jpick Posted December 20, 2014 Report Share Posted December 20, 2014 Can anyone tell me the freq. that the SA-12 single box design...http://www.sundownaudio.com/index.php/products/subwoofers/item/sa-series.html is? According to my calculations, it is around 27hz, but I'm using a port calc, and I'm not even close to being a port expert. Thanks in advance! Link to comment Share on other sites More sharing options...
brent379 Posted December 20, 2014 Report Share Posted December 20, 2014 i cant open their spec and cut sheet, but they are recommending 1.5-2.0 cubes ported at 35 hz, so im about 99.9% sure the answer to your question is 35hz. wouldnt make sense to recommend one thing and give a spec/ cut sheet of another thing. Link to comment Share on other sites More sharing options...
jpick Posted December 20, 2014 Author Report Share Posted December 20, 2014 You are correct brent. It is right at 2.0 cubes net, before sub displacement, after port displacement, but I still get 27 when I calculate the port on a website calculator. But like I said, I haven't done a lot of port work. I've read something about x amount or square inches of port area, per cubic feet, but according to forum member Krakin, in the "understanding ports" thread, says: "Most of everything you have read has been greatly oversimplified, the port per cube guideline is rubbish, and your estimation on flares and their threshold on chuffing isn't accurate as the velocity to make chuffing apparent varies on frequency." And I can tell you, just from reading that thread, he knows WAY more than I do about ports. I just want to know, what "formula" do I use to determine what my box is tuned to. I think I want to adjust the tune frequency a little, but without knowing what it is now, or how to calculate what it will be after I make changes, I'm afraid to mess with it and get it right where I want it for my listening preference. And just FYI, you have to have "SketchUp Viewer" to open the spec and cut sheet, which is a free program, in case you are interested it getting it. Link to comment Share on other sites More sharing options...
brent379 Posted December 20, 2014 Report Share Posted December 20, 2014 http://www.diysubwoofers.org/misc/portcal.htm There is the link for the formula if you want to do it by hand. Idk what online calculator your using but the two I would trust the most is either the one from psp-inc.Com or the12volt.Com Torres also has a pretty decent calculator program that a lot of people use. I combine torres and winisd. Winisd will show you vent velocity. Once you understand vent velocity then yes, the whole port per cube rule goes out the window. It's pretty much useless. And I was on my work computer and can't download programs like that lol Link to comment Share on other sites More sharing options...
SQL50 Posted December 20, 2014 Report Share Posted December 20, 2014 Put it on torres and see what you get. I'll tell you this much, and as you've already read 12-16 in per foot on slot ports, that's just a general guideline and it works for most subwoofers. I try to build closer to 16, and it's always worked for me. I know a lot of it depends on how much power that your running to a certain sub, with a certain amount of x max etc. But to keep from overcomplicating things, stick kind of close to 16 and you'll be satisfied. If your working on a daily driver, and you don't plan on competing (which I'm sure it is with a single sa 12), doing that will be just fine. If you do the math. Sundown recommends 16 in of port per foot net. It's not as complicated as it's made out to be. Link to comment Share on other sites More sharing options...
SQL50 Posted December 20, 2014 Report Share Posted December 20, 2014 Like Brent said, all port area is, is port velocity, which I've went on the 30 m/s or under and have had zero port noise. But back to my statement, the 12-16 in rule of thumb is for someone that's building a box and hasn't had much experience doing so. It works for THE MOST PART. There's many variables that determine that, but most likely sticking close to 16 is going to yield no port noise/minimum depending on power etc. How much are you wanting to put on it? Link to comment Share on other sites More sharing options...
brent379 Posted December 20, 2014 Report Share Posted December 20, 2014 Sql50 I agree with you on it being a general guideline for small daily systems. I've noticed that if your running no more then 1000 rms 12-16 per cube should suffice, but when you start going bigger that rule of thumb diminishes. Link to comment Share on other sites More sharing options...
jpick Posted December 20, 2014 Author Report Share Posted December 20, 2014 Like Brent said, all port area is, is port velocity, which I've went on the 30 m/s or under and have had zero port noise. But back to my statement, the 12-16 in rule of thumb is for someone that's building a box and hasn't had much experience doing so. It works for THE MOST PART. There's many variables that determine that, but most likely sticking close to 16 is going to yield no port noise/minimum depending on power etc. How much are you wanting to put on it? I am going to run the Sundown SCV-2000D at 2 ohms, as close as I can get it to around 600-750 watts. Yes it is a daily driver, not for competition. I do however intend to probably buy a second SA12 before too long, depending how pleased I am with the first one, hence the reason for the 2000D. I have, and tried using WinISD, and I came out of that feeling like I had just read an entire book in German, not being able to speak or read German. I will check into the other sites you both have mentioned, and study more on the "understanding ports" thread. But I really appreciate all your help guys. Thanks! Link to comment Share on other sites More sharing options...
Joe X Posted December 20, 2014 Report Share Posted December 20, 2014 Here's a resource on port calculations: http://www.jlaudio.com/header/Support/Tutorials/Enclosure+Ports/Tutorial%3A+Enclosure+Ports/287541 Ideal port area is calculated with the Richard Small's estimate, here are the equations: http://www.carstereo.com/help/Articles.cfm?id=21 DO NOT use use the table for radiating surface area, get that instead from the manufacturer of your sub(s), hope that clears up your questons. Link to comment Share on other sites More sharing options...
jpick Posted December 20, 2014 Author Report Share Posted December 20, 2014 Ok, here is what I came up with using Torres Box Calculator... https://www.dropbox.com/s/7kuafu6c9h9fhxs/SA12.png?dl=0 For anyone who may be considering using the box. Edit: Picture didn't work. Link to comment Share on other sites More sharing options...
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