Infinite Baffle and the Audiophile

FrantzM

Member Sponsor & WBF Founding Member
Apr 20, 2010
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#1
Hi

Audiophiles have had an interesting relationship with bass reproduction. I will not go too long on this I can only say that lately they have become more understanding of the importance of bass in general (say from 200 to 1 Hz) in the reproduction of music. My personal observation is that the cleaner the bas the cleaner the rest of the spectrum. Better bass reproduction allows a better representation of the treble for example, a weird psycho-acoustics phenomenon.
I am not sure what drove this; I believe Home Theater has a lot to do with this, much more so that we, audiophiles, would care to admit. Maybe car audio too, since car fanatics have taken bass reproduction to an exalted level whatever we, audiophile, may want to think of these subwoofers on wheels … When they go by and shake the whole house, I am sure deep, very deep inside, some audiophiles wonder why their subs and speakers aren’t doing the same when some music clearly demand it, NO I am not talking about Hip-Hop. If Hovhaness Mount Helen Symphony on Delos doesn’t shake your house and your bowels, then you weren’t listening to the Mount Helen Symphony... The whole point of this particular symphony is to make you think about a volcanic eruption and with the right system it delivers!!
So reluctantly and no almost proudly audiophiles are using subwoofers and there is a plethora of subwoofers. Of course with the usual audiophiles’ claims, hyperboles, half-truths and myths: Among these:
… Big subwoofers are slow and will never match the “speed” of smaller subs
It impossible to integrate subwoofers with mains
Subwoofers “smear” ……….. Replace the dots with your favorite audiophile term …its Christmas day you are free to do it...

Thus the prices of subwoofers and their quality. All subs are not created equal; there are better subs than others... There is a type of subs that is almost rejected by the audiophile community. It happens to be the least expensive subs in most instances with respect to the performance: The Infinite Baffle (IB) subwoofer. I think only one member here has an IB. Amir in one post asks for the price of the subs… I will venture a number for JonFo who has this sub, not more than 5K and likely half of that … IB outperform very easily any commercial subs you care to mention for a fraction of their prices. I like to do a little arithmetic for IBs just to illustrate the point. Let’s take a superlative subs such as the JL Audio Gotham... About $13,000. For that price one can built an IB that would go in the single digit at 130 dB in a 20 X 30 X 15 (feet) room. You would also add a sophisticated digital EQ system that outperforms any you can find in ANY commercial sub and likely have about 10,000 watts of power on this sub for the price … As for the quality of IB bass it has to be heard to be really understood. It is so good that subsequently all subs sound …well .. Slow and fat in comparison. IBs are not difficult to make. Rather easy as matter of fact. One problem is real estate. IBs require an empty space. Other problems are sound leakage and structural vibration. Any good subs would create such problem, IBs take it to a different level. The sneer about IB from many audiophiles, is that they are not interested in “shaking the house”… This is not what IB do , they are however capable of such, more so than other inside the music room , commercial subs…
A few numbers: Take for example an IB with four 18 inch
Driver Cost $2000 for the 4. You would get equally good result with drivers for half the price…
Amp cost $3000 for about 4000 watts you can get more power for half the price. You don’t need an audiophile-grade amplifier for this purpose, any commercial capable of high power at low frequency is good enough for the purpose: QSC, Crown, even Behringer etc and before you jump, these are usually superior to any amplifier you are likely to find in the most celebrated or expensive subwoofers
$2000 Drop in any EQ you would like to hear although the lowly behringer DCX-2496 at $300 will do a job to match any audiophile subwoofer tuning apparatus you want to think of. It takes time to learn but results are worth it
$4000 for construction if you hire a contractor.
In other word if you have even modest DIY skills and a few hours to spare an IB sub is doable and a $5000 IB subs will surpass in performance and sound quality ANY commercial subs you can name , think of or spend your money on. Not opinion, people, fact, objective and subjective is there is such a thing as a subjective fact ? but allow me such in the spirit of the holidays
An IB sub with 4 15 AE subs such as those JonFo use will go flat (Eq'd ) to 5 Hz at 120 dB in a 30 X 20 X 15 room. Easy clean and with power to spare and if you think it will be “slow”, an IB audition is required in your audiophile journey. IME and that of many including Richard Vandersteen, the best bass you will ever hear …
Oh ! One more thing they are invisible.. They are usually not in the room … Invisible... So why aren’t they more popular?
Opinions are welcomed

