View Full Version : quick design questions

12-19-2008, 08:43 PM
aright i ordered 3 4" aero ports, i want to know how much airspace they will take up inside the box so i can calculate the overall dimensions to have 4cuft

the ports will be 16.66" long is what the PP site said with thier calculator, is that from flare to flare or the tube length in the center?

also a hdc315 is .23 cft displacement correct?

12-19-2008, 09:31 PM
bump did i not make my questions clear enough?

i would like to know how much volume the 3 4" aero;s will take up inside of my box, or do you even have to calculate this when finding the net volume of the enclosure?

and also the hdc315 has a displacement of .23 correct?

12-20-2008, 12:05 AM
if i just calculate the displacement of the port as the whole length flare to flare but only 4" radius (straight pipe) will that affect displacement that much?

not sure on calculation to figure out displacement of the curved area of the port, if someone could help me on aim or pm or here that be great

psp calculator said for 3 4" they would have to be Flare Length Port required 15.66

and thats 4.0 cu ft at 38 hz

would that 15.66" be from flare to flare also when cutting the ports to length? first time dealing with them not really sure

12-20-2008, 01:34 PM
no help?

i found this calculation :

Lv = length of the vent tube (in meters)
N = number of ports (unitless)
c = speed of sound (in meters/second)
Rm = mouth radius of the flare (in meters)
Rt = throat radius of the flare (in meters)
Rf = flare radius (in meters)
Fb = frequency of port resonance (in Hertz)
Vb = size of enclosure (in cubic meters)
V = Volume of air in the flare

Rm = Rf + Rt


V = pi*Rf*Rm*Rm - (pi*pi*Rm*Rf*Rf/2) + (2*pi*Rf*Rf*Rf/3)

but without ports on hand i cant figure it out, does anyone know the Rf Rm of a 4" aero? im trying to have this design done and built by next weekend

if no one feels like helping me learn this then i guess i can pay someone for a design, i have mostly everything done just need to figure out the displacement of these ports

12-20-2008, 05:18 PM
bump i think i got th calculation right if someone wouldnt mind checking my math, i got each tube to come out to roughly .12 cu' of displacement

12-20-2008, 06:43 PM
yes that's correct...it's just volume of a cylinder

12-21-2008, 03:09 AM
thanks, would you happen to know if the 5" that needs to be cut to compensate for the flares is from the calculation of straight port or the calculation of flare port from the psp calculator?

Straight Length Port required 14.62
Flare Length Port required 15.62

what it says on site, which measurement should i use and subtract 5 from?

12-21-2008, 03:10 AM
double post