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Old 2nd April 2012, 05:59 PM   #1
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Default cross sectional area shapes

do transmission lines and other designs that rely on wave formations see a cross section as purely an area of space, or does the cross sectional shape affect the chambers ability to form the 1/3 or 1/4 wave?

i drew some rough shapes below, are these all equal in terms of the terminus output for the same area? i assume certain shapes will affect the internally reflected wave acting on the cone, same sides all resonating the same etc?

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Old 2nd April 2012, 06:39 PM   #2
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by gafhenderson View Post
do transmission lines and other designs that rely on wave formations see a cross section as purely an area of space, or does the cross sectional shape affect the chambers ability to form the 1/3 or 1/4 wave?

i drew some rough shapes below, are these all equal in terms of the terminus output for the same area? i assume certain shapes will affect the internally reflected wave acting on the cone, same sides all resonating the same etc?

Click the image to open in full size.

For 1/4 Wave action enclosures, I tend to stick with easily fabricated shapes - which usually means 3 or 4 sided. What I have noticed is that a wide and very shallow aspect ratio can induce coloration most noticeable in the vocal range ( PAWO); and that while bass extension may be equally deep, exactly square profiles seem to exhibit less resolution/ "articulation" in lower octaves than those with "golden ratio" dimensions
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Old 2nd April 2012, 08:58 PM   #3
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Quote:
Originally Posted by chrisb View Post
For 1/4 Wave action enclosures, I tend to stick with easily fabricated shapes - which usually means 3 or 4 sided. What I have noticed is that a wide and very shallow aspect ratio can induce coloration most noticeable in the vocal range ( PAWO); and that while bass extension may be equally deep, exactly square profiles seem to exhibit less resolution/ "articulation" in lower octaves than those with "golden ratio" dimensions
just being somewhat dumb here, would that mean it would be less of an acoustic impact to build a folded line sub with a very shallow profile (thick walled) as the ranges a sub usually works over is usually fairly far from vocals?

whereas a speaker that will handle vocals would suit a 'fuller' profile closer the golden ratio?
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Old 2nd April 2012, 09:29 PM   #4
chrisb is offline chrisb  Canada
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Originally Posted by gafhenderson View Post
just being somewhat dumb here, would that mean it would be less of an acoustic impact to build a folded line sub with a very shallow profile (thick walled) as the ranges a sub usually works over is usually fairly far from vocals?

whereas a speaker that will handle vocals would suit a 'fuller' profile closer the golden ratio?

If I understand the 2-part question correctly, I think yes

issues with some sub drivers is getting them to fit in very shallow boxes, particularly if folded
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Old 2nd April 2012, 09:58 PM   #5
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Originally Posted by chrisb View Post
If I understand the 2-part question correctly, I think yes

issues with some sub drivers is getting them to fit in very shallow boxes, particularly if folded
thanks for the advice.

as a ratio of driver depth to cabinet depth, what kind of area would you aim for?

eg 10cm mounting depth, 20cm depth 1:2
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Old 3rd April 2012, 04:23 AM   #6
GM is offline GM  United States
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While 'sound is round', where the WLs are large compared to the container's CSA, i.e. has a ~uniform particle density, then within reason the shape doesn't much matter until it has to go around a bend or drive a terminus. As a CSA's rectangular aspect ratio increases though, at some point friction begins to dampened pipe action enough to be noticed. Studying up on air handling duct systems will tell all.

Golden or acoustic ratios are used to average out eigenmodes in a box or duct. Some say it doesn't matter enough to bother in 1/4 WL designs due to the stuffing and in the typically acoustically tiny cabs popular these days they're probably right, but in the large cabs I'm known for, it makes a difference.

GM
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