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lukeamdman

(8) Ported Incriminator Audio Judge 21" build

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I've been modeling ported enclosures for my IA 21s for a few months and have also received a lot of feedback from Ricci and LTD02. 

 

25hz+, I'm completely satisfied with the system.  On the low end of the SPL spectrum, I'm around 130db at 10hz and 136db at 17hz. After 6+ months of testing various levels of boost <10hz, in my room it just doesn't add anything. 10hz is definitely noticeable/enjoyable, so I don't want to lose any SPL there.

 

The current plan is 8 of these:

 

W58v2bF.png

 

 

Outside dimensions with double baffle:

 

22.5" wide

28.5" tall

51.25" deep

 

(3) 6.5" x 3.5" ports.  Port length is 68".

 

Net internal volume: 11.8cu.ft

 

Tune should end up between 13-14hz.  

 

With a ~13hz tune, I'll actually add 3-4db at 10hz and a bunch up to ~20hz, not to mention lowering distortion across the board and also lowering the system resonance with almost double the internal cabinet volume per driver.

 

This looks awesome! Some quick comments: These ultra low ports really suffer from compression quickly. How big is the port? Are you sure you don't want to break up that 90 with 2 45's? or do a sweeping bend with back-cut MDF? Why not make the box even bigger and get rid of the bend altogether?

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This looks awesome! Some quick comments: These ultra low ports really suffer from compression quickly. How big is the port? Are you sure you don't want to break up that 90 with 2 45's? or do a sweeping bend with back-cut MDF? Why not make the box even bigger and get rid of the bend altogether?

 

(3) 6.5" x 3.5" ports.  Port length is 68".

 

The larger I make the boxes the further I have to move the mains/center/tv towards the front row.  The current size is a compromise but really don't want to consume any more space in the room.

 

Keep in mind there will be EIGHT of these ported cabs + 2 Othorns and my mains are pretty substantial as well (30" deep, 25" wide, 75" tall).

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Okay, I normally try to shoot for about 80" of port area for an 18" high output drier and even that I can compress, I realize that is a very large port by almost any standard...

 

Have you researched 21" PR's by chance, it might allow you to make the box a little smaller which sounds like mighty be a priority for yo?

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(3) 6.5" x 3.5" ports.  Port length is 68".

 

The larger I make the boxes the further I have to move the mains/center/tv towards the front row.  The current size is a compromise but really don't want to consume any more space in the room.

 

Keep in mind there will be EIGHT of these ported cabs + 2 Othorns and my mains are pretty substantial as well (30" deep, 25" wide, 75" tall).

 

Going to be quite a feat fitting EIGHT LLT's in a room like yours, Luke. Good luck!

 

A little piece of advice (you don't have to take)...don't compromise the design just to fit as many in there. If things look bad, consider half as many as an option.

 

My room is narrower but taller and probably as long. I could fit four proper LLT's up front and two for sure in the back but could make four (in back) work but then mounting rear surrounds would be a challenge as then I have effectively reduced the length of the room by 4ft or more.

 

 

 

Okay, I normally try to shoot for about 80" of port area for an 18" high output drier and even that I can compress, I realize that is a very large port by almost any standard...

 

Have you researched 21" PR's by chance, it might allow you to make the box a little smaller which sounds like mighty be a priority for yo?

 

I remember Exodus briefly teased (and I think released) some 21" PR's.

 

Who else makes 21" PR's?

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Why not make the box even bigger and get rid of the bend altogether?

 

 

A little piece of advice (you don't have to take)...don't compromise the design just to fit as many in there. If things look bad, consider half as many as an option.

 

Trying to get a 13hz tune with a ~48" long port is challenging.

 

If I add 3cu.ft to the box AND reduce the ports from 3.5" tall to 2.75" I can make the port work without a bend, but it seems like that would be a wash since I'd just be adding additional port compression in one area to reduce it in another?

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11cuf is SUPER small for a 21" driver LLT system.

Just sayin'.

 

I'd make each enclosure at least 20-30cuft, each. That's real LLT land.

 

 

Did you ever get a copy of the T/S for these drivers? That would.... help a lot. You can "wing it" with not reliable T/S in a sealed system but you better know what's up when doing a resonant system.

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11cuf is SUPER small for a 21" driver LLT system.

 

Just sayin'.

 

I'd make each enclosure at least 20-30cuft, each. That's real LLT land.

 

 

Did you ever get a copy of the T/S for these drivers? That would.... help a lot. You can "wing it" with not reliable T/S in a sealed system but you better know what's up when doing a resonant system.

