Infinite Baffle and/ or high xmax 12 incher: 50-200 Hz? - diyAudio
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Old 4th April 2003, 05:00 AM   #1
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Default Infinite Baffle and/ or high xmax 12 incher: 50-200 Hz?

Anyone know the maths/ formulas for Infinite Baffle resonances,
how IB performs in * upper bass* (50-200 Hz); or use
the Peerless XLS (or another high xmax 12 incher) up to 200 Hz?

– or Anyone have a theory or a hunch??

(Lambda would be good up higher, but too dear to ship here).

There are lot sof arguments about what alignment produces best bass . . . Sealed is tighter than vented, but less full, etc.

Linkwitz opts for the Peerless XLS 830500 in a sealed box in his sub design the Thor
http://www.linkwitzlab.com/thor-intro.htm
This driver has Fs of 18 Hz, but in a modest box size has an Fb 35 Hz.
It’s only intended to run up to 40 Hz, for home theatre.

Linkwitz states there:
“Above resonance the moving mass, Mms = 166 g, dominates the driver motion according to force = mass x acceleration”

So above 35 Hz in a sealed, the sound is a little slow.

I’m looking for a sub +bass to go from about 20 – about 200 Hz, in a stereo pair.

A transmission line that goes down to 20 Hz will be too bulky.

Linkwitz has an excellent compact dipole bass design, but it requires two Peerless XLS a side, and for the application in mind, I don’t want the xepnse.

Infinite Baffle (IB), with roof mounted drivers seems the best option – no vented boxes to upset the wife!

The “Cult of the Infinitely Baffled FAQ” has a basic FAQ:
http://t-3.cc/users/audioworx/page101-IB-FAQ.html

Anyone on this forum have experience with either IB and/or
a good high xmax 12 incher running up to 200 Hz?

TIA
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Old 4th April 2003, 06:18 AM   #2
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if u mean IB as in a large sealed box perhaps just use the normal sealed box equations with the size eg-3000litres


i get the idea that some ppl use their ENtire attic space???
if so those equations dont count.

the shiva is another similar driver.15mm excursion.,
titanic...xxx drivers at > http://respl.com/home.html

if u can put it in a large box up in the attic.perhaps just choose ur box size to what u want the resposne to be

the only difference is u get a much larger sized box if u want :-D
and then the driver is more thermally protected.

eg fit in that sealed box of 6cu ft u cud never fit in ur lounge.

forgive me if im wrong i dont know about IBs
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Old 4th April 2003, 06:36 AM   #3
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Wink large box in the attic: but with a Peerless XLS?

Yes mikee, the idea was to use the entire attic space, often that's what IBers do.

It wouldn't be too hard to measure & calculate the entire space.

I wonder if I plug that volume into the box size of say Unibox, how valid the answers would be, with an unusually large volume?

Building a large box up in the attic could be the way to go.
Finish becomes a non-issue J

I think the Shiva is excellent as a sub, but more of a sub-bass driver than a bass.
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Old 4th April 2003, 06:42 AM   #4
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oh yes i just realised,, u said 50hz + not 20hz lol

www.eminence.com (high resonance high efficiency ones)

18sound





personaly i would prefer to build a large box in there-eg www.diysubwoofers.com > EBS

i dont know any other drives designed for sealed boxes i prefer ported.

have protection
rather than have an truelly almost infinite baffle! 25watts rms ? lol>perhaps that would be rather loud anyway.

with a eminence 100db speaker in a large box it would be fine altthough those are generaly ported.
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Old 4th April 2003, 06:47 AM   #5
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Quote:
Linkwitz states there:
“Above resonance the moving mass, Mms = 166 g, dominates the driver motion according to force = mass x acceleration”

So above 35 Hz in a sealed, the sound is a little slow.

The same applies for every direct radiating speaker. But this does not mean that a speaker is "sounding slow" above resonance !
It means that diver excursion is decreasing with increasing frequency which in turn leads to a flat frequency response with the help of the increasing radiation resistance of the driver's diaphragm.

Regards

Charles
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Old 4th April 2003, 10:27 AM   #6
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Default ‘sub-oriented’ driver up to 200 Hz?

Encouraging
So do you, or have you heard anyone run a good high xmax ‘sub-oriented’ driver up to 200 Hz, with good results?
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Old 5th April 2003, 02:46 PM   #7
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200hz is fine
perhaps some alignments mite go up in Db at that zone...

i crossover at 70hz so that i dont boom my voices loudly :P otherwise i would crossover higher. :-D

(this probably shows that i have a speaker that rolls off at a high frequency so the higher stuff is abit too loud and i try making it louder making the higher stuff louder anyway hahahaha)

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Old 5th April 2003, 03:33 PM   #8
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rick57, an IB is simply a very-very large sealed box, so you can use your favorite sealed box software to calculate the theoretical bass response. As with any box type, you'd need to consider the subwoofer(s) + room acoustics + placement to really get an idea of the response. But why such a high cutoff frequency of 200Hz? Apart from higher modulation distortion, the drivers would easily be localized at such a high operating frequency.

In this case (and in most cases IMO), the Shiva is a better driver compared to the XLS since it is more efficient.

Cheers

Isaac
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Old 6th April 2003, 11:20 PM   #9
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when i do IBs in winisd the response isnt that amazing
what is the typical response of a large IB?

i have seen some good jbls,they needed 300litres but wud go to 20hz with 95db efficiency :-D
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Old 7th April 2003, 04:45 AM   #10
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> Shiva is a better driver than the XLS since it is more efficient.

f4ier, well yes a little more efficient, but IIRC Linkwitz in testing for new drivers for the Phoenix, found that the XLS had less distortion

> why a high cutoff frequency of 200Hz? the drivers would easily be localized at such a high operating frequency.

Yes I would need to locate the bass as close as possible to the rest - if IB, considering mounting mid & treble up near the ceiling.

> Apart from higher modulation distortion

Are you referring to the doppler affect?
20 - 200 is 3.25 octaves.
Many mids might do say 180 - 3000, which is more than 4 octaves. Two ways will of course do more.
There is a trade -off, e.g. if you only run the bass the say 120 Hz, the mids must cover more.
(First breakup mode on the XLS is at 470 Hz).

Does anyone think that IMD is more of a problem with a bass driver?
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