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Different Slot Port ratio's ,..equal diff lengths ??

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  • #16
    Re: Different Slot Port ratio's ,..equal diff lengths ??

    I have never seen one that would give you a different port volume as long as the area stayed the same.

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    • #17
      Re: Different Slot Port ratio's ,..equal diff lengths ??

      If you look at the actual equation used to calculate tuning, there is nothing in it that even remotely relates to the perimeter. It does deal with diameter and number of ports.

      Whoever told you this or wrote that program is pretty bad wrong...to the point of totally erroneous.

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      • #18
        Re: Different Slot Port ratio's ,..equal diff lengths ??

        Sorry if I was incorrect. Please do not go by what I said.

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        • #19
          Re: Different Slot Port ratio's ,..equal diff lengths ??

          Originally posted by winslow View Post
          If you look at the actual equation used to calculate tuning, there is nothing in it that even remotely relates to the perimeter. It does deal with diameter and number of ports.

          Whoever told you this or wrote that program is pretty bad wrong...to the point of totally erroneous.
          Can u show me a link to calculate PORT SLOTS not round slots, to prove that this is erroneous ?

          Here is the one i used :http://www.mobileinformationlabs.com...0lenth%201.htm

          Try it and see if you come to same lengths using round port vs slot port?

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          • #20
            Re: Different Slot Port ratio's ,..equal diff lengths ??

            I just tried that calculator. Using a known build, I tried a 3 cube enclosure with two 4in ports.This came out to 33in. A slot port of 25in came out to about 25in. What we don't know is how that site is doing it's calculations. In contrast, my slot port is 31in and tuning is right at sim in wbcd.
            My Facebook audio pagehttps://www.facebook.com/pages/Mosai...3888294?ref=hl

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            • #21
              Re: Different Slot Port ratio's ,..equal diff lengths ??

              Originally posted by isaeagle4031 View Post
              I just tried that calculator. Using a known build, I tried a 3 cube enclosure with two 4in ports.This came out to 33in. A slot port of 25in came out to about 25in. What we don't know is how that site is doing it's calculations. In contrast, my slot port is 31in and tuning is right at sim in wbcd.
              What does this mean " A slot port of 25in came out to about 25in. ?? and what is wbcd ?

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              • #22
                Re: Different Slot Port ratio's ,..equal diff lengths ??

                A pair of 4"id (round) vents have an area of 4*pi*2, or 25.1 sq.in.
                Your calculator wanted a 33" long vent to tune that 3cf box to (whatever).

                Same software (or website) using a 25 sq.in. slot vent (maybe 1" x 25", or 2" x 12.5") wanted a length of only 25" for the same box/tuning.

                eagle BUILT that box with an equivalent slot vent, and made it 31" long, and it came out correctly to wbcd's predictions (should NOT be 25"). wbcd is another one of Jeff Bagby's softwares (stands for WooferBox?Design - not sure actually, I use WinISD). maybe it's WooferBoxDesignCalculator? - which I guess would be "wbdc".

                chris

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                • #23
                  Re: Different Slot Port ratio's ,..equal diff lengths ??

                  Originally posted by Chris Roemer View Post
                  A pair of 4"id (round) vents have an area of 4*pi*2, or 25.1 sq.in.
                  Your calculator wanted a 33" long vent to tune that 3cf box to (whatever).

                  Same software (or website) using a 25 sq.in. slot vent (maybe 1" x 25", or 2" x 12.5") wanted a length of only 25" for the same box/tuning.

                  eagle BUILT that box with an equivalent slot vent, and made it 31" long, and it came out correctly to wbcd's predictions (should NOT be 25"). wbcd is another one of Jeff Bagby's softwares (stands for WooferBox?Design - not sure actually, I use WinISD). maybe it's WooferBoxDesignCalculator? - which I guess would be "wbdc".

                  chris


                  Try it with a square port 5"x5" and it should be much closer.

                  Try an example with just one port to make things less complicated maybe

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                  • #24
                    Re: Different Slot Port ratio's ,..equal diff lengths ??

