# 6th order bandpass



## mikeE72 (Nov 8, 2008)

hi all iv been mesin around online and on win isd and have found that you can hit astonishingly high numbers(150+ dbs) by using a sixth order bandpass. i also have heard that if not built right they sound like crap so i figure ill build one for one of the minni subs (ed 7kv2s) i picked up and try it out. jw who all has built one what i should expect andany tips or pointers.

thanks


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## kenk (Feb 27, 2008)

I believe the Klipsch Promedia 2.1 sub is 6th order bandpass. Hits pretty hard for a 6


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## Hispls (Mar 12, 2008)

I find bandpass in general pretty dependant on driver. Some drivers do well in a realistic size box, some just won't do in anything that you can work with.

Any box with a port is capable of huge SPL at the expense of linearity. If you narrow the band enough it'll peak very loud. 

I've personally made a few bandpasses just to play around, but my goals have been something musical. 

Be careful with your measurements (though I don't think they're as sensitive as some folks would have you believe). Don't skimp on port area if you plan to use much power, and really, I avoid bandpass unless there's a damn good reason... like an install where having all the sound port into the cabin is the best method.


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## cbrunhaver (Jun 28, 2006)

WinISD is probably not modeling the port losses correctly. This can lead to a huge different in the resulting output.

Also, higher order bandpass designs, like other highly resonant systems are a little tricky to make sure they match up with the simulation properly and so you need yo be able to at least to impedance measurements to make sure the tuning come out correctly.


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## mikeE72 (Nov 8, 2008)

k thanks i was hoping to be able to actually try this but those subs are pieces of sh#t and im not even going to bother with a driver that unreliable. i may try it with some infinity 8s though


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## TXwrxWagon (Sep 26, 2008)

can you define the "6th order bandpass"... that's alot misleading....

are you talking (2) woofers in ported enclosures firing into a common ported/trans-line style chamber?

In my experience bandpass enclosures are (by design) focused on giving a sweet spot or "node" to boost a lacking frequency in a system response.

I have never encountered a dedicated bandpass enclosure that was as overall fulfilling as a properly set up sealed or ported/bass-reflex enclosure, in the car environment.

Rob


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## Hispls (Mar 12, 2008)

TXwrxWagon said:


> can you define the "6th order bandpass"... that's alot misleading....


I believe this is the accepted definition:


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## quality_sound (Dec 25, 2005)

That's a dual reflex bandpass. You can make a 6th order IB or sealed enclosure if you want.


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## Hispls (Mar 12, 2008)

Was going by the info here:
The Subwoofer DIY Page - 6th Order Bandpass Systems

Any other/better links would probably help make sure everyone is on the same page here.


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## quality_sound (Dec 25, 2005)

When I get some time I'll see if I can find a lionk but basically, anything you add to a sub system increases it's "order." Take that same "6th order BP" and add a passive filter and it's a 7th order which is why you don't use "orders" to define an enclosure type.


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## Brian Steele (Jun 1, 2007)

mikeE72 said:


> k thanks i was hoping to be able to actually try this but those subs are pieces of sh#t


What's wrong with them?


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## Ryan from Ohio (Nov 4, 2006)

The Sundown E8's and the Tang Band Neo W8-1363SB work well.

Ive run the TB in a 6th with excellent results. The pass band modeled large.

I dont use win ISD to look at "spl" at all. I do use it however for port calculation and looking at the magnitude section.


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## Brian Steele (Jun 1, 2007)

quality_sound said:


> When I get some time I'll see if I can find a lionk but basically, anything you add to a sub system increases it's "order."


Most certainly.




quality_sound said:


> Take that same "6th order BP" and add a passive filter and it's a 7th order which is why you don't use "orders" to define an enclosure type.


Not quite. It's still a 6th order enclosure, but a 7th (or higher, depending on the filtering) order system 

The alignments described on my site refer to the order of the alignment without taking into consideration any additional electronic filtering.

Vance Dickason refers to them as "vented rear chamber bandpass enclosures", which is probably the most accurate description.


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## Brian Steele (Jun 1, 2007)

Ryan from Ohio said:


> The Sundown E8's and the Tang Band Neo W8-1363SB work well.
> 
> Ive run the TB in a 6th with excellent results. The pass band modeled large.
> 
> I dont use win ISD to look at "spl" at all. I do use it however for port calculation and looking at the magnitude section.


