If I have a sub enclosure that is one single chamber and I'm trying to determine the tuning frequency:
do (2) 3"(diameter) by 4.5" (length) ports equal a 6" (diameter) by 4.5" (length) port or a 3" (diameter) by 9" (length) port?

 

Using the basic mathematical equation to find the area of a circle [A=pi(r^2)]:

The area of ONE 3" port is 7.065"

The area of TWO 3" ports is 14.13"

The area of FOUR 3" ports is 28.26"

The area of ONE 6" port is 28.26"

So two 3" ports do not equal one 6" port in area.

 

wow... i should be ashamed... so (2) 3" ports will have the same area as roughly (1) 4.25" port

 

Roughly, yes.

Are your plans asking for TWO 3" ports, but you only want to use one?

 

I have an enclosure that looks similar in shape to a zenclosure... it is an mdf/fiberglass mix that stops just before the space under the rear strut bar... you can't get an idea of its shape without looking inside... I'd say the true internal volume is around 1-1.15 cubic ft (sealed)without the driver... I have a RF HX2 10 being driven by a bridged Crossfire 402 (400X1)... it sounds like a** with too much airspace being sealed for my sub... I bought (2) 3"X4.5" ports and (2) 2.75"X5.25" ports and want to see if I can get a better sound out of it before buying something else... trick is that it's only about 8" deep

 

reverse fire?

also in the mathematics you must include length in that problem

 

the volume would be 31.79 for each of the 3"(diameter) by 4.5" (length) totaling 63.58

127.17

63.58

 

firing toward the hatch
(1) 2.75"X5.25" port @ 1 cubic ft = 47hz
(2) 2.75"X5.25" port @ 1 cubic ft = 63hz

 

Speaker first, tuning later. This is my first post here, I just recently bought a Z and I'm just looking around. I'm 50 and have built sound systems since I was very young. Since you already have your enclosure, figure volume first, then decide if you want sealed or ported and find your speaker from there. If you go ported, then work on the port volume you'll need. I use several programs for calcs, but I tend to stay with SoundEasy for tuning, we can even plug in the cabin volume and get you a closer look an real world before you turn the first screw.