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Discussion Starter · #1 ·
I've done a little reading on the Infinite baffle design. From what I can see I don't get it. I've seem eight drivers systems and smaller four driver systems. Is there a throat design or a volume of the box thing..? I guess I have to start to think outside of the box. It seems almost like a bandpass,where the air rush acts like a driver which would let me understand the need for multiple drives.
 

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The "throat" you see is nothing less than what people do to minimize the area of the wall they must cut out. It takes a lot less speace and is more stuctally sound to mount the drivers in a baffle than into the drywall itself and it takes less wall space. Could you imagine the wall space need for 8 or 12 15" drivers on a wall.
 

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Well, what exactly do you want to know. The answer about the "throat" of some installs has been answered. We can't answer any questions if we dont know what we are answering to.
 

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I've had an IB setup for about 3 weeks now. I'm running 4 Adire Audio Tempest drivers and 1400 watts. It is absolutely incredible.


One of the reasons for the multiple drivers is that most drivers are more linear in the first x percent of cone movement. Each driver you add results in all drivers having to move less for the same overall SPL. This also results in more accurate sound at that SPL level.


When building an IB, a primary goal should be to make sure that any "throat" or manifold has no effect at all on the sound. I believe the FAQ over on the Cult forum talks about proper sizing if a manifold is used. It's pretty simple.


If you're trying to figure out what the "trick" is with IB subs, you're probably making it too complicated. The beauty is in the simplicity. In my opinion, it's about as much the opposite of a bandpass design as you can get. Many, if not most, bandpass designs sacrifice sound quality and a wide bandwidth for higher SPL over a narrow range of frequencies and maybe a smaller enclosure.


IB subs sacrifice some SPL for sound quality and a frequency range that extends well into subsonic levels. Which is another reason for multiple drivers. You get the SPL levels you need and keep the sound quality and frequency range.


-Chris


Oh, I meant to post that I've measured over 110 DB on my Radio Shack SPL meter, uncorrected, at 18Hz. That's about 119 DB corrected. There wasn't a hint of distress at that level and I could have turned it up more though I'm not sure how much. Just wasn't sure my house could take it.
 

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The problem with cone speakers - and especially woofers - is what to do with the rear wave. A cone vibrates in two directions, putting out both a front and a rear compression wave. The two waves are out of phase with each other, and at long wavelengths (low frequencies) tend to cancel each other out.


One way to prevent that is to fire the rear wave into a sealed box, not letting any of it out. A decent solution, but one with complications.


A couple other ways are to flip the phase around so that the rear wave reinforces the front wave instead of cancelling it. Rear-loaded horn, passive radiator, and ports all do this to varying degrees.


'Infinite baffle' designs simply throw the rear wave away. Kind of like a sealed box with an infinite volume. There's a major benefit to that. Every reinforcement scheme has some sort of interference between the two waves. And sealed boxes interfere with cone movement. So while IB designs don't get the benefit of reinforcing the front wave (and are not so efficient), they "speak" very cleanly.


The term "infinite baffle" comes from how the rear wave is thrown away. The design acts like the board in which the woofer is mounted is infinitely large so that the wave can never get around it.


Throats don't enter into the "how it works". The shape of the baffle is not important to the concept.
 

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Very well explained!! I'm torn between attempting one of those installs in my new house(dedicated HT), or a dual 15-18" monster sonosub..


brickie
 

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It's my intention to minimize construction (although it may not work out as simple as I want), so an IB is not in the cards. I'm making do with a a couple ported 12".


A new house would be a luxury for HT! Good luck with yours!.
 

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You wanna break new ground? Try a servo-driven IB with a large, relatively massive (stiff) piston. I'll bet the earth moves!
 

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Discussion Starter · #11 ·
Sorry I wasn't clear on the question but regardless you guys came up with great answers. I'll have to give this some thought.I just had a cabinet maker build me some monsters and now this throws a whole new spin on things.Thanx for the input.
 

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An IB is basically a sealed sub with Vb at least 4 x Vas. Without a box acting as a high-pass filter, low-bass efficiency and extension can be quite high.
 

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In other words, install the subs in a solidly-built wall with a space behind it that you don't mind having filled with ("out-of-phase") bass.
 

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Great answer to the question.


I went IB after going as big as I could get with multiple Velodynes and found the IB able to easily surpass other designs.


I did a write-up of my IB install using 4 AV15 drivers (w/pics)


You can even do IB's that look like regular (well, ones with 4 drivers on them :cool: ) sub boxes by putting the manifold box in the room and the throat exits to the 'infinite' baffle.


This is my IB (pic taken with my acoustically transparent screen removed):

http://www.mindspring.com/~jonfoulke...s/image017.jpg
 

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Quote:
Originally posted by Larry Fine
In other words, install the subs in a solidly-built wall with a space behind it that you don't mind having filled with ("out-of-phase") bass.
Out of phase with what? The sound on the other side of the wall? Why does that matter? Depending on how you mount the subs, your wall may need to be solidly built or it may not. If you use a manifold like the one pictured above, the movement of the drivers mostly cancels out and the wall need not be very sturdy at all.


-Chris
 
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