Increasing sub box volume
10-18-2011, 11:03 PM
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Increasing sub box volume I currently have a rectangular box that I built myself. It's ugly, but it serves it's purpose of having enough volume to support my subs. I want to build a wedge shaped box that will look cleaner, however I still need a certain amount of volume. Obviously, I can do so by altering the dimensions of the box, but I'm putting this box behind the back seat so I'm limited to that area. I've heard a little bit about "filling" the box with something to increase volume. I don't understand how this works because logically, it would decrease volume. It has something to do with the "isothermic" properties? Right? ANYWAY, I need to decrease my dimensions but maintain or increase volume. Ideas?
10-21-2011, 07:10 PM
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Yes, it can change the "virtual" size of the box. Take for instance, I have a JL Audio W3 12" sub in my car. I have a sealed box, so we'll use it as an example. Ideal volume for a sealed box for my sub would be 1.2 cubic feet, dimensions would be 23"(w)x14"(h)x10"(d), pulled straight from my user's manual. However, I didn't want a two foot wide box in my trunk as I still like being able to use my trunk 
so I was in a similar spot. Whenever you're going to modify the volume of your box so you can gain more space, keep in mind you're going to lose some power, and your frequency response isn't going to be as good, even if you use stuffing. You're not gonna pound out the bottom end of the sub in a smaller box and it won't be as loud, is what I'm getting at.
A good rule of thumb is to keep as many of the dimensions the same as possible. I shrank the width of my box down to 16", and increased the depth to 14", bringing my internal volume to roughly 1 cubic foot. I used 1 1/4" MDF board to construct my box, countersank my screws, caulked the inside of all the joints, and stuffed it about halfway full of polyfill stuffing I got from Hobby Lobby. Any crafts store will have it- it's the same stuff inside your pillows. What resulted is a setup that is still pretty close to what JL specifies, I probably could've gotten away without the stuffing but I don't like to skimp on sound, even though I doubt I would've noticed it- better to have it and not need it, I think.
The technicalities of it are that having stuffing inside the box is like having more air. In any box, but most noticeably in sealed ones, when the sub goes in, it compresses the air inside the box. When it pushes out, pressure inside drops. Compressing and decompressing air results in the internal temperature of the box going up or down, respectively. Adding stuffing results in a change in how the pressure and temperature act in the box- it absorbs the heat and pressure differently than a box filled with just air would, therefore slightly increasing the virtual volume of the box. Now if you have a ported box that's a whole different can of worms lol so ultimately, yes you can put stuffing inside of your box to make it sound like a bigger box, but if your sub requires 1.5 cubic feet, and your box is only .7 cubic feet, adding stuffing inside is not going to get it to 1.5. You might add a few tenths but that's basically it. If you could get me some idea of what you're working with where you want to install the box, and what kind of sub you have, PM me and I'll see if I can figure something up for you. Me and a friend of mine do car audio on the side
so I was in a similar spot. Whenever you're going to modify the volume of your box so you can gain more space, keep in mind you're going to lose some power, and your frequency response isn't going to be as good, even if you use stuffing. You're not gonna pound out the bottom end of the sub in a smaller box and it won't be as loud, is what I'm getting at. A good rule of thumb is to keep as many of the dimensions the same as possible. I shrank the width of my box down to 16", and increased the depth to 14", bringing my internal volume to roughly 1 cubic foot. I used 1 1/4" MDF board to construct my box, countersank my screws, caulked the inside of all the joints, and stuffed it about halfway full of polyfill stuffing I got from Hobby Lobby. Any crafts store will have it- it's the same stuff inside your pillows. What resulted is a setup that is still pretty close to what JL specifies, I probably could've gotten away without the stuffing but I don't like to skimp on sound, even though I doubt I would've noticed it- better to have it and not need it, I think.
The technicalities of it are that having stuffing inside the box is like having more air. In any box, but most noticeably in sealed ones, when the sub goes in, it compresses the air inside the box. When it pushes out, pressure inside drops. Compressing and decompressing air results in the internal temperature of the box going up or down, respectively. Adding stuffing results in a change in how the pressure and temperature act in the box- it absorbs the heat and pressure differently than a box filled with just air would, therefore slightly increasing the virtual volume of the box. Now if you have a ported box that's a whole different can of worms lol so ultimately, yes you can put stuffing inside of your box to make it sound like a bigger box, but if your sub requires 1.5 cubic feet, and your box is only .7 cubic feet, adding stuffing inside is not going to get it to 1.5. You might add a few tenths but that's basically it. If you could get me some idea of what you're working with where you want to install the box, and what kind of sub you have, PM me and I'll see if I can figure something up for you. Me and a friend of mine do car audio on the side
Last edited by gxpintn; 10-21-2011 at 07:18 PM.