Did you use a series-tuned alignment?

I used a 6th order BP enclosure for my first car subwoofer. Sounded great.


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## quality_sound (Dec 25, 2005)

Brian Steele said:


> Most certainly.
> 
> 
> 
> ...


My point was that order isn't a good way to define the enclosure because while that may _start_ as a 6th, it will be a higher order as you add things like varying levels of passive filtering, maybe a passive radiator, etc. 

Also, I don't believe electronic filtering changes the order while passive filtering does. I really need to see if I can find that article. It's WAAAAAAY old and was in CSR, or AS&S back in the day. Could have been CA&E but I don't think it was.

To me, "vented rear chamber bandpass" is just a wordy way of saying "dual reflex" used to either justify their level of education or make others feel inferior.


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## Brian Steele (Jun 1, 2007)

quality_sound said:


> My point was that order isn't a good way to define the enclosure because while that may _start_ as a 6th, it could be a higher order.


There is no way to change the "order" of the enclosure unless you actually change the enclosure. It is the therefore best way IMO to define a type of enclosure.



quality_sound said:


> Also, I don't believe electronic filtering changes theorder while passive filtering does.


You are confusing "electronic filtering" with "active filtering". In any case, I disagree. For example, a 6th order vented system is usually created by the use of active filtering near the end of its passband - doing so with passive filtering will likely result in ridiculously-sized and expensive components.




quality_sound said:


> To me, "vented rear chamber bandpass" is just a wordy way of saying "dual reflex" used to either justify their level of education or make others feel inferior.


Interestingly enough, if I remember correctly, the term "reflex" arose out of an old and inaccurate understanding of how such systems work, so I'm not surprised that Vance Dickason chooses not to use that term...


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## quality_sound (Dec 25, 2005)

Brian Steele said:


> There is no way to change the "order" of the enclosure unless you actually change the enclosure. It is the therefore best way IMO to define a type of enclosure.


As I remember the article even adding another sub changes the order. Passive 6dB/oct. filtering added ione order, 12dB added 2, etc. Hence the reason the "order" system was confusing. The author even specifically used the "6th order bandpass" as his example since it's the most commmonly used named "order' enclosure.



> You are confusing "electronic filtering" with "active filtering". In any case, I disagree. For example, a 6th order vented system is usually created by the use of active filtering near the end of its passband - doing so with passive filtering will likely result in ridiculously-sized and expensive components.


I don't believe the size or cost of the passive filtering components was part of the discussion.



> Interestingly enough, if I remember correctly, the term "reflex" arose out of an old and inaccurate understanding of how such systems work, so I'm not surprised that Vance Dickason chooses not to use that term...


I was under the impression it came from each opening, or vent, in an enclosure.


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## Brian Steele (Jun 1, 2007)

quality_sound said:


> I don't believe the size or cost of the passive filtering components was part of the discussion.


Your premise was that active filtering did not contribute to the "order" of a system, that only passive filtering counted. I'm saying that not only is that incorrect, it's also impractical for many subwoofer alignments, including the common 6th order vented.




quality_sound said:


> I was under the impression it came from each opening, or vent, in an enclosure.


Hmm.. if that was the case, if I replaced my one 3" vent in my vented subwoofer with 2 2" vents, that would make it a dual reflex system . Clearly that's not the case.


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## Brian Steele (Jun 1, 2007)

quality_sound said:


> As I remember the article even adding another sub changes the order. Passive 6dB/oct. filtering added ione order, 12dB added 2, etc.


Doing all of that does not change the ENCLOSURE. 

It changes the order of the entire system.


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## Ryan from Ohio (Nov 4, 2006)

Brian Steele said:


> Did you use a series-tuned alignment?
> 
> I used a 6th order BP enclosure for my first car subwoofer. Sounded great.


Heres some pics of it:


























And my graph:









Rear chamber 1.75 tuned to 30 Hz
Front chamber .6 tuned to 60 Hz


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## TXwrxWagon (Sep 26, 2008)

bandpass = making up for a problem @ a specific frequency, whether its a short coming of the woofer chosen or the box/frequency focus...

If anyone has found, in the car environment, that a bandpass system is "SQ"... oh lord help your ears...

