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Walmart pillows

post #1 of 40
9/5/09 at 2:04pm
Thread Starter 
How do they work as a sub box stuffing? They're cheap and i was thinkng of pickin up some for a dual sealed shiva setup i'm doing. please lemme know. thanks!
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post #2 of 40
9/5/09 at 2:53pm
great question. lots of folks would like to know too. i can't imagine they work as well as fiberglass, but fiberglass has its downsides, so at least knowing what the performance tradeoff is would be useful information.
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post #3 of 40
9/5/09 at 2:59pm
I can't remember who, but someone ran tests on before/after measurments with the cheap walmart pillows. It helped out with resonance over 100 hz. If I can think of it maybe I'll be able to find the thread.
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post #4 of 40
9/5/09 at 3:24pm
resonance is one thing. i think mr. hurd posted some stuff on that. maybe he is the guy that you are thinking about.

the other matter is increasing the effective enclosure size. noussaine did some tests using polyfill that showed pretty good results. how those results compare to fiberglass or to walmart pillows is another matter.
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post #5 of 40
9/5/09 at 3:27pm
Thread Starter 
Yes i'm more interested in increasing my effective enclosure size.
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post #6 of 40
9/5/09 at 4:19pm
No clue about increasing enclosure size. I don't think it will help that much, just because of the way the fiber structure is setup in the pillows. When trying to "increase" the enclosure size you're trying to slow the air down some. How much a couple pillows will slow down the air compared to a pretty heavily stuffed box is probably not going to be on the same page. I may be wrong, but if you're wanting to stuff, I'd go polyfill. They sell it at walmart and it's not horribly expensive.
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post #7 of 40
9/5/09 at 5:22pm
Quote:
Originally Posted by brandonnash View Post


When trying to "increase" the enclosure size you're trying to slow the air down some.

not quite correct. the physics is that the compressed air creates heat. the hot air creates pressure. the pressure is the problem. fiberglass, absorbs the heat by translating it into physical motion. the tiny little fibers vibrate. this reduces the instantaneous heat build up. the result is a sub stuffed with fiberglass behaves thermodynamically similarly to a non-stuffed sub of much larger volume.
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post #8 of 40
9/5/09 at 6:36pm
Quote:
Originally Posted by LTD02 View Post

not quite correct. the physics is that the compressed air creates heat. the hot air creates pressure. the pressure is the problem. fiberglass, absorbs the heat by translating it into physical motion. the tiny little fibers vibrate. this reduces the instantaneous heat build up. the result is a sub stuffed with fiberglass behaves thermodynamically similarly to a non-stuffed sub of much larger volume.

Please don't get upset.
I'm not about to pretend that I know anything about this subject.
And, I'm not issuing a challenge.
I'm just trying to grasp what you just said, and I hope you can explain it so that even I can understand it.

The difficulty I'm experiencing is, intuitively, it seems as if you stated it backward.
I mean no offense, help me to understand, please.

It seems to me that stuffing--whether Polyfil or Fiberglass--would vibrate, and that the mechanical energy within the stuffing (vibrations) would be converted into heat energy.

Okay, simultaneously, air is compressed by the driver movements and the temperature of the compressed air rises, but I don't yet understand how the air temperature causes the stuffing to vibrate.

And, immediately following the air compression cycle is an air expansion cycle.
If compressed air rises in temperature, does expanded air drop in temperature? And, does the drop in air temperature cause vibration in the stuffing?

I'm no expert--that's why I am asking the questions. I just want to understand this.
Sorry if it seems like a challenge. I assure you it is not.
I'm just trying to understand.
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post #9 of 40
9/5/09 at 6:45pm
Quote:
Originally Posted by PassingInterest View Post

Please don't get upset.
I'm not about to pretend that I know anything about this subject.
And, I'm not issuing a challenge.
I'm just trying to grasp what you just said, and I hope you can explain it so that even I can understand it.

The difficulty I'm experiencing is, intuitively, it seems as if you stated it backward.
I mean no offense, help me to understand, please.

It seems to me that stuffing--whether Polyfil or Fiberglass--would vibrate, and that the mechanical energy within the stuffing (vibrations) would be converted into heat energy.

Okay, simultaneously, air is compressed by the driver movements and the temperature of the compressed air rises, but I don't yet understand how the air temperature causes the stuffing to vibrate.

And, immediately following the air compression cycle is an air expansion cycle.
If compressed air rises in temperature, does expanded air drop in temperature? And, does the drop in air temperature cause vibration in the stuffing?

