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Take into consideration that however far the sub moves the air in the port must move the same amount when you consider the sub cone are in comparison to your port. So if your port is 50 sq in and your speaker is 50 sq in and your sub moves at say 50 MPH your port moves at 50 MPH. But if your port would be 25 sq in that air would have to move at 100MPH. (just examples) now what if you made your port 3.5 sq inches. You'd have 700mph air in the port. Would you have a sonic boom and a new DB record

I dunno i was just bored and wanted to post and see what you guys think.

Please Lud, dont respond till the end. I'd like to see what everyone else thinks before you dash my hopes

 
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The speed of sound depends on altitude, tho. The higher you go the lower the speed of sound is. A plane that can break the sound barrier at sea level is more impressive than a plane that can break the sound barrier at 20,000 ft.

And I think that's why the SR-71 can fly at mach 3.2 or whatever; because it's flying at like 80,000 ft.

So, take your sub to the top of a mountain when you test your theory and you'll have better luck

 
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notta clue

 
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I believe before the sub can squish the air out at 700 mph, the air within the box will compress. It'll be more like a sealed box with a leak, and there will be chuffing from the port.

 
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I have no friggin clue to be honest with you, but, I will give you math so you can figure it out on your own, but only on a theoretical level. (figuring in things like momentum are way too subjective)

velocity = distance/time

speed of sound at sea level = 340.29 m / s

full excursion of an adire tumult (to my knowledge highest xmax driver on market) is 34 mm each way,
so,
68 mm total = .068 meters = distance
1 hz = 1 cycle per second,
or,
136 mm's of total movement,
so,
136 mm's in one second,
or,
.136 meters in a second.

who wants to take over?

HINT:
what we're looking for is what frequency, at full excursion, will have 340.29 meters per second
AND
if the frequency is over 80 Hz (dbdrag frequency cap), what sort of linear excursion would be required at 79 hz so as to reach such a freq.

 
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Ummm, I'm guessing. But do I take

340.29 divide by .136 = 2502.1323 Hz? So this would be a very high frequency that the sub can't produce or maybe distort?

And if you were to run it at 79 Hz, you would need a sub with an xmax of around 2.154 meters. Okay!!! Woah... I'm not sure, so please correct me.

 
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haha...this is the greatest idea in the history of the world...i don't know how well our little cars would handle having a sonic boom emitted from the trunk, but i would definitely pay to see it...soo if you find that sub with the 3' of excursion or whatever you need, make sure you record all this...good luck!

 
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the SPEAKER wouldnt have to move at the speed of sound. Just get it to within a % then make the port that % of the speaker.

 
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Hmmm,
I got the 2502.13, but for the linear extension needed for 79hz, I get 1.077. How'd I screw that up?

 
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http://www.mtxaudio.com/caraudio/pro...oofers/RFL.cfm

DAMN. Thats some serious excursion

 
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1.077 each way, 2.154 meters peak to peak... 7 feet of cone motion is a silly amount.


josh, that motion still applies to the air. it would have to move 7 feet 79 times per second

 
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^^ Yeah, had a little too much on my mind at the time to realize how simple that was, I just always look at linear excursion one-way so I wasn't used to seeing it that way. Thats pretty funny how the notion of the sonic boom was just killed by science.

Scientific reasoning 1, sonic boom 0.

 
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it's an interesting concept but something makes me think it couldnt happen

is moving air capable of creating a sonic boom or does it havet o be an object moving thru the air?

 
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thats why i was saying the speaker didnt have to move that much. that since a port 1/4 the size of the speaker, the air in the port would have to move 4 times faster. 1/8 the port air would move 8 times faster. so if you took that into consideration you take the 7' excursion and then bring that down to something actually doable, say 3.5". thats a 24-1 ratio. so if you had a speaker with a 3.5" excursion with a port that was 1/24th the size of the speaker. BOOM!!!! lol

I hope you guys know this ISNT a serious topic. But i was just wondering what would be necessary.

 
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Would the port be hella small and probably sound like a leak in a sealed box?

 
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If it worked it would sound a bit louder than a leak

well if it were an 18 that would be 1/24 of pi x r^2 so....10.6 sq in port for an 18, right?. thats pretty small but not a sliver by any means.

 
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One time I glued my fingers together with crazy glue.

 
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So Random...haha.

 
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Why do you think it would so loud? A whip creates a sonic boom, but is not necessarily all that loud. Besides, I'm pretty sure the loudness of sonic booms are not measured the same way as continuous noises. They can't really be compared (especially in the context of a dB drag, as you suggested in your original post).

Besides, a sonic boom is caused by an object passing through the barrier created by its own sound waves. I don't believe you can get air to create a sonic boom. It's the air molecules themselves that create the barrier, I think, so to talk of air creating a sonic boom is to talk of air travelling faster than itself...

Of course, I'm no physicist. I could have this all wrong.

 
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That makes sense to me somewhat, since the air going through the port should make no noise, correct. So air moving faster than sound isn't really a big deal.

 
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this can happen. if anyone has used termlab to desing boxes or even bass box pro they have something on there called vent velocity...

the theory that it will sound like a sealed box with a hole in it is correct. the speaker will also underpeform. like when people hear they need 12 sq inches of port and make it 12 tall and one inch wide. i belive it has alot to do with the back pressure in the box...


we need to ask some outlaw iasca competitors..they put the mic right in the port for port wars....the faster you can move that air you could acctually fool the old mics because of presure on the diaphram. never really got in to that though..last ported box i built i could sit in the port

 
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^^^ and he's no skinny twerp (like me)

 
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alex is a big bitch

 
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haha, ludlam holds nothing back.

 
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I'm still wondering how Ludlam knows Alex. I mean, I KNEW he got around but geeshhh.

 
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Whoa, little early for a long night of drinking and no bed-warmer isn't it?

 
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i was drunk off robotussin when i posted that


its true im not a small man.

check out the double chin...6'2" about 225

 
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If your 6 ft 2, that weight is pretty decent then. Haha, nice drunk picture.

 
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haha..happy haloween!!

 
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I think your fly is down in that pic Alex