Cj Kumz Posted November 21, 2014 Report Share Posted November 21, 2014 Ok so we all know the general rule for aero ports is 9-12sq inches per cube and slot ports is 12-16sq inches per cube right. And we also know that Xmax, cone area and tuning frequency will affect port area. So in two examples lets look at an AQ HDC3 15 which has an Xmax of 36mm and we want to tune to 35hz in a 4 cube box. AQ suggests 64sq inches of port for a 4 cube box as you can see above. That's example 1. Then according to the Xmax theory a 4 cube box at 35hz will require a port area of 131sq inches which is 32.75sq inches per cube as shown above. So what method do you box builders use? And what are your reasons? Vw Polo Pioneer Deh-6050UB Sundown Saz-3500d DD Audio 9500 15'' 5.5 cubic feet box with 10 inch port @ 38hz I live to hear the Bass drop!!! Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted November 21, 2014 Report Share Posted November 21, 2014 So like many things, reality is more complex than what the formulas can tell you. The vent calculator you used in your second example is based on keeping port velocity down at a fairly conservative speed. It also assumes you will be pushing the sub to its limits in terms of extension, both these things result in it giving you a pretty big number. If you were to use this number you would certainly be fine and wouldn't have any port velocity problems. What you would also have is a huge port, that is a mile long, which can have its own set of issues. It has been my experience that if you round over all the edges of the port and use generous flares you can get away with port area that's around 75% of what the port area calculator tells you. Another thing to factor is how much power you are going to be pushing to the sub. If you only put RMS power to that HDC15 you can use a lot less port than if you are going to through 4K at it. WinISD can be a good tool for helping you determine how power is going to effect port velocities. Lower port velocities are always better, but I try to keep things at or below the high 20's m/sec. So using the HDC15 example I would probably shoot for a port in the 90 sq in area. "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...
hdorre Posted November 21, 2014 Report Share Posted November 21, 2014 Meh, i threw away that ratio after talking with Singer and Butler like a yr ago. They both recommend me with a 4" aero and 2-2.1 cube box... which comes out to 5.9sqin/cube. Then.. To test.. I did (2) 3" ports in 2.1 subs, which was closer to the "ratio" at 6.7sqin/cube. Guess what box performed better.. Sure, application matters.. But this opened my eyes.. On top of that, I started modeling my port/vent velocity for those boxes, along with friends'.. and did some reading.. I saw a common theme. On 5/8/2011 at 7:38 PM, Kranny said: On 5/8/2011 at 7:35 PM, 'Maxim' said: It hurts me inside when I read stuff like this and remember you're 15 LMFAO so true Mitsubishi 3000GT (Old Build) Headunit: Pioneer 80PRS Frontstage: (2) McLaren Audio MLT-2 Tweeters & (4) PRV Audio MR Series Neo 6.5" Mids Substage: 4 15" Hybrid Subs - Tantric Motors & Sundown Softies Amps: Banda 2.4D Amp (Tweets), American Bass VFL 350.4 (Mids), and (2) Ampere 3800s Electrical :Singer 260A Alt & JY Power Lithium 2005 Chevy Colorado Ext Cab Headunit: Pioneer 80PRS Frontstage: 4 PRV 700Ti Tweets & 6 10" Delta Mids on 3000wrms Substage: 6 Fi BTL 18s in a 4th Order Walkthrough on 3 Wolfram 4500s Electrical: Singer "390" and JY Power My Official Feedback Thread Link to comment Share on other sites More sharing options...
Cj Kumz Posted November 22, 2014 Author Report Share Posted November 22, 2014 So like many things, reality is more complex than what the formulas can tell you. The vent calculator you used in your second example is based on keeping port velocity down at a fairly conservative speed. It also assumes you will be pushing the sub to its limits in terms of extension, both these things result in it giving you a pretty big number. If you were to use this number you would certainly be fine and wouldn't have any port velocity problems. What you would also have is a huge port, that is a mile long, which can have its own set of issues. It has been my experience that if you round over all the edges of the port and use generous flares you can get away with port area that's around 75% of what the port area calculator tells you. Another thing to factor is how much power you are going to be pushing to the sub. If you only put RMS power to that HDC15 you can use a lot less port than if you are going to through 4K at it. WinISD can be a good tool for helping you determine how power is going to effect port velocities. Lower port velocities are always better, but I try to keep things at or below the high 20's m/sec. So using the HDC15 example I would probably shoot for a port in the 90 sq in area. Thanks a lot. So in general the box size won't affect how much port area you use? Like the 90sq in would that be the same for a 3, 4 and 5 cube box with the same sub? Currently I have an hdc315 in a 4 cube box with about 64sq inches and considering a box change Vw Polo Pioneer Deh-6050UB Sundown Saz-3500d DD Audio 9500 15'' 5.5 cubic feet box with 10 inch port @ 38hz I live to hear the Bass drop!!! Link to comment Share on other sites More sharing options...
Cj Kumz Posted November 22, 2014 Author Report Share Posted November 22, 2014 Meh, i threw away that ratio after talking with Singer and Butler like a yr ago. They both recommend me with a 4" aero and 2-2.1 cube box... which comes out to 5.9sqin/cube. Then.. To test.. I did (2) 3" ports in 2.1 subs, which was closer to the "ratio" at 6.7sqin/cube. Guess what box performed better.. Sure, application matters.. But this opened my eyes.. On top of that, I started modeling my port/vent velocity for those boxes, along with friends'.. and did some reading.. I saw a common theme. Ok so the main issue when designing a box is velocity? As long as its undercontrol then we safe Vw Polo Pioneer Deh-6050UB Sundown Saz-3500d DD Audio 9500 15'' 5.5 cubic feet box with 10 inch port @ 38hz I live to hear the Bass drop!!! Link to comment Share on other sites More sharing options...
Krakin Posted November 22, 2014 Report Share Posted November 22, 2014 Count the number of fingers and toes you have, keep the velocity below the amount of those added together in meters per second. 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...
alaskanzx5 Posted November 22, 2014 Report Share Posted November 22, 2014 Anyone know a good port velocity calc? t1500bdcp 2 t2d4 15" 1 t600.4 1 t400.2 1 set p1 tweets singer alt, tons of wiring, smd vm-1, 80prs, back seat delete, still in the works, aiming for a 145-147 with the ability to play 25hz up to 50hz. Link to comment Share on other sites More sharing options...
Joe X Posted November 22, 2014 Report Share Posted November 22, 2014 Anyone know a good port velocity calc? Any modeling software will do but the results are theoretical as usually assume there are no losses, the better way to know is to measure it. Link to comment Share on other sites More sharing options...
alaskanzx5 Posted November 22, 2014 Report Share Posted November 22, 2014 How do you measure it? t1500bdcp 2 t2d4 15" 1 t600.4 1 t400.2 1 set p1 tweets singer alt, tons of wiring, smd vm-1, 80prs, back seat delete, still in the works, aiming for a 145-147 with the ability to play 25hz up to 50hz. Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted November 22, 2014 Report Share Posted November 22, 2014 How do you measure it? Hot wire anemometer is the best way. Not a really common tool unfortunately. "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...
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