Building my first ported box

[dropkick13 0]

I have built a few MDF sealed boxes and now im building something to fit underneath my truck seat so I'll have to use fiberglass AND it will be my first ported box. How do i go about building the baffle inside the box?

[helotaxi 46]

Why do you need a baffle inside the box? I would use PVC for the ports so after accounting for the displacement of hte port and subs and calculating what you need in the way of port length and diameter and box volume, the build is just like a sealed box.

[dropkick13 0]

Why do you need a baffle inside the box? I would use PVC for the ports so after accounting for the displacement of hte port and subs and calculating what you need in the way of port length and diameter and box volume, the build is just like a sealed box.

Here's a picture showing what I mean:

http://edesignaudio.com/im2/boxcuts/12%20rec%20vented.jpg

I'm talking about everything going on inside the box

[///M5 2,833]

Out of mdf. You won't be able to use the uneven fiberglass side of the box for the port though. What you propose isn't trivial.

[helotaxi 46]

You're talking about a really complex build. Use PVC. Much easier and more predictable results.

[mrray13 30]

what kind of truck? sub?

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[///M5 2,833]

06 Silvy, E/C -- sub, something with some oomph.

[mrray13 30]

why need 'glass then? none in my box, and it's a ported 12. none in IluvJDM's box either.

of course, sean, you would think them inadequate. only 1/2" mdf with a brace on the big panels. but for the life of me, i can't hear it flex.

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[///M5 2,833]

*refrains from commenting

[mrray13 30]

*refrains from commenting

lol, don't do that. honestly, i'd wish you'd speak your mind, i can only learn.

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[///M5 2,833]

To put it simply, it makes the response peaky and of course you know that isn't my thing. Sometime in the next 6 months I will do a measurement on a good box and some thin wood thing and post the differences in the tech section. I would do it sooner, but won't have access to a vibrometer locally for at least 2 months and I also don't have any underbuilt boxes to measure. I didn't refrain to not help anyone learn, but my reasoning was that it still may not be a concern of yours or more importantly in this case the OP. It all depends on your expectations and goals of a system. As you know I tend to lean WAY towards the SQ side so me stating that it wouldn't be okay for dropkick isn't fair as I don't really know what he is looking for although I expect he will be fine with a slightly peakier response in particular if it means more output from other posts of his that I have read. In this case your solution very well may be viable, but of course if possible I would still try to make things more structural.

[mrray13 30]

To put it simply, it makes the response peaky and of course you know that isn't my thing. Sometime in the next 6 months I will do a measurement on a good box and some thin wood thing and post the differences in the tech section. I would do it sooner, but won't have access to a vibrometer locally for at least 2 months and I also don't have any underbuilt boxes to measure. I didn't refrain to not help anyone learn, but my reasoning was that it still may not be a concern of yours or more importantly in this case the OP. It all depends on your expectations and goals of a system. As you know I tend to lean WAY towards the SQ side so me stating that it wouldn't be okay for dropkick isn't fair as I don't really know what he is looking for although I expect he will be fine with a slightly peakier response in particular if it means more output from other posts of his that I have read. In this case your solution very well may be viable, but of course if possible I would still try to make things more structural.

if the timing is right, i'll volunteer my enclosure. i'd love the road trip anyway. we can keep things fairly constant as we can use one vehicle, sub, power. i'd like to see the results of something like this.

if all that is ok with you.

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[///M5 2,833]

Of course, it would be good to hang out with you in my neck of the woods. To do a physical measurement of the flex though I will have to do it out of vehicle, perhaps in my basement although I'd prefer to do it free-field so we could compare acoustic response along with the physical without having to subtract out any room/cabin gain. Our other option would be to quickly build another box. I imagine the two of us could whack something out rather quickly and I'd be glad to volunteer the $15 for mdf.

[mrray13 30]

Of course, it would be good to hang out with you in my neck of the woods. To do a physical measurement of the flex though I will have to do it out of vehicle, perhaps in my basement although I'd prefer to do it free-field so we could compare acoustic response along with the physical without having to subtract out any room/cabin gain. Our other option would be to quickly build another box. I imagine the two of us could whack something out rather quickly and I'd be glad to volunteer the $15 for mdf.

name a time, so i can get it arranged. might even bring the wifey if she behaves, hehe

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[dropkick13 0]

I also need to fiberglass to save some mounting space. From what I gather, the Fi Q is what I'm wanting for my setup but because of my limited mounting space I might be forced to grab a SSD or BL.

you guys mind walking me through the basic build process of doing the ported box? I got winisd so i know ill need to do some calculations to get the size of the port. Obviously I'm just confused on what is going on inside the box. I understand the concept of directing the flow to the port but that's about it.

