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Port ratio and port area questions


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16 minutes ago, DiBo said:

I go for sound. I don't build for numbers. I should've clarified that. Four numbers I Tune higher. In that case I make the port larger and shorter. For sound I usually make the port recommended +/- 10% or so and longer. I like to peak around 32-36hz if possible. Obviously vehicle resonant frequency is going to vary from vehicle to vehicle. You will get more output with a larger port but you won't get any lows. With those 8's I'd tune around 35 and I'd go with about 18in² of Port area for 72in² total. Length will determine tuning. Triticum calculator wasn't far off in my opinion for those 8's. And when I say off I mean off in terms of my preferences. So I stand corrected about my first statement. Honest mistake

I mean port velocity numbers not dbs! Like what program are you using that is givin you that Information . I don't see that on Torres so I'm assuming you are using different modeling software? And I can't seem to make port area much bigger than about mid 60s before I can't get it to tune lower like 39 either , will post some Torres pages when I get back to my computer, didn't save em on my phone

2009 Silverado 1500, 7.5" lift, 37x12.50r17s, Built Gen 4 5.3L ( 4.8l flat pistons, decked 243s, SS2 Cam, Pac 1218 springs, ported intake, 120mm TB, Long tubes, 3" duals HP tuner software tuned by me), 4l80e swapped and 4.56 gears. All done by me. stereo is Pioneer avh 600ex, all stinger rca, jp23 v1.5, skar rp150.4, and hertz hpd4. 2 SHCA 6.5 8ohm, 1 SHCA 3.5", and 1 DS18 tw120pro in each door. The 3.5 mid and 3.5" tweeters are powered by the skar rp150.4, the 6.5s are powered by the hertz bridged @4 ohms. Dual runs   of 3/0 welding cable, 300a alternator, 2 Vmax AGMs up front. current sub is a AB XR 12 ( dual 2 ohm) with bottom spider cut out in 2.25 cubes at 32hz

 

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1 hour ago, ehall8702 said:

I mean port velocity numbers not dbs! Like what program are you using that is givin you that Information . I don't see that on Torres so I'm assuming you are using different modeling software? And I can't seem to make port area much bigger than about mid 60s before I can't get it to tune lower like 39 either , will post some Torres pages when I get back to my computer, didn't save em on my phone

WinISD for modeling

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Yeah this one's gonna be tough to keep it around 2ft³ and get a higher port area. I just put some numbers in and I can't get it tuned under 37+/- while keeping Port area over 48". Might need to use an aero Port. Port area per ft goes rt out the window with this one. Gonna be around 25+/-with only 50in² of Port area. 

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35 minutes ago, DiBo said:

Yeah this one's gonna be tough to keep it around 2ft³ and get a higher port area. I just put some numbers in and I can't get it tuned under 37+/- while keeping Port area over 48". Might need to use an aero Port. Port area per ft goes rt out the window with this one. Gonna be around 25+/-with only 50in² of Port area. 

I was attempting to get 3.25 net since the subs displacement is .06 each.  Slot port of 13x 4 (I think since I'm not at my computer ) will let me get long enuff to get down to 34hz with ,again I think, 65 sqin port area. That's giving each sub .75 cubes .

2009 Silverado 1500, 7.5" lift, 37x12.50r17s, Built Gen 4 5.3L ( 4.8l flat pistons, decked 243s, SS2 Cam, Pac 1218 springs, ported intake, 120mm TB, Long tubes, 3" duals HP tuner software tuned by me), 4l80e swapped and 4.56 gears. All done by me. stereo is Pioneer avh 600ex, all stinger rca, jp23 v1.5, skar rp150.4, and hertz hpd4. 2 SHCA 6.5 8ohm, 1 SHCA 3.5", and 1 DS18 tw120pro in each door. The 3.5 mid and 3.5" tweeters are powered by the skar rp150.4, the 6.5s are powered by the hertz bridged @4 ohms. Dual runs   of 3/0 welding cable, 300a alternator, 2 Vmax AGMs up front. current sub is a AB XR 12 ( dual 2 ohm) with bottom spider cut out in 2.25 cubes at 32hz

 

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1 hour ago, ehall8702 said:

I was attempting to get 3.25 net since the subs displacement is .06 each.  Slot port of 13x 4 (I think since I'm not at my computer ) will let me get long enuff to get down to 34hz with ,again I think, 65 sqin port area. That's giving each sub .75 cubes .

I thought I saw .5 ft per driver ported. I might've misread. 3ft³ or bigger would make things a lot easier. 

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I've been in the mountains all weekend, didn't see this thread until I just got home.  

First off, my port area calculator is not meant to be the final, definitive word when it comes to how much port area you need.  Its intended for people who don't have access to box simulation software (like WinISD, BassBoxPro, etc) or for people who don't want to spend the time to use that kind software.  That being said, my calculator will usually get you a pretty good number and if anything it errors a bit on the side of caution (which mean more port area), but simulation software will always be better.  

Some people here may disagree with me on this, but high port velocities are bad, ALWAYS and EVERY TIME. This is simple physics.  Wind resistance through the port takes energy out of a system and turns it into heat, energy that would otherwise be output.  Wind resistance quadruples every time you double air velocity.  This is why port compression is no big deal when you go from 5 m/sec of port velocity to 10 m/sec, the numbers are still small.  When you get above 20 m/sec it becomes pretty noticeable and above 30 m/sec it absolutely eats your lunch.  I have measure this exact situation myself and have posted the results of that testing on this forum for everyone to see it.  

