jwjordan322 Posted June 13, 2014 Report Share Posted June 13, 2014 OK, so this weekend I plan on building a ported box for my sub. I have a Kenwood kfcxw12, and specs are found here..Kenwood Excelon KFC-XW12 12" 4-ohm subwoofer at Crutchfield.com... I have a couple questions. I currently have a sealed box. - how do I determine what I should tune my box port to? In looking for loudness that's not in any way harmful to the sub itself but the most bang possible and most efficient. - and I've tried a couple calculators for ported boxes, and what does port length refer to after filling in volume, tuning frequency, port height/width, - I see 2.68 is reccomended c/f would be going a little bigger to maybe 2.3 have negative effects or no? - and in a nutshell does the size of the port determine the tuning fq? This will be in the trunk of a cobalt facing up, port possibly facing frontwards toward the cabin unless that's not recommend. Link to comment Share on other sites More sharing options...
Krakin Posted June 13, 2014 Report Share Posted June 13, 2014 More port area = higher tuning Shorter port length = Higher tuning Less enclosure volume = Higher tuning ---------------------------------------------------- Less port area = lower tuning Longer port length = lower tuning More enclosure volume = lower tuning Also when you say 2.68 square feet, I hope you mean cubic feet and are referring to box volume (after displacements). Krakin's Home Dipole Project http://www.stevemeadedesigns.com/board/topic/186153-krakins-dipole-project-new-reciever-in-rockford-science/#entry2772370 Krakin, are you some sort of mad scientist? I would have replied earlier, but I was measuring the output of my amp with a yardstick . . . What you hear is not the air pressure variation in itself but what has drawn your attention in the two streams of superimposed air pressure variations at your eardrums An acoustic event has dimensions of Time, Tone, Loudness and Space Everyone learns to render the 3-dimensional localization of sound based on the individual shape of their ears, thus no formula can achieve a definite effect for every listener. Link to comment Share on other sites More sharing options...
Weigel21 Posted June 13, 2014 Report Share Posted June 13, 2014 Yeah, those are sealed enclosure subs, they have a very low EBP. I'm not entirely sure they can be placed in a ported enclosure without having a peaky response curve. Still, the recommended internal volume for ported is 2cuft with 1.5-2.5 being allowable. Recommended tuning with the "ideal" enclosure looks to be around 40Hz. You can plug the T/S Parameters into a program such as WinISD and plot the response curve (though it doesn't account for cabin gain or anything) and get a rough idea as to weather a particular size and tuning could work well or not. Not sure where you found 2.68 being recommended, I seen it no where in the manual or on the package. The internal volume of the enclosure (after factoring in port and sub displacement) along with the diameter and length of the port tube or in the case of a slot port, the HxWxL will determine the tuning of the enclosure. Often, having the subs and port facing the rear of the vehicle provide greater/more desirable output, but it's not a guarantee. Oh, and one needs to use a subsonic filter to protect the subs from beating them selves to death. Usually it is recommended to have a SSF activated within 5Hz below the tuning and with a sharp 24dB/Oct slope. That or have an extremely low tuned enclosure or never play anything with frequencies below the port tuning frequency. Guess if you were feeding the subs half their rated power or less then they wouldn't tear themselves apart either. Link to comment Share on other sites More sharing options...
jwjordan322 Posted June 13, 2014 Author Report Share Posted June 13, 2014 Yess, I meant c/f. And that's without displacement, not sure how to figure displacement. I've had my system for years but never got into the real details and mass info of everything involved. It was a cheap best buy/Walmart originally, but has been upgraded since minus the box which has all kinds of screw holes and isn't even the right size. But I'm learning just have lots of questions Link to comment Share on other sites More sharing options...
jwjordan322 Posted June 13, 2014 Author Report Share Posted June 13, 2014 Yess, I meant c/f. And that's without displacement, not sure how to figure displacement. I've had my system for years but never got into the real details and mass info of everything involved. It was a cheap best buy/Walmart originally, but has been upgraded since minus the box which has all kinds of screw holes and isn't even the right size. But I'm learning just have lots of questions Link to comment Share on other sites More sharing options...
