MarcoPT Posted October 1, 2018 Report Share Posted October 1, 2018 hey there this is my 3rd box build but the first slot ported... my question is, port area, im at around 23sq in per cube do i need do worry or its ok? the box is for a single 12", a DB sa2712 , im giving it around 1.8k/ 1.9k of power, they recomended 1.9cft but im going with 2cft tune to 36 or 38hz, still deciding... port air speed at 36hz peaks at 55 ft per sec at 32hz port air speed at 38hz peaks at 56 ft per sec at 35hz now my box desing leave me with this port is 3.54 x 13.40 in i could go a bit larger like 4 in to get air speed down to 42ft per sec but it will but up the port area to around 26.7 sq in what would be the best option? if port area at 26.7 isnt a problem i can go 4 in and lower the air speed..... just dont want to lose cone control i like to keep the box on the small like 2 cubes after sub and port displacement Link to comment Share on other sites More sharing options...
mothra Posted October 1, 2018 Report Share Posted October 1, 2018 for me I like a high velocity around 25-28 m/s which is roughly 82-91 ft/s. I'd shrink that port to get a higher velocity and tune lower. this is just how I do things. I try to tune low and get high velocity. it give a wider frequency response and keeps box size down a bit. if nothing changes, nothing changes You don't know what you don't know, till you don't know Link to comment Share on other sites More sharing options...
MarcoPT Posted October 1, 2018 Author Report Share Posted October 1, 2018 i like to tune around the fs of the sub to help kep the cone control (correct me if im wrong), that why my lowest tune started at 35 that i go up as go larger to get a nice compromisse betwen air velocity, port area and tune.... with that air velocity u dont get port noise? thats my afraid, my first desing i had a port with 2.75 in but the air velocity was very high, and i dont want port noise, u get me? the mdf or plywood is very expenssive i want to get it right the the first time lol this is a dally system guys not for spl competicion but yes im a bit of a bass head i want a nice spl but a nice sq too, and i want to be able to play every tipo of music... my corrent sub is a dual 12" pioneer 400 rms each 2 cubes per sub tune to 34 round port form dls and sound great, but i need space... thats why 2 week sub out 1 powerfull in... im setting subsonic somewere between 25 and 30hz my tune curve: Link to comment Share on other sites More sharing options...
MarcoPT Posted October 1, 2018 Author Report Share Posted October 1, 2018 my port velocity Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted October 1, 2018 Report Share Posted October 1, 2018 I have to respectfully, but firmly disagree with mothra. Higher port velocity has absolutely no benefit. When you increase air velocity by 2x, the air resistance increases 4x. Any energy lost to air resistance is lost output, not to mention the annoying port noise you get from high port velocities. If the goals is to flatten the frequency response you will get much more effective and consistent results be simply reducing box net volume. Also reducing port area to increase port velocity does NOT increase cone control, it does exactly the opposite, it reduces cone control! I have tested all of these things myself and I can show you the methods and results of my testing if you are interested. Now with that being said, if your port velocity peaks at 16.5 m/sec, you have nothing to worry about and you could easily reduce your port size a bit if you so desired and save some space. Assuming your port is reasonably laid out and you round over all the sharp edges you shouldn't have to worry about port noise until you get much over 22 m/sec of peak port velocity. "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...
Joe X Posted October 1, 2018 Report Share Posted October 1, 2018 5 hours ago, MarcoPT said: hey there this is my 3rd box build but the first slot ported... my question is, port area, im at around 23sq in per cube do i need do worry or its ok? the box is for a single 12", a DB sa2712 , im giving it around 1.8k/ 1.9k of power, they recomended 1.9cft but im going with 2cft tune to 36 or 38hz, still deciding... port air speed at 36hz peaks at 55 ft per sec at 32hz port air speed at 38hz peaks at 56 ft per sec at 35hz now my box desing leave me with this port is 3.54 x 13.40 in i could go a bit larger like 4 in to get air speed down to 42ft per sec but it will but up the port area to around 26.7 sq in what would be the best option? if port area at 26.7 isnt a problem i can go 4 in and lower the air speed..... just dont want to lose cone control i like to keep the box on the small like 2 cubes after sub and port displacement So I modeled for your DB sa2712 a box 2 net @ 36Hz with 40 raw square inches of port area and 1900W power: } That should be enough at least for a daily setup, if you are worried for an inaudible 0.3 dB gain you may take a second look, now if you are doing a very long port with many turns that's not going to help your cause either. Link to comment Share on other sites More sharing options...
MarcoPT Posted October 1, 2018 Author Report Share Posted October 1, 2018 i should be able to feet a simple L shape port in my box, since im going with a box that is the full width of the trunk, i have perty much 40 in to play with so lets recap... as long as i keep port area on the 20s and port air velocity below 19s i wil be fine, rigth? knowing that i have room to play with the port size Link to comment Share on other sites More sharing options...
Joe X Posted October 1, 2018 Report Share Posted October 1, 2018 Anything above 25 m/s may not be best but up to about 30 m/s may be passable, if you overdo port area your port displacement can go out of control along with box weight and size and may not benefit you in a meaningful way, upper teens would be enough for most setups. Link to comment Share on other sites More sharing options...
MarcoPT Posted October 1, 2018 Author Report Share Posted October 1, 2018 how this s looking? port air velocity 18.18 m/s at 30hz port area at 21 per cube tune to 35hz looks nice, i think lol Link to comment Share on other sites More sharing options...
Joe X Posted October 2, 2018 Report Share Posted October 2, 2018 42 square inches of port area like you have will be just fine. Link to comment Share on other sites More sharing options...
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