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#1
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18" Sub Port Size Question
I am buiding an 18" sub to add to my PA system for live music. I
purchased the driver from an online vendor. Parts Express sells the same driver and has a recomended design produced by anonymous software. I'm assuming that the design is adequate. My question is regarding the port size. The suggested port diameter is 4.5" @ 2.7" long. The closest manufactured port I can find is 4" dia by 4" long (I can cut it to length). Standard PVC pipe steps up from 4" to 6". Would a 4" dia tube work OK or would it seriously affect performance? If I can use the 4" dia tube, would I need to shorten the length? Should I use a 6" diameter tube and alter the length? Am I concerned about something I shouldn't be concerned about? I've included some of the design and speaker parameters below. I would appreciated any insights. ---Box--- Vb = 9.029 cu.ft V(total) = 9.141 cu.ft Fb = 35 Hz F3 = 36.34 Hz Fill = minimal --Vents-- No. of Vents = 2 Vent shape = round Vent ends = one flush Dv = 4.5 in (port diameter) Lv = 2.71 in (port length) --Driver Parameters-- Fs = 27.4 Hz Qms = 5.59 Vas = 14.9 cu.ft Xmax = 5.5 mm Qes = 0.3 Re = 5.55 ohms Le = 1.57 mH Z = 8 ohms Pe = 600 watts |
#2
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"Joel Ramsey" wrote in message
m... I am buiding an 18" sub to add to my PA system for live music. I purchased the driver from an online vendor. Parts Express sells the same driver and has a recomended design produced by anonymous software. I'm assuming that the design is adequate. My question is regarding the port size. The suggested port diameter is 4.5" @ 2.7" long. The closest manufactured port I can find is 4" dia by 4" long (I can cut it to length). Standard PVC pipe steps up from 4" to 6". Would a 4" dia tube work OK or would it seriously affect performance? 2 x 4 inch ports should be OK for a single 18" driver. If I can use the 4" dia tube, would I need to shorten the length? You would need to make them about an inch shorter. Just off the top of my head. Stephen |
#3
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Parts Express. They are near me and I visit their warehouse often.
The port length depends on a few variables. They sell speaker design books and software that can be of great use. Be careful on such large speakers moving such large amount of air. The velocity in a smaller port will be higher and can cause turbulence noise. Check the Web, someone may have the size you needed or flared ports for less noise. John "Joel Ramsey" wrote in message m... I am buiding an 18" sub to add to my PA system for live music. I purchased the driver from an online vendor. Parts Express sells the same driver and has a recomended design produced by anonymous software. I'm assuming that the design is adequate. My question is regarding the port size. The suggested port diameter is 4.5" @ 2.7" long. The closest manufactured port I can find is 4" dia by 4" long (I can cut it to length). Standard PVC pipe steps up from 4" to 6". Would a 4" dia tube work OK or would it seriously affect performance? If I can use the 4" dia tube, would I need to shorten the length? Should I use a 6" diameter tube and alter the length? Am I concerned about something I shouldn't be concerned about? I've included some of the design and speaker parameters below. I would appreciated any insights. ---Box--- Vb = 9.029 cu.ft V(total) = 9.141 cu.ft Fb = 35 Hz F3 = 36.34 Hz Fill = minimal --Vents-- No. of Vents = 2 Vent shape = round Vent ends = one flush Dv = 4.5 in (port diameter) Lv = 2.71 in (port length) --Driver Parameters-- Fs = 27.4 Hz Qms = 5.59 Vas = 14.9 cu.ft Xmax = 5.5 mm Qes = 0.3 Re = 5.55 ohms Le = 1.57 mH Z = 8 ohms Pe = 600 watts |
#4
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#6
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Parts Express sells tapered tubes as well.
"Joel Ramsey" wrote in message m... I am buiding an 18" sub to add to my PA system for live music. I purchased the driver from an online vendor. Parts Express sells the same driver and has a recomended design produced by anonymous software. I'm assuming that the design is adequate. My question is regarding the port size. The suggested port diameter is 4.5" @ 2.7" long. The closest manufactured port I can find is 4" dia by 4" long (I can cut it to length). Standard PVC pipe steps up from 4" to 6". Would a 4" dia tube work OK or would it seriously affect performance? If I can use the 4" dia tube, would I need to shorten the length? Should I use a 6" diameter tube and alter the length? Am I concerned about something I shouldn't be concerned about? I've included some of the design and speaker parameters below. I would appreciated any insights. ---Box--- Vb = 9.029 cu.ft V(total) = 9.141 cu.ft Fb = 35 Hz F3 = 36.34 Hz Fill = minimal --Vents-- No. of Vents = 2 Vent shape = round Vent ends = one flush Dv = 4.5 in (port diameter) Lv = 2.71 in (port length) --Driver Parameters-- Fs = 27.4 Hz Qms = 5.59 Vas = 14.9 cu.ft Xmax = 5.5 mm Qes = 0.3 Re = 5.55 ohms Le = 1.57 mH Z = 8 ohms Pe = 600 watts |
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