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Discussion Starter #1 (Edited)
So this might be a strange question, but if you read the whole thing it makes sense.

I am a high school science teacher, and I am doing a demonstration regarding the hearing range of humans(generally regarded as around 20hz-20khz). I use a tone generator on the computer hooked up to speakers to demonstrate the high end, and for the low end, I hook up the computer to a home amp powering my IDmax 12v.3 in a sealed box.

The idea is they can obviously hear 50hz, 40hz, 30hz, etc, but when I start playing a 12 or 17hz tone, they can see the cone moving, and feel the vibrations, but they cannot hear it because our ears cannot pick up the sound. I explain to them briefly about subwoofer efficiencies in that it is going to be louder at 50z than 20hz just because of the sub design and box parameters, so I am not implying at all that 15hz should be as "loud" as 55hz.

1. Am I way off with this? I don't think I am, but I am open to suggestions. As I understand it, if there are vibrations, there is sound. We just can't hear this sound.

2. Can an Idmax in around 1.25-1.5 cubes sealed reproduce 15hz? I believe it can to a certain degree.

3. Anyone have any good (legal) programs for test tones? The ones I have used in the past are shareware and expire.

Any suggestions are great.
Thanks!
 

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sure it will reproduce it. but as you mentioned, it will not produce it as loudly as higher freq. it takes 4X the cone movement for every octave you lower, so 15 hz is gonna move alot compared to 30 hz for the same power.
 

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I wonder if any students will get into car audio due to this lecture. I wish my science teacher would've done this. Cool stuff.
 

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Discussion Starter #4
minibari-that is what I was thinking. I do try to explain that to them briefly without getting too technical.

adrenalinejunkie-thanks, some might! The funny and disappointing part of it is when the students who "think" they know a lot want to argue with me. They don't know Image Dynamics or that the IDmax is pretty much one of the best subs out there, so they want to say that kicker, or Fosgate, etc is better. Those arguments exhaust me.


Any other ideas or suggestions? Any thoughts on a tone generator program?
 

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Measure the output and prerecord the tones at varying outputs to account for the differing sub output levels.

BTW you will get mechanical noises that some will swear is the fundamental tone if you go to high drive levels.
 

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Discussion Starter #6
sssnake, yes, at 12hz, you can hear the cone moving and maybe hear air, but no bass. I will have to explain that the mechanical noise is not a tone at that frequency.
 

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Add about 7 more IDMaxes and show them how the room will vibrate even though you can't hear the bass. I can hear a little below 18hz in the car with huge cabin gain and a pair of 15 but below that you can sense energy and things will move around both inside and outside of the car but you can't hear it.

My car has a factory spoiler and once when I was playing either a 10 or 15hz tone I wasn't sure the subs were working but looking at the spoiler told me otherwise.
 

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minibari-that is what I was thinking. I do try to explain that to them briefly without getting too technical.

adrenalinejunkie-thanks, some might! The funny and disappointing part of it is when the students who "think" they know a lot want to argue with me. They don't know Image Dynamics or that the IDmax is pretty much one of the best subs out there, so they want to say that kicker, or Fosgate, etc is better. Those arguments exhaust me.


Any other ideas or suggestions? Any thoughts on a tone generator program?
trueRTA has a free version that has a nice tone generator in it.
 

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Discussion Starter #12
Eric Stevens replied to my private message and said similar things, in that it will produce sound but not at a high volume. Hopefully it is still viable as a demonstration.
 

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if you want to show the effects of the sub-sonic sound. take some pots and pans or stack of plates (anything that will vibrate and make noise) and place them 5' from the sub......even though you wont hear the sub, you will see and hear the pans rattling.
 

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Discussion Starter #16
Today is the lab, and it appears that it should work well. Kids can hear it three classrooms down, and apparently the assistant principal went outside to tell some kid to turn down the bass!

I assume this would be less viable with a ported box because of drop off after the port frequency, but what if it was more of a home theater box that was ported around 20-25hz? I guess if it is heard that far away, I don't want it too much louder, but hopefully the kids enjoy the lab and learn. And hopefully it expands their ideas of good subs past kicker, rockford, and alpine.
 

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Today is the lab, and it appears that it should work well. Kids can hear it three classrooms down, and apparently the assistant principal went outside to tell some kid to turn down the bass!

I assume this would be less viable with a ported box because of drop off after the port frequency, but what if it was more of a home theater box that was ported around 20-25hz? I guess if it is heard that far away, I don't want it too much louder, but hopefully the kids enjoy the lab and learn. And hopefully it expands their ideas of good subs past kicker, rockford, and alpine.
depends on what freq the port is tuned to. with an FS of 25hz, you can tune those REALLY low.
 

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Not to get get too much off topic, but Is this the software that will show what frequencies a song will play? I thought I heard something about this a while back.
Yes. Highlight a section of the song, go to analyze > plot spectrum, increase resolution to the highest, and set it to log instead of linear.

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That's funny that the kids insist on the "Best Buy" brands being the best. I've gotten into the same arguments with people. People think because they bought a couple 10s in a prefab from Best Buy that they're the car audio expert because their system "knocks" and rattles their trunks. It's unfortunate, if they were receptive to learning, they could really enjoy the hobby, most I've encountered though refuse to accept that anything can be louder than a Kicker square sub. I try to educate them, but they claim that I'm just jealous of their system because I only have one sub and they have 2.
 

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Yes. Highlight a section of the song, go to analyze > plot spectrum, increase resolution to the highest, and set it to log instead of linear.

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eThat's funny that the kids insist on the "Best Buy" brands being the best. I've gotten into the same arguments with people. People think because they bought a couple 10s in a prefab from Best Buy that they're the car audio expert because their system "knocks" and rattles their trunks. It's unfortunate, if they were receptive to learning, they could really enjoy the hobby, most I've encountered though refuse to accept that anything can be louder than a Kicker square sub. I try to educate them, but they claim that I'm just jealous of their system because I only have one sub and they have 2.

I had already found the info on some other thread, thanks though. :)
 
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