TS2GFrank Posted March 4, 2014 Report Posted March 4, 2014 Sorry for my noob question .I've been trying to learn more about building enclosures so I've been reading up on everything I can and even playing around with Torres. One thing I still don't quite understand is port tuning. Everyday I see pics of enclosures with HUGE ports and they play really well when it comes to low-end. But when I'm designing a box in Torres it seems like smaller the port the lower the tuned frequency. I even plug in my boxes dimensions which were built for SPL by someone else and if I make the port smaller the tuning freq goes down and my ports are pretty big but my box is tuned to about 43hz. How does this work??
Kotoma Posted March 4, 2014 Report Posted March 4, 2014 I would like to know this aswell! 2 x DD Redline 818 2 x DD m2b 1 x Gladen SQX 165 Component set Sony DSX-S3000BTX
iKidwell Posted March 4, 2014 Report Posted March 4, 2014 take into account how large the boxes with the huge ports are. The amount of port that you have is dependent on how big your box is and what your subs like. You won't see a pair of 12's with a 14"x8" port because that's just too big (unless you're burping). But if you want your port to seem big for the box, (imo anything over 15 sq in of port per foot looks like a big ass port) and tune low, then you'd need the port to be long, which ends up taking up a bunch of internal space for the box. c'mon now, if i was shooting an 8 year old, it wouldnt be MY 8 year old. i recently got a Pyle PL1590BL and i was building an enclosure for it tuned to 25 hz. i didn't have any tools to cut a circle so i hit it with a big hammer. 2003 Infiniti G35 Sport Sedan Build in Progress
PolishThunder Posted March 4, 2014 Report Posted March 4, 2014 I have been researching a lot about this too, I have found that WinISD is a great program to use for port tuning. Its free to download and there are a few videos showing how to use it. You can download the pro alpha version free here: http://www.linearteam.dk/default.aspx?download=winisdpro I like the Alpha version better but there is also a beta version that's a little bit different. Another good source to learn about anything with audio is the Loudspeaker Design Cookbook by Vance Dickason. Its more advanced but there is a free pdf version of the book here: https://docs.google.com/file/d/0B_l73GVBBlIUNTc2YTc2YTktNTNmYi00YWNmLTlmY2ItZTU0MTRhMzdkYTAy/edit
Triticum Agricolam Posted March 4, 2014 Report Posted March 4, 2014 The tuning of the port is determined by the relationship between the size the of the box, the area of the port and the length of the port. If you keep everything else the same and make the port longer the tuning will go down, if you make the port area smaller the tuning will go down, or if you make the box larger the tuning will go down. If you do the opposite of any of those things, the tuning will go up. I also recommend you get WinISD and just play around with it, you can learn a lot. If you need help just let us know. If you want to learn more about how ported boxes work you can look at my post here: http://www.stevemeadedesigns.com/board/topic/180344-seeking-design-info-beyond-box-calculators/?p=2669271 "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:
Krakin Posted March 4, 2014 Report Posted March 4, 2014 How large a port is is not dependent a single bit on the internal volume of the enclosure. The port area per cubic foot is not a way to determine how much port area to put into your design, and it will not determine how large of a bandwidth you have unless you have such a small port that it compresses the air enough to seem like it plays low. You determine the amount of port area you need based off of the amount of cone area you have, the xmax of the drivers in use, and the tuned frequency of your choosing. Note that volume IS NOT one of the variables listed. The reason that you use these variables is to be able to find the amount of area that you need to get the velocity of the air going in and out of the port low enough so that you do not get an uncontrolled velocity of air coming out. This is called port compression, port flares allow a controlled change in velocity as air exits a port. This can prevent turbulence in the boundary layer, close to the port wall, from becoming audible. As the air velocity is raised a little further, turbulence within the straight section of the port becomes an issue.The reason a ported speaker works is because the air in the port causes a 180 degree phase shift in the air behind the driver. When the air comes out of the port, at least at the tuning frequency, it is in-phase with the front of the driver, giving a boost to the output. As air in the core of the port becomes turbulent, this phase shift decreases, thus reducing the in-phase contribution made by the port. The total output of the box no longer rises at the same rate as input power is increased, and the port is said to be compressing. Eventually the port acts as a mere hole in the box, short circuiting the acoustic output of the driver and allowing excursion to become uncontrolled. If you want to learn a whole lot about The Loudspeaker Cookbook by Vance above this post is an amazing book. If you want to learn about the origins of ported enclosures along with car engines and some other things you can refer to this document on the Helmholtz Resonator. https://play.google.com/books/reader?id=Xy4DAAAAQAAJ&printsec=frontcover&output=reader&authuser=0&hl=en&pg=GBS.PP1 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 4, 2014 Report Posted March 4, 2014 You determine the amount of port area you need based off of the amount of cone area you have, the xmax of the drivers in use, and the tuned frequency of your choosing. Note that volume IS NOT one of the variables listed. This. The whole port area per cube idea drives me nuts, though I understand how it came to exist. Also, just to clarify, Krakin and I are not contradicting each other. When I say port tuning is determined by box volume I just mean that changes is box volume will change your tuning if you leave your port area and length the same. When it comes to determining how much port area you need, box volume is irrelevant. "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:
Krakin Posted March 4, 2014 Report Posted March 4, 2014 I saw your post and thought that some people would see that as contradicting, but then ADD kicked in and I hit the home button. Lol 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.
Seymore Posted March 5, 2014 Report Posted March 5, 2014 take into account how large the boxes with the huge ports are. The amount of port that you have is dependent on how big your box is and what your subs like. You won't see a pair of 12's with a 14"x8" port because that's just too big (unless you're burping). But if you want your port to seem big for the box, (imo anything over 15 sq in of port per foot looks like a big ass port) and tune low, then you'd need the port to be long, which ends up taking up a bunch of internal space for the box. I don't even care what you just said, that last quote in your signature made me bust my balls. The best of luck to you, good sir. the best of luck in life. 2001 Civic LX SedanPioneer DEH-7500HD Big 3 in 1/0 Knu CCARockford P500-4RF Punch P165-S in doorsRF Punch P165 in rear deckFront doors deadened with DamplifierNextSQ's new HDS208 8" in a T-line whenever it FINALLY COMES OUT I CAN FINALLY AFFORD IT Bend over and I'll show ya. how is it 2 days work? half a day at most, i may be an idiot, but im not an idiot.
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