                    I used an example for a box that I have actually built and a program, wbcd-woofer box & circuit designer, that I know to be accurate. I am not sure how or why the program you linked has a difference other than it maybe compensating for the volume taken up by the port.

                    ime, I would not trust the accuracy of that site. Neither of the port types are correct in their lengths. Surface area and length vs net volume determine tuning freq of the enclosure. While there is some validity to friction of the two port types based on the perimeter, IMO it is for our purposes a non issue. For high SPL car audio, it maybe, but not in home audio.

                    Oh and I meant 25sq in came out to a length of 25in which I know to be about 5 in short for my tuning of 25hz.
                    My Facebook audio pagehttps://www.facebook.com/pages/Mosai...3888294?ref=hl

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                    • #25
                      Re: Different Slot Port ratio's ,..equal diff lengths ??

                      Originally posted by isaeagle4031 View Post
                      I used an example for a box that I have actually built and a program, wbcd-woofer box & circuit designer, that I know to be accurate. I am not sure how or why the program you linked has a difference other than it maybe compensating for the volume taken up by the port.

                      ime, I would not trust the accuracy of that site. Neither of the port types are correct in their lengths. Surface area and length vs net volume determine tuning freq of the enclosure. While there is some validity to friction of the two port types based on the perimeter, IMO it is for our purposes a non issue. For high SPL car audio, it maybe, but not in home audio.

                      Oh and I meant 25sq in came out to a length of 25in which I know to be about 5 in short for my tuning of 25hz.
                      Just a question : the wbcd site you calculate on , does it have a Specific calculator for Slot ports or do u just convert from a round port calculation??

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                      • #26
                        Re: Different Slot Port ratio's ,..equal diff lengths ??

                        Let me this time preface what I am about to say with "This is my opinion, I have nothing to back it up."

                        The calculator that was used at the beginning of this thread has a selector titled "Are You Using a Slotted Port?" This is adding in an end correction of calculated port length minus half the width of the port. This is not well coded and will give different answers if you switch the height and width. At this point I would not trust anything calculated by this site.

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                        • #27
                          Re: Different Slot Port ratio's ,..equal diff lengths ??

                          wbcd is an excel based program, not a site. I am doing ths conversion from round port to slot port and adjusting the net volume for my enclosure. I have also used winisd and it agreed with wbcd.

                          I think that Duane maybe correct with the site adding in end correction. Except in the example I gave, it called for a shorter slot port than it did for a pair of 4" Ports.
                          My Facebook audio pagehttps://www.facebook.com/pages/Mosai...3888294?ref=hl

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                          • #28
                            Re: Different Slot Port ratio's ,..equal diff lengths ??

                            WBCD is Jeff Bagby's "Woofer Box and Circuit Designer" software. Runs in Excel on the PC. A popular and comprehensive box / circuit designer.
                            I was so much older then, I'm younger than that now.
                            OS MTMs http://techtalk.parts-express.com/sh...d.php?t=220388
                            Swope TM http://techtalk.parts-express.com/sh...d.php?t=221818
                            Econowave and Audio Nirvana AN10 fullrange http://techtalk.parts-express.com/sh...d.php?t=216841
                            Imperial Russian Stouts http://techtalk.parts-express.com/sh...=1#post1840444
                            LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

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                            • #29
                              Re: Different Slot Port ratio's ,..equal diff lengths ??

                              Good god. The formula does not care about the shape...all it cares about is the area of the port to calculate the port volume.

                              Go look at the equation yourself.

                              Why are you being so obtuse?

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                              • #30
                                Re: Different Slot Port ratio's ,..equal diff lengths ??

                                Originally posted by winslow View Post
                                Good god. The formula does not care about the shape...all it cares about is the area of the port to calculate the port volume.

                                Go look at the equation yourself.

                                Why are you being so obtuse?
                                If this was directed at my last post- the web site calculator IS using shape to try to apply an end correction. Try it out.

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