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post #31 of 47 Old 08-22-2018, 07:50 AM - Thread Starter
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Originally Posted by popalock View Post
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Originally Posted by Louquid View Post
So would the unsealed garage door be an issue for IB? If not I may just leave them open to the garage. Rather than build a wall and seal a space off.
If you use your garage as the IB chamber, do you realize how absoutley ridiculous your garage door is going to shake, rattle and flex? Assuming your garage door is closed and the pressure has no other place really to escape, imagine a large volume of air violently being pumped in to and out of your garage in rapid succession.

I wouldn't be surprised if you could hear your garage rattling through your living room walls.

Yes, I realize. Thats why I also asked of the dual opposed IB manifold would help with box room vibrations at all.

Though I did try it last night with just my current subs in the open garage and it wasnt that bad. Its a 8'x21' metal door. Pretty heavy and there isnt much flex to it. The vinyl panels on the outside of the door rattled at the lower frequencies, but I could only hear it up close. I know things will change if I upgrade the subs.

Worst case I can build a second wall and make a large enough space to do this.

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post #32 of 47 Old 08-22-2018, 11:04 AM
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Originally Posted by Louquid View Post
Yes, I realize. Thats why I also asked of the dual opposed IB manifold would help with box room vibrations at all.

Though I did try it last night with just my current subs in the open garage and it wasnt that bad. Its a 8'x21' metal door. Pretty heavy and there isnt much flex to it. The vinyl panels on the outside of the door rattled at the lower frequencies, but I could only hear it up close. I know things will change if I upgrade the subs.

Worst case I can build a second wall and make a large enough space to do this.
The back wave of your sealed sub simply pressurizes the small sealed box (air spring). When you set up your IB, dual opposed or not, the pressure will be literally transferring from room to room. Sometimes when I open the door to my garage I hear the garage shake. Imagine doing that in rapid succession. Wouldn't be hard to find out what the resonance of your garage is.

Here. Just for you:

Dual opposed will help cancel mechanical transfer to the wall you are mounting it too, but the air pressure transfer is a totally separate issue.

Yeah, worst case scenario enclosing the space is a solid idea. Not a huge deal.
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post #33 of 47 Old 08-22-2018, 06:35 PM
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Originally Posted by Ftoast View Post
I think you're right about a port doing little/no good with the "enclosure" (garage) not sealed. Just like modeling with a really large and leaky box where a port will likewise add little/nothing.
Here is what I model ported vs sealed:

SPL:

Excursion:


I mean...a free 20db gain @ 3Hz... Why not???

A couple assumptions on the ported:

1. 20'L x 20'W x 10'H = 4,000ft^3.
2. Port depth would be based on the dept of the manifold.

Why a port depth of 20"? Refer back to post #7 . My thought is to basically make a cross brace across a similar manifold for rigidity, but leave the back panel off to act as the port. That way you can make the manifold and port in one without having to cut an additional port hole in the wall.

Anyone see a problem with this? Just kind of spit balling because I haven't done it myself. That said, worst case scenario is to just seal up the back of the manifold and proceed as a normal IB...
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post #34 of 47 Old 08-22-2018, 07:23 PM
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IB Sub or Porting Sub Into Living Room

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Originally Posted by popalock View Post



Why a port depth of 20"? Refer back to post #7 . My thought is to basically make a cross brace across a similar manifold for rigidity, but leave the back panel off to act as the port. That way you can make the manifold and port in one without having to cut an additional port hole in the wall.



Anyone see a problem with this? Just kind of spit balling because I haven't done it myself. That said, worst case scenario is to just seal up the back of the manifold and proceed as a normal IB...

My worry would be the woofers were now radiating into the back space. Isn’t the point of the manifold on the IB to point the source directly into the room? If the manifold was open and the drivers caddy corner to the opening (aka the port) wouldn’t they also radiate into the other space/room? Effectively turning them into free air?


