tat2jerry Posted January 7, 2019 Author Report Share Posted January 7, 2019 11 hours ago, Triticum Agricolam said: No such thing as too much port area as long as you can fit the ports is the space you have. It would help to know what your tuning frequency is, but assuming its somewhere around 32 hz four 6" ports is plenty of port area for the power you are running. When using more than two aero ports, they begin to be less efficient compared to just one or two larger ports, however you have enough port area its not going to be a big deal. As far as compared to a 120 sq in slot port, again you have enough port area it shouldn't make much difference. Do whatever you think will make you happier, either is a good choice. I will caution you to be careful with excursion due to the size of your box and the power you will be running. You will want to have your subsonic filter properly set. I actually used your calculator to get the 130 sq inches, it said optimal was 150 sq inches. i'm actually wanting to tune around 36-37 hz. Link to comment Share on other sites More sharing options...
tat2jerry Posted January 7, 2019 Author Report Share Posted January 7, 2019 11 hours ago, Triticum Agricolam said: I will caution you to be careful with excursion due to the size of your box and the power you will be running. You will want to have your subsonic filter properly set. please explain in more detail please..i'm not 100% understanding what you're saying Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted January 7, 2019 Report Share Posted January 7, 2019 1 hour ago, mothra said: I have a couple simple rules, port shouldn't be longer than 20" and velocity shouldn't be lower than 20m/s. port area shouldn't be a target when designing an enclosure. keeping port length under 20" will prevent having port resonance and port wall flexing. having a velocity of 20m/s minimum allows to tune lower and still keep a really responsive system. Limiting yourself to a 20" long port is going to make for either really high tuning, or really low port area. Neither of which is desirable in most cases. As far as keeping port velocity ABOVE 20 m/sec, that's where you completely lose credibility with me. Air resistance robs energy (output) from your system and it quadruples for every doubling of velocity, you want velocity as low and you can get it while keeping everything else in balance. Also, what do you think happens to your port velocity when you aren't playing at max volume? It drops right off. Its like saying I prefer cars that always drive at a minimum of 45 MPH. That's not possible in practice. "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...
DiBo Posted January 7, 2019 Report Share Posted January 7, 2019 11 minutes ago, tat2jerry said: please explain in more detail please..i'm not 100% understanding what you're saying Subs can bottom out pretty easily without the subsonic filter set to keep really low frequencies from playing. With a lot of power in a pretty much maxxed out enclosure sz, the subs will reach xmax Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted January 7, 2019 Report Share Posted January 7, 2019 13 minutes ago, tat2jerry said: please explain in more detail please..i'm not 100% understanding what you're saying Below the tuning frequency of a ported box, it loses it ability to restrict cone movement, the sub begins to perform like it is in free air. The larger the box is and/or the more power you run the more quickly cone excursion will increase. If your cone moves too far bad things will happen (spiders hit top plates, coils hit back plates, etc). Here is a graph showing the cone excursion of your subs in your box tuned to 36 Hz: That red line is Xmax, you can exceed that by a bit, but you don't want to push it too far. As you can see you reach Xmax a little below 30 Hz. Your subsonic filter, if properly set, will reduce cone excursion and keep you from going way above that red line. "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...
tat2jerry Posted January 7, 2019 Author Report Share Posted January 7, 2019 2 hours ago, Triticum Agricolam said: I agree with you that tuning is going to be difficult, those ports are going to have to 30+" long, but it is still possible. I also agree that if you tune too high the output is likely to be peaky. If you make a port absolutely unreasonable big, yes it will cease to function as a ported box, but that point is MUCH more port area than most people would think and you almost always run into other problems (like too long of a port) before you get to that point. The OP isn't anywhere near that point with four 6" aeroports. So please tell me, at what point do YOU consider it to be too much port area? Please be specific. Ok so I don't have enough free space for 4 6" ports that long. And since you seem to know what you're talking about, if I run 7 cubes, what port area for a square side port at 35hz Link to comment Share on other sites More sharing options...
mothra Posted January 7, 2019 Report Share Posted January 7, 2019 28 minutes ago, Triticum Agricolam said: Limiting yourself to a 20" long port is going to make for either really high tuning, or really low port area. Neither of which is desirable in most cases. As far as keeping port velocity ABOVE 20 m/sec, that's where you completely lose credibility with me. Air resistance robs energy (output) from your system and it quadruples for every doubling of velocity, you want velocity as low and you can get it while keeping everything else in balance. Also, what do you think happens to your port velocity when you aren't playing at max volume? It drops right off. Its like saying I prefer cars that always drive at a minimum of 45 MPH. That's not possible in practice. explain how low port area is not desirable? large ports are just cosmetic. in a ported enclosure the port takes over musical playing when the sub/speaker can no longer do so, when they overlap that's where the db gain comes into play. so if you tune low, it's the port that's playing those notes. complementing that with a higher port velocity allows that port to move similar air as a large speaker. having a low port velocity will cause the port to not play notes through, it'll have air settling in the port especially when you have a large port area. since we are in his forum, I guess that Steve has too little port area and too high of a velocity too. he didn't rip that phone book to shreads b/c he has a low port velocity. he ripped it b/c it has a high port velocity. 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...
Triticum Agricolam Posted January 7, 2019 Report Share Posted January 7, 2019 7 minutes ago, tat2jerry said: Ok so I don't have enough free space for 4 6" ports that long. And since you seem to know what you're talking about, if I run 7 cubes, what port area for a square side port at 35hz I’m traveling today, but I can get you some numbers when I get back this evening. "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...
tat2jerry Posted January 7, 2019 Author Report Share Posted January 7, 2019 Just now, Triticum Agricolam said: I’m traveling today, but I can get you some numbers when I get back this evening. thank you Link to comment Share on other sites More sharing options...
ckeeler11 Posted January 7, 2019 Report Share Posted January 7, 2019 1 hour ago, mothra said: explain how low port area is not desirable? large ports are just cosmetic. in a ported enclosure the port takes over musical playing when the sub/speaker can no longer do so, when they overlap that's where the db gain comes into play. so if you tune low, it's the port that's playing those notes. complementing that with a higher port velocity allows that port to move similar air as a large speaker. having a low port velocity will cause the port to not play notes through, it'll have air settling in the port especially when you have a large port area. since we are in his forum, I guess that Steve has too little port area and too high of a velocity too. he didn't rip that phone book to shreads b/c he has a low port velocity. he ripped it b/c it has a high port velocity. LOL What?? Low port area causes compression. Compression robs you of output. Also after a certain level you get chuffing which robs you of any decent sound quality. Some reading: http://jahonen.kapsi.fi/Audio/Papers/AES_PortPaper.pdf Link to comment Share on other sites More sharing options...
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