Happy Holidays to you all …
 

audioguy

WBF Founding Member
Apr 21, 2010
2,732
12
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Near Atlanta, GA but not too near!
#2
I contemplated an IB sub in my current theater while it was under construction. The ONLY reason I did not pursue it was not knowing what the FR would be when it was installed given the locations I had to pick from.

While I recognize EQ could have made it better, if the uncorrected EQ is bad enough even EQ has it's limitations. I wasn't willing to risk it. Had I been smart enough to seek out some sophisticated (and accurate) modeling program, I might have gone for it.

In fact, I could still pursue it if such a modeling program existed. I could vent it into the next room even though it is a finished room.

Anyone know of such a program?

And Merry Christmas
 
#3
My ears were burning this morning, now I know why ;-)

Franz, thanks for bringing up this topic, as I believe many audio-centric forum members might be missing a great opportunity to enjoy ultimate bass reproduction if their listening room setup allows for an IB deployment.

First, I’ll support Franz’s assertion that IB bass is among the cleanest you’ll ever hear, regardless of price.
Examples of ultra-low distortion bass are rare, but IBs deliver that low distortion even at crazy high volumes.

I had an audiophile acquaintance (that also has electrostats) that just came over a week ago to audition my setup, here is the quote from him in an email after the visit:

Thank you so very much for the hospitality yesterday and allowing me to come hear your incredible sound system. I have NEVER experienced anything like I heard yesterday. Over the years I have heard some very good sounding systems, however NONE of them compare to yours. I am green!
During the session he commented that the bass integration with my electrostats was perfect and that he had never heard low bass sound so good. Now, a good bit of that is due to the well-treated room and a good room corrector at work, but without the inherent baseline quality of the IB sub, it’s difficult to achieve this level of results.
To underscore how wowed he was over quality of the bass, He’s adding an IB to his listening room as we speak.

So whether it is that SACD of classical organ music, or the high-resolution audio (5.1 24/96) from a Steve Wilson mastered disc (his Grace for Drowning is magical on this system), the bass just supports the music, never calling attention to itself.

Electrostats are notoriously finicky in terms of integration with dynamic woofers and subs, and I have to say I’ve worked at getting my system dialed in over the years, but as far as I’m concerned, only an IB really does them justice.

I had two Velodyne 18’s in the same room with the same electrostats, and while nice, it is no contest, the IB outperforms the Velos by a wide mark. Both on objective measurements and subjective results.
 
#4
As for cost of an IB, they are even cheaper than you mention Franz.

I believe in terms of purchased components, I have under $1,500 in my IB. Now, the labor to build the manifold and install it was me and a friend, but if I had to hire it out, I guess it would still be well under $1,000 for labor.

As for amps, I did start with a Crown pro amp, which worked well enough, but for grins one day I put in one of my Sunfires as the sub amp, and that gave it another layer of tightness and control I had not expected. So a good quality amp (but nothing crazy mind you) will deliver that last bit of quality.

An amp that I’d be interested in trying for this might be the class G (same as Sunfire) Dayton audio SA1000, which has plenty of power for a 4x15 IB array. It integrates crossovers and basic EQ, making deployment fairly simple into an existing 2ch system. With an LFE input, it should work well with pre/pros as well. At under $500, a real steal.
 
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#5
I contemplated an IB sub in my current theater while it was under construction. The ONLY reason I did not pursue it was not knowing what the FR would be when it was installed given the locations I had to pick from.

...

In fact, I could still pursue it if such a modeling program existed. I could vent it into the next room even though it is a finished room.

