Triticum Agricolam Posted March 11, 2015 Report Share Posted March 11, 2015 My port design is laid out like the example on the bottom right so I used 2.227 as K. I did the math (I'm not very good at math) and came up with 28.2, not sure what 28.2 means. Here is a screen shot of my original box design parameters on Ultimate Car Audio App and a screen shot of the box design I'm using (not my box). Mayhem 18 will be on top. Is 28.2 my port length in inches? Or is my box design on my program already accurate? I only have an Android tablet am am not able to use Torres. Edit: My desired port frequency is 33 hz. The 28.2 number you got is the tuning frequency of your box with a 25" long port. Slot port end correction can shorted up a port a LOT. To get a 33 Hz tune with a 6.33 cu ft net airspace box, 89.06 sq in of port and 2.227 end correction your port will need to be ~14" long. "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...
Knocker Posted March 11, 2015 Author Report Share Posted March 11, 2015 Here's your box in Torres, it looks like the software you are using and Torres are pretty close in this case: My port design is laid out like the example on the bottom right so I used 2.227 as K. I did the math (I'm not very good at math) and came up with 28.2, not sure what 28.2 means. Here is a screen shot of my original box design parameters on Ultimate Car Audio App and a screen shot of the box design I'm using (not my box). Mayhem 18 will be on top. Is 28.2 my port length in inches? Or is my box design on my program already accurate? I only have an Android tablet am am not able to use Torres. Edit: My desired port frequency is 33 hz. The 28.2 number you got is the tuning frequency of your box with a 25" long port. Slot port end correction can shorted up a port a LOT. To get a 33 Hz tune with a 6.33 cu ft net airspace box, 89.06 sq in of port and 2.227 end correction your port will need to be ~14" long.Thank you guys. All this leaves me thinking there may be quite a few people unaware that they are driving around with lower tunings than they think they have. Since apparently you do this for a living I will take your word for it and shorten the port to 14 inches and adjust the net volume accordingly. Link to comment Share on other sites More sharing options...
Joe X Posted March 12, 2015 Report Share Posted March 12, 2015 Thank you guys. All this leaves me thinking there may be quite a few people unaware that they are driving around with lower tunings than they think they have. Since apparently you do this for a living I will take your word for it and shorten the port to 14 inches and adjust the net volume accordingly. It would be great if you took the time to measure your actual tuning after you build and let us know. In this case at least the difference in results is too wide. Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted March 12, 2015 Report Share Posted March 12, 2015 Thank you guys. All this leaves me thinking there may be quite a few people unaware that they are driving around with lower tunings than they think they have. Since apparently you do this for a living I will take your word for it and shorten the port to 14 inches and adjust the net volume accordingly. I think you are right and there are lot of people who are tuned lower than they might think. Fortunately if you are going to be off, its almost always better to be low than to be too high, IMHO. The difference between the alternate styles of port length calculations usually isn't as much as it is in your case. No matter what way you do it, it is still only an estimate. The length I calculated (14") does seem short and I don't want to be the one to give you bad advice. What you can do is cut the port long, temparily assemble the box, and then see where you tuning is. If its lower than you want you can shorten the port and retest until you get where you want to be. This is mostly likely what I would do if I were in your shoes, that being said, I do test the tuning on almost every box I build and usually my stuff ends up a little on the low side anyway. The 14" is probably going to be pretty close, I just am not 100% confident in it. "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...
Knocker Posted March 13, 2015 Author Report Share Posted March 13, 2015 So I was just reading a thread you guys were on a while back about port length and end correction and it was very informative. There was a link to a port length calculator and I used it and it turned out that 28.2 number I came up with earlier was my port length in centimeters. 11.1 inches! This whole thing is amazing to me and I will definitely be starting long, testing, then opening the box if I have to like you showed user how to do. I will post my results. I was planning on using my driver excursion to measure tuning. Is the impedance method better? Here are my results by the way... Link to comment Share on other sites More sharing options...
Knocker Posted March 13, 2015 Author Report Share Posted March 13, 2015 Thank you guys. All this leaves me thinking there may be quite a few people unaware that they are driving around with lower tunings than they think they have. Since apparently you do this for a living I will take your word for it and shorten the port to 14 inches and adjust the net volume accordingly. It would be great if you took the time to measure your actual tuning after you build and let us know. In this case at least the difference in results is too wide. Thank you guys. All this leaves me thinking there may be quite a few people unaware that they are driving around with lower tunings than they think they have. Since apparently you do this for a living I will take your word for it and shorten the port to 14 inches and adjust the net volume accordingly.I think you are right and there are lot of people who are tuned lower than they might think. Fortunately if you are going to be off, its almost always better to be low than to be too high, IMHO.The difference between the alternate styles of port length calculations usually isn't as much as it is in your case. No matter what way you do it, it is still only an estimate. The length I calculated (14") does seem short and I don't want to be the one to give you bad advice. What you can do is cut the port long, temparily assemble the box, and then see where you tuning is. If its lower than you want you can shorten the port and retest until you get where you want to be. This is mostly likely what I would do if I were in your shoes, that being said, I do test the tuning on almost every box I build and usually my stuff ends up a little on the low side anyway. The 14" is probably going to be pretty close, I just am not 100% confident in it. Forgot to hit the quote button... See above^^^ Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted March 13, 2015 Report Share Posted March 13, 2015 So I was just reading a thread you guys were on a while back about port length and end correction and it was very informative. There was a link to a port length calculator and I used it and it turned out that 28.2 number I came up with earlier was my port length in centimeters. 11.1 inches! This whole thing is amazing to me and I will definitely be starting long, testing, then opening the box if I have to like you showed user how to do. I will post my results. I was planning on using my driver excursion to measure tuning. Is the impedance method better? Here are my results by the way... Looks good. I'll be curious to hear what your results are. The driver excursion method is fine, its easy, require almost no tools, and should get you really close. The impedance method works too, and is fast. But you need special tools to use it and sometimes it is hard to pinpoint exactly where the impedance is the lowest. The way I usually check tuning is with a calibrated mic. If you put the mic close to the cone and play a sine wave sweep you will see a very pronounced dip in the output coming from the cone right at the tuning frequency. But you have to have a mic to test this way. "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...
Knocker Posted March 13, 2015 Author Report Share Posted March 13, 2015 So I was just reading a thread you guys were on a while back about port length and end correction and it was very informative. There was a link to a port length calculator and I used it and it turned out that 28.2 number I came up with earlier was my port length in centimeters. 11.1 inches! This whole thing is amazing to me and I will definitely be starting long, testing, then opening the box if I have to like you showed user how to do. I will post my results. I was planning on using my driver excursion to measure tuning. Is the impedance method better? Here are my results by the way...Looks good. I'll be curious to hear what your results are.The driver excursion method is fine, its easy, require almost no tools, and should get you really close. The impedance method works too, and is fast. But you need special tools to use it and sometimes it is hard to pinpoint exactly where the impedance is the lowest. The way I usually check tuning is with a calibrated mic. If you put the mic close to the cone and play a sine wave sweep you will see a very pronounced dip in the output coming from the cone right at the tuning frequency. But you have to have a mic to test this way. I have a tiny mic built in to my Tab S and a cool app that measures SPL. It's obviously kind of a joke but for measuring amplitude I bet it would be ok. Between that and actually looking at the driver excursion during the sine sweep it should do the trick. Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted March 13, 2015 Report Share Posted March 13, 2015 Yeah the mic in your Tab S might work, its certainly worth a try. You want to get the mic about an inch or two from the cone, just make sure the cone doesn't hit it! "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...
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