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post #35 of 47 Old 08-22-2018, 08:01 PM
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Originally Posted by Trimlock View Post
My worry would be the woofers were now radiating into the back space. Isn’t the point of the manifold on the IB to point the source directly into the room? If the manifold was open and the drivers caddy corner to the opening (aka the port) wouldn’t they also radiate into the other space/room? Effectively turning them into free air?


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Yeah. Good point. Thinking about it more...you gotta be right.

Clearly physics would dictate the air pressure take the path of least resistance. Duh!

Guess a seperate port hole it is! Probably for the better anyway as it would be easy to make the port hole small enough to avoid cuffing while obtaining a higher tune.

Plugging in the model earlier I think I remember something around 130db @ 10Hz is within the realm of possibility.

Approaching @MKtheater levels there!
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post #36 of 47 Old 08-23-2018, 04:56 AM
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Originally Posted by popalock View Post
If you use your garage as the IB chamber, do you realize how absoutley ridiculous your garage door is going to shake, rattle and flex? Assuming your garage door is closed and the pressure has no other place really to escape, imagine a large volume of air violently being pumped in to and out of your garage in rapid succession.

I wouldn't be surprised if you could hear your garage rattling through your living room walls.
This absolutely will *not* be the case. We actually have built this exact setup in my friend's garage housing 18" Fi IB3's venting into his living room and nothing rattles at all. Surprisingly, the bass is not that aggressive outside, either.

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post #37 of 47 Old 08-23-2018, 04:58 AM
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Originally Posted by markmon1 View Post
This absolutely will *not* be the case. We actually have built this exact setup in my friend's garage housing 18" Fi IB3's venting into his living room and nothing rattles at all. Surprisingly, the bass is not that aggressive outside, either.
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post #38 of 47 Old 08-23-2018, 08:02 AM
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Originally Posted by popalock View Post
Here is what I model ported vs sealed:

I mean...a free 20db gain @ 3Hz... Why not???
While those graphs can be accurate, those are assuming a large sealed rear enclosure which makes air have to transfer through the port. If you seal some large enclosures behind each sub, that can work...and those huge gains down low are why I'm recommending having the woofers and ports facing into the room while a large box seals the rear of each woofer.

However, without a sealed box at the back to pressurize into the port, you'll be instead dealing with a very large and air-leaking garage. This can also be modeled accurately in winISD similar to what you posted..but you'll have to change the Ql parameter to something around 0-0.5 which you'll find in the "Box" tab under "Advanced" near the bottom. 10-15 represents a well-sealed enclosure (like a sealed box attached behind the subs) while a 0-0.5 Ql represents an unsealed or poorly sealed enclosure (like the average garage).

Something tall and narrow to fit between the studs (like a 7ft-tall, 16inch-wide and 2ft deep enclosure). This could also somewhat protect the back of the sub/s from any little critters that may sneak into the garage, like mice or bats..if that's ever been a problem. This is also a reason that a direct port right into the unsealed garage could be a bad idea. Bugs and rodents from the garage are now bugs and rodents with an easy path into your theater.

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post #39 of 47 Old 08-23-2018, 08:24 AM
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Ported IB is actually called a SLLT. If your drivers are using the garage for the box then it will have lots of bass in there. I mean the back of the drivers are facing into it. Remember that not all drivers will act nicely if porting them. Your UM drivers will be great at porting. I would not tune at 3hz though, I would tune at 10hz and you will get single digits in room. I have lots of room gain and I get a -3 dB point of 4.3 hz not counting the huge peak I get at tune, -3 dB from the rest of the response. I would just cut two circles in the wall and a big port that all vent into the room. Since the UM will not require a massive enlocure to act like IB I would build a false wall in the garage(If it can fit) to trap the back waves of bass but big enough to act like IB. I did this in my room.

