Knocker Posted March 10, 2015 Report Posted March 10, 2015 Up until yesterday I wasn't even aware of end correction and the phenomenon it is used to compensate for. Fortunately my tuning only drops by 1 hz. Is this something that is commonly overlooked? For those who don't know what end correction is, apparently when the side of an enclosure is used as a port wall and the port comes to an end and the wall continues on, the woofer "sees" the port as continuing on for the length of half the width of the port. So a 20 x 4 port that is 25 inches long is actually seen by the driver as being 27 inches long. Curious as to whether or not my software compensated for this when it asked if I had any common walls.
MrBigs63' Posted March 10, 2015 Report Posted March 10, 2015 Some softwares do account for end correction. A lot don't. It doesn't matter for a lot of people because they just guestimate on a lot of factors with building their box anyway. They don't factor in things like 45 displacement, bracing displacement, or port wall displacement. On the other hand, one hert or less here or there isn't that big of a deal in most applications. It is something that should be accounted for if you want to get your tuning to an exact figure, but for the general application, most people don't really need to tune to an exact number.
Joe X Posted March 10, 2015 Report Posted March 10, 2015 Torres calculator accounts for it, if you have the chance enter the data of your box in it and see what happens.
Krakin Posted March 10, 2015 Report Posted March 10, 2015 End correction doesn't account for a hertz or two. It can completely change of a box. 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.
Knocker Posted March 10, 2015 Author Report Posted March 10, 2015 End correction doesn't account for a hertz or two. It can completely change of a box. I see what you mean. It made my port 2.375 inches longer which dropped my enclosure volume by .14 cubes which increased my port area/enclosure volume ratio.
Krakin Posted March 10, 2015 Report Posted March 10, 2015 Port area per volume means nothing. 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.
Triticum Agricolam Posted March 10, 2015 Report Posted March 10, 2015 End correction is an area that I think is largely overlooked, there are several ways to account for it, some are more sophisticated than others. Like JoeX said, Torres does account for it, though in a fairly simplistic way. A more accurate way is to calculate the port length/tuning manually use different end correction factors (referred to as 'k') dependent on how your port is laid out. This image shows the different values of 'k': Obviously its in german, but you can figure it out pretty easily. The port length formula is similar to the one presented here: http://www.diysubwoofers.org/misc/portcal.htm You kinda have to like math to do things this way, but that's part of the fun for me. "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:
Knocker Posted March 10, 2015 Author Report Posted March 10, 2015 My port design is laid out like the example on the bottom right so I used 2.227 as K. I did the math (I'm not very good at math) and came up with 28.2, not sure what 28.2 means. Here is a screen shot of my original box design parameters on Ultimate Car Audio App and a screen shot of the box design I'm using (not my box). Mayhem 18 will be on top. Is 28.2 my port length in inches? Or is my box design on my program already accurate? I only have an Android tablet am am not able to use Torres. Edit: My desired port frequency is 33 hz.
Knocker Posted March 11, 2015 Author Report Posted March 11, 2015 End correction is an area that I think is largely overlooked, there are several ways to account for it, some are more sophisticated than others. Like JoeX said, Torres does account for it, though in a fairly simplistic way. A more accurate way is to calculate the port length/tuning manually use different end correction factors (referred to as 'k') dependent on how your port is laid out. This image shows the different values of 'k': Obviously its in german, but you can figure it out pretty easily. The port length formula is similar to the one presented here: http://www.diysubwoofers.org/misc/portcal.htm You kinda have to like math to do things this way, but that's part of the fun for me. Still learning how to use this forum but I think I may have to use the "quote" thing to get you to see my question above. Really curious about how that math works and if I got the right answer and how to use it.
Joe X Posted March 11, 2015 Report Posted March 11, 2015 Here's your box in Torres, it looks like the software you are using and Torres are pretty close in this case:
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