Joe X Posted April 4, 2014 Report Share Posted April 4, 2014 aero port rule of thumb is 9-12 sq in of port per foot ok, so that's where my lack of math skills comes into play... To clarify, you are saying I need 9-12 sq in of port per cubic foot of the box, or length of the port? Do you have T/S parameters for those subs? if no you are going to produce a generic box that no one knows if it's going to be any good for the subs. Link to comment Share on other sites More sharing options...
TzA Posted April 4, 2014 Author Report Share Posted April 4, 2014 This shows what I am seeing on the calculators, at the provided in Krakin's post above. The length of the port for two ports is 49.44. Does this mean I will have 2 - 8" x 24.72" ports. Is there a more efficient way of doing this? The top portion of the calculator suggests that the minimum diameter be 12.5", so 2 - 8" ports will give me a diameter of 16"? F O. Link to comment Share on other sites More sharing options...
Krakin Posted April 4, 2014 Report Share Posted April 4, 2014 That would be (x2) 8" ports at 49.44" a piece. This is much longer than I would have a 35 Hz port be. For 35 I would suggest 32" at the longest to keep the air acting as a single mass. This means that I would try to make the port have less port area, as this would require not as long of a port to abtain the same tuning. Edit: you can also increase internal net volume to lower tuning. Krakin's Home Dipole Project http://www.stevemeadedesigns.com/board/topic/186153-krakins-dipole-project-new-reciever-in-rockford-science/#entry2772370 Krakin, are you some sort of mad scientist? I would have replied earlier, but I was measuring the output of my amp with a yardstick . . . What you hear is not the air pressure variation in itself but what has drawn your attention in the two streams of superimposed air pressure variations at your eardrums An acoustic event has dimensions of Time, Tone, Loudness and Space Everyone learns to render the 3-dimensional localization of sound based on the individual shape of their ears, thus no formula can achieve a definite effect for every listener. Link to comment Share on other sites More sharing options...
TzA Posted April 5, 2014 Author Report Share Posted April 5, 2014 That would be (x2) 8" ports at 49.44" a piece. This is much longer than I would have a 35 Hz port be. For 35 I would suggest 32" at the longest to keep the air acting as a single mass. This means that I would try to make the port have less port area, as this would require not as long of a port to abtain the same tuning. Edit: you can also increase internal net volume to lower tuning. That loses me, if I shorten the port, wont that increase the freq.? With that said, what else would I have to modify to keep the freq. @ about 35? If I were to do x2 6" x 26.71", that would give me the same frequency, but that is only 12" of port diameter.. F O. Link to comment Share on other sites More sharing options...
Krakin Posted April 5, 2014 Report Share Posted April 5, 2014 Shorten port length = higher tuned frequency Larger port area = Higher tuned frequency Smaller NET volume = Higher tuned frequency Longer port length = Lower tuned frequency Lower port area = Lower tuned frequency Larger NET volume = Lower tuned frequency The reason I say you should want a shorter port is not that that will give you the tuned frequency you are aiming for, but to keep the air inside of the port acting as a single mass. Think of a Newton's cradle, as one ball swings down and hits the others that are at rest you want the motion to travel instantly. You want the air inside of the port to act the same. However, if you have a port length exceed 1/12th the length of the resonant frequency then the air inside of the port will no longer be controlled and not act as a single mass. Krakin's Home Dipole Project http://www.stevemeadedesigns.com/board/topic/186153-krakins-dipole-project-new-reciever-in-rockford-science/#entry2772370 Krakin, are you some sort of mad scientist? I would have replied earlier, but I was measuring the output of my amp with a yardstick . . . What you hear is not the air pressure variation in itself but what has drawn your attention in the two streams of superimposed air pressure variations at your eardrums An acoustic event has dimensions of Time, Tone, Loudness and Space Everyone learns to render the 3-dimensional localization of sound based on the individual shape of their ears, thus no formula can achieve a definite effect for every listener. Link to comment Share on other sites More sharing options...
TzA Posted April 5, 2014 Author Report Share Posted April 5, 2014 Shorten port length = higher tuned frequency Larger port area = Higher tuned frequency Smaller NET volume = Higher tuned frequency Longer port length = Lower tuned frequency Lower port area = Lower tuned frequency Larger NET volume = Lower tuned frequency The reason I say you should want a shorter port is not that that will give you the tuned frequency you are aiming for, but to keep the air inside of the port acting as a single mass. Think of a Newton's cradle, as one ball swings down and hits the others that are at rest you want the motion to travel instantly. You want the air inside of the port to act the same. However, if you have a port length exceed 1/12th the length of the resonant frequency then the air inside of the port will no longer be controlled and not act as a single mass. I think I will be ok (if not, great) if I just do two 6" ports @ 26.71" then? this will give me a shorter length but a lower port area. What do you think? Maybe I am just not wrapping my head around this... F O. Link to comment Share on other sites More sharing options...
Krakin Posted April 5, 2014 Report Share Posted April 5, 2014 I'm not sure at what point you will get port noise at different areas with your subs, as I haven't been able to use them before, but all I can really say is to just build something now. Just by getting yourself a box done you will learn a whole lot more about your constraints than I will be able to help you with. Practice teaches an insane amount of knowledge. Just try to get as much area as you can and keep it below 1/12th of the wave-length. Krakin's Home Dipole Project http://www.stevemeadedesigns.com/board/topic/186153-krakins-dipole-project-new-reciever-in-rockford-science/#entry2772370 Krakin, are you some sort of mad scientist? I would have replied earlier, but I was measuring the output of my amp with a yardstick . . . What you hear is not the air pressure variation in itself but what has drawn your attention in the two streams of superimposed air pressure variations at your eardrums An acoustic event has dimensions of Time, Tone, Loudness and Space Everyone learns to render the 3-dimensional localization of sound based on the individual shape of their ears, thus no formula can achieve a definite effect for every listener. Link to comment Share on other sites More sharing options...
TzA Posted April 5, 2014 Author Report Share Posted April 5, 2014 ok. And I guess they say that is the beauty of aero ports, is that they can be changed more easily than a slot... F O. Link to comment Share on other sites More sharing options...
TzA Posted April 7, 2014 Author Report Share Posted April 7, 2014 I'm not sure at what point you will get port noise at different areas with your subs, as I haven't been able to use them before, but all I can really say is to just build something now. Just by getting yourself a box done you will learn a whole lot more about your constraints than I will be able to help you with. Practice teaches an insane amount of knowledge. Just try to get as much area as you can and keep it below 1/12th of the wave-length. Is this for each port or both together? F O. Link to comment Share on other sites More sharing options...
Krakin Posted April 7, 2014 Report Share Posted April 7, 2014 Make the ports the same diameter. Krakin's Home Dipole Project http://www.stevemeadedesigns.com/board/topic/186153-krakins-dipole-project-new-reciever-in-rockford-science/#entry2772370 Krakin, are you some sort of mad scientist? I would have replied earlier, but I was measuring the output of my amp with a yardstick . . . What you hear is not the air pressure variation in itself but what has drawn your attention in the two streams of superimposed air pressure variations at your eardrums An acoustic event has dimensions of Time, Tone, Loudness and Space Everyone learns to render the 3-dimensional localization of sound based on the individual shape of their ears, thus no formula can achieve a definite effect for every listener. Link to comment Share on other sites More sharing options...
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