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Discussion Starter #1
Doesn't it freaking kill you guys when manufacturers don't list this number ???
Urgggghhh !

I get that it will be different depending on how the sub is mounted, face mounted, back mounted, etc, but this info is SO important, they need to tell me the displacement mounted 9 different freaking ways, and let me take my pick !

I know their are those who will say it doesn't make that big a difference.... But when I calculate everything else in my enclosures to the third decimal point.... Then get to sub displacement, what, I'm just supposed to toss that out the window ? Kind of makes the rest of my precise calculations pointless.

I have even called a few manufacturers who don't seem to be 100% sure of their own products ? Seriously ? Those freaking guys need to get a job at Home Depot ! At least their, nobody expects you to know anything.

Freaking kills me. How do you guys deal with this ?
 

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It doesn't really matter as much as you think. Model a 2 cf box in WinISD and factor in a sub with 2 liters of displacement vs. one with 2.5 liters (0.07cf vs. 0.088cf). A difference of 0.018cf isn't going to make a difference. A rough estimate for displacement as all that is needed. Getting more precise won't change the response in any appreciable way.
 

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Getting more precise won't change the response in any appreciable way.
Fish Chris, I know you like to be very exacting but subwoofer enclosures do not need to be that exact. I doubt you would even be able to notice an audible difference in two enclosures that have 10% different enclosure volumes.
 

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Agreed. It's not gonna make a huge difference if any of the box is .15 cubes smaller or whatever the displacement is
 

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Discussion Starter #5
I don't build sloppy chit ! I calculate things for a reason. And btw, in my next... {well two builds from now, in fact, I just got my first of two Skar 18" subs last evening :)} So that enclosure is going to be REALLY small, for two 18" subs... believe it or not only 1.78 cubes ! Specs call for 3.56 for one in a typical tuned ported enclosure. Now, the closest I can figure.... and I have to 'figure' because again, nobody tells you this super important info :( is .4 to .45 cubes for a totally internally mounted 18" subwoofer. So here we are talking about an enclosure which is only 1 3/4 cubes to begin with, and you guys don't think a displacement of nearly 1/2 a cube is going to matter much ? Thats 30 freaking % ! Screw "guessing". I want to know exactly how much this stinking thing is going to take up.
 

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Discussion Starter #6
I'm going to call Skar Monday. I hear they are worthless to talk to, but I'm going to give them a shot anyway.
 

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Having a box half the size as suggested is worse than just the displacement not being there. I'm not sure what you think you're gonna get out of that

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Discussion Starter #8
Having a box half the size as suggested is worse than just the displacement not being there. I'm not sure what you think you're gonna get out of that

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Apparently you have not studied up on Isobaric clam shell configurations. These require "exactly half" of what the same sub woofer, by itself, in a standard tuned ported enclosure requires.
Check this video, specifically starting at about 4:40

And the info contained therein, confirms what I have been seeing in my pair of 15"s isobarically mounted in a very small tuned ported enclosure too.

All of this said, I'm thinking about going back up closer to the cubes recommended for 'one' of these 18"s (up to 4 1/2 cubes) just for the sake of more low bass. But I already know that using as little as 1.75 cubes in this configuration will sound very tight and clean.
 

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Apparently you have not studied up on Isobaric clam shell configurations. These require "exactly half" of what the same sub woofer, by itself, in a standard tuned ported enclosure requires.
Check this video, specifically starting at about 4:40

And the info contained therein, confirms what I have been seeing in my pair of 15"s isobarically mounted in a very small tuned ported enclosure too.

All of this said, I'm thinking about going back up closer to the cubes recommended for 'one' of these 18"s (up to 4 1/2 cubes) just for the sake of more low bass. But I already know that using as little as 1.75 cubes in this configuration will sound very tight and clean.
If you are talking about a 4th order then it should be fine. I didn't know that's what you were doing

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Discussion Starter #10
I hate that this forum has no edit function... But I wanted to add, What I expect to get from this is a LOT of deep bass / subwoofer Volume Displacement (Vd) without making a box so huge, it fills the whole supercab section of my truck. BTW, I did once build a 10 cu ft (OD) box for the same two 15"s Im running in 1,5 cubes right now... and yes, it took up a huge amount of space in my truck... had to shoehorn it in :) lol Just not trying to go down that same road again. If I were going to do all that, Id just go ahead and wall it.
 

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I hate that this forum has no edit function... But I wanted to add, What I expect to get from this is a LOT of deep bass / subwoofer Volume Displacement (Vd) without making a box so huge, it fills the whole supercab section of my truck. BTW, I did once build a 10 cu ft (OD) box for the same two 15"s Im running in 1,5 cubes right now... and yes, it took up a huge amount of space in my truck... had to shoehorn it in :) lol Just not trying to go down that same road again. If I were going to do all that, Id just go ahead and wall it.
There is edit here

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You could also measure using rice. The main things you need is cone displacement and magnet displacement.

1. Tape up any holes in the magnet. Then place the sub’s magnet in a dish about the same height as the magnet. Fill dish with rice. Remove sub from dish. Level rice in bottom of dish. Measure height of dish - height of rice, then calculate displacement using dish dimensions.

2. Fill subwoofer cone with rice. Then pour rice into dish. Calculate how much rice is in the dish to determine displacement.

3. Measure ribs of sub frame and calculate displacement as simple rectangles of a certain thickness multiplied by number of spokes on sub frame.
 

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Discussion Starter #17
You could also measure using rice. The main things you need is cone displacement and magnet displacement.

1. Tape up any holes in the magnet. Then place the sub’s magnet in a dish about the same height as the magnet. Fill dish with rice. Remove sub from dish. Level rice in bottom of dish. Measure height of dish - height of rice, then calculate displacement using dish dimensions.

2. Fill subwoofer cone with rice. Then pour rice into dish. Calculate how much rice is in the dish to determine displacement.

3. Measure ribs of sub frame and calculate displacement as simple rectangles of a certain thickness multiplied by number of spokes on sub frame.
I looked all over for those stinking things too ! So I'm dumb, blind, and now working on the def part :) lol
 

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Discussion Starter #18
You could also measure using rice. The main things you need is cone displacement and magnet displacement.

1. Tape up any holes in the magnet. Then place the sub’s magnet in a dish about the same height as the magnet. Fill dish with rice. Remove sub from dish. Level rice in bottom of dish. Measure height of dish - height of rice, then calculate displacement using dish dimensions.

2. Fill subwoofer cone with rice. Then pour rice into dish. Calculate how much rice is in the dish to determine displacement.

3. Measure ribs of sub frame and calculate displacement as simple rectangles of a certain thickness multiplied by number of spokes on sub frame.
Ya' know, honestly, just picking up and manipulating one of these 18"s is a major chore ! Im going to try to talk with a Skar tech Monday. I'm guessing a surface mounted 18" might be .25 to .30... and I know how to calculate for the offset, of mounting it internally.... So it will probably be more like .30 to .40 cubes.

Id sure like to know more about running two of these isobarically, also. Thinking more towards 4 cubes... which is still pretty small for two 18"s
 

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Ya' know, honestly, just picking up and manipulating one of these 18"s is a major chore !
You know, when I started my commercial sub business, I didn't think about the long term issues of moving 18” and 24” drivers as I agree, they are beasts. Glad I hired people to do that for me now. :)
 
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