I'm no expert--that's why I am asking the questions. I just want to understand this.
Sorry if it seems like a challenge. I assure you it is not.
I'm just trying to understand.

in physics, there is a gas law where we learn pv=nrt (link below). for purposes here, as pressure increases, temperature rises. temperature is a measure of heat. heat is nothing more than vibration, well, to oversimplify. when air molecules virbrate, the temperature rises. it takes a lot more energy to vibrate the glass particles in fiberglass than the surrounding air. so, in some sense, the fiberglass sucks energy out of the air as it begins to vibrate. as a result the air vibrates less. the air temperature is lower. the internal air pressure is lower. and the subwoofer thinks there is more air in the sub. i.e., it thinks the box is larger than it is. this all happens instantaneously, so it's not like turning up the thermostat and waiting a half hour for the room to heat up. think at the speed of molecules...fractions of a second.

http://en.wikipedia.org/wiki/Ideal_gas_law
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post #10 of 40
9/5/09 at 6:49pm
It works, it lowered my tuning nearly a third octave:
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post #11 of 40
9/5/09 at 6:53pm
awesome dan, can you link to the pictures of the purchase, so we can see exactly which ones you purchased?
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post #12 of 40
9/5/09 at 6:58pm
The current label is a green and tan, I've used some of those too:
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post #13 of 40
9/5/09 at 6:58pm
Quote:
Originally Posted by NEO Dan View Post

It works, it lowered my tuning nearly a third octave:

Cool. Did you measure to see the drop in tune? I believe all my future boxes will get heavy stuffing with pillows.
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post #14 of 40
9/5/09 at 7:00pm
alternative hypothesis dan, is it possible that your pillows are doing very little to absorb heat and are just semi-blocking off air flow to your port? having the same length port, but semi-blocked would also reduce the tuning frequency, wouldn't it? hhmmm...
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post #15 of 40
9/5/09 at 7:01pm
There was ~18 or 20 oz of fill in the pillow IIRC
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post #16 of 40
9/5/09 at 7:07pm
Quote:
Originally Posted by LTD02 View Post

alternative hypothesis dan, is it possible that your pillows are doing very little to absorb heat and are just semi-blocking off air flow to your port? having the same length port, but semi-blocked would also reduce the tuning frequency, wouldn't it? hhmmm...

Nope, absloutly no blockage whatsoever in this configuration.
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post #17 of 40
9/5/09 at 7:11pm
have you (or anyone you know of) tested these pillows in a sealed sub with similar results?
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post #18 of 40
9/5/09 at 7:12pm
i'm pressing because wal mart pillows offer a lot of advantages over fiberglass. lots of folks would just want to know that they actually work.
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post #19 of 40
9/5/09 at 7:15pm
Not to my knowledge.
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post #20 of 40
9/5/09 at 7:18pm
well, let's keep an eye out for such.
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post #21 of 40
9/5/09 at 8:08pm
Quote:
Originally Posted by LTD02 View Post

in physics, there is a gas law where we learn pv=nrt (link below). for purposes here, as pressure increases, temperature rises. temperature is a measure of heat. heat is nothing more than vibration, well, to oversimplify. when air molecules virbrate, the temperature rises. it takes a lot more energy to vibrate the glass particles in fiberglass than the surrounding air. so, in some sense, the fiberglass sucks energy out of the air as it begins to vibrate. as a result the air vibrates less. the air temperature is lower. the internal air pressure is lower. and the subwoofer thinks there is more air in the sub. i.e., it thinks the box is larger than it is. this all happens instantaneously, so it's not like turning up the thermostat and waiting a half hour for the room to heat up. think at the speed of molecules...fractions of a second.

http://en.wikipedia.org/wiki/Ideal_gas_law

LTD, I don't stand a chance of ever grasping any portion of the Wiki page, but thanks for the link anyway. I did try.

Your explanation on the other hand, helped me a great deal.
You're talking at the molecular level. Now it makes sense, what you said earlier.
As the temperature of a substance rises, the molecules within that substance vibrate with more...uh, vigor, I guess (and the electrons jump to orbital bands farther from the nucleus, thereby causing expansion of said substance).
And, anything in contact with something warmer than itself, will absorb some of that heat energy that a state of equalibrium may be reached.
And, differing materials absorb heat energy at different rates--some can absorb considerably more heat energy than another without being similarly affected proportionately physically in regards to expansion.
Or, stated differently, some materials require more heat energy to reach the same level of excitement, or expansion.
And, polyfil relieves the surrounding air of some of the heat energy it contains (in a fraction of a second).
Or, am I way off?

