glassing MDF enclosure

[Quentin Jarrell 671]

Like M5 stated a few pages back. Sound waves propagate just like water waves. And just like you are saying. When a tsunami hits Japan from an earthquake in the middle of the pacific does the water from the epicenter reach Japan? No, the energy is transferred from one molecule to another. However if close enough to the epicenter there is enough energy to displace the original. water to some degree

Just like a large system in a vehicle. You can hear and feel the sound 100 feet away but the air in the box is no reaching you. It move and arbitrary 5 feet due to the amount of kinetic energy at the epicenter and as energy is disappated over a larger and larger area it turns into a domino effect pushing the next molecule and so on.

[///M5 2,833]

Think of a standard condenser/electret microphone.  Fundamentally they are made from two parallel plates.  The top plate is exposed to atmosphere and any sound field.  When the top plate moves the capacitance between the bottom and top plate changes.  This is how they measure sound.  An audio signal has to MOVE the top plate in order for the microphone to work.

Go back to my reference on how to impart motion.  And in the case of the microphone it isn't via resonance.

[hdrox88 142]

Ok, I'll have a go at this. Do I have a degree? No, so take this for what it is. Just my basic understanding of "motion" and reading as an outside party on this debate.

Ramteid says a subwoofer(AC) does not move air in the same fashion that a leaf blower(DC) moves air. Both do move air molecules, just not in quite the same fashion.

Put two one way check valves on a sealed subwoofer enclosure, one as an inlet, the other as an outlet. Does the subwoofer move air when it is playing?

When you overheat your subwoofer and the coil starts to stink, how does the smell get from the location of the subwoofer in the rear of your vehicle to the location of your nose in the front of the vehicle?

Put a large plastic bag on the end of a leaf blower. Run it for one second. Reverse polarity or whatever is needed to operate the motor in reverse. Run it for one second. What happened?

Movement is movement, but I'm not seeing that as the problem here. It seems that the argument is that AC motion and DC motion are different, while both are still a form of movement. While one + - cycle of a subwoofer cone won't send one particular air molecule from the sub to the front seat at a single shot. It is possible for the molecule to eventually get there as it moves around with its buddies.

This probably helped no one. But in the slim chance that it would, there was my .02

[ramteid 17]

Like M5 stated a few pages back. Sound waves propagate just like water waves. And just like you are saying. When a tsunami hits Japan from an earthquake in the middle of the pacific does the water from the epicenter reach Japan? No, the energy is transferred from one molecule to another. However if close enough to the epicenter there is enough energy to displace the original. water to some degree

Just like a large system in a vehicle. You can hear and feel the sound 100 feet away but the air in the box is no reaching you. It move and arbitrary 5 feet due to the amount of kinetic energy at the epicenter and as energy is disappated over a larger and larger area it turns into a domino effect pushing the next molecule and so on.

 

i know that they propagate similar to water waves, i never said they didnt.

 

Ok, I'll have a go at this. Do I have a degree? No, so take this for what it is. Just my basic understanding of "motion" and reading as an outside party on this debate.

Ramteid says a subwoofer(AC) does not move air in the same fashion that a leaf blower(DC) moves air. Both do move air molecules, just not in quite the same fashion.

Put two one way check valves on a sealed subwoofer enclosure, one as an inlet, the other as an outlet. Does the subwoofer move air when it is playing?

When you overheat your subwoofer and the coil starts to stink, how does the smell get from the location of the subwoofer in the rear of your vehicle to the location of your nose in the front of the vehicle?

Put a large plastic bag on the end of a leaf blower. Run it for one second. Reverse polarity or whatever is needed to operate the motor in reverse. Run it for one second. What happened?

Movement is movement, but I'm not seeing that as the problem here. It seems that the argument is that AC motion and DC motion are different, while both are still a form of movement. While one + - cycle of a subwoofer cone won't send one particular air molecule from the sub to the front seat at a single shot. It is possible for the molecule to eventually get there as it moves around with its buddies.

This probably helped no one. But in the slim chance that it would, there was my .02

a leaf blower is a creation of wind while a subwoofer is just transfering energy through the air. smelling the voice coil has more to do with, well, smell and its ability to travel through air.

[///M5 2,833]

i know that they propagate similar to water waves, i never said they didnt.

Yes you did, said they don't move...and do again, right below here. Which is it?

 

a leaf blower is a creation of wind while a subwoofer is just transfering energy through the air. smelling the voice coil has more to do with, well, smell and its ability to travel through air.

How does this leaf blower create wind? And what is wind? To make a more clear analogy, does an air pump move air? I'd hope you say yes to this, now think about the diaphragm in an air pump. How is that different than a subwoofer? Do you claim there is a difference between water and air? If you move your hand in the water doesn't the water move? The same can be said for air. If you grab an Asian hand fan and move it through the air, the air moves doesn't it? How is this different than a subwoofer such that the sub doesn't move air?

I am also curious how you think the smell moves? Smell is air is it not? By definition then if it travels isn't the air also traveling?

[ramteid 17]

 

i know that they propagate similar to water waves, i never said they didnt.

