How do i make a 3.5cubic sub box act like a 10 cubic - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 18 Old 02-14-2017, 11:47 PM - Thread Starter
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How do i make a 3.5cubic sub box act like a 10 cubic

I READ HOW POLYFIL MAKES A SMALLER SUBBOX ACT LIKE A BIGGER BOX

I JUST DONT NO HOW MUCH TO ADD IM PLANING TO USE

Fairfield Poly-Fil Traditional White Quilt Batting, Crib Size, 45-Inch by 60-Inch FROM AMAZON IN TWO 3.5 CUBIC FOOT SUB BOXS WITH 1INCH THICK WALLS

AN TWO Rockford Fosgate Punch P1S2-15 SUBS AND ONE Dayton Audio RSS390-PR 15" Aluminum Cone Passive Radiator SET FOR 15.5HZ PER BOX I PLAN TO GIVE EACH SET 750WATTS

AT 4OHMS MY HOME THEATHER

SO HOW much acoustic treatment do i need TO MAKE A 3.5CUBIC SUB BOX ACT LIKE A 10 CUBIC SUB BOX?
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post #2 of 18 Old 02-15-2017, 12:00 AM
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Its really easy, just build it like a 10 cuft

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post #3 of 18 Old 02-15-2017, 12:08 AM
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I thought this was going to be a rant about people (I've been guilty) looking for more performance than their space will allow ha
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post #4 of 18 Old 02-15-2017, 05:46 AM
 
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Quote:
Originally Posted by John O'Connell View Post
I READ HOW POLYFIL MAKES A SMALLER SUBBOX ACT LIKE A BIGGER BOX
If that's what you read it was incorrect. Stuffing a box will lower the Q, which in some ways is similar to what happens with a larger box, but it's only similar, not the same. Model the effect yourself in WinISD. In 'box' mode open the 'advanced' tab, change the Qa from the default 100 (no damping) to 10 for fully filled, 5 for stuffed and compressed.

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SO HOW much acoustic treatment do i need TO MAKE A 3.5CUBIC SUB BOX ACT LIKE A 10 CUBIC SUB BOX?
No amount will do that. Also, stuffing is used only in sealed cabs, not ported or PR.
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post #5 of 18 Old 02-15-2017, 06:25 AM
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How to make a 3.5ft3 box into 10ft3....
Bend the theories of physics.... and if ya figure out how to do that, let me know.... Id love to figure out how to stuff 30ft3 of volume into a 5ft3 space...
Thanks!
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post #6 of 18 Old 02-15-2017, 06:29 AM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
If that's what you read it was incorrect. Stuffing a box will lower the Q, which in some ways is similar to what happens with a larger box, but it's only similar, not the same. Model the effect yourself in WinISD. In 'box' mode open the 'advanced' tab, change the Qa from the default 100 (no damping) to 10 for fully filled, 5 for stuffed and compressed.
Didn't know that's how you did that. I will remember that! I've tried it on multiple box designs and so far I've found no boxes like being stuffed
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post #7 of 18 Old 02-15-2017, 07:09 AM
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Add a TON of power, and a really nice shelf filter and make sure your driver can handle the wattage without blowing*

*its not "just" that simple but using a shelf filter can help change the F3 of a sealed driver, which is what I'm assuming we are talking about.
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post #8 of 18 Old 02-15-2017, 07:33 AM
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Just connect each box to an additional 7 cu ft box in a closet or garage via Einstein-Rosen bridge. Audioquest or MonsterCable probably carry them.
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post #9 of 18 Old 02-15-2017, 08:13 AM
 
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Quote:
Originally Posted by EndersShadow View Post
using a shelf filter can help change the F3 of a sealed driver, which is what I'm assuming we are talking about.
A filter will lower the system response but it won't add the necessary driver excursion to make use of it. No matter how you try you can't fit 50 pounds of potatoes into a 20 pound capacity bag.
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post #10 of 18 Old 02-15-2017, 09:27 AM
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^
that "sound of a sack of potatoes" reference is about the obscure and now forgotten first iteration of the bose bass module,

called the "Blivet Sub"

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post #11 of 18 Old 02-15-2017, 11:23 AM
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Wow. I can't believe nobody mentioned to do an isobaric system?

