I want to know if my subwoofer box is a good design. Here's the dimensions:
Depth 1: 3.5"
Depth 2: 8"
Height: 12"
Width: 59.5"
These are the outer dimensions and the material is 3/4" MDF. There are two pieces of 3/4" MDF seperating the two subwoofer chambers in the center. Each chamber is 25" wide, allowing for the amplifier to be recessed into the box without being rattled. It's a wedge shaped box. It's also sealed (not ported). I don't have enough room for ported boxes.
Does it need any work?
1992 Chevrolet pickup; Jensen VM9412 HU; Alpine 4x6 2-way dash speakers x 2; Pyle Blue Label 4x6 3-way rear speakers x 2; Pyle Blue Label 12" subs x 2; Crunch GVP700.2 "Ground Pounder" subwoofer amplifier; Custom Subwoofer box
The optimum shape for any enclosure would have dimensions in a ratio of 1 x 1.6 x .6
This is known as the "golden ratio". Honestly, i've never seen a box built for a car with the golden ratio.
As long as your subs have enough space behind the pole vent to cool the magnet, your design is just fine. It is quite rectangular, so the backwave of the subwoofers may give it unusual harmonics. You can reduce this by stapling 1" thick fiberglass to the interior walls of the enclosure. You can skip the side that the subs mount to. At the very least, use a pound or so of poly-fil. You would have .74 cubic feet gross box volume on each side, minus however much volume is taken up by the amp recession. Look for 10's with a recommended box volume of about .7 cubic feet.
Your other option would be to port the box and use smaller subs. This can get complicated, but you would get more of the deepest bass frequencies (30-50hz) with 2 ported 8's than with a pair of sealed 10's.
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This is a shameless bump.
EDIT: I edited 1 of the numbers in the post above.
Thanks for the reply. I already have a set of 12's that work great. I can increase the depth as necessary or up to 1.5 inches, whichever comes first. My current amp pushes 175 watts x 2 @ 4-ohms. The subs are 4-ohms. Do you think I need to increase the enclosure depth?
By all means!
If you believe you can still squeeze the box in, make it larger. Don't know what 12's you have, but they usually require a minimum of about 1 cubic foot, and likely they will have better response characteristics in ever larger boxes.
Ok, so I've increased the depth by 1.5" (lost .5" of leg room, but it'll be worth it). According to a calculator I found online, that gives me about .8 cubic feet of internal volume. How much polyfil would you recommend?
If needed, I can remove two of the three internal dividers and increase the width of each chamber to 29. I can use rubber feet to keep the amp from rattling.
Do you think it would mess with the subs in any way if I drilled a hole in the third internal seperator? If it wouldn't, where would I drill it?
Generally a pound of poly-fil for each cubic foot. I had originally it figured to be .74, so that extra inch and a half of depth should put you to more like 1.0 per side. What dimensions do you have?
You don't need to remove the dividers, but if it gets you some more airspace it may be a smart idea.
The subs will operate more effectively if they have their own sealed enclosure. Drilling a hole between the 2 chambers wouldn't be a catastrophe, but you would lose the benefit of the separate enclosures. Why would you want a hole? A divider isn't absolutely necessary, but it gets you a free decibel sometimes. Plus, if one sub should ever fail, the other sub will be isolated from damage.
The new dimensions are:
Width: 29" (after the two dividers are removed).
Depth 1: 5"
Depth 2: 9.5"
Per sub chamber. Each sub chamber is identical right down to the placement of the hole. I haven't yet removed the two dividers. There are three of them, so if I only remove the two I plan on removing, I'll get more airspace. The current width with them in place is 25".
I just measured and found that I can increase the height by an extra 5 inches. If I do this, the shape of the box would be a little weird, but I could get away with removing .75" of depth and still have a 1 cubic foot box.