ShawnM Posted June 22, 2016 Report Share Posted June 22, 2016 Rough example of my design and situation .... Tuning to 34 hz.... 13 cubes - port 7x37.5 (SLOT port) - winisd calls for 33.5 length on its calculator but if I find a SLOT port calculator online 'car stereo.com' etc. And select the slot option it gives me 14.95" length!?(unselect the slot option and it's 33.5 just like winisd) but Translate the 14.95 back to winisd and it says that will bring tuning up to somewhere around 50 hz with that port length. This IS a slot port using outside of box as port so which length do I go with!? First box I'm designing myself and just want to make sure I get the port right. The short port option seems wronge to me compaired to prior designs I've received both by my friend who has plenty experience and even Mark from CAF who i purchased my last design from ... in his old youtube video on designing a box he uses the winisd length for his slot style ported encloser. I really want to get this one myself vs have my buddy design it for me lol any help/input would be appreciated. Thanks. Link to comment Share on other sites More sharing options...
Krakin Posted June 23, 2016 Report Share Posted June 23, 2016 I would use WINisd and get the port velocity down, I haven't messed with audio for a couple of years since starting college, but I believe you want to keep it below 14 m/s. 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...
Shmuggie Posted June 23, 2016 Report Share Posted June 23, 2016 Thanks for the reply krakin! but I'm just concerned with which length will give me the tuning I am after. I haven't chosen my exact port size yet but out of the few possibilities i have ... none exceed 65ft/s which should be fine as port will also be kerfed. Original example is not my exact plot but just enough to provide the example. I guess my question could have been a little more simple tho lol .... does anyone know WHY a calculator would give a shorter port length for a 'slot' port??? http://www.carstereo.com/help/Articles.cfm?id=31 http://www.mobileinformationlabs.com/HowTo-1Woofer-Box-CAL%20Port%20lenth%201.htm Both of thoseach calculators give same answer. If you enter 13 cubes- 34hz - H-7 and W-37.5 Selecting yes slot gives 14.75 Selecting no slot gives 33.7 which is same as ANY other calculator on the net gives as well as winisd shows 33.5 so I'm leaning toward the 33.5 Those lengths make a massive difference on displacement before I can proceed with my box design. Link to comment Share on other sites More sharing options...
Shmuggie Posted June 23, 2016 Report Share Posted June 23, 2016 And sorry for posting from different accounts. Couldn't remember my pswrd so had to make a new one shawnm on my laptop but my phone autologged me into my original (this one) so thats a bonus lol Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted June 23, 2016 Report Share Posted June 23, 2016 So with slot ports the port performs like it is longer than it actually is, this is because it interacts with the side walls of the enclosure. There is a way to account for this called end correction. WinISD has some basic end correction options (for flanged vs non-flanged ports), it doesn't have proper end corrections for slot ports though. Due to this it will probably tune you lower than you intend. The carstereo.com calculator does have slot port end correction, but it isn't intuitive to use. When you select "slot port" it subtracts half the width of the port from the port length, which is a valid method for end correction. The trick is you have to enter the smaller dimension of your port in as the width. So if you port is 7 x 37.5, make sure you enter 7 for width and 37.5 for height. If you out 37.5 for width it's going to subtract half of that from the port length which is not what you want. "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...
Shmuggie Posted June 23, 2016 Report Share Posted June 23, 2016 Thanks for the explanation, makes sense now! I knew there was no way 14" could be right and just needed some confirmation. I appreciate the info ? Link to comment Share on other sites More sharing options...
Krakin Posted June 23, 2016 Report Share Posted June 23, 2016 Sorry taking to fast track math courses right now and I completely didn't related what I was saying to being about area and not length. My bad. 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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