Anyone know of such a program?
A decade ago I use Cara-CAD and the RPG room acoustics modeling programs, which for their day, we're quite helpful. But tech has moved beyond that, and for a system of your quality, I'd suggest contacting Amir about doing a fluid-model analysis of your room. that will be helpful in understanding not only where any sub should go, but also what possible results you might expect if you combine the IB + another sub in the room to even out modes.

The brute-force method is to use your existing sub, locate it as ideally as possible with relation to where an IB manifold would go and then measure the response. Then rinse and repeat in alternate locations to confirm.

Before I cut the hole for my IB, I placed a sub at that spot and measured, then listened to it in that location for a month or two to ensure I'd be happy with the results.

Merry Christmas.
 

FrantzM

Member Sponsor & WBF Founding Member
Apr 20, 2010
6,469
0
0
#6
Hi

I unfortunately can't do IB right now. Living in appartment. Will move to a house soon and I will have an IB in it ... And I will also use sealed DIY or commercial subs to smooth out the bass ...
 
Apr 3, 2010
16,022
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Seattle, WA
#7
My personal observation is that the cleaner the bas the cleaner the rest of the spectrum. Better bass reproduction allows a better representation of the treble for example, a weird psycho-acoustics phenomenon.
Love the topic Frantz :). Hope to post some thoughts on this myself later. For now, this is actually not a weird psycho-acoustics at all. The math explains it well.

The room creates resonances. These show up as exaggerated peaks in the frequency response. We call see and understand this. What we don't realize is that the same resonance creates longer decay for notes in time domain. Every bass transient then creates a trail that did not exist in the original music. The bass trail masks other sounds in its way even at different frequencies. Imagine a 20 msec bass note now lasting 200 msec.

Fix the bass response by reducing the resonance and it magically also shortens the trail in time domain! And with it, all of a sudden you hear better clarity in upper frequency ranges which are no longer stomped on by the bass frequencies.

This is why when room EQ is applied, people are amazed at the improved imaging, clarity of mid-range, etc.
 
May 30, 2010
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#8
Can an IB be built in a room or space adjacent to the front wall? What would be the best position for the speakers?
 

FrantzM

Member Sponsor & WBF Founding Member
Apr 20, 2010
6,469
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#9
Can an IB be built in a room or space adjacent to the front wall? What would be the best position for the speakers?
Yes .. The position of the overture, since that all you really need after all, would be determined by the brute force method, that is moving around a "normal" sunb until you find the best position on the front wall. Their is no clear rule but the overture has to be large enough as to not create a port effect. so a rectangle with the smallest dimesnion that of the drivers is good enough. one can also use a line array , in other words lining -up the drivers along the front wall vertically once the position has been found. A little more visible but it works. Often in an IB on will hear about a manifold. it allows the mounting of multiple drivers in a relatively compact way,the drivers then vent to the room through an opening.

.

JonFo uses an inverse mounting where the drivers are in the room ... Very unusual and extremely elegant solution when the space availabe cannot accomodate the drivers.
I did build an IB for a friend and it was the easiest subwoofer I have ever entertained. We simply mounted the driver on a manifold ( 4 drivers) made an opening in the wall, mount the manifold and that was it .. It took us about 10 hours from start to finish. I did start to build my own but the project got ditched by a catastrophe. .. I know for sure that it is the way I will go when the constraints of living in condominium dwelling are removed...
There several places on the Internet where one can find information about IB subs.. This one is the best I know of and reading caerfully the FAQ or asking questions will have you going in a matter of days ...
Cult of the Infinitely baffled

IB (manifold IB in particular) allow multiple driver, thus the resulting displacement of individual drivers, hence their distortion is reduced. IBs distortion within their band can be as low as that of electronics, that is in the tenth of percent at very loud level. I would have estimated the one we build with four Fi drivers would be around .5 % at 25 Hz at 95 dB ... The sub was capable of more than 115 dB , we gave up testing because it was getting so loud at 20 hz as to cause physical discomfort and strange creaking noise in the concrete house ... This is in itself sounds like IBs are al brawl and no finesse, which is where they shine ... They are so clean as to appear to be lacking at first listen ... so used we are to the high level of IM and Harmonic distortion of most subs...
 
