*Sigh* people are so idiotic

Apparently the "fastest Ferrari ever".

Fastest or quickest.

The cat is out of the bag and the build log has begun!

Swing by and I will give you another liter or two.

That's not near enough to get Romanian!

I have lots of booze here, I am sure we can get something.

Tequila, whiskey, brandy or rum are the only spirits I'll drink straight up; gin & vodka only in cocktails.

Edited March 1, 201213 yr by Penguin4x4

A bunch of french pricks at my gate

A bunch of french pricks at my gate

Sean I have some questions about stuffing a sealed enclosure, over at SMD someone inquired about stuffing, I went on to explain this.

its maybe the easiest way to "increase" the volume. it actually alters the rate that the air inside the box changes temperature. lets use a sealed box as an example-

when your cone is at rest, the pressure inside the box is considered ambient. when the cone goes in, the pressure inside the box goes up. when you pressurize air, the temperature goes up. when the cone goes out, the pressure inside goes down, and temperature goes down. we're not talking about a couple of degrees, its generally a very small temperature change.

but once you add polyfill or fiberglass insulation, or something of that sort, it absorbs and radiates the heat at a different rate than just air. its a slower rate very similar to having more air, just like having a bigger box. it only works because there is so much surface area in proportion to mass, and finer materials tend to work better.

But the problem is it reaches diminishing returns quickly and will only work up to a certain point. Last time I looked into stuffing it was about 1 lb/ft^3

Some douchecanoe said this

Wow.....

Ok yeah, the poly fill would have an extremely small effect on tempterture differential but is NOT what's causing the desired effect.

What's causing the desired effect is a decrease in standing waves. The back waves from the cone are dispersed and slowed down, causing the driver to act as if it's in a slightly bigger box while maintaining the compression needed for cone control at high excursion.

and I responded

Not to call you out, but to get standing waves especially at such low frequencies wouldn't the volume of the car have to be huge? You really don't see standing waves in a car... more in home audio..

From what I've read stuffing is based solely on the principle of acoustical energy being turned into thermal energy, albeit very small change.

and he then replied

yes, you can still get standing waves inside a sealed box at low frequencies. imagine a bathtub full of water and the waves on the water are hitting the edges, coming back, hitting the opposite edge, and coming back, etc. Should give you a good visual of what's going on inside a sealed box.

Edited March 1, 201213 yr by Julian

Closed box,

It also becomes necessary to introduce large amounts of absorbent material to damp dimensional resonances or standing waves, and to reinforce or brace the panels to reduce vibration. Fortunately, filling the enclosure with glass fibre or similar light absorbent material has the effect of partially changing the air operation from adiabatic to isothermal, which reduces the velocity of sound and may increase the effective volume of the box by as much as 40%.

-Audio Engineer's Reference Book

If I'm reading that correctly, the absorbent material would help attentuate the panel resonances and standing waves, and it allows the inside temperature to remain nearly constant.

Edited March 1, 201213 yr by stefanhinote

I knew I was right... lolz

It still mentions the use of fiber for damping the standing waves, but I believe that's mainly just for reducing enclosure resonance & sound coloration.

I'm still just reading tid bits from books, certainly not a reputable source.

I need to pickup that book..

I need to pickup a few audio related books in general

I need to pickup that book..

I need to pickup a few audio related books in general

I have an online collection.

Ill send you a pm later.

I need to pickup that book..

I need to pickup a few audio related books in general

I have an online collection.

Ill send you a pm later.

yes yes

I need to pickup that book..

I need to pickup a few audio related books in general

I have an online collection.

Ill send you a pm later.

yes yes

Yes yes?

http://motherjones.com/politics/2012/02/santorum-health-spending-medicaid-contraception-hypocrisy

On top of that, don't members/former members of Congress have access to great health insurance? That's not helping his cause

Closed box,

It also becomes necessary to introduce large amounts of absorbent material to damp dimensional resonances or standing waves, and to reinforce or brace the panels to reduce vibration. Fortunately, filling the enclosure with glass fibre or similar light absorbent material has the effect of partially changing the air operation from adiabatic to isothermal, which reduces the velocity of sound and may increase the effective volume of the box by as much as 40%.

-Audio Engineer's Reference Book

If I'm reading that correctly, the absorbent material would help attentuate the panel resonances and standing waves, and it allows the inside temperature to remain nearly constant.

So the reduction of standing waves causes an increase in the propagation of energy, which results in a dQ without the concomitant dT?

while the box without poly fill would experience changes in T without changes in Q, caused by dP

Also, the sound is slowed because the medium is more compressible than air alone and also more dense?

Awesome ^^

Closed box,

It also becomes necessary to introduce large amounts of absorbent material to damp dimensional resonances or standing waves, and to reinforce or brace the panels to reduce vibration. Fortunately, filling the enclosure with glass fibre or similar light absorbent material has the effect of partially changing the air operation from adiabatic to isothermal, which reduces the velocity of sound and may increase the effective volume of the box by as much as 40%.

-Audio Engineer's Reference Book

If I'm reading that correctly, the absorbent material would help attentuate the panel resonances and standing waves, and it allows the inside temperature to remain nearly constant.

So the reduction of standing waves causes an increase in the propagation of energy, which results in a dQ without the concomitant dT?

while the box without poly fill would experience changes in T without changes in Q, caused by dP

Also, the sound is slowed because the medium is more compressible than air alone and also more dense?

I'm not sure what any of your terms such as dQ and dT are referring to.

For this scenario:

The polyfill changes the interior "air operation" in the box. Allows for the temp. to stay consistent, instead of rising. Lower temp = lower speed of sound (velocity).

I don't know how the temp. change effects how the enclosure acts, sorry.

Polyfill also diffuses standing waves (resonance), which could reduce sound coloration, but I don't believe that's the reason why it makes the enclosure's volume more effective.

I could be wrong here, but I think it's just another issue.

I know in HT, multiple subwoofers can be used in a way to create interference that cancels out standing waves, thus improving the FR.

Closed box,

It also becomes necessary to introduce large amounts of absorbent material to damp dimensional resonances or standing waves, and to reinforce or brace the panels to reduce vibration. Fortunately, filling the enclosure with glass fibre or similar light absorbent material has the effect of partially changing the air operation from adiabatic to isothermal, which reduces the velocity of sound and may increase the effective volume of the box by as much as 40%.

-Audio Engineer's Reference Book

If I'm reading that correctly, the absorbent material would help attentuate the panel resonances and standing waves, and it allows the inside temperature to remain nearly constant.

So the reduction of standing waves causes an increase in the propagation of energy, which results in a dQ without the concomitant dT?

while the box without poly fill would experience changes in T without changes in Q, caused by dP

Also, the sound is slowed because the medium is more compressible than air alone and also more dense?

I'm not sure what any of your terms such as dQ and dT are referring to.

For this scenario:

The polyfill changes the interior "air operation" in the box. Allows for the temp. to stay consistent, instead of rising. Lower temp = lower speed of sound (velocity).

I don't know how the temp. change effects how the enclosure acts, sorry.

Polyfill also diffuses standing waves (resonance), which could reduce sound coloration, but I don't believe that's the reason why it makes the enclosure's volume more effective.

I could be wrong here, but I think it's just another issue.

I know in HT, multiple subwoofers can be used in a way to create interference that cancels out standing waves, thus improving the FR.

dQ= change in heat

dT= change in temp

Im just trying to understand this from the things ive learned in my physical biochem class but idk enough about waves to really grasp whats goin on

Is it the temp change that has the most effect to cause the slowed wave or the change in medium through which the wave propagates?