I'm about to start building a new box for my Phoenix Gold TantrumX 10DVC. The specs for a ported enclosure call for 0.85 cu. ft. with a 2" diameter port that is 9" long. These are the SQ dimensions. What I'm curious about is how do I figure out what the frequency of this enclosure will be? I want it to sound as clean as possible, but still hit pretty deep. The manual gives me a number for "Fs"-31.9 Hz. I thought that Fs is the frequency in which the subs impedance is at its maximum. Is there any way to use 2 ports instead of one? I figured that the volume of the port is what is importand, so if I had two smaller ports with the same internal volume as on bigger one it should sound the same. Am I correct in assuming so? Thank you all for helping me out!
no, that's not correct if you have 1 port that is 2" x 9" and you decide to do 2 ports they will be somewhere will be 2" x 17 each, tuning is a wierd thing, what you think is right is usually wrong. the internal volume of 2 smaller ports might equal the same internal volume but the tuning frequency would be completely different. there's a few sights i use to figure out my ports, mainly i use
https://www.carstereo.com they're calculator is awesome and easy to use.
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what!?!?! you want some??
It's not a matter of the volume of the port... It's a matter of the surface area of the oppening.
Basically, it works this way: The bigger the oppening, the longer the port must be in order to reach a certain frequency, which is an inverse function. What this means, is that if you are going to double the number of ports, you either need to halve the port area, or double the port length, in order to keep the tunning frequency.
For a given opening size, the longer the port, the lower the tuning frequency.
If you think about it it makes sense... Lower frequencies have a longer wave length, thus they must travel a greater distance ( port length) in order to come out in sync with the front wave.
Thanks guys! That makes sense. I'll check out the site you recommended kickerstang.
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Here is a good calculator to use with figuring ports https://www.carstereo.com/help2/Articles.cfm?id=31
I brought up your manual to have a look, and used the vent length calculator, knowing that the specs were for a 2" X 9" tube. The tuning frequency came out to be 30.85 Hz. for your SQ enclosure when built to the volume PG demands. You should, of course, follow their recommendations to the letter. Why would you want to use 2 ports? If PG's engineers say to use one, I'd do what they say.
...(Just for general knowledge...a 30.85 wave length is 36.5 feet long, which is somewhat longer than the tube length! ...) ;)
You see in the manual that the SPL size is 3 X 12. That makes the SPL box tuned at 39.75 Hz. Note that they prefer the SQ tuning for quality, but the SPL tuning "fits the basshead's need for maximum output while sacrificing some sound quality".
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.