New Construction - DIY Sub Box or IB ?? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 29 Old 07-12-2019, 03:14 PM - Thread Starter
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Question New Construction - DIY Sub Box or IB ??

Hello All:

I am in the process of constructing a media/home theater room that has been about 10 years in the making. I have a great unfinished basement that I am framing right now.

I am trying to plan out the sound, which has given me the most headaches in designing this.

In order to meet the WAF, I need a flat front wall. So I am planning in wall speakers of some sort with a 120" acoustic screen. The entire media room is built with de-coupled framing, clips/channel planned for the ceiling (9.5' tall), green glue/double drywall, backerboxes, etc. Thus, I hope to have this somewhat soundproof.

The kicker is the subs. I want a good, punch you hard bass set up and I am fairly handy so was looking at DIY. Of course, down the rabbit hole I go and i see infinite baffle setups. These are intriguing to me, but I need to control the sound outside the room. So in the drawing attached I am looking at building a screen wall about 24" forward of the soundproof shell. Would this be enough space (250 cu ft) for a IB setup? Or should i just plan on setting a VBSS or marty setup flush with the forward wall and build a grill to cover it?

Any help would be appreciated as I am confused at this point.

PS I did talk to the Soundproofing Company and they are not worried about me creating a triple leaf wall with a cavity as I am thinking about.

Ethan
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post #2 of 29 Old 07-12-2019, 06:47 PM
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WAF...in the basement

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post #3 of 29 Old 07-13-2019, 07:15 AM
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If it were me, I would definitely go the IB route. Of course I'm a bit biased though....

The benefits are plentiful !
- No boxes eating real estate in the HT room
- No designing real estate hogging boxes = super easy design
- Unmatched freq response














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post #4 of 29 Old 07-13-2019, 08:30 AM
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Having both a IB and boxes... Id go boxes. Yes it takes up real estate but its flexible, if something changes, so can it. When i got a new projector, had to move my seating back 2 feet.... bingo, right in a -20dB null.... lol nothing you can do about it sub wise.

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post #5 of 29 Old 07-14-2019, 05:01 PM - Thread Starter
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[quote=rms8;58291238]If it were me, I would definitely go the IB route. Of course I'm a bit biased though....

The benefits are plentiful !
- No boxes eating real estate in the HT room
- No designing real estate hogging boxes = super easy design
- Unmatched freq response

[quote=rms8;58291238]

Very impressive! RSM8

Question - what do you do for soundproofing? Does the IB Arrays vibrate the house?

How big is the space behind the arrays? I am unsure if 250 cu ft that I have available is enough.

Ethan

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post #6 of 29 Old 07-14-2019, 05:10 PM
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I'd do a false screen wall (minimalist -goalposts) and put either Marty's or VBSS's behind it along with your L/C/R speakers (Say some DIY SG HTM-12's). You could probably go in-wall for the surrounds to meet WAF (as I did), but you really want good speakers for your front three).

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post #7 of 29 Old 07-14-2019, 05:13 PM
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10xVas is the general rule, you can go with less. It will vibrate and travel through the house, but so will boxed subs. How bad will depend on your house construction and manifold.
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post #8 of 29 Old 07-14-2019, 05:37 PM
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post #9 of 29 Old 07-14-2019, 06:01 PM
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@rms8 Very unique looking theater - It looks awesome!

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post #10 of 29 Old 07-15-2019, 10:30 AM
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How much cash do we have to spend exactly, and what are the exact dimensions of a box that you can handle?
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post #11 of 29 Old 07-15-2019, 11:31 AM - Thread Starter
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Quote:
Originally Posted by buggers View Post
How much cash do we have to spend exactly, and what are the exact dimensions of a box that you can handle?
Cost wise I am flexible. My initial plan was dual HSU VTF-3's but that really is out of my budget. I would like to spend around $800 or less total for two units.

The dimension is flexible right now. I am building the room shell and can adjust the "screen" wall to fit what is needed. If I go the VBSS route, then I would offset the screen wall about 24" to allow me to recess the boxes.

