# Does sub box "shape" make a difference, or only volume?



## 1hawaii50 (Jun 21, 2008)

I'm going to be doing an install in a freind's 08 Suburban, and he wants a "false floor" built for the rear cargo area. The false floor will house the amplifier (Rockford 25 to life power 1000) and wiring. He wants either a single 12", dual 10", or dual/triple 8" subs, but he wants the false floor to be used as the sub box. He doesn't want to have to deal with a massive sub box in the cargo area. My question is, if the false floor is built 6-8" high, will it be "thick" enough for a proper sub enclosure. I have plenty of space to work with length/width-wise, but the depth is going to be the problem. I guess I'm trying to ask if a shallow box will work ok, as long as I have the needed volume (make up the difference with the length and width)? He's also still undecided on the subs, so I'm open to any recommendations there also. The sub channel on the amp will be putting out 650-700w rms x 1 @ 2ohms, and 925-1000w rms x 1 @ 1ohm.


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## JediMentality (May 7, 2008)

For sealed boxes, especially, the shape doesn't matter. What matters is the size/volume. Depth matters if the subs vent through the bottom of the motor/magnet. I believe you should have at least a pole vent diameter's distance from the back of the box.


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## Electrodynamic (Nov 27, 2007)

+1 to what Jedi said. The shape means very little when it comes to what you're asking about - volume. As long as the volume is where you need it, whether it's a shallow box or deep box doesn't matter. With 6" of internal depth you'll be looking at fairly shallow subwoofers, but if it's 8" of depth you can use almost anything. But a 'false floor' that's 8" deep might negate the purpose of a false floor because it will be fairly tall. My enclosure is 5.5" deep and my floor is only going to be raised 0.5" above the normal floor height. If it was 8" deep I would lose a lot of my trunk space.


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## 14642 (May 19, 2008)

Yup. all of this is correct. However, connecting two boxes with a tube or small passageway DOESN't work the same way. Just thought I'd add that.


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## 1hawaii50 (Jun 21, 2008)

Since the box will be all 90 degree angles, should I use a deflex pad behind the sub?


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## neverman (Feb 27, 2009)

Are you guys sure shape doesn't matter? The whole industry is going to exotic curves instead of boxes in the Home arena and it's more costly to do so. Standing waves, reflected waves? Is it too focused a frequency in a sub box to matter? I know it matters for mid-range. I'm just asking, obviously volumn is the main factor but can we totally disregard shape?

Squares are bad~


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## 14642 (May 19, 2008)

1hawaii50 said:


> Since the box will be all 90 degree angles, should I use a deflex pad behind the sub?


Send me the money you'd spend on a "deflex" pad. I'll put it to better use.


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## 1hawaii50 (Jun 21, 2008)

I thought you wanted to deflect the waves coming off of the back of the box to keep them from hitting the cone?


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## chad (Jun 30, 2005)

neverman said:


> Are you gys sure shape doesn't matter? The whole industry is going to exotic curves instead of boxes in the Home arena and it's more costly to do so. Standing waves, reflected waves? Is it too focused a frequency in a sub box to matter? I know it matters for mid-range. I'm just asking, obviously volumn is the main factor but can we totally disregard shape?
> 
> Squares are bad~


Squares/parallel surfaces are only bad if the enclosure is allowed to go nodal, ain't gonna happen with a sub enclosure you are gonna put in a car.

Same answer with your deflex pad.


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## Infinity (Jun 28, 2005)

Andy Wehmeyer said:


> Yup. all of this is correct. However, connecting two boxes with a tube or small passageway DOESN't work the same way. Just thought I'd add that.


I was going to ask specifically about that. What are the constraints, and can you elaborate a bit? I could get a lot more room if I could pull a trick like this.


