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Chorus Port Tubes


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I read suggestions on this forum to get more bass from Chorus 1s is to use 7" port tubes.  So I made four 7" tubes out of thick poster paper.  Yes I went for fire Red :)


Anyhow it did give the bass more Snap and if I put my hand by the ports I can now feel air pumping out where as with the holes I really did not feel much air.


I did not even seal them, they are just in via friction fit.  I rolled them up put them in the holes let them expand so they were tight then just taped the edges so it would not unroll.  


Just wondering what the relationship is between bass and port tube length and or diameter.


Obviously the short (thickness of the wood 3/4") holes had less bass.   But what would a tube 4" do vs 7" or 3" diameter vs 4" diameter?


I used a calculator for 38hz and it was around 7" using 5 cubic feet for the chorus size.   The Chorus has a K48 woofer that looks like it can go to 30hz.  So why not use 30hz as the frequency?  I think that gives around 9" tubes.  


Can anyone clarify the pros and cons of going to long for the port tube?  

Edited by BobK
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Guess it could get muddy or inaudible the difference. Going to try it?

38hz is getting pretty low over the stock 45hz(40?), with a - +3 db THE

Given the depth of the box, 7 inch may be the optimum. But, easy to confirm given the  poster paper.

Let us know please,thanks!

Edited by billybob
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Does anyone have the T-S parameters on the woofer so we can run a box response type thing?

It seems to me we can assume the interior of the box is about 80% of the outside measurements (to account for the riser, thickness of walls, and displacement caused by the bass driver, horns, and ports. But maybe someone has more detailed information.


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You don't get something for nothing.  I would guess that as you get more lower bass extension you would lose efficiency.  And there has to be a point at which the lower limits of the woofer are reached, no matter how long you make the port.  The PDF indicates the range of the driver is 30Hz to 3000Hz.  The box tune is 39Hz.


Edited by wvu80
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Found this in another post:


I emailed Eminence about 15677 years ago and was told it is the K-48-E woofer with Fs 42 hz, qt.35, vas 166 liters, 97udb 1w/1m and 4 ohm impedance. Was used in the Chorus II I was told.


Specs seem to be different from the PDF above. Chorus and Chorus II both use the same K-48 woofer. Can't confirm if they are actually accurate.

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