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post #12 of 29 Old 07-15-2019, 11:37 AM - Thread Starter
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Quote:
Originally Posted by Mocs123 View Post
I'd do a false screen wall (minimalist -goalposts) and put either Marty's or VBSS's behind it along with your L/C/R speakers (Say some DIY SG HTM-12's). You could probably go in-wall for the surrounds to meet WAF (as I did), but you really want good speakers for your front three).

Mocs I generally agree with you here. The other thing I want to do with the screen wall is mount a couple of cheap 32" tv's on the side to allow for multi sports viewing on football days. So i need something a little stronger for a wall.

For LCR speakers I haven't purchased anything yet but will need to soon. I was eyeing the Revel W253L for the front inwalls and the RSL C34e for surounds/atmos duty.

I am open to build the LCR's, but the HTM's would cost fairly close to the Revels I am looking at ($300 ea).

I appreciate the replies but i think the longer i research and read, the more lost i am getting. I want to make a great audio choice that meets a budget number, hence why I am trying to figure out this DIY thing.

Thanks.

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post #13 of 29 Old 07-20-2019, 08:55 PM
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Quote:
Originally Posted by EJ Husker1 View Post
Cost wise I am flexible. ... I would like to spend around $800 or less total for two units.
For two subs, $800 or less is not very flexible.

Do you already have an amp?

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post #14 of 29 Old 07-21-2019, 01:25 AM
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Back in 2008 when I did my IB sub line array the IB subs were value priced, truly, now they seem outta price to their lower manuf cost.
Unless you contain your IB backwave it will go thru your home, as stated 10x VAS is rule of thumb.


Building your front 250cu ft sealed space, you could put 4 on a 1/4 grid and then have a SBA pressure wave moving front to rear.... which is many people do w/o realizing it when they stack their subs inside the mains .....
IF budget is tight, then 2 now and add 2 later may be a option, build & wire for it then block the un-used 2 driver holes.
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post #15 of 29 Old 07-21-2019, 04:44 AM
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Quote:
Originally Posted by N8DOGG View Post
Having both a IB and boxes... Id go boxes. Yes it takes up real estate but its flexible, if something changes, so can it. When i got a new projector, had to move my seating back 2 feet.... bingo, right in a -20dB null.... lol nothing you can do about it sub wise.
You can build the IB subs into your platform firing into your seating, then you're impervious to any room nulls because the subs originate at your location.


Quote:
Originally Posted by EJ Husker1 View Post
Mocs I generally agree with you here. The other thing I want to do with the screen wall is mount a couple of cheap 32" tv's on the side to allow for multi sports viewing on football days. So i need something a little stronger for a wall.

For LCR speakers I haven't purchased anything yet but will need to soon. I was eyeing the Revel W253L for the front inwalls and the RSL C34e for surounds/atmos duty.

I am open to build the LCR's, but the HTM's would cost fairly close to the Revels I am looking at ($300 ea).

I appreciate the replies but i think the longer i research and read, the more lost i am getting. I want to make a great audio choice that meets a budget number, hence why I am trying to figure out this DIY thing.

Thanks.
You cannot beat the sound quality of IB subs with boxed subs. I strongly recommend IB. 250 cubic is plenty for IB subs, depending on how many you need. While the rule is vas x 10, you can easily do vas x 4 with almost no noticeable difference - at least with Fi IB subs.
You could start with 2 Fi 18's IB's at $279ea and an EP4000 amp for $329. Super easy to add more subs later if needed.
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post #16 of 29 Old 07-21-2019, 06:57 AM - Thread Starter
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Originally Posted by markmon1 View Post
You cannot beat the sound quality of IB subs with boxed subs. I strongly recommend IB. 250 cubic is plenty for IB subs, depending on how many you need. While the rule is vas x 10, you can easily do vas x 4 with almost no noticeable difference - at least with Fi IB subs.
You could start with 2 Fi 18's IB's at $279ea and an EP4000 amp for $329. Super easy to add more subs later if needed.
I appreciate your thoughts here. So to be a true IB setup does the 250 cubic feet need to be sealed like an aquarium to function correctly?

