (i.e. non-tapering) transmission line? Are the parameters for the 'gradient' of taper particularly difficult to work out?

Thanks for your help!

Judah.


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## Anthony (Oct 5, 2006)

I'm not familiar with the TL or ported design theory as much, but there are a few people here who are. Hopefully they will chime in. 

I do know from acoustics classes that sound hates hard corners.  Put another way, for every hard corner edge, you get an impedance change. The most obvious case is baffle step, where the speaker starts to radiate into full space instead of just the front half. At the edges you get a soft of muffled diffraction source. It's of low amplitude, but it can be treated like the speaker re-radiating at that corner. This can cause interference distortion and some phase distortion, as the re-radiation occurs with a slight time delay.

Apply this lesson to ports and it is a good reason to make a smooth flare instead of a hard transition. I'm sure these effects are more audible in some cases and might not even be noticed in others.

I have no idea how it applies in TL theory.

Good luck,
A


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## Geoff St. Germain (Dec 18, 2006)

There's some information here that might be helpful: http://www.quarter-wave.com/

Martin J. King's MathCAD worksheets can be used to calculate the effects of various lines on the speaker's output.


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## Guest (Sep 19, 2007)

Thanks for those tips - will take a look at the q-wave site too!


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