why does this piece of paper move so much?

[Death By Bass 10+ year member]

Port air velocity is going to vary over frequency. At and below tuning, port velocity will be very high. This is completely normal.

its not port velocity... a 6.5inch woofer isn't going to create any sort of velocity, in a port, thats three times the size of the woofer... //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[Immacomputer 10+ year member]

its not port velocity... a 6.5inch woofer isn't going to create any sort of velocity, in a port, thats three times the size of the woofer... //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

The speaker isn't really the one moving the air. The speaker is playing frequencies that change the pressure in the enclosure. When the speaker plays certain frequencies, the enclosure begins to resonate. When the enclosure resonates, the air in the port moves quickly. The air in the port will be at it's highest velocity around resonance, or the tuning frequency of the enclosure.

 

[Death By Bass 10+ year member]

The speaker isn't really the one moving the air. The speaker is playing frequencies that change the pressure in the enclosure. When the speaker plays certain frequencies, the enclosure begins to resonate. When the enclosure resonates, the air in the port moves quickly. The air in the port will be at it's highest velocity around resonance, or the tuning frequency of the enclosure.

in theory, the enclosure is tuned to 40Hz... in practice, it has most output at around 30Hz...

it has to be acting as a transmission line... 1/4 of 30Hz is around 2.9 meters, which is the distance from the back of the woofer, to the bottom of the box, and back up to the port opening...

 

[Immacomputer 10+ year member]

Either way, the velocity is from the enclosuse system rather than the driver. Whether it's acting like a TL or a ported design, what you're seeing is normal.

 

[Death By Bass 10+ year member]

Either way, the velocity is from the enclosuse system rather than the driver. Whether it's acting like a TL or a ported design, what you're seeing is normal.

there is no velocity though...

you can barely feel the air moving in the port...

I've had enclosures move 4 times as much air, and still not move a piece of paper as much...

if this is how much velocity there is with 1 woofer, what will happen with eight woofers?

 

[Immacomputer 10+ year member]

Try it and let us know?

 

[Death By Bass 10+ year member]

Try it and let us know?

yeah, I will... //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[smd4life 5,000+ posts]

its because the paper is limp wristed

 

[fwb_1234 10+ year member]

Maybe you found the resonant frequency of the paper. At the install shop I went to, the guys had found a song that struck the resonant frequency of the corrugated aluminum sides and when they played it, it all shook. (Of course, it was stuck to the wall so it wasn't as dramatic.)

Or, it could have to do with the way the box is "tuned." You say its tuned to 40hz, so at levels below that (30-33), that port is just like a hole in a box. You aren't creating any sort of air-pressure resonance/resistance/interaction at such a level, so the air is just going out and then back in. I think the reason that it reacts so suddenly there and not below is b/c the speaker isn't playing efficiently at that level. I'm sure you've seen a response curve before for a subwoofer or such, and I bet that a response curve for that thing drops of STEEPLY after about that point. SPL is played in the upper ranges b/c that's where a speaker is most efficient. (Hence, for SPL, you would want to emphasize those higher freq. when you port the box.)

 

[BassAddictJ 5,000+ posts]

speaker creates sound....

sound is moving air....

....air moves light objects (such as paper)

even a 6.5 inch speaker in the right box and the right enviroment will make paper move....then again i can sneeze and make that paper move as much

 

[smd4life 5,000+ posts]

its because the paper is limp wristed

im gonna go with this...

 

[Death By Bass 10+ year member]

speaker creates sound....
sound is moving air....

....air moves light objects (such as paper)

even a 6.5 inch speaker in the right box and the right enviroment will make paper move....then again i can sneeze and make that paper move as much

its not air moving! unless ofcourse the box is somehow quadrupling the amount of air the speaker moves?

I posted a pic of the box already, but I'll post it again //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[PV Audio 5,000+ posts]

your tuning to 40hz for a home speaker tower?

He has already shown that he doesn't know what he's doing.

 

[PV Audio 5,000+ posts]

That is air moving out of the port bud, look at how it oscillates to the change in pressure as the cone moves in and out. What else could it possibly be? The paper is moving, and is only moving at that point. The open end of the paper flutters as the air pushes it away and pulls it back. I don't know what else you're looking for.

 

[kicker06 10+ year member]

if it sounds good, who cares?