Dd9515 king Posted April 29, 2013 Report Share Posted April 29, 2013 My friend and me have a wall with a 8in width 33.5 tall and 17in long it had 9in from the back. We added on the port internally witch made the port 21in so 5in from the back of the box. It plays a lot lower now. So my question is did adding the length or the load of the subs on the back wall. Link to comment Share on other sites More sharing options...
bkolfo4 Posted April 29, 2013 Report Share Posted April 29, 2013 When you added length and made the opening of a 9" wide port only 5" wide, you lowered the tuning. Current system: 1997 Blazer - (4) Customer Fi NEO subs with (8) American Bass Elite 2800.1s Previous systems: 2000 Suburban - (4) BTL 15's and (4) IA 40.1's = 157.7 dB at 37 Hz. 1992 Astro Van - (6) BTL 15's and (6) IA 40.1's = 159.7 dB at 43 Hz. Link to comment Share on other sites More sharing options...
Dd9515 king Posted April 30, 2013 Author Report Share Posted April 30, 2013 So the distance from the back of the box to the opening of the port has nothing to do with it? Link to comment Share on other sites More sharing options...
bkolfo4 Posted April 30, 2013 Report Share Posted April 30, 2013 Yes. You took a 9"' wide port and now only have a 5" wide opening. That really is not a good thing. Should have stopped 9" from the back wall and then extended the port parallel to the back wall (a L port). You have choked the port. Lowers tuning and changes how it works at high volumes. Current system: 1997 Blazer - (4) Customer Fi NEO subs with (8) American Bass Elite 2800.1s Previous systems: 2000 Suburban - (4) BTL 15's and (4) IA 40.1's = 157.7 dB at 37 Hz. 1992 Astro Van - (6) BTL 15's and (6) IA 40.1's = 159.7 dB at 43 Hz. Link to comment Share on other sites More sharing options...
Krakin Posted May 1, 2013 Report Share Posted May 1, 2013 You need to keep your port width constant through the whole box. 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...
Dd9515 king Posted May 1, 2013 Author Report Share Posted May 1, 2013 Its a center port. I thought u went back till half the mouth of the port to equal both sides. Link to comment Share on other sites More sharing options...
bkolfo4 Posted May 1, 2013 Report Share Posted May 1, 2013 If it is a center port, then you can go to 4.5" from the back. Going 5" from the back is close enough to 4.5" that you are getting extra length from the partial "corner" that is formed. So. . .yes, your tuning was lowered by extending the port. Current system: 1997 Blazer - (4) Customer Fi NEO subs with (8) American Bass Elite 2800.1s Previous systems: 2000 Suburban - (4) BTL 15's and (4) IA 40.1's = 157.7 dB at 37 Hz. 1992 Astro Van - (6) BTL 15's and (6) IA 40.1's = 159.7 dB at 43 Hz. Link to comment Share on other sites More sharing options...
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