Rob


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## Ryan from Ohio (Nov 4, 2006)

Well dont puke then sir, as my 6th order provided the bass in my setup.

McIntosh MX4000/MDA 4000, PG 215ix, Rainbow Profi w/CAL25, Eclipse EA4000.

Anyone who heard my car had no complaints, thats for sure. It filled in nicely and provided ample but not overpowering output- got plenty low also.

I wanted to try something different and it was the ticket for sure.

I wish I could of snagged a Sundown e8 from Woofercooker but just wasnt able to. Looks to be a perfect dirver for an 6th order setup


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## quality_sound (Dec 25, 2005)

Brian Steele said:


> Doing all of that does not change the ENCLOSURE.
> 
> It changes the order of the entire system.



True enough, but do 99% of the people calling it a "6th order BP" know that? Apparently not and failing to correct them perpetuates the misinformation.


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## quality_sound (Dec 25, 2005)

Ryan from Ohio said:


> Heres some pics of it:
> 
> And my graph:
> 
> ...


NO offense, but you couldn't pay me to use that box. Those are some _massive_ peaks in the response and it drops like a rock under 30Hz. I don't know if the transfer function would even be able to make up for that.


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## Brian Steele (Jun 1, 2007)

quality_sound said:


> True enough, but do 99% of the people calling it a "6th order BP" know that?


Yes, actually 99% of the people do know that - prove me wrong


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## Brian Steele (Jun 1, 2007)

TXwrxWagon said:


> bandpass = making up for a problem @ a specific frequency, whether its a short coming of the woofer chosen or the box/frequency focus...
> 
> If anyone has found, in the car environment, that a bandpass system is "SQ"... oh lord help your ears...
> 
> Rob


Then you'd better not plan on using any subwoofer box in the trunk of a sedan as part of a SQ system - unless you remove that acoustic LP filter commonly referred to as a "rear seat"...


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## Ryan from Ohio (Nov 4, 2006)

quality_sound said:


> NO offense, but you couldn't pay me to use that box. Those are some _massive_ peaks in the response and it drops like a rock under 30Hz. I don't know if the transfer function would even be able to make up for that.


Well the F3 was around 27-28 Hz. The Fs of the sub was 30 Hz- so I dont see it as that _big_ of a deal...


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## Brian Steele (Jun 1, 2007)

Ryan from Ohio said:


> Heres some pics of it:
> 
> 
> 
> ...


Whoa, that's a really big box for one 8" 

I might have tried something slightly different, e.g, with that driver, and assuming the measured t/s parameters were nearly identical to the published ones, series-tuned 6th order bandpass, rear volume 0.4 cu.ft., 2" flared vent around 17" long (or a shelf vent with the same cross-section and length 16"), feeding into the front volume of 0.25 cu.ft. tuned with a 2" flared vent 7" long (or a shelf vent with the same cross-section and length 6"). Fr will be around 30 Hz, and Ff with be around 68 Hz. This should result in a passband that slopes upward from a knee at around 33 Hz to another knee around 70 Hz.The amount of the slope and the actual location of the knees will depend on the amount of box losses. That should produce some pretty interesting results in-car when you take cabin gain and the effect of the subwoofer's LP filter into consideration.


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## Hispls (Mar 12, 2008)

quality_sound said:


> NO offense, but you couldn't pay me to use that box. Those are some _massive_ peaks in the response and it drops like a rock under 30Hz. I don't know if the transfer function would even be able to make up for that.



Those "peaks" can be EQ'd out and really I'm not sure what singe 8" doesn't roll off to unuseable under 30hz anyway.

Box looks OK to me, but as I said much earlier the only reason I've used bandpass is in application where there's no good path for soundwaves to get from trunk to cabin and you can extend the ports up and through the rear deck.


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## Ryan from Ohio (Nov 4, 2006)

Hispls said:


> Those "peaks" can be EQ'd out and really I'm not sure what singe 8" doesn't roll off to unuseable under 30hz anyway.
> 
> Box looks OK to me, but as I said much earlier the only reason I've used bandpass is in application where there's no good path for soundwaves to get from trunk to cabin and you can extend the ports up and through the rear deck.


My point exactly. 8" subs are not known for low end extension...


