BlindAssassin111 Posted May 8, 2020 Report Posted May 8, 2020 Looking to build a box for a SA-10 v2 D2 wired to 1 ohm, and was going to start with the recommended box specs from sundown but my issue has been even at the recommended 1 cuft, 15 in^2 of port area, tuned to 35 Hz and at the rated 1000w I was getting a peak port air velocity of ~46.4 m/s which is way above what it should be. Decided to make the port area larger (increased to 21 in^2) and was able to get it to a peak of ~31 m/s which is below the 10% of the speed of sound but still high. Current design is for a 10.5" X 2" port that is 40" long which I know is above the recommended port area per cu.ft. but I can't find a way to even use the suggested values without issue. Does anyone have any recommendations for what I should use for port area and why? I can't use an aero port as my max width is 33" and no matter what I couldn't get it to a length that would work for me so I am going to have to go slotted (unless I am being an idiot, which is possible). Any help is appreciated as I have been spending almost every night trying to figure out what I could do to fix this and still come to the issue of a large port area or too high of air velocity.
BlindAssassin111 Posted May 13, 2020 Author Report Posted May 13, 2020 Anyone have an answer to this? Going to be building the box very soon and want to make sure my design is going to be fine prior to doing so.
1point21gigawatts Posted May 13, 2020 Report Posted May 13, 2020 Whatever percentage you increase you port area past recommended, you should increase the enclosure volume the same percentage or close to and vise versa to even out. My next enclosure build is 15.7% larger than recommended volume after displacements and the port area is 15.3% larger than recommended. But the problem you have created with the build you designed is that your port area is 40% larger than recommended, thus your enclosure volume has to be about 40% larger than recommended which would be 1.4 cubic feet. Sundown only give a 25% leeway past recommended enclosure volume before it’s too much and has too much air space, which severely takes away from the subwoofers output. I know you are wanting the bass to be lower and move more air, thus hitting harder. But by going too far you have made a design that is gonna do the complete opposite. Don’t go past 25% increase with sundown subwoofers. I run a sundown zv5 15. Most my gear is sundown. The specs you do not want to exceed is 1.25 cubic feet and 18.75 sq” of port area. Don’t exceed it, not even tenth or hundredth of a point. That’s a 25% increase of volume and port area and you can drop the frequency to 32hz or 33hz, if you want. I would. And I would only increase the volume and port area by 20%. That’s 1.2 cubic feet with a port area of 18 sq” and I would tune it to 33hz. “How can we help you?” “And don’t forget to tell them that the customer isn’t always right.”
BlindAssassin111 Posted May 13, 2020 Author Report Posted May 13, 2020 29 minutes ago, 1point21gigawatts said: Whatever percentage you increase you port area past recommended, you should increase the enclosure volume the same percentage or close to and vise versa to even out. My next enclosure build is 15.7% larger than recommended volume after displacements and the port area is 15.3% larger than recommended. But the problem you have created with the build you designed is that your port area is 40% larger than recommended, thus your enclosure volume has to be about 40% larger than recommended which would be 1.4 cubic feet. Sundown only give a 25% leeway past recommended enclosure volume before it’s too much and has too much air space, which severely takes away from the subwoofers output. I know you are wanting the bass to be lower and move more air, thus hitting harder. But by going too far you have made a design that is gonna do the complete opposite. Don’t go past 25% increase with sundown subwoofers. I run a sundown zv5 15. Most my gear is sundown. The specs you do not want to exceed is 1.25 cubic feet and 18.75 sq” of port area. Don’t exceed it, not even tenth or hundredth of a point. That’s a 25% increase of volume and port area and you can drop the frequency to 32hz or 33hz, if you want. I would. And I would only increase the volume and port area by 20%. That’s 1.2 cubic feet with a port area of 18 sq” and I would tune it to 33hz. The only reason I increased port area was for port air velocity, trying to avoid port noise as much as possible but can't seem to escape it... 1.2 ft^3, 18 in^2 at 33Hz gives me a port velocity of ~37.5m/s, which is quite a bit above the recommended max air velocity. Am I worrying too much about this or? Cause if so I have no issue going back down to a more reasonable port area if so, just find it strange that the recommended specs give very high port air velocities.
1point21gigawatts Posted May 13, 2020 Report Posted May 13, 2020 8 minutes ago, BlindAssassin111 said: The only reason I increased port area was for port air velocity, trying to avoid port noise as much as possible but can't seem to escape it... 1.2 ft^3, 18 in^2 at 33Hz gives me a port velocity of ~37.5m/s, which is quite a bit above the recommended max air velocity. Am I worrying too much about this or? Cause if so I have no issue going back down to a more reasonable port area if so, just find it strange that the recommended specs give very high port air velocities. What program are you using? And if you’re worried about port noise and can’t seem to calculate the correct design then use an aero port that are flared on each side. That will make the port velocity cut in half from the figures you’re yielding now. “How can we help you?” “And don’t forget to tell them that the customer isn’t always right.”
BlindAssassin111 Posted May 13, 2020 Author Report Posted May 13, 2020 7 minutes ago, 1point21gigawatts said: What program are you using? WinISD, have the correct t/s parameters entered, have it wired as 1 ohm (selected parallel for the box) entered 1000w and it shows the correct voltage for a 1 ohm load at that power.
1point21gigawatts Posted May 13, 2020 Report Posted May 13, 2020 1 minute ago, BlindAssassin111 said: WinISD, have the correct t/s parameters entered, have it wired as 1 ohm (selected parallel for the box) entered 1000w and it shows the correct voltage for a 1 ohm load at that power. WinISD is still in beta mode and isn’t completed so it still has errors. I don’t use it. I want to use it for 6th order designs but I don’t trust it. “How can we help you?” “And don’t forget to tell them that the customer isn’t always right.”
1point21gigawatts Posted May 13, 2020 Report Posted May 13, 2020 10 minutes ago, 1point21gigawatts said: What program are you using? And if you’re worried about port noise and can’t seem to calculate the correct design then use an aero port that are flared on each side. That will make the port velocity cut in half from the figures you’re yielding now. “How can we help you?” “And don’t forget to tell them that the customer isn’t always right.”
1point21gigawatts Posted May 13, 2020 Report Posted May 13, 2020 An aero port flared on both sides will solve the port velocity problem. “How can we help you?” “And don’t forget to tell them that the customer isn’t always right.”
BlindAssassin111 Posted May 13, 2020 Author Report Posted May 13, 2020 What area would I use for an aero port? I constantly see different recommendations for this and it is hard to figure out what is truth and what is noise.
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