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Port questions


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So I'm trying to spec out my sub box build, and I'm needing some help. I will be running a sundown u series 18 on a soundqubed s1-2250 at 1 ohm. Recommended from sundown is 4 cubes ported and 64 sq inches of port area tuned to 32. Using the stickied "triticum's port area calc", it is saying I should be up around 79-82 sq inches of port. Of course that is not taking anything in depth into account, just power and rough box net air space... is there something else I should use to calculate my needed port area? I was wanting to run an aero port and so basically I can do 6 4 inch ports for a total of 75 sq inches, or 3 6 inch ports for a total of nearly 85 sq inches. I don't have the room to run a 10 inch port. I am imagining it would be better to go with the 3 6's due to what I've read... am I correct in thinking that? Why or why not?

 

Also, I was using the  mobile information labs port length calc for this, is there a better calc that I should be using? And with calc I was using, is the round port length given per port, or is that total length for all ports combined?

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All I know is that Triticum Agricolam is REALLY GOOD at building and designing enclosures. He is Forum famous, for sure. I tried using that formula to design a slot port enclosure and since it had a lot of port area in reference to the net volume, it made it impossible for me to tune it low, no matter the length of the port. It stayed around 39hz. So there has to be a flaw somewhere. Idk. 

:stupid:“How can we help you?”
:guido:
“And don’t forget to tell them that 
the customer isn’t always right.”

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11 hours ago, 1point21gigawatts said:

All I know is that Triticum Agricolam is REALLY GOOD at building and designing enclosures. He is Forum famous, for sure. I tried using that formula to design a slot port enclosure and since it had a lot of port area in reference to the net volume, it made it impossible for me to tune it low, no matter the length of the port. It stayed around 39hz. So there has to be a flaw somewhere. Idk. 

I know it makes me have to make my port(s) long af lol... doesn't look like I'll be able to do aeros unfortunately. Definitely can make it happen on a slot though.

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But think of this, if the figures I fed that formula couldn’t deliver, what makes you think that the formula or calculator is full proof and worth using? And then think of this, subwoofer companies have designers and builders too, so they can present good specs for their subwoofers and good enclosure designs and specs. People often say that companies just do a little bit of guesstimating rather than calculating and testing when it comes to the enclosure recommendations. But that isn’t true. Just make the enclosure 10% to 20% bigger than recommended and then increase the port area the same percentage. That’s what a lot of people do anyways. I run a sundown zv5 and the new enclosure I’m building for it is has a 12% increase in net volume after displacements and 12% increase in port area. Sundown says it’s okay, I think up to 25%. There’s a flaw in that port area calculator or the formula is flawed. I typed in a 5 cubic foot enclosure tuned to 32hz on 3500 rms for a slot port and it told me optimal port area is 109”. That’s crazy and super wrong. But to see if it would work, I designed an enclosure to see. Enclosure’s net volume was 5 cubic feet and Port was 6.5”x16.5”, making the port area 107.25”. No matter what size the port length was, the tuning would stay at about 39hz. This is because there was too much port area for the enclosure’s volume. Don’t use it. Just do mathematics and increase the recommended enclosure volume and port area the same in percentage, around 15% would be fine. So the port area that calculator says you need would be about the same with this calculation but the enclosure volume would be bigger with this calculation, thus evening things out. 

:stupid:“How can we help you?”
:guido:
“And don’t forget to tell them that 
the customer isn’t always right.”

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3 hours ago, 1point21gigawatts said:

But think of this, if the figures I fed that formula couldn’t deliver, what makes you think that the formula or calculator is full proof and worth using? And then think of this, subwoofer companies have designers and builders too, so they can present good specs for their subwoofers and good enclosure designs and specs. People often say that companies just do a little bit of guesstimating rather than calculating and testing when it comes to the enclosure recommendations. But that isn’t true. Just make the enclosure 10% to 20% bigger than recommended and then increase the port area the same percentage. That’s what a lot of people do anyways. I run a sundown zv5 and the new enclosure I’m building for it is has a 12% increase in net volume after displacements and 12% increase in port area. Sundown says it’s okay, I think up to 25%. There’s a flaw in that port area calculator or the formula is flawed. I typed in a 5 cubic foot enclosure tuned to 32hz on 3500 rms for a slot port and it told me optimal port area is 109”. That’s crazy and super wrong. But to see if it would work, I designed an enclosure to see. Enclosure’s net volume was 5 cubic feet and Port was 6.5”x16.5”, making the port area 107.25”. No matter what size the port length was, the tuning would stay at about 39hz. This is because there was too much port area for the enclosure’s volume. Don’t use it. Just do mathematics and increase the recommended enclosure volume and port area the same in percentage, around 15% would be fine. So the port area that calculator says you need would be about the same with this calculation but the enclosure volume would be bigger with this calculation, thus evening things out. 

Guess I misunderstood your first post. Wouldn't that cause loading issues? I would imagine that would make it very quick, easy, and probable to cause mechanical damage to the soft parts of a sub, would it not? If I'm wrong I'm happy to be and always love to learn, could you show me some reading material on it? I'm not really aware of how the extra power messes with the sub to box relationship and needs obviously lol. Don't imagine there was, but was there an issue with port velocity/compression? How did you measure the tuning? Any chance the box surroundings or internal clearances caused it to peak around 39? How much does port length mess with port velocity? And if you had too much port area, wouldn't that cause too low of a tuning and if it was bad enough unload the sub?

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No issues with my design. More port area doesn’t mean lower tuning. There are more factors to weigh in. I wouldn’t of even had to design an enclosure to know that 109” of port area is too much for 5 cubic feet of net volume. But I did anyways to see what happened. You should be good with whatever enclosure choice you make because the numbers aren’t crazy far off because of the rms of the amp. But if you had a stronger amp, the numbers would get crazy and make it hard to design an enclosure using that port area calculator. 

:stupid:“How can we help you?”
:guido:
“And don’t forget to tell them that 
the customer isn’t always right.”

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