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15" paraflex kick C-2D

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Discogimp View Drop Down
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    Posted: 27 March 2022 at 12:28pm
Hi all not been on for a while but i'm looking to try and add some kick bins
and found the plans for the C-2D 1X15" which is fine but i want to narrow it
by 50mm over all on the sides so it doesn't over hang my subs.

If i narrow it should i extend the length?

if these are around the 74hz where should i start crossing them over as was thinking at 100 - 250 hz

Cheers Pete
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 28 March 2022 at 10:12am
Originally posted by Discogimp Discogimp wrote:


If i narrow it should i extend the length?


No. The Paraflex designs are based on a series-connected set of resonant pipes or ducts that exit at the mouth, where the rear of the driver also sits in a larger resonant pipe.

The resonant frequencies of a pipe are set by its length and limited by the cross-sectional area, plus any losses due to the rigidity and viscosity of the surface that bounds the inner air volume. A square pipe is a little different to that of a cylinder, too. I

If you make the sections longer, you will change their tuning.

A good illustration of the resonance of pipes can be found here, in relation to wind instruments:
https://newt.phys.unsw.edu.au/jw/pipes.html

And there is an open access paper comparing analytical methods for both cylindrical and rectangular pipes here:
https://www.researchgate.net/publication/27246314_The_Acoustic_Resonance_of_Rectangular_and_Cylindrical_Cavities

Analytical models fall a little short of reality once the pipe is terminated, but the principle is sound.

Even if you don't get all of the maths, the figures and diagrams will help get the differences right in your mind.

Long story short, if you want the same tuning frequencies then you would need to at least increase the height of the box to accommodate the loss of width, paying attention to maintaining the cross sectional areas as you look 'into' each individual pipe you can see in the plan view.

However, that has its limits as the aspect ratio of each pipe gets further away from square and becomes more of a slot. I think you can already see this behaviour in some of the published cabinet designs.

You should also try to consider the mass of a bend or corner where the path length differs at the outer and inner sides. By narrowing that corner, you're changing the shape of the wavefront as it comes around the bend.

Edited by toastyghost - 28 March 2022 at 10:14am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Discogimp Quote  Post ReplyReply Direct Link To This Post Posted: 28 March 2022 at 1:47pm
Hi thanks for that, makes sense what your saying about the keeping the area of the port the same by making it higher............but like you say it probably isn't that simple. Cry

Maybe I'll make the original then the higher version and see I can hear any massive difference as spose I could not glue the top and bottom panels and move them in bit by bit and see what happens.

Thanks for the reply.

Pete
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