Obviously he listed what he has but...

You can make a 3.5cuft APPEAR as a 7cuft box if you mounted the two drivers in a clamshell.

It's not the most efficient or cost effective practice but it WILL make a 3.5cuft enclosure appear as one double it's size. It's the only real way. Stuffing will do jack.
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post #12 of 18 Old 02-15-2017, 11:41 AM
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Quote:
Originally Posted by John O'Connell View Post
I READ HOW POLYFIL MAKES A SMALLER SUBBOX ACT LIKE A BIGGER BOX

I JUST DONT NO HOW MUCH TO ADD IM PLANING TO USE

Fairfield Poly-Fil Traditional White Quilt Batting, Crib Size, 45-Inch by 60-Inch FROM AMAZON IN TWO 3.5 CUBIC FOOT SUB BOXS WITH 1INCH THICK WALLS

AN TWO Rockford Fosgate Punch P1S2-15 SUBS AND ONE Dayton Audio RSS390-PR 15" Aluminum Cone Passive Radiator SET FOR 15.5HZ PER BOX I PLAN TO GIVE EACH SET 750WATTS

AT 4OHMS MY HOME THEATHER

SO HOW much acoustic treatment do i need TO MAKE A 3.5CUBIC SUB BOX ACT LIKE A 10 CUBIC SUB BOX?
Nothing can triple the volume of your enclosure except to build a bigger one. The physical size difference between a 3.5 and a 10 isn't as much as you think.
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post #13 of 18 Old 02-15-2017, 12:22 PM
 
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Quote:
Originally Posted by Scott Simonian View Post
Wow. I can't believe nobody mentioned to do an isobaric system?
I never mention an isobaric because I don't see the sense in paying for two drivers but only getting the maximum SPL of one.
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post #14 of 18 Old 02-15-2017, 03:33 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
I never mention an isobaric because I don't see the sense in paying for two drivers but only getting the maximum SPL of one.
Yeah, no kidding. That wasn't the point though. I wasn't trying to save him money or gain SPL.

He wanted to know how to make an enclosure larger than it really is (to the driver) and I gave him the answer.
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post #15 of 18 Old 02-15-2017, 05:27 PM
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I got this!

Calculate your 3.5 cubic foot box measurements in centimeters.

Take those measurements and use inches instead

3.5 X 2.54 = 8.89 cubic feet

Then throw a kilogram of fill in per "cubic foot" and you'll be really close!

I had a girlfriend tell me I'm proof you can pack 500 pounds of dookie into a 160 pound package--won't work with subs though.

About 7 years ago I built a sub with isobaric 15's to get deeper response and it did work. Of course, I already had a pair of 15's laying around and used a passive radiator to save on the 3.3 cubic foot enclosure. It does work but--I would not suggest it unless you absolutely have no other choice. The clamshell isobaric with the magnet sticking out really impressed my wife with the Mad Max look.
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post #16 of 18 Old 02-15-2017, 05:52 PM
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Quote:
Originally Posted by Steve Hanna View Post
Nothing can triple the volume of your enclosure except to build a bigger one. The physical size difference between a 3.5 and a 10 isn't as much as you think.
Remember, the box volume is internal volume minus speaker volume minus port volume minus bracing volume. The speaker volume is the same in either box. Assuming 3/4 inch thick walls you need to add 1.5 inches to either a 3.5 or a 10 cubic ft box. The cube root of 3.5 is about 18 1/4 (plus 1 1/2 for wall thickness)= 19 3/4 The cube root of 10 is about 25 1/4 (plus 1 1/2 inches thickness or 26 3/4.

For a cube, you are talking about adding approximately 7 inches to each side dimension to go from 3.5 cu ft to 10 cu ft. Maybe for a sealed box with wool stuffing you can get that down to 6 inches a side.

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post #17 of 18 Old 02-15-2017, 08:47 PM
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Use something like this:


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post #18 of 18 Old 02-15-2017, 09:39 PM
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Quote:
Originally Posted by Augerhandle View Post
Use something like this:

Wow,.... its bigger on the inside!
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