In your case ehall8702, you are wanting to put a LOT of power into a relatively small enclosure,  once you get over around 1,000 watts per cubic foot, getting enough port area to effectively avoid port noise and high port velocities becomes almost impossible.  Its just the nature of the physics and you do the best you can.  There is good news though, you are only going to have issues related to not having enough port area when you are playing at maximum output, and right around the tuning frequency.  As long as you aren't competing with the system that's going to be a VERY small amount of the time (for most people, it also depends a bit on the type of music you listen to).  Because of this, you make your best effort to get as much port area as you can, and you accept that it won't be perfect all the time, and chances are you will still be very happy with the system. 

 

"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."

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60in² of Port area in a 3.25ft³ enclosure is plenty imo and experiences. I had 2200 Watts going to a U series 15 with only 52in² Port area. I had no port noise and posted a 145+ DB score with this setup. I could imagine 3k plus would've been another story. With 4-8's and 2500 Watts max I'd imagine he'd be ok. 

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1 hour ago, Triticum Agricolam said:

I've been in the mountains all weekend, didn't see this thread until I just got home.  

First off, my port area calculator is not meant to be the final, definitive word when it comes to how much port area you need.  Its intended for people who don't have access to box simulation software (like WinISD, BassBoxPro, etc) or for people who don't want to spend the time to use that kind software.  That being said, my calculator will usually get you a pretty good number and if anything it errors a bit on the side of caution (which mean more port area), but simulation software will always be better.  

Some people here may disagree with me on this, but high port velocities are bad, ALWAYS and EVERY TIME. This is simple physics.  Wind resistance through the port takes energy out of a system and turns it into heat, energy that would otherwise be output.  Wind resistance quadruples every time you double air velocity.  This is why port compression is no big deal when you go from 5 m/sec of port velocity to 10 m/sec, the numbers are still small.  When you get above 20 m/sec it becomes pretty noticeable and above 30 m/sec it absolutely eats your lunch.  I have measure this exact situation myself and have posted the results of that testing on this forum for everyone to see it.  

In your case ehall8702, you are wanting to put a LOT of power into a relatively small enclosure,  once you get over around 1,000 watts per cubic foot, getting enough port area to effectively avoid port noise and high port velocities becomes almost impossible.  Its just the nature of the physics and you do the best you can.  There is good news though, you are only going to have issues related to not having enough port area when you are playing at maximum output, and right around the tuning frequency.  As long as you aren't competing with the system that's going to be a VERY small amount of the time (for most people, it also depends a bit on the type of music you listen to).  Because of this, you make your best effort to get as much port area as you can, and you accept that it won't be perfect all the time, and chances are you will still be very happy with the system. 

 

955b73dc-ba31-464a-a4cb-5569ce51cb7d-ori
 

 

that's about the best I can come up with. that's 53 wx16hx13d outside dimensions. port is so big im actually under my desired net volume.  And triticum , I very much value your opinion and knowledge, everything I read that you have said makes sense and you back it up with facts so if you so something will work ima go for it.  also my amp puts out 1200 @2 ohms and 3k @.5 ohms so if I just have to I can wire up to 2 ohms . I don't want to not use all my amp, especially after impedance rise, ill be using only like a 1/4 of its full power.

I have 58" total width if I port either front or up, if less than 58 I can port side and use a straight port without a turn in it. 

2009 Silverado 1500, 7.5" lift, 37x12.50r17s, Built Gen 4 5.3L ( 4.8l flat pistons, decked 243s, SS2 Cam, Pac 1218 springs, ported intake, 120mm TB, Long tubes, 3" duals HP tuner software tuned by me), 4l80e swapped and 4.56 gears. All done by me. stereo is Pioneer avh 600ex, all stinger rca, jp23 v1.5, skar rp150.4, and hertz hpd4. 2 SHCA 6.5 8ohm, 1 SHCA 3.5", and 1 DS18 tw120pro in each door. The 3.5 mid and 3.5" tweeters are powered by the skar rp150.4, the 6.5s are powered by the hertz bridged @4 ohms. Dual runs   of 3/0 welding cable, 300a alternator, 2 Vmax AGMs up front. current sub is a AB XR 12 ( dual 2 ohm) with bottom spider cut out in 2.25 cubes at 32hz

 

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4 hours ago, DiBo said:

WinISD for modeling

man  I have absolutely no idea how to use winisd, totally baffles me lol

2009 Silverado 1500, 7.5" lift, 37x12.50r17s, Built Gen 4 5.3L ( 4.8l flat pistons, decked 243s, SS2 Cam, Pac 1218 springs, ported intake, 120mm TB, Long tubes, 3" duals HP tuner software tuned by me), 4l80e swapped and 4.56 gears. All done by me. stereo is Pioneer avh 600ex, all stinger rca, jp23 v1.5, skar rp150.4, and hertz hpd4. 2 SHCA 6.5 8ohm, 1 SHCA 3.5", and 1 DS18 tw120pro in each door. The 3.5 mid and 3.5" tweeters are powered by the skar rp150.4, the 6.5s are powered by the hertz bridged @4 ohms. Dual runs   of 3/0 welding cable, 300a alternator, 2 Vmax AGMs up front. current sub is a AB XR 12 ( dual 2 ohm) with bottom spider cut out in 2.25 cubes at 32hz

 

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