Yes you did, said they don't move...and do again, right below here. Which is it?

 

a leaf blower is a creation of wind while a subwoofer is just transfering energy through the air. smelling the voice coil has more to do with, well, smell and its ability to travel through air.

How does this leaf blower create wind? And what is wind? To make a more clear analogy, does an air pump move air? I'd hope you say yes to this, now think about the diaphragm in an air pump. How is that different than a subwoofer? Do you claim there is a difference between water and air? If you move your hand in the water doesn't the water move? The same can be said for air. If you grab an Asian hand fan and move it through the air, the air moves doesn't it? How is this different than a subwoofer such that the sub doesn't move air?

I am also curious how you think the smell moves? Smell is air is it not? By definition then if it travels isn't the air also traveling?

 

and again, you continue to nitpick. does a leaf blower not pull in air and push it out on another end? that would be wind. the smell inside of the enclosure will reach the front of the vehicle without the sub ever being on, from my understanding, the air will move around and circulate any way, sound waves are not the reasoning. like i have stated over and over, i mean that sound waves to dont force the air to move, as in creation of wind, it vibrates the air back and forth, most people seem to catch on to that when i explain it to them. the only thing that the sub will do, when it comes to air moving around, is introduce heat into the environment, causing the air molecules to move faster.

[///M5 2,833]

The sub when operating in correctly should be having pistonic motion. Not unlike every other piston you can imagine that means it is part of an air pump.

Even if you neglect this portion of the equation and have a sound wave that magically appears out of nowhere it will also move air, or water, or steel or whatever. If you have kinetic energy you have motion or the inverse holds true as well, if something is moving you have kinetic energy. If a wave propagates it is moving....

It wasn't nitpicking, but clarifying. All wind can be modelled with a combination of DC & AC vectors. By default a leaf blower has a lot of AC. It is a vaned pump. Meaning its output is just like a speaker. In fact being vaned the DC component only comes from a superposition of AC input energy. Hmm, sounds just like a speaker doesn't it? Or an air pump, or an engine....list goes on.

[///M5 2,833]

the smell inside of the enclosure will reach the front of the vehicle without the sub ever being on, from my understanding, the air will move around and circulate any way, sound waves are not the reasoning.

Never once did I say that the speaker was the ONLY source of motion in a car, just refuting the argument where you state it imparts no motion.

I've built countless systems to measure acoustic fatigue. Yep, fatiguing and breaking METAL parts with only acoustics. Acoustic energy is kinetic and can create quite the motion.

Every thought why you hear tire noise in your car? Some is yes mechanically coupled, but that portion is much easier to damp than the acoustically transferred portion.

[hdrox88 142]

Air/Wind=air molecules moving

Air/Propagation=air molecules moving

Air/Vibration=air molecules moving

 

Is this debate about if a subwoofer or a leaf blower can move air? Or where they are moving the air to? If you don't believe a subwoofer makes an air molecule move in one way or another...

[///M5 2,833]

I wouldn't call it a debate. Someone is just not understanding Physics. I actually don't even comprehend the misconception. Claiming subwoofers don't move air is teh crazy.

[ramteid 17]

I never meant that a sub did not move air. I tried explaining exactly what i meant but you continue to nitpick. I said exactly what i meant, as i a subwoofer does not create wind, as in the air molecules near the sub to not get forced to the front of the vehicle by sound waves. I already stated that my ability to convey what i was meaning was lacking, but you continue to nitpick. There is a difference between wind and sound, are both types of movement? Yes. Are they exactly the same? No.

[jcarter1885 995]

I never meant that a sub did not move air. I tried explaining exactly what i meant but you continue to nitpick. I said exactly what i meant, as i a subwoofer does not create wind, as in the air molecules near the sub to not get forced to the front of the vehicle by sound waves. I already stated that my ability to convey what i was meaning was lacking, but you continue to nitpick. There is a difference between wind and sound, are both types of movement? Yes. Are they exactly the same? No.

 

If you cant clearly clarify or convey what you mean then maybe your own definition or understanding is not fully correct. 

[///M5 2,833]

Laplace made it very clear, even convinced Newton.

[ramteid 17]

I never meant that a sub did not move air. I tried explaining exactly what i meant but you continue to nitpick. I said exactly what i meant, as i a subwoofer does not create wind, as in the air molecules near the sub to not get forced to the front of the vehicle by sound waves. I already stated that my ability to convey what i was meaning was lacking, but you continue to nitpick. There is a difference between wind and sound, are both types of movement? Yes. Are they exactly the same? No.

If you cant clearly clarify or convey what you mean then maybe your own definition or understanding is not fully correct.

I believe that i made it clear what i meant. I just didnt put enough detail in it or give definitions to help convey it. There have been 2 individuals who have been able to understand what i am saying and another who continues to nitpick.

[ncc74656 2]

in my last post i laid out what i thought you were trying to say but now it makes more sense having read the rest of the responses.

however at this point i do not see that we have a debate anymore as everyone appears to be agreeing on the physical principles and the only issue now is how everyone is interpreting/conveying the same notions.