Okay, so that is a consideration of the compression of the air.
But, what happens during the expansion of the air? Or, is that part irrelevant?
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post #22 of 40
9/5/09 at 8:17pm
Quote:
Originally Posted by PassingInterest View Post

LTD, I don't stand a chance of ever grasping any portion of the Wiki page, but thanks for the link anyway. I did try.

Your explanation on the other hand, helped me a great deal.
You're talking at the molecular level. Now it makes sense, what you said earlier.
As the temperature of a substance rises, the molecules within that substance vibrate with more...uh, vigor, I guess (and the electrons jump to orbital bands farther from the nucleus, thereby causing expansion of said substance).
And, anything in contact with something warmer than itself, will absorb some of that heat energy that a state of equalibrium may be reached.
And, differing materials absorb heat energy at different rates--some can absorb considerably more heat energy than another without being similarly affected proportionately physically in regards to expansion.
Or, stated differently, some materials require more heat energy to reach the same level of excitement, or expansion.
And, polyfil relieves the surrounding air of some of the heat energy it contains (in a fraction of a second).
Or, am I way off?

Okay, so that is a consideration of the compression of the air.
But, what happens during the expansion of the air? Or, is that part irrelevant?

you have got it.

when the driver decompresses the exact opposite happens. the air pressure drops. as a result it cools. that cool air then sucks heat out of the fiberglass. this warms the air in the enclosure ever so slightly. as a result, the driver moving outward thinks there is more air in the enclosure than there really is.

the fiberglass is providing a damping effect on the heat rise / heat decline in the internal air as the driver moves in and out. as a result the pressure is damped as well. it doesn't rise so fast on the instroke and it doesn't fall so fast on the outstroke.

now go build something. ;-)
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post #23 of 40
9/5/09 at 9:02pm
Quote:
now go build something. ;-)

You too
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post #24 of 40
9/5/09 at 9:05pm
Quote:
Originally Posted by LTD02 View Post

i'm pressing because wal mart pillows offer a lot of advantages over fiberglass. lots of folks would just want to know that they actually work.

I stuffed a bunch of them in my sealed enclosures by NeoDan's recommendation. He knows 25x more than I do, so I did it!


The way I see it, many companies put polyfill in their expensive speakers/subs. Walmart pillows are polyfill......that's pretty much all I need to hear.


The only downside to Walmart pillows is when you try stuffing 12-18 in the same cart and stroll through the store.

Yelling "Shut up and stay in the cart Fluffy" while beating on them does keep people from asking questions though!
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post #25 of 40
9/5/09 at 9:58pm
eric, good data. did you measure before and after? how much did the pillows change the quantitative metrics?
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post #26 of 40
9/5/09 at 10:00pm
Quote:
Originally Posted by penngray View Post

You too

lol...got me...i'm stuck in a spot where i can't; or i most certainly would!
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post #27 of 40
9/6/09 at 1:54am
Quote:
Originally Posted by NEO Dan View Post

Nope, absloutly no blockage whatsoever in this configuration.

But how much volume do the pillows take up in the box. Would there be any difference to you removed the casing from the pillow and just left the stuffing in the box?
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post #28 of 40
9/6/09 at 5:05am
Quote:
Originally Posted by Erich H View Post

The only downside to Walmart pillows is when you try stuffing 12-18 in the same cart and stroll through the store.

Yelling "Shut up and stay in the cart Fluffy" while beating on them does keep people from asking questions though!

And laughter ensues at 7 in the morning.
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post #29 of 40
9/6/09 at 6:32am
Quote:
Originally Posted by Erich H View Post

The only downside to Walmart pillows is when you try stuffing 12-18 in the same cart and stroll through the store.

Yelling "Shut up and stay in the cart Fluffy" while beating on them does keep people from asking questions though!

I almost fell out of my chair laughing!
That's pretty stinkin' hilarious!

LTD02--Thanks for the explanations.
You have succeeded where few others ever have--you made me learn something.
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post #30 of 40
9/6/09 at 6:51am
Quote:
Originally Posted by Erich H View Post

The only downside to Walmart pillows is when you try stuffing 12-18 in the same cart and stroll through the store.

Yelling "Shut up and stay in the cart Fluffy" while beating on them does keep people from asking questions though!


THAT WAS YOU!!!!


J/K Very funny!
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