May 30, 2010
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#10
Yes .. The position of the overture, since that all you really need after all, would be determined by the brute force method, that is moving around a "normal" sunb until you find the best position on the front wall.(...) .
Frantz,

Thanks. But what is considered the best response when placing a IB sub? The flattest response integrated in a large area? Its there any thumb rule to help measuring the response or should I consider it as a normal sub?

BTW, thanks for the link - unhappily the links to the recommended speakers does not work anymore.
 
Jul 1, 2010
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#11
They are usually not in the room … Invisible... So why aren’t they more popular?
They require a good bit of thought, planning, and labor, and you don't get to buy "the right stuff." And let's face it; this is a consumer hobby.

I mean what's more fun? Going down to the high end store and buying a couple (or more) of Deep Supreme Luxinators (given 5 stars by Audio Intelligence Online), taking them home, plugging them in, then posting on WBF about the palpable expansion of your sound stage, or cutting a hole in your floor, building a reinforced plywood box in your crawl space and hooking it all up to a couple of dirt-cheap pro audio amps and an equalizer that your buds will look down their noses at? :)

Tim
 

mep

Member Sponsor & WBF Founding Member
Apr 21, 2010
9,483
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#12
They require a good bit of thought, planning, and labor, and you don't get to buy "the right stuff." And let's face it; this is a consumer hobby.

I mean what's more fun? Going down to the high end store and buying a couple (or more) of Deep Supreme Luxinators (given 5 stars by Audio Intelligence Online), taking them home, plugging them in, then posting on WBF about the palpable expansion of your sound stage, or cutting a hole in your floor, building a reinforced plywood box in your crawl space and hooking it all up to a couple of dirt-cheap pro audio amps and an equalizer that your buds will look down their noses at? :)

Tim
I don’t think that’s it at all Tim. Many people probably think they could never build something that will sound better than companies who make subs for a living. Plus, there is woodworking involved that some people have no skills at and it would be intimidating. Then throw in the fact that you have to have the type of room that you have access to build in an IB. It’s just much easier to buy a sub.

However, this article has got me thinking. I have the space on the left side wall where I could do this. The main thing that intimidates me is the requirement to have the outboard electronic crossover/bass management system that converts your analog to digital and back again and then setting up the bass management for all of the subs. It would be great to have someone come to your house that has been through it and help you get it set up. I am definitely interested though.

And yes, subs do increase the size of the soundstage. As I have said before, there is space in bass. My new sub should be arriving this Thursday. For the money I paid for it, I could have gone the IB route. I probably still will. Maybe two 15” subs in a manifold.
 
Jul 1, 2010
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#13
I don’t think that’s it at all Tim. Many people probably think they could never build something that will sound better than companies who make subs for a living. Plus, there is woodworking involved that some people have no skills at and it would be intimidating. Then throw in the fact that you have to have the type of room that you have access to build in an IB. It’s just much easier to buy a sub.

However, this article has got me thinking. I have the space on the left side wall where I could do this. The main thing that intimidates me is the requirement to have the outboard electronic crossover/bass management system that converts your analog to digital and back again and then setting up the bass management for all of the subs. It would be great to have someone come to your house that has been through it and help you get it set up. I am definitely interested though.

And yes, subs do increase the size of the soundstage. As I have said before, there is space in bass. My new sub should be arriving this Thursday. For the money I paid for it, I could have gone the IB route. I probably still will. Maybe two 15” subs in a manifold.
Of course, Mark, that was meant as a joke. I myself would rather buy a sub than do all that's required to put in an IB system it's quite intimidating.

And of course bass expands sound stage. Everything does.
 
Aug 25, 2010
954
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Destiny
#14
In fact, I could still pursue it if such a modeling program existed. I could vent it into the next room even though it is a finished room.

Anyone know of such a program?
Hello Audioguy

Yes it really quite simple all you need to do is take any box program and model the drivers in a large box. Basically what you want to do is have the drivers in a very large box about 10X the Vas of the driver. You can get freeware box programs that will tell you what the driver response will be without EQ.

