BassDoctor Posted March 6, 2014 Report Share Posted March 6, 2014 Let's say that we have a ported box that sits at 1.0ft^3 and is tuned to 40hz. The enclosure has 16in^2 of port per cube. A subwoofer x is used, and is powered by 1000w. Now, assuming this, is there any difference in having a port of 1x16, 2x8, or 4x4? They all come out to the same port area, but is any one better or worse than the other? If so, why? 04 Honda Accord LX Sedan Kenwood Excelon X998 XS Power D3400 XS Power D1200 Singer 275A alternator with factory bypass 64 sqft SecondSkin Damplifier Build to be decided Link to comment Share on other sites More sharing options...
Krakin Posted March 6, 2014 Report Share Posted March 6, 2014 Port per cube means nothing. Download the Torres box calculator and mess around with it to see the affects of different volumes, port areas, and lengths. http://www.stevemeadedesigns.com/board/topic/38791-torres-box-tuning-calculator-updated-818/ 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...
timc31610 Posted March 6, 2014 Report Share Posted March 6, 2014 I think the question is, does it matter what dimensions the port are as long as they equal the desired port area? In his scenario he needs 16 square inches of port, does it matter if it's 8" x 2" or 16" x 1". I would think it wouldnt matter as long as you reach your desired area. My Build Log 94 Civic http://www.stevemeadedesigns.com/board/topic/188644-94-civic-4-door-build-loq-suggestions-wanted-will-be-super-slow-mo/ Faceebook reluctantly Link to comment Share on other sites More sharing options...
BassDoctor Posted March 6, 2014 Author Report Share Posted March 6, 2014 Port per cube means nothing. Download the Torres box calculator and mess around with it to see the affects of different volumes, port areas, and lengths. http://www.stevemeadedesigns.com/board/topic/38791-torres-box-tuning-calculator-updated-818/ I think the question is, does it matter what dimensions the port are as long as they equal the desired port area? In his scenario he needs 16 square inches of port, does it matter if it's 8" x 2" or 16" x 1". I would think it wouldnt matter as long as you reach your desired area. Thanks for replying guys. Yes, that is correct. The case in the OP is hypothetical, I am not looking for a certain box size, tuning, or port area, and so Torres isn't much help in this situation-- though I do enjoy using it for other things. I am asking if the dimensions of the port opening affect port noise, efficiency, anything like that. 04 Honda Accord LX Sedan Kenwood Excelon X998 XS Power D3400 XS Power D1200 Singer 275A alternator with factory bypass 64 sqft SecondSkin Damplifier Build to be decided Link to comment Share on other sites More sharing options...
Krakin Posted March 6, 2014 Report Share Posted March 6, 2014 Oh okay. Let's say he is looking for just 16 sq inches of port area, as that is what subwoofer X at 40 hz calls for. As long as you get the desired area it is fine. There are other factors that are involed in the final tuning such as common walls that the box and port share together. There is also a increase in performance the closer you get to a 1:1 ratio for LxW such as 4in x 4 inch port. It gets even better the closer towards a circle you get. As this gives less surface area for the air to come in contact with on the inside walls of the port. Once again though, don't associate port area per cube with how to tune a box properly. 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...
Triticum Agricolam Posted March 6, 2014 Report Share Posted March 6, 2014 I think the question is, does it matter what dimensions the port are as long as they equal the desired port area? In his scenario he needs 16 square inches of port, does it matter if it's 8" x 2" or 16" x 1". I would think it wouldnt matter as long as you reach your desired area. Yeah, it does matter. Well I should say it can matter. The reason is a port 1" tall and 16" wide has a lot more internal surface area than a port 4" tall and 4" wide. Even though they have the same amount of port area the short and wide port is going to have more air resistance than the square shaped port. This is why a round port of the same port area is the most efficient. There is actually a formula for figuring out how much efficiency loss there is as you go away from a square shaped port. I can post it if anyone is interested. Just for example a square port will be 94% as efficient as a round port of equal port area. The 1"x16" port will only be 64% as efficient. Now as long as your port is a little bigger than it really needs to be the shape becomes less of an issue. When your port velocities start getting higher port shape becomes more of an issue. "Nothing prevents people from knowing the truth more than the belief they already know it.""Making bass is easy, making music is the hard part."Builds: Link to comment Share on other sites More sharing options...
timc31610 Posted March 6, 2014 Report Share Posted March 6, 2014 I think the question is, does it matter what dimensions the port are as long as they equal the desired port area? In his scenario he needs 16 square inches of port, does it matter if it's 8" x 2" or 16" x 1". I would think it wouldnt matter as long as you reach your desired area. Yeah, it does matter. Well I should say it can matter. The reason is a port 1" tall and 16" wide has a lot more internal surface area than a port 4" tall and 4" wide. Even though they have the same amount of port area the short and wide port is going to have more air resistance than the square shaped port. This is why a round port of the same port area is the most efficient. There is actually a formula for figuring out how much efficiency loss there is as you go away from a square shaped port. I can post it if anyone is interested. Just for example a square port will be 94% as efficient as a round port of equal port area. The 1"x16" port will only be 64% as efficient. Now as long as your port is a little bigger than it really needs to be the shape becomes less of an issue. When your port velocities start getting higher port shape becomes more of an issue. I would like to see the formula. Is there a formula to determine the proper port area for a sub? My Build Log 94 Civic http://www.stevemeadedesigns.com/board/topic/188644-94-civic-4-door-build-loq-suggestions-wanted-will-be-super-slow-mo/ Faceebook reluctantly Link to comment Share on other sites More sharing options...
Krakin Posted March 6, 2014 Report Share Posted March 6, 2014 Port noise is affected by the amount of area the port has at a certain tuning.X driver needs Y area to be able to play to the speaker's full potential without noise. This noise is caused by having not enough area, or more specifically enough usable velocity from the port. You can gain a higher usable velocity from either adding more area to the port or having a larger flare radius. There is, however, a limit to how much a flare can help a certain port.For this graph the numbers on the x-axis are the port's diameter, on the Y is the radius of the flare, and the numbers plotted are the maximum usable velocity in meter/seconds. A great tool for learning in even more depth about enclosures would be WinISD. This will graph the output (in a reflection-less environment), air velocities, and much more. To be able to work with the velocities you need you can use this calculator for a quick estimate of the amount of area needed. http://www.carstereo.com/help/Articles.cfm?id=31 For a site that is dedicated, pretty much, to just the design of ported enclosures check this out. http://subwoofer-builder.com/ ^^^^ Really recommend that site! 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...
Krakin Posted March 6, 2014 Report Share Posted March 6, 2014 I would like to see the formula. Is there a formula to determine the proper port area for a sub? The formulas used in the calculator I posted above. http://www.carstereo.com/help/Articles.cfm?id=21 For much more detailed formulas you can check these out. http://www.diysubwoofers.org/misc/portcal.htm It can get even more complicated, but that would probably take some schooling to figure out. 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...
timc31610 Posted March 6, 2014 Report Share Posted March 6, 2014 Thanks guys! I now have homework ahead of me...lol My Build Log 94 Civic http://www.stevemeadedesigns.com/board/topic/188644-94-civic-4-door-build-loq-suggestions-wanted-will-be-super-slow-mo/ Faceebook reluctantly Link to comment Share on other sites More sharing options...
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