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## JediMentality (May 7, 2008)

neverman said:


> Are you gys sure shape doesn't matter? The whole industry is going to exotic curves instead of boxes in the Home arena and it's more costly to do so. Standing waves, reflected waves? Is it too focused a frequency in a sub box to matter? I know it matters for mid-range. I'm just asking, obviously volumn is the main factor but can we totally disregard shape?
> 
> Squares are bad~


Yeah, shape more noticeably affects the frequencies beyond those of the sub region (mid-high range). For sub enclosures, there maybe a minute difference with some shapes versus others when you are talking about reflections and such, but they are audibly imperceptible by the human ear, even among the best. What counts the most for sealed sub enclosure is volume, dampening (i.e. bracing), and fitment (i.e. no leaks). If standing waves seem like a big issue to you, then just don't center your sub on all axis.


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## brownmoses (Jul 23, 2008)

this cant be right. i have read several times in different places that a cube enclosure (same height, width, and depth)was terrible for a subwoofer's performance/sound.


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## Electrodynamic (Nov 27, 2007)

What Andy, Chad, Jedi, and myself have said in this thread holds up unless you're talking about balls-out SPL where the shape and smoothness of the port and certain areas of the enclosure can mean tenths of decibels.

If you don't believe us, build a spherical enclosure (in the places you're reading, they probably agree that is the best shape) and then compare the sound you receive from that enclosure to that of a regular box (with the volume being identicle). I think after you've spent a couple hundred hours building the spherical enclosure you'll look back on it and wish you would have spent the time listening to speakers instead of slaving over the round enclosure. You see, in car audio it's not _that_ critical to justify building exotic shaped subwoofer enclosures. On mids, that's a different story. But on subwoofers we are usually talking about running them below 80 Hz (on this forum that's a stretch even), and as soon as you fire up the motor the ability for you to discern between the differences of an exotic shaped subwoofer enclosure and a regular box goes out the window.


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## rollandburn (Aug 2, 2008)

Andy Wehmeyer said:


> Yup. all of this is correct. However, connecting two boxes with a tube or small passageway DOESN't work the same way. Just thought I'd add that.


Hi, could you elaborate on this? I have a sealed box with two shallow 10's in it that sit in the footwells behind the seats and the space between them is reduced almost to a 'channel' or 'small passageway' where the box goes over the transmission hump in the floor of the car. I've not been able to get the best response from this box and have been wondering if the shape of the box had anything to do with it. Does this comment indicate that there is a circumstance where the shape does matter?
Thanks!


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## 94VG30DE (Nov 28, 2007)

Do the 10s sit on one side, and just have dead space on the other side of the "tunnel hump"? Otherwise, if one sub was on each side, I'm not sure the small passage in between the two spaces would matter that much, as each driver would still in essence be playing in their own volume.


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## rollandburn (Aug 2, 2008)

94VG30DE said:


> Do the 10s sit on one side, and just have dead space on the other side of the "tunnel hump"? Otherwise, if one sub was on each side, I'm not sure the small passage in between the two spaces would matter that much, as each driver would still in essence be playing in their own volume.


here's a shot of the box....



Fiberglass subwoofer box for Porsche 911 - DiYMA Gallery

You can see that the passage is a fair size..... I'd say the two subs share the same volume.


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## Infinity (Jun 28, 2005)

Yeah. I'm wondering at what point does it choke it to 2 volumes? Is there a simple equation or is it just try and see?


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## 94VG30DE (Nov 28, 2007)

> You can see that the passage is a fair size..... I'd say the two subs share the same volume.


I'd say you could completely block that passage with a board, and it probably would not impede performance. Looks like each driver has its own separate (but equal) volume in the box, so the channel doesn't matter. 


> Yeah. I'm wondering at what point does it choke it to 2 volumes? Is there a simple equation or is it just try and see?


That's what I'm curious about too. There is some interesting fluid dynamics behind that. I don't have the modeling software to handle that...


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## TheDavel (Sep 8, 2006)

A boxes shape may matter- 

Chad or anyone here that has the inside track- speak on cabinet diffraction response anomalies


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