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Box Volume is Box Volume, right?
Box Volume is Box Volume, right?
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Old 2nd November 2008, 07:03 PM   #1
skooter is offline skooter  United States
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Default Box Volume is Box Volume, right?

I think Kicker is going to make my L5s good, so I am looking at building a box for them. They came in a factory portted box that is way deeper than wide, which takes up lots of room in my cherokee. Now if I take the internal volume and keep it the same but in a different dimention of box with the same port will it sound the same. another words I want to make a box that is wider and and take out some of the box depth, and use the same port tube in it. Make sence! or would they be better in a sealed box.
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Old 2nd November 2008, 09:53 PM   #2
Perry Babin is offline Perry Babin  United States
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If you go from a deep box that's just large enough to fit the woofer on the face of it to a box that's just deep enough to clear the magnet (like a P/U truck box), you'll likely see a difference in output. A long time ago when I had the desire/energy to build enclosures, I tried several and the shallow boxes always had less low end even though the internal volume was the same. If you don't go to an extremely shallow enclosure, you shouldn't see a big difference.

A sealed enclosure will typically be smaller than a ported enclosure. Consult the owner's manual for the woofer. The manufacturer should have the dimensions for several of each type of enclosure.
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Old 2nd November 2008, 10:34 PM   #3
skooter is offline skooter  United States
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Default Thank you all for the help!

I just looked at the website and got lots of box figures, mostly sealed and slot port boxes.
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Old 3rd November 2008, 02:24 PM   #4
jol50 is offline jol50  United States
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I just use winISD these days, but I don't stare at the curve I model all the subs I've used lately and compare them. If one has more 30Hz for example, I know it has more there than others and seems to be best way to determine changes in sub setup. I can say I want more whatever and see if I will get it with a new setup. If you swap car that affects it of course, but you can still get an idea. Far as boxes I would tend to agree with Perry but never specifically tested for it. Never had good luck with shallow (or truck) boxes or boxes that face something close by unless it can act like a horn. I think you need some 'dispersion' room of something like 6" from the driver minimum. That puts you around 1 foot deep for a typical sub. But often installs are all about compromise.

Have to remember some like low bass and others more SPL type tight bass....some manufacturers just like to advertise the smallest box possible, some do that for highest power handling. Some will give you an honest range. I like low bass so I always end up with a larger box. Guess what I mean is now is the time to change it if you want to.
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Old 4th November 2008, 03:01 AM   #5
skooter is offline skooter  United States
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this is simular to the box I am going to build for the Kicker L5s. it is 14 " deep bottom and 7" deep top. with 1.75 internal volume.
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File Type: jpg subwoofer pics 005.jpg (68.8 KB, 53 views)
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Old 4th November 2008, 05:17 AM   #6
MatthewS is offline MatthewS  United States
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I have been doing a lot of this latley, here are my thoughts/suggestions.

1: It is known and often debated that box depths and shapes can affect frequency response, and what I gathered was it's done by the boxes effect or cause of standing waves. What I gathered is it is preferred to have at least 1" clearance from the rear of the driver (if for anything, proper voice coil venting) and that boxes with unusual shapes help prevent standing waves in the enclosure, so a little slant to the box can help.

2: I don't like Kickers factory port placement on the side of the box (at least all the pre-fab's I've seen). To me this suggests that the output of the port will be 90 degrees off phase (someone will correct me I'm sure) with the woofers output. In my mind that means a port setup that could yield a 3db gain over a certain bandwidth would only yield 1.5db gain? Weather the drivers are front or rear firing it's still 90 degrees out of phase with the final product. At least thats how I understand it. The moral here is that I try and keep the port on the face of the box with the drivers. If you don't have room for the port, you can take the area of the factory port, convert it to a square with PIE*radius-squared OR 3.14*R^2 and get your square inches. Leave the port length the same unless you want to change the tuning frequency. If the square still won't fit, you can make a slot that will fit between the drivers using two numbers that equal the area you got from the equation. Ie. if you got 30^in of port area, you can make a slot thats 3"x10" on the face of the box. If your going to try and make a slot, try not to go less then 2" wide or port air velocity will be great enough that port noise may be audible. Also try and keep the internal ends of the port no closer then 2" from the back of the box. If you have a 10 "deep box, and run into a situation where your port needs to be 15" long, you can put a bend in it at the back of the box (like an L shape) it is critical in this situation that your bend from the rear of the box is equal to your port width. Maintaining port width is important.

Hope this helps. I come from the old school of sealed boxes. But my recent ventures into ported enclosures has forced me to rethink things a bit. A properly tuned port system will yield tremendous results and rivaled SQ. However some sacrafices are usually made. Space is one of them. The other is a narrow bandwidth. For example to tune a box very low and end up with a 'reasonably' sized enclosure, you may end up with nothing much over 80hz in response. Conversley to tune it higher, your low end will suffer. However if size is no object, and "the trunks the limit" You can have your cake and eat it too (high output and flat frequency response across the band).

Good luck..

- Matt
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