Krakin Posted June 13, 2014 Report Share Posted June 13, 2014 For a box calculator I will recommend Torres Box Calculator. http://www.stevemeadedesigns.com/board/topic/38791-torres-box-tuning-calculator-updated-818/ IT is simple to use. Along with the port calculator to find the sq inches needed for you port. http://www.carstereo.com/help/Articles.cfm?id=31 Krakin's Home Dipole Project http://www.stevemeadedesigns.com/board/topic/186153-krakins-dipole-project-new-reciever-in-rockford-science/#entry2772370 Krakin, are you some sort of mad scientist? I would have replied earlier, but I was measuring the output of my amp with a yardstick . . . What you hear is not the air pressure variation in itself but what has drawn your attention in the two streams of superimposed air pressure variations at your eardrums An acoustic event has dimensions of Time, Tone, Loudness and Space Everyone learns to render the 3-dimensional localization of sound based on the individual shape of their ears, thus no formula can achieve a definite effect for every listener. Link to comment Share on other sites More sharing options...
Krakin Posted June 13, 2014 Report Share Posted June 13, 2014 And Wiegel he is going to most likely have no idea what you are talking about if he doesn't know some of the basics about port design.. Krakin's Home Dipole Project http://www.stevemeadedesigns.com/board/topic/186153-krakins-dipole-project-new-reciever-in-rockford-science/#entry2772370 Krakin, are you some sort of mad scientist? I would have replied earlier, but I was measuring the output of my amp with a yardstick . . . What you hear is not the air pressure variation in itself but what has drawn your attention in the two streams of superimposed air pressure variations at your eardrums An acoustic event has dimensions of Time, Tone, Loudness and Space Everyone learns to render the 3-dimensional localization of sound based on the individual shape of their ears, thus no formula can achieve a definite effect for every listener. Link to comment Share on other sites More sharing options...
jwjordan322 Posted June 13, 2014 Author Report Share Posted June 13, 2014 Yeah, those are sealed enclosure subs, they have a very low EBP. I'm not entirely sure they can be placed in a ported enclosure without having a peaky response curve. Still, the recommended internal volume for ported is 2cuft with 1.5-2.5 being allowable. Recommended tuning with the "ideal" enclosure looks to be around 40Hz. You can plug the T/S Parameters into a program such as WinISD and plot the response curve (though it doesn't account for cabin gain or anything) and get a rough idea as to weather a particular size and tuning could work well or not. Not sure where you found 2.68 being recommended, I seen it no where in the manual or on the package. The internal volume of the enclosure (after factoring in port and sub displacement) along with the diameter and length of the port tube or in the case of a slot port, the HxWxL will determine the tuning of the enclosure. Often, having the subs and port facing the rear of the vehicle provide greater/more desirable output, but it's not a guarantee. Oh, and one needs to use a subsonic filter to protect the subs from beating them selves to death. Usually it is recommended to have a SSF activated within 5Hz below the tuning and with a sharp 24dB/Oct slope. That or have an extremely low tuned enclosure or never play anything with frequencies below the port tuning frequency. Guess if you were feeding the subs half their rated power or less then they wouldn't tear themselves apart either. So my sub's shouldn't be ported, and on crutchfield it gives me that ported reccomendation. Link to comment Share on other sites More sharing options...
jwjordan322 Posted June 13, 2014 Author Report Share Posted June 13, 2014 And on a tablet so winisd is unfortunately not possible Link to comment Share on other sites More sharing options...
Krakin Posted June 13, 2014 Report Share Posted June 13, 2014 You can do a simple calculation to find what is known as the EBP where you take the Fs of the driver and divide it by the Qes. This number gives a suggested enclosure for the speaker in use. A common rule of thumb indicates that for EBP>100, a driver is perhaps best used in a vented enclosure, while EBP<50 indicates a sealed enclosure. For 50<EBP<100, either enclosure may be used effectively. Krakin's Home Dipole Project http://www.stevemeadedesigns.com/board/topic/186153-krakins-dipole-project-new-reciever-in-rockford-science/#entry2772370 Krakin, are you some sort of mad scientist? I would have replied earlier, but I was measuring the output of my amp with a yardstick . . . What you hear is not the air pressure variation in itself but what has drawn your attention in the two streams of superimposed air pressure variations at your eardrums An acoustic event has dimensions of Time, Tone, Loudness and Space Everyone learns to render the 3-dimensional localization of sound based on the individual shape of their ears, thus no formula can achieve a definite effect for every listener. Link to comment Share on other sites More sharing options...
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