I see in your picture the subs are just mounted to an OSB panel. That looks easy to do. For my situation I picture building the screen wall, drywall the outside and then running OSB along the backside for mounting the drivers. Then I can do a simple cutout in the drywall and cover with speaker grill cloth.

On the amp side is there anything much to setting those up? I don't have fancy software or calibration equipment.

Thanks.

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post #17 of 29 Old 07-21-2019, 07:03 AM - Thread Starter
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Originally Posted by mtbdudex View Post
Back in 2008 when I did my IB sub line array the IB subs were value priced, truly, now they seem outta price to their lower manuf cost.
Unless you contain your IB backwave it will go thru your home, as stated 10x VAS is rule of thumb.


Building your front 250cu ft sealed space, you could put 4 on a 1/4 grid and then have a SBA pressure wave moving front to rear.... which is many people do w/o realizing it when they stack their subs inside the mains .....
IF budget is tight, then 2 now and add 2 later may be a option, build & wire for it then block the un-used 2 driver holes.

On the backside of the 250 cubic foot space, I am planning a soundproof wall (decoupled framing/double drywall/green glue). Will that not limit the sound out from a IB setup or is a IB nearly impossible to contain?

I don't quite understand your comment on a SBA pressure wave. Do you mean that reflections from the back of the space will radiate back forward through the screen wall to the seating area? I had thought of lining the back wall with linacoustic or something similar help deaden the wall inside the 250 cubic feet area. Maybe I shouldn't do that?

Thank you.

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post #18 of 29 Old 07-21-2019, 07:20 AM
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Quote:
Originally Posted by EJ Husker1 View Post
I appreciate your thoughts here. So to be a true IB setup does the 250 cubic feet need to be sealed like an aquarium to function correctly?



I see in your picture the subs are just mounted to an OSB panel. That looks easy to do. For my situation I picture building the screen wall, drywall the outside and then running OSB along the backside for mounting the drivers. Then I can do a simple cutout in the drywall and cover with speaker grill cloth.



On the amp side is there anything much to setting those up? I don't have fancy software or calibration equipment.



Thanks.
Doing an array like markmon1 will require some strengthening of the wall (especially if it's a screen wall). That's slot of mass moving the same direction all at once.

A manifold like I have will help cancel some vibrations but will also eat into some of your backspace real estate.
The space behind the drivers doesn't have to be sealed tight, just well separated from the front side to avoid cancellations.

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post #19 of 29 Old 07-21-2019, 09:17 AM
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I'll add my own comments. I have had 2 IB subs. The first was two Avalanche 18s in a manifold in a 20' x 16' x 9' room. The second is what I have now... 4 FiCar Audio IB3 18" subs in a line array in an open loft (look at my Avatar). The benefit of IB is very low distortion, they dig really deep (single digits), they sound more musical and there are no boxes in the room. The draw back is moving the drivers after installation is a ton of work, you need more drivers for the same SPL as ported enclosures (15-30hz) and not as much mid bass punch as ported enclosures. You could put multiple boxed enclosures behind your false wall so the no box issue isn't really an issue for you. You'd then have much more flexibility in moving the subs after the fact and you'd have more of the chest slam. Re: midbass with IB subs... if you have the ability to wire for nearfield subs, you could add them later and really get the physical feel of the drivers with the clean sound of an IB. I have four 12" drivers in sealed enclosures directly behind my back row firing directly into those chairs and they pair with the for IB subs really well. It all depends on your short term budget and long term budget and doing the groundwork now to allow for subwoofer expansion later on. And remember this, whatever you do now will never be enough. You will add more later, so if you keep that in mind now your life will be much easier later. Lastly, regardless of whether you go IB or ported, search for and read the Harman White Paper by Todd Welti on subwoofer placement and the AVS thread on "Double Bass Array" before you do anything. They will answer a lot of questions you don't even know to ask.


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post #20 of 29 Old 07-21-2019, 10:08 AM
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Quote:
Originally Posted by EJ Husker1 View Post
On the backside of the 250 cubic foot space, I am planning a soundproof wall (decoupled framing/double drywall/green glue). Will that not limit the sound out from a IB setup or is a IB nearly impossible to contain?