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post #40 of 47 Old 08-23-2018, 08:37 AM
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I have had two IBs open to the attic. The first was dual Avalanche 18s and now 4 FiCar IB318s. One thing to consider is the woofer sd is not insulated so if your garage gets hot in the summer or cold in the winter it will affect the temp in your theater room. The extent depends on how many 18s you use and the temp variation. The effortless low bass and lack of distortion and musicality of IB subs is phenomenal. To me the main drawback, as noted before, is the lack of midbass. If you want significant midbass then you need LCR that provide that or near field subs behind your seated position. I have four 18" drivers on the front wall and four sealed 12" drivers behind my back row firing directly into the seats. I love the 18s but the NFS had surprisingly dramatic impact.

The first photo shows the IB at the front and the darker second photo shows the 12" enclosures behind the back row.

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post #41 of 47 Old 08-23-2018, 09:45 AM
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Originally Posted by Ftoast View Post
While those graphs can be accurate, those are assuming a large sealed rear enclosure which makes air have to transfer through the port. If you seal some large enclosures behind each sub, that can work...and those huge gains down low are why I'm recommending having the woofers and ports facing into the room while a large box seals the rear of each woofer.

However, without a sealed box at the back to pressurize into the port, you'll be instead dealing with a very large and air-leaking garage. This can also be modeled accurately in winISD similar to what you posted..but you'll have to change the Ql parameter to something around 0-0.5 which you'll find in the "Box" tab under "Advanced" near the bottom. 10-15 represents a well-sealed enclosure (like a sealed box attached behind the subs) while a 0-0.5 Ql represents an unsealed or poorly sealed enclosure (like the average garage).
Ok, assuming it's an uber leaky box, it would be the same for both sealed and ported, correct? I went ahead and changed the Ql in both models to a Ql of 1 but kept all else the same:

SPL w/Low Ql


Huge overall SPL lossess accross the board... However, I wonder why there is such a general overall advantage to the ported across the frequency spectrum. Some sort of anomaly? I typically adjust the Ql to see if I can keep excursion in check in a sealed setup...Pretty interesting how much it effects an IB alignment... <----Weird saying that since a true IB would be open to the world. I wonder if Ql in the context of IB simply means rigidity of the baffle wall and/or efficient separation from the front and back waves? It has to be, because if you were to open the garage door to make it a true IB, it wouldn't change the response because VAS requirements have already been met. Hummm...

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Originally Posted by Ftoast View Post
Something tall and narrow to fit between the studs (like a 7ft-tall, 16inch-wide and 2ft deep enclosure). This could also somewhat protect the back of the sub/s from any little critters that may sneak into the garage, like mice or bats..if that's ever been a problem. This is also a reason that a direct port right into the unsealed garage could be a bad idea. Bugs and rodents from the garage are now bugs and rodents with an easy path into your theater.
Speaker grill cloth over the rear of the port? Window screening? Seems like it would be somewhat easy to address. Obviously wouldn't be a great idea to have the port directly on the floor.
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post #42 of 47 Old 08-23-2018, 10:12 AM
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Originally Posted by MKtheater View Post
Ported IB is actually called a SLLT. If your drivers are using the garage for the box then it will have lots of bass in there. I mean the back of the drivers are facing into it. Remember that not all drivers will act nicely if porting them. Your UM drivers will be great at porting. I would not tune at 3hz though, I would tune at 10hz and you will get single digits in room. I have lots of room gain and I get a -3 dB point of 4.3 hz not counting the huge peak I get at tune, -3 dB from the rest of the response. I would just cut two circles in the wall and a big port that all vent into the room. Since the UM will not require a massive enlocure to act like IB I would build a false wall in the garage(If it can fit) to trap the back waves of bass but big enough to act like IB. I did this in my room.
Haven't checked the UM-15's, but I don't think porting to 10Hz is possible with the Fi's. Just tried six ways from Sunday and keep getting a negative port length.