 

I have most of the specs, and it was enough for Josh/LTD to match the sims to a close mic.  Definitely enough to use the models has a trustworthy guideline.

 

Yeah 11.8cu.ft isn't huge, but that is the net internal after driver/bracing/port.  16cu.ft before all that.  I am going to bump the size a little to 17cu.ft with 13cu.ft net internal but keep the tune the same 13hz. 

 

They way I've played it out in my mind I have two options:

 

1.  Gain 3-4db best case by doubling the size of the boxes to ~25cu.ft net internal, BUT, build only 4

2.  Gain 6db by building twice as many boxes but at half the size

 

 

Thoughts?

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Stick to sealed. Reason: your room size and listening desires. Get a set of Crowsons. Easy. Doesn't sound BADASS but who cares. Enjoy yourself first.

 

 

 

Option #2: Build proper LLT's. 11.8cuft is Tiny. 16cuft is still tiny, especially for 21" drivers. Dude, when does the external volume of a system matter? :P I wasn't using our usual "extreme escalation of numbers" in my rec for 20-30cuft boxes. That's them breaks if you want a proper LLT system. Don't cut corners and make it too small or you'll just have a run-of-the-mill undersized resonant system. Might as well get ID subs.

 

I know the reality sucks to hear but that's just the real deal. Don't skimp. You'll just end up unhappy and waste time, money and efforts.

 

A real LLT will have HUGE gains down near Fb. Not just "3-4dB" more. No, more like 10-12dB (driver to driver) all in that juicy upper single digits to 30hz range. Yeah!

 

 

So with the "stick to sealed" path you can maybe lower the amount of boost you're using and let a set of Crowsons do all the heavy lifting saving you TONS of amplifier headroom to play the rest of the system real good. :)

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Option #2: Build proper LLT's. 11.8cuft is Tiny. 16cuft is still tiny, especially for 21" drivers. Dude, when does the external volume of a system matter? :P

 

I was just making sure you knew it wasn't 11.8cu.ft before driver/bracing/port and netting only like 7cu.ft or something. 

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How goes it Luke?

 

Trying to find the motivation to get started :D

 

I'm sure this winter I'll get a little stir crazy and will start a few of them. 

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Ehh. No reason to have to build something new after wrapping up the sealed project. Live with it for a while. Enjoy the fruits of your labor and some extra money in your pocket. :)

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Ehh. No reason to have to build something new after wrapping up the sealed project. Live with it for a while. Enjoy the fruits of your labor and some extra money in your pocket. :)

 

Yeah that's the other thing.  It sounds pretty dang good as is!

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Right on. Hard to get motivated for a whole lotta work when everything is setup and kicking ass already.

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Right on. Hard to get motivated for a whole lotta work when everything is setup and kicking ass already.

 

Numbers like this make it really hard to get motivated :D

 

GTG_zpsy8ilttlj.png

 

 

Captured that during a GTG yesterday. 

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Skip the mega-enclosures and get some Crowsons.  I initially thought I would have to double up on subwoofer enclosures and amps until I bought a set.  

 

JSS

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Skip the mega-enclosures and get some Crowsons.  I initially thought I would have to double up on subwoofer enclosures and amps until I bought a set.  

 

JSS

 

99% sure that's what I'm doing next. 

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Skip the mega-enclosures and get some Crowsons.  I initially thought I would have to double up on subwoofer enclosures and amps until I bought a set.  

 

JSS

 

 

99% sure that's what I'm doing next. 

 

Yep...just ordered some Crowsons. 

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Yep...just ordered some Crowsons. 

 

You have issues. LOL

 

This is probably a good move for you. Moving to giant ported cabs would've been a ton of work for questionable reasons. How often are you running out of headroom with the 8 21's below 20Hz? I'd guess VERY rarely and only when demoing the most abusive material way beyond regular listening levels. Crowson's will probably up the amusement park ride factor a whole lot more for a whole lot less work.

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You have issues. LOL

 

This is probably a good move for you. Moving to giant ported cabs would've been a ton of work for questionable reasons. How often are you running out of headroom with the 8 21's below 20Hz? I'd guess VERY rarely and only when demoing the most abusive material way beyond regular listening levels. Crowson's will probably up the amusement park ride factor a whole lot more for a whole lot less work.

 

Even with 7db of boost at 10hz I haven't seen the amps clip below 20hz yet, and that's at or above reference with the subs 20db hot during demoes.  During "normal" movie watching levels (-5 to -10 on the main dial) without the bass running stupid hot, cone excursion isn't visible on any driver in my HT. 

 

From what I've gathered from a few other members, that boost at 10hz will be removed the second these Crowsons are installed. 

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