I don't quite understand your comment on a SBA pressure wave. Do you mean that reflections from the back of the space will radiate back forward through the screen wall to the seating area? I had thought of lining the back wall with linacoustic or something similar help deaden the wall inside the 250 cubic feet area. Maybe I shouldn't do that?

Thank you.

The backchamber of a IB is basically the inside of a huge sealed sub, not impossible but needs good planning and execution to minimize LFE transference.
Your on the right track.

My utility room is my backchamber, it's lined with 9" pink fluffy all the walls, and I did my best at sealing so the wave would not leak out.
Honestly at "normal" HT listening levels , -15db MV, it totally works can't really hear it on main floor.
However when you run say -3db or 0db MV it does transfer upstairs thru the home.




No matter what, containing LFE is not practical unless your room is a sealed concrete bunker, only a few I know have done that.


Read this on SBA
https://www.avsforum.com/forum/19-de...ter-build.html


If I had a re-do on my home, I'd have put the HT under the garage, and fully encased the 4 walls with engineered foundation walls with a 30" IB chamber up-front and use (4) 24" SI drivers and then 36" deep rear for absorption depth.
engineered foundation walls have studs 24" on center which helps absorb above 20hz energy.
For my HT, I used 2x6 and offset stud construction, so all 4 my walls have drywall on 24" centers.


Going the IB route, if you choose a line-array on the bottom that helps by anchoring it to the floor and also having braces from your wall front to the back wall.
Or, using a IB manifold will allow cancellations of speaker cone movement.

Consider how you will get into your IB backchamber to install/service.
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post #21 of 29 Old 07-21-2019, 02:22 PM
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Quote:
Originally Posted by lloyd401 View Post
Doing an array like markmon1 will require some strengthening of the wall (especially if it's a screen wall). That's slot of mass moving the same direction all at once.

A manifold like I have will help cancel some vibrations but will also eat into some of your backspace real estate.
The space behind the drivers doesn't have to be sealed tight, just well separated from the front side to avoid cancellations.

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Nah. I have no issues. This is a screen wall. Note that I did the sibs at the bottom of the wall not the middle. No reinforcement required at all.
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post #22 of 29 Old 07-21-2019, 02:28 PM
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Quote:
Originally Posted by EJ Husker1 View Post
On the backside of the 250 cubic foot space, I am planning a soundproof wall (decoupled framing/double drywall/green glue). Will that not limit the sound out from a IB setup or is a IB nearly impossible to contain? <br />
<br />
I don't quite understand your comment on a SBA pressure wave. Do you mean that reflections from the back of the space will radiate back forward through the screen wall to the seating area? I had thought of lining the back wall with linacoustic or something similar help deaden the wall inside the 250 cubic feet area. Maybe I shouldn't do that? <br />
<br />
Thank you.
<br />
<br />
Nah you won’t need any of that. You’re not building a huge box. You just need reverse wave cancelation. Most my room is just separating the main room by drywall. It’s not even air tight. I have holes for cables. At one point I wanted a 10” by 36” opening and Fi said that probably be ok as well. I sealed that up though. <br />
<br />
On the other side of my wall is an 11” opening of dry wall. It was originally planned to access DVD players and game consoles. The screen is above that. The bottom half of the subs peak into the room. The top half fire into drywall but are spaced back enough it doesn’t hit or anything.

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Quote:
Originally Posted by markmon1 View Post
Nah. I have no issues. This is a screen wall. Note that I did the sibs at the bottom of the wall not the middle. No reinforcement required at all.
Cool, I may look into that when I move my theater to another room.

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post #24 of 29 Old 07-21-2019, 03:10 PM
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Quote:
Originally Posted by EJ Husker1 View Post
I appreciate your thoughts here. So to be a true IB setup does the 250 cubic feet need to be sealed like an aquarium to function correctly?

I see in your picture the subs are just mounted to an OSB panel. That looks easy to do. For my situation I picture building the screen wall, drywall the outside and then running OSB along the backside for mounting the drivers. Then I can do a simple cutout in the drywall and cover with speaker grill cloth.

On the amp