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## SUX 2BU (Oct 27, 2008)

Bandpasses can be fun to play around with just for something a little beyond the usual ported/sealed/IB configurations. And you can splash them up with some plexi windows. All the same stuff that used to be done when they were new and cool around 1992  Not that they still aren't fun though. If you want more output from a smaller driver at the expense of a bigger box, bandpasses can do that. It's too bad the pre-fab world has really trashed the bandpass name due to crappy boxes you can buy at Walmart.

I'd break that box down into the even more simpler term of "ported bandpass". usually people like calling them by their 'order' to sound all techy-tweeky. Whichever.


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## Brian Steele (Jun 1, 2007)

SUX 2BU said:


> I'd break that box down into the even more simpler term of "ported bandpass".


All BP boxes are ported, unless of course you've elected to replace the ports with passive radiators . It's not a very good way to describe them IMO.

Also, a 6th order series-tuned BP will look exactly like a 4th order BP externally (because the vent for the second chamber exits into the first chamber, not externally). Would you still call that a "ported bandpass"? 




SUX 2BU said:


> usually people like calling them by their 'order' to sound all techy-tweeky.


I don't know about your "people", but I do it because it's the best way to describe the enclosure. YMMV


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## quality_sound (Dec 25, 2005)

Exactly why I stick with single-reflex, dual-reflex, and series tuned.


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## SUX 2BU (Oct 27, 2008)

Brian Steele said:


> All BP boxes are ported, unless of course you've elected to replace the ports with passive radiators . It's not a very good way to describe them IMO.
> 
> Also, a 6th order series-tuned BP will look exactly like a 4th order BP externally (because the vent for the second chamber exits into the first chamber, not externally). Would you still call that a "ported bandpass"?
> 
> ...


Some people think of how passive filtering is accomplished with orders, rather than how the enclosure is designed. Some guy who was a fancy 24 dB passive xover on his box (whatever it might be) could go around saying "I got a 4th order enclosure". You see the regular sealed box and say, "Huh?" He looks at his passive setup on the box and says "What?" Anyways, you got your terms and I got mine.


Yeah, I would call 'sealed bandpass' a BP that has a sealed rear chamber and ported (obviously) front chamber. You got me on the series-tuned though, with port from the rear entering the ported front chamber. The 'ported bandpass' description wouldn't differentiate between the two unless you call it a "series-tuned bandpass". Is not the series-tuned described as being an 8th order enclosure? I guess keeping the numbers straight vs. two-word descriptions is why I describe them how I do.


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## Brian Steele (Jun 1, 2007)

SUX 2BU said:


> Some people think of how passive filtering is accomplished with orders, rather than how the enclosure is designed. Some guy who was a fancy 24 dB passive xover on his box (whatever it might be) could go around saying "I got a 4th order enclosure". You see the regular sealed box and say, "Huh?" He looks at his passive setup on the box and says "What?" Anyways, you got your terms and I got mine.


First, I think you're mixing up "enclosure" and "system", and second, if he addes a 24dB passive x-over on his sealed box, then that's neither a 4th order enclosure or a 4th order system - it's a 6th order system.




SUX 2BU said:


> Yeah, I would call 'sealed bandpass' a BP that has a sealed rear chamber and ported (obviously) front chamber. You got me on the series-tuned though, with port from the rear entering the ported front chamber. The 'ported bandpass' description wouldn't differentiate between the two unless you call it a "series-tuned bandpass". Is not the series-tuned described as being an 8th order enclosure?


Nope. An 8th order bandpass enclosure usually has the output from the front and rear enclosures filtered through an additional enclosure and vent. The old Bose AM5 series used an 8th order bandpass enclosure.


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## SUX 2BU (Oct 27, 2008)

Okay, well you out-tweaked me. I can see where I made some errors. Congrats. 

Hmmmmm a question: so when a person says they have a 6th order 'system', how do you know it's not a 2nd order enclosure with a 4th order filter or a 4th order enclosure with a 2nd order filter on it? 

I guess where I'm going is using 'orders' can lead to confusion except for the rather-few who have it all down pat.

I found this link to be pretty clearly descriptive of orders for enclosures. A little moreso than the diysubwoofers.org link
Subwoofer Enclosures, Sixth and Eigth Order/Bass Reflex and Bandpass


I like this. Maximum tweak-impression points at the next SQ show:
"Isobaric quasi-8th order series-tuned dual-reflex bandpass enclosure"

Looks cool too. Would be a PITA to design I bet though.