You can determine the number of drivers you need and the EQ needed. What you have to watch is the X-Max on the drivers as they will simply run out of excursion depending on what your lowest target frequency is and you should have them high-pass filtered to protect them from over-excursion.

Here's a free-bee box program Win ISD or Win ISD Pro you can use either but with the Pro Version you can look at driver excursion.

http://www.linearteam.dk/default.aspx?pageid=winisd

Rob:)
 
May 30, 2010
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#15
They require a good bit of thought, planning, and labor, and you don't get to buy "the right stuff." And let's face it; this is a consumer hobby.

I mean what's more fun? Going down to the high end store and buying a couple (or more) of Deep Supreme Luxinators (given 5 stars by Audio Intelligence Online), taking them home, plugging them in, then posting on WBF about the palpable expansion of your sound stage, or cutting a hole in your floor, building a reinforced plywood box in your crawl space and hooking it all up to a couple of dirt-cheap pro audio amps and an equalizer that your buds will look down their noses at? :)

Tim
Tim,

I think you are overlooking the planing project and considering that just adding some bass extension is an easy job. Unhappy we want quality, not only quantity. And first of all we need to know exactly what we are "buying". A good plan must be "certified", and getting this quality stamp is not easy - a golden rule of audio DIY is that the builder should not be the judge or even part of the jury.

I appreciate debates in forums because everything in audio is a compromise, nothing is perfect, and people have different views on it. Until know I have heard only positive things about IB. I would also like to have the views of the opponents :) and what the defenders have to say about them.
 
Aug 25, 2010
954
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Destiny
#16
And first of all we need to know exactly what we are "buying". A good plan must be "certified", and getting this quality stamp is not easy - a golden rule of audio DIY is that the builder should not be the judge or even part of the jury.

That's rather silly and defeats the purpose. If you are serious about DIY you have plenty of tools at your disposal to verify your end result. That's what measurements are for, they confirm that you got the engineering part correct and they won't lie to you if you are doing them correctly.

When I DIY a pair of speakers I don't worry about getting my design certified. I build the cabinets, take measurements in the cabinets, design the crossovers and then measure the finished system. It works very well.

Rob:)
 

FrantzM

Member Sponsor & WBF Founding Member
Apr 20, 2010
6,469
0
0
#17
Hi

The biggest drawback of the IB is its immovability. Once it is there it is there. One must carefully chose where you will put that opening on your front wall or ceiling or floor. It is mistake to think of IB as quantity only. It si quality and of a nature that has to be heard to be believed.
It is not magic. This quality comes from the fact that IB affords multiple drivers. Bass, low bass in particular is about moving air. Lot of it. IB affords the audiophile to move quantity of air that is simply impossible in a commercial design. Example , you want to use 8 18 inch drivers? Deal, Done once you have the overture of your manifold, you can then have 8 drivers in that manifold with each driver working in its most linear region... and of course producing the lowest distortion possible, while being able to track the micro to macro dynamics of the music or other thing you want to listen to ... Meanwhile IB cost little, very little. You throw away the compromise of the box... The drivers are essentially operating in free air. You can eq for the flattest bass you can down to single digits and up to 100 Hz with ease, since you have so much headroom.. Let's take an example. An IB with 4 long excursion Drivers driven by 4000 watts or more (oh Yes you can and it doesn't have to be expensive) in a 30 X 20 X 15 room.. such an IB will be able to deliver 120 dB at 20 Hz without much EQ... You then EQ the darn thing down not up …with so much headroom you can afford to do that and still you are pushing the whole contraption to even lower THD level in the low bass ... The thing with IB is HEADROOM .. Lot of it, thus agility . You do have power too, lot of it, yet that i not what you need, that is what you have. Coupling that with additional commercial subs if you need to smooth out the bass in the room and you have the best bass your money can buy. The cost to make an IB with 8 superlative drivers such as the Fi IB318 ( less than $1000 for 4) and 4000 watts or of Pro amp would be low.. I venture $5000 including a contractor for the woodwork, wall cutting, driver mounting and wall finishing ... Expect single digits in the low bass at substantial output and you can have the flattest bass you will have experienced or you can have house curves and shape the bass the way you want it .. Tilt is for the low, flat, tilt up you can because you have the headroom to never run the drivers hard. Then you smooth out the response in the bass with one or two smaller subs ... Say a pair of JL AUdio Fathom F 113 and you add digital DSP and be fine .. very fine... Total? Less than $10,000 and I am pushing .. As for the measurements on IBs it is a sub, albeit a fixed sub. The method most people use is to get a small subs and find the best locationin the front wall, I know I am repeating, then yo mount the manifold or drivers there.. power the darn thing and measure as if it were a "normal" subwoofer. EQ is the same you would have done for a "normal" sub ...
Disadvantages? I don't see many
Planning? Within what audiophiles routinely do ... We lift our cables for God Sake ! And plan their routes!!!
And if you don't like the results? It is best to start with 2 drivers and a manifold ... Could be less than $1000 including amplifier ... If you really , but really don't like it .. You close the wall and are out of $1000 .. The vagaries of an audiophiles, we have spend much more and lost much more on gear we hated thereafter ... I doubt it though .. IBs are that good $ 1,000 will have you shaking your head in disbelief .. Often more than your head .. :)
 