I just mentioned 3-4Hz because that seemed like the only option with the Fi's to keep the port size reasonable. One of those, why not / something for nothing scenarios. Porting @ 3Hz is not at all practical and 99.88% of the time no content will dig THAT low. That said, the models are showing a very notable overall SPL increase across the board in very leaky (Ql-1) boxes and a small overall increase on the other end of the Ql spectrum (Ql-10).
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post #43 of 47 Old 08-23-2018, 10:38 AM
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Haven't checked the UM-15's, but I don't think porting to 10Hz is possible with the Fi's. Just tried six ways from Sunday and keep getting a negative port length.

I just mentioned 3-4Hz because that seemed like the only option with the Fi's to keep the port size reasonable. One of those, why not / something for nothing scenarios. Porting @ 3Hz is not at all practical and 99.88% of the time no content will dig THAT low. That said, the models are showing a very notable overall SPL increase across the board in very leaky (Ql-1) boxes and a small overall increase on the other end of the Ql spectrum (Ql-10).
I did not have good luck porting my Fi's at 6hz, I sold them because I really wanted to try porting low and ended up getting the SI's, which worked much better. The FI is the better driver but I would leave it sealed in a IB and run an LT if needing more low end. The UM and SI's can be ported nicely. My XXX-18s can be ported as well as shown by Ricci and the power ported 18. My two ported XXX-18s have stronger low end than the 8 sealed Fi and the SI. Lacking some mid bass though and I want to add two more.
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post #44 of 47 Old 08-23-2018, 11:44 AM
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However, I wonder why there is such a general overall advantage to the ported across the frequency spectrum. Some sort of anomaly?
Higher across the entire range shouldn't be happening like that. You might want to doublecheck that both graphs are using the same amount of drivers/subs and that both graphs are set for the same distance (either 1m or whatever your seating-distance is).
The graphs look like one is set for multiple drivers VS the other at one driver, or one is left at default 1m while the other was adjusted to include seating-distance.
Distance is set inside the "signal" tab while number of drivers is in the "drive" tab.

In a very leaky enclosure, ported, IB or sealed will all perform roughly equally...about the same as standard IB.
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post #45 of 47 Old 08-23-2018, 12:58 PM
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Restarted winISD and re-entered all of the perimeters. Still acting funky. Guess it's a moot point because it's not practical anyway. I only mentioned it if he wasn't wanting to build separate chamber within his garage.

@Louquid . If you want to go ported, clearly building separate chamber would be optimal. How much room would you have to work with? We can model based on your stated limitations to get a better idea of what would work in a SULT enclosure with both the Fi's and the UM-15 if you like.

FYI. You could potentially gain 9-12db @ port tune by porting your UM-15's. If you feel that is potentially enough, you might forgo the Fi's all together.
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post #46 of 47 Old 08-25-2018, 09:34 AM
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Originally Posted by Ftoast View Post
Bugs and rodents from the garage are now bugs and rodents with an easy path into your theater.
You can get metal mesh of various parameters from most hardware shops.
Then add speaker cloth on the HT-facing hole.


The metal keeps out the rodents and the cloth keeps out the bugs.

Just remember to never store or do anything smelly in your garage!
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post #47 of 47 Old 08-25-2018, 09:54 AM
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As mentioned, if you put your existing subs in a horn, you'll only need one opening from the garage, and it can be sealed with sealant for stopping bugs and smells; and you'd gain 18db over IB and 6db over ported.

If you have 2 15's, make it 32 inches wide, if you have 2 18's, make it 40inches wide.

The mouth can be a different set of dimensions as horns only care about the cross-sectional area of any given segment and the total horn-length...

In any case, no matter what you do it will be better than what you have now in terms of efficiency, frequency extension, and space for even MORE woofers. Just don't tell the wife about your moon-laser plans!!!

(Just because she can't see the box anymore, doesn't mean it gonna be quieter LOL!!!!! )
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