I'm Brandon by the way

[Mino 2]

first of all you need to measure the exact space u have to work with height width and length

[///M5 2,833]

1st -- you can raise your seat 3/4" by just setting the brackets on mdf blocks. This will help some, otherwise I see about 2cuft of space being possible total. This area has to include the port volume, box internal volume, and sub volume. Personally I think upfiring is the easiest to fit under your seat as there is some space into the interior of the seat it can easily fire into.

After this, you sort of have to choose an overall port area. The port length is inversely proportional to the area meaning the more port area the longer the port. At that point it becomes a game of playing with the numbers to make sure that it fits on the inside of your box. Less port area could mean port noise, but most definitely a shorter port.

[dropkick13 0]

1st -- you can raise your seat 3/4" by just setting the brackets on mdf blocks. This will help some, otherwise I see about 2cuft of space being possible total. This area has to include the port volume, box internal volume, and sub volume. Personally I think upfiring is the easiest to fit under your seat as there is some space into the interior of the seat it can easily fire into.

After this, you sort of have to choose an overall port area. The port length is inversely proportional to the area meaning the more port area the longer the port. At that point it becomes a game of playing with the numbers to make sure that it fits on the inside of your box. Less port area could mean port noise, but most definitely a shorter port.

I figured I would have to throw some washers down or something to raise the seat. The problem is that I cut the back tabs behind the seat to allow the back to fold down. Because of this, I'm limited to how much I can raise the seat but even raising it 1/4" will give me another .1-.2 cu ft and every little bit will help.

How will upfiring change the sound vs downfiring? Either way, girls will enjoy sitting back there I suppose.

Then, how do I go about choosing an overall port area? You are sticking to me using MDF for the port, right? Do you have any pictures of some boxes you have built so I can get an idea of what is going on?

[///M5 2,833]

Here is why it is difficult, theoretically this could fit in 2cuft but knowing what the space under the seat is it won't be trivial to say the least. It is a bummer you trimmed your tabs as lifting will really, really help.

1.2cuft net for the box

~34hz tune

20sq in port that is ~37" long

[dropkick13 0]

Here is why it is difficult, theoretically this could fit in 2cuft but knowing what the space under the seat is it won't be trivial to say the least. It is a bummer you trimmed your tabs as lifting will really, really help.

1.2cuft net for the box

~34hz tune

20sq in port that is ~37" long

I can weld something to extend the tabs if need be so that should not be TOO big of a deal. Now, using other people's calculations is not ideal but Subthump boasts that their box has 2 cu ft of internal volume so i SHOULD be able to get at least that but you are right about there being a big difficulty in being accurate. If it is a big deal, i could make a cheap 'model' of my box with ply wood instead of MDF and fill it with water and get the volume that way but that is probably too much effort and money (have to fiberglass that too).

You still say I should build the port with MDF right? I think you sent me some links in another thread but do you have anything that will show me how to build the port?

[///M5 2,833]

A pvc tube is fine, but you don't have enough length to fit it under your seat which is why I would do mdf. You will have to make a labyrinth on one side of the seat though to even get it long enough. For instance above try to draw a 2"x10" port that is 37" long in your box...you can see it isn't so easy. If it weren't for the hump in the middle of the truck it would be way easier.

[dropkick13 0]

A pvc tube is fine, but you don't have enough length to fit it under your seat which is why I would do mdf. You will have to make a labyrinth on one side of the seat though to even get it long enough. For instance above try to draw a 2"x10" port that is 37" long in your box...you can see it isn't so easy. If it weren't for the hump in the middle of the truck it would be way easier.

i see what you mean.... do you know if it has been done (correctly)?

[dropkick13 0]

There's always the option of doing one or two 10" subs. The 10" Q's don't require nearly as much volume. Would that work or would it not really give me what I'm wanting?

Sean, I PM'ed you about an amp too.

Edited November 18, 2007 by dropkick13

[///M5 2,833]

The problem with going smaller is that you end up with a longer port which even gets harder to implement. It can be done for sure, but there are compromises. You could tune higher and get more output with a shorter port or use a smaller port area and potentially have port noise. If you labyrinth the port on one end of the box you could use thinner mdf (1/2") for the port.

[dropkick13 0]

The problem with going smaller is that you end up with a longer port which even gets harder to implement. It can be done for sure, but there are compromises. You could tune higher and get more output with a shorter port or use a smaller port area and potentially have port noise. If you labyrinth the port on one end of the box you could use thinner mdf (1/2") for the port.

What would Sean do? Just sacrifice the 3/4" and use 1/2" MDF for the port? Or you think I should go with a smaller port area and hope luck is on my side with no port noise?