strocket Posted June 15, 2015 Report Posted June 15, 2015 Hey guys, New to the forum. I can already tell this is one of the better forums because everyone is so helpful to each other and I haven't seen much flaming going on. So I've built boxes in the past, but this one is my first ported box. I built the box to go behind the seat of a 2010 Tundra Crew Max. I designed the box (or at least tried too) around two JL Audio 8W3V3 pushed by a JL Audio XD600. I've been reading other posts and have found that port placement and size is dependent on the box size and shape. When designing this I took my max depth and height and then adjusted the width to get the proper recommended volume. JL recommends .35 cubic feet for a ported box with the port tuned to 35 Hz. On their instructions they also recommended to use a 2" internal diameter port. At first I thought that those port recommendations were specific to the sub itself and not so much to the box they had designed which was just a regular square box, which obviously wouldn't fit behind the seat. Here is what I came up with.... I was very happy with how it turned out.............. until I put it in the truck. It sounds clean. But doesn't have any punch!! It seems almost as if the notes are very flat and muffled. I just cant seem to get it very loud. I redid all of my measurements and each section actually came out to be .05 cubic feet too small. With out the ports installed I got .35 cubic feet of space after woofer displacement. So I used that number along with 2" internal port diameter and the port tuned to 35 Hz for a port length of 18.28" Does anyone have any ideas as to what the problem could be. I know I'm going to be building another one because I'm just not satisfied with the way this one sounds. My height has to stay at 18" and depth at the bottom to 8.25" and height at the top to 5". Any help is greatly appreciated!!
Triticum Agricolam Posted June 16, 2015 Report Posted June 16, 2015 One problem is you don't have enough port area. I don't know why manufacturers give such bad specs for boxes, but they do. A single 2" port per sub is nowhere near enough. A single 4" port for both subs or a 3" port for each would be sufficient. You are going to have a tough time fitting either in your box though. If you are willing to rebuild, I do a new box with one common chamber and a slot port with at least 12 sq in of area. 16 sq in would be better. "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:
strocket Posted June 16, 2015 Author Report Posted June 16, 2015 The port would have to be pretty long though huh? With the port only being able to be at a max 6" wide since I'm trying to build a wedge type box.
Triticum Agricolam Posted June 16, 2015 Report Posted June 16, 2015 Yeah, a lot longer than what you have now. For a 14 sq in port, it would have to be 38" long. Here is a wedge shaped box I did for a SA-8 just to give you an idea for how you can implement a port like this: The port decreases in height as you get farther down and the box gets wider to keep the cross sectional area roughly the same. It works well. "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:
strocket Posted June 16, 2015 Author Report Posted June 16, 2015 So then when using a slot port, its not calculated based on recommended volume? Are there any calculators that can be used when designing a wedge box and a slot port to adjust the height of the port account for the taper? Also, I really appreciate the help!!
Triticum Agricolam Posted June 16, 2015 Report Posted June 16, 2015 A slot port is calculated the same way any other port is. Tuning is determined by the net volume of the box, the area of the port, and the length of the port. There probably aren't any calculators out there that will automatically adjust the height of the port for you, you will just have to figure it out by hand. I use SketchUp to design the boxes I build, it makes doing this kind of stuff a lot easier. "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:
strocket Posted June 16, 2015 Author Report Posted June 16, 2015 WOW!! I just took a look at your profile! I must say, your work is amazing. You've defiantly taken box building to a new level. I just downloaded sketchup and drew a rough drawing. But I noticed that most of your builds have crazy airspace. Should I use the recommended airspace by the manufacture? Also, does the location of the port in relation to the subs make a difference in sound quality? Obviously with the little depth I have to work with the subs are going to have to face forward. Should the port also face forward or can it come out the side the way the wedge you designed did?
Triticum Agricolam Posted June 16, 2015 Report Posted June 16, 2015 Thanks for the compliment, I'm glad you like my work! The location of the port does make a difference, but it doesn't have to be on the same face as the subs. I would suggest having it come out the side like the box I did, that seems to work well for trucks. Changing the amount of net airspace will change how much output you get around the tuning frequency. You could increase the net volume of your box to get some more low end output, but you will need to be careful though since as you increase net volume you also increase cone excursion and you don't want to bottom out your subs. If you increase the net volume you should also increase your port area some. If it were me I'd probably increase the net volume to 1 - 1.2 cu ft and port area to 16 sq in. You will have to recalculate how long the port needs to be to keep the 35 hz tuning. "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:
strocket Posted June 18, 2015 Author Report Posted June 18, 2015 Hey Triticum.... was wondering if you could give me some assistance with sketchup. I'm working on the new box design and cant figure out how to cut tapers on the "wood". Im working on fixing the face and need to cut the angles in so it sits flush.
Triticum Agricolam Posted June 18, 2015 Report Posted June 18, 2015 Can you post some screenshots of what you have so far? "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:
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