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## Brian Steele (Jun 1, 2007)

SUX 2BU said:


> Hmmmmm a question: so when a person says they have a 6th order 'system', how do you know it's not a 2nd order enclosure with a 4th order filter or a 4th order enclosure with a 2nd order filter on it?


You don't - because they haven't provided enough information. That would be akin to determining Xmax or output capability from someone simply saying that they had a "12 woofer". More information is required. 

That said, when someone's typically referring to a subwoofer, particularly a car audio one, they are usually referring to an UNASSISTED alignment, so if someone told me that they had a 6th order bandpass system, my first GUESS would be that it's a 6th order box, not a 4th order box with 2nd order filtering.




SUX 2BU said:


> I found this link to be pretty clearly descriptive of orders for enclosures. A little moreso than the diysubwoofers.org link
> Subwoofer Enclosures, Sixth and Eigth Order/Bass Reflex and Bandpass


It might be interesting to find out why they think a series-tuned bandpass enclosure is just "quasi-sixth order"... 





SUX 2BU said:


> I like this. Maximum tweak-impression points at the next SQ show:
> "Isobaric quasi-8th order series-tuned dual-reflex bandpass enclosure"
> 
> Looks cool too. Would be a PITA to design I bet though.


Long name for something that will likely sound like crap .


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## SUX 2BU (Oct 27, 2008)

Brian Steele said:


> Long name for something that will likely sound like crap .



lol Probaby yeah. And all that effort that 2 of those subs in a regular vented enclosure would probably outpeform. Back in '92 though, that'd be the BOMB! :laugh:


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## mikeE72 (Nov 8, 2008)

hey thanks for all the input and i think im going to give it a go just this time with the tb 6.5s in an spl style setup. i came up with one on win isd and it peaked out right about at 162 dbs and change from 50w rms and though that doesnt account for losses even a 20db loss would stil be in the 140s which i think is pretty impresive for a 6.5. also if anyone has any experience with building one i would appreciate it if they could pass some of that wisdome on.

thanks


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## kh971 (Oct 20, 2008)

A good friend of mine used to build these boxes all the time, with RF subwoofers. He got really good at it. He took First place in Pro Class at IASCA with one 10'' in a plexi box. 
Man would it get loud!!!


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## Ryan from Ohio (Nov 4, 2006)

mikeE72 said:


> hey thanks for all the input and i think im going to give it a go just this time with the tb 6.5s in an spl style setup. i came up with one on win isd and it peaked out right about at 162 dbs and change from 50w rms and though that doesnt account for losses even a 20db loss would stil be in the 140s which i think is pretty impresive for a 6.5. also if anyone has any experience with building one i would appreciate it if they could pass some of that wisdome on.
> 
> thanks


Heres some advice. DOnt use winISD for SPL...lol

Its obvious youve just played with numbers and are looking only at SPL. Take a look at the magnitude chart. I bet its tuned high and you squeezed that passband tight.

Whatever its peaked at thats the only frequency you can play.

Im gonna place my bet on the sub exploding


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## mikeE72 (Nov 8, 2008)

yes your right it would be tuned high in fact at 75 and 170 hz and for normal bass duties this would be much to high but i think the fi q 18 handles the lower octaves quite well and i would be using this as more of a super loud upper bass. also i would have it high passed at about 60hz and the low passed at 250 wher the cut offs are on win. and why would the sub explod??:shrug:


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## Ryan from Ohio (Nov 4, 2006)

Give it a try and let us know 

With enclosures like this if you get to ambitious you can run into issues. Such as blowing your sub.

Ive heard of subs literally tearing themselves apart before...


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## mikeE72 (Nov 8, 2008)

o ok thanks ive never actually heard of that before but i gues its possible. what exactly do you think would cause this and what could i do to help prevent it?


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## Hispls (Mar 12, 2008)

mikeE72 said:


> o ok thanks ive never actually heard of that before but i gues its possible. what exactly do you think would cause this and what could i do to help prevent it?


The same thing that causes destroying a speaker running in ported, exceeding the mechanical limits. Typically happens running below the point where the port(s) unload...the difference is in IB, sealed, or ported alignment, you'd hear it and back off, in a bandpass you usually don't hear the speaker crying for mercy until it's way too late.


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