enclosure porting

nobody in the car audio forums seems to want to help me, i need to know if instead of using a 3" by 9.75" long port like my sub specs say too, if i can use two 1.5" by 9.75" ports instead. will this still give me the same results? the reason i want to know is that my box won't allow me to use the 3" port, which is 3.5" OD any help would be greatly appreciated thanx.

Should not make a big difference audibly with two ports and 1/2 the diameter.Jeff

Velocity Custom Home Theater

Mobile Audio/Video Specialist

Morden, Manitoba CANADA

Yes, half the diameter & half the length.Jeff

Velocity Custom Home Theater

Mobile Audio/Video Specialist

Morden, Manitoba CANADA

thanx, that helps alot, when it comes to wiring and installing, i'm a genius, but when it comes to all the technicalstuff with boxes,porting,Qs,Fe, andthe rest of it, i'm not as smart as i think lol. thanx again

I disagree. Port length is dependent on area, not diameter. Two 1.5" diameter ports only have a combined area of 3.53 square inches while a 3" port has an area of 7.07 square inches. To keep the tuning frequency the same the 1.5" ports would need to be a little less than 5" in length instead of 9.75".

but if were to use two ports, 1.5" dia. that were 9.75" long your saying its not the same  as one 3" dia. and 9.75"long?

bigunner1 wrote: but if were to use two ports, 1.5" dia. that were 9.75" long your saying its not the same  as one 3" dia. and 9.75"long?

Yes, thats what I'm saying. If you want to use two 1.5" ports they only need to be 4 7/8" long.