May 30, 2010
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#18
That's rather silly and defeats the purpose. If you are serious about DIY you have plenty of tools at your disposal to verify your end result. That's what measurements are for, they confirm that you got the engineering part correct and they won't lie to you if you are doing them correctly.

When I DIY a pair of speakers I don't worry about getting my design certified. I build the cabinets, take measurements in the cabinets, design the crossovers and then measure the finished system. It works very well.

Rob:)
Rob,

I respect the DIY approach - I manufactured a lot of DIY speakers to finance my hifi addictions when I was a student, and a few of my friends currently follow the DIY approach and we frequently discuss technical aspects, mainly of tube amplifier DIY. If I had the time I would love to come back to DIY.

But assuming that the few measurements that a non-expert, such as myself, can carry using the modern PC based tools available - and I have and use a few of them :) - can confirm that such system is superior or comparable to the best subwoofers available in the market is not an easy assessment. IMHO, in this hobby getting what you call the "engineering" aspect is not enough, something else coming from long experience and knowledge is also needed.

I have to say I am seriously considering the IB. But the back wall of my listening room is a 1.5 feet thick stone wall - experimental drilling is out of question. I will only try it if I have confidence in the project.

Thanks for your advice.
 
May 30, 2010
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Portugal
#19
Hi

The biggest drawback of the IB is its immovability. Once it is there it is there. One must carefully chose where you will put that opening on your front wall or ceiling or floor (...) .
Just the big question for me. It seems there is no unanimous opinion on these matters.
To make it worst some people clearly state that positioning the opening is very critical and putting it in the wrong position will spoil it ... :(
 

FrantzM

Member Sponsor & WBF Founding Member
Apr 20, 2010
6,469
0
0
#20
Subwoofers are one area where measurements, ver easily correlate to what one hears .... If it is reasonably flat in the bass, then it sound like that... I can understand that one has to approachIB with some reserve when you are dealing with a 1.5 feet brick wall... The point is that you have to find the position where a normal, commercial wsubwoofer would sound the best along the front wall, once this is done, then you have to take the leap of faith ... As I said you don't go big, you simply use a pair of driver and power them with any available high power amp you have handy ... If you don't like what you hear from the 2 drivers then you close the wall , end of the story. My experience is that any person who's tried this doesn't come back .. The two drivers will outperform most any commercial subwoofer you can dream of ... as for sound quality the only competition for IBs c might be dipole subwoofers .. My extremely superficial dabbling with them was that they seem to tax the drivers too much, likely due to the fact that some frequencies have to be boosted to compensate for the cancellation dues to the out of phase back wave ... I quickly abandoned this idea when the size of the baffle started looking like a strange wall in the listening room ... IBs are completely invisible, taking no space in the listening room ...
I also would not put an IB in the back of the listening room for 2-channel listening. YMMV
 

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