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Infinite baffle modeling?


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fugit 
Copper - Posts: 169
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Joined: May 19, 2004
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Posted: December 16, 2005 at 9:56 AM / IP Logged  

Is it possible to use unibox to model a speaker in an IB situation?  I saw on another forum that you can multiply the vas by ten and use the max amount of ft3 airspace in the closed box.  I'm not sure if that sounds right so I though I'd ask.

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haemphyst 
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Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: December 16, 2005 at 3:14 PM / IP Logged  
You cannot "model" an infinite baffle. An IB is exactly what it says - infinite.
If you put it in an enclosure - ANY kind of enclosure, you will NEVER get IB response. No matter how big the box. Your speaker will always be in a box that is simply too big, but NEVER in a true IB, unless you put it in an IB.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
stevdart 
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Posted: December 16, 2005 at 4:55 PM / IP Logged  
I'm trying to remember where I saw this, but something tells me that 56 cu ft is used if you want to see how the driver should respond in IB.  At least that figure was used by the author of the article I read.  But if you're mounting this in your vehicle, you should just measure the approximate cubic feet that will make up the enclosure.
Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
fugit 
Copper - Posts: 169
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Joined: May 19, 2004
Location: United States
Posted: December 16, 2005 at 5:46 PM / IP Logged  

So, then what your saying haemphyst is that if you put some 6x9's in the rear deck of your car and they have no enclosure that the trunk itself is then the enclosure?  What about leaks due to it not being "airtight" do they make that much difference?  Just wondering.  I'd like to have the enclosure type that would be best suited for my speakers but I don't have time or money to try all three.  I used like 20 ft3 for a closed box in unibox and it made the curve look better than in the various others I've tried.  Guess I'll try 56 and the doors space and see what I see.  Thanks for the info fellas.  Nice sig haemphyst.  My buddy and I were having a discussion about just that subject the other day.

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Velocity Motors 
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Joined: March 08, 2002
Location: Manitoba, Canada
Posted: December 16, 2005 at 6:33 PM / IP Logged  
IB = Free Air.
Their designed to operate in an enviroment that is not air tight.
Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: December 17, 2005 at 11:42 AM / IP Logged  
Modeling IB systems is easy.  Use 10X the Vas of the woofer (as this is also the minimum air volume required for the installation.)  IB in a vehicle is rather difficult, by the way: unless you have a really large trunk you may not have 10X Vas available.  Plus, it's not really "free air" as in order to work correctly, the IB front wave and rear wave must be completely separated and sealed off from one another.  This means you can have no air leaks between the front and back of the woofer.  The best way to accomplish an IB installation in a car would be to mount and seal the speakers into the roof of the car with the magnets facing out into the air.  Not very practical.  Infinite baffle modeling? -- posted image.  IB is a true basshead's solution, by the way. as it is perhaps the most efficient way to use a woofer.  The downside is the speaker will quickly reach its mechanical limits and you have to under-power by about 1/3 the RMS value to protect the driver, and IB mounted speakers are far more prone to distortion than any other alignment, which is why often multiple drivers are used (additional db before distortion sets in.)  IB usually requires some fairly sophisticated EQ capability to make them sound right.  Lots of home theatre IB lovers use the Behringer "Feedback Destroyer Pro" as a multi-band low-frequency parametric EQ for their IB systems.  Again, not practical in a car.
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fugit 
Copper - Posts: 169
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Joined: May 19, 2004
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Posted: December 17, 2005 at 12:43 PM / IP Logged  
Once again, thanks for making me smarterInfinite baffle modeling? -- posted image..  I love this place.
"I'm Rick James bi***, enjoy yo' self Ah Ah Ah"
Dave Chappelle as Rick James
fugit 
Copper - Posts: 169
Copper spacespace
Joined: May 19, 2004
Location: United States
Posted: December 17, 2005 at 12:46 PM / IP Logged  
I don't know why it posted on me, I didn't mean to make two.  Anyway, I thought of a fairly simple solution to just try them out.  I'm going to make some small boxes of mdf that would equal the airspace I'd have in the doors or pods I could make.  then just listen to them.  Duh.
"I'm Rick James bi***, enjoy yo' self Ah Ah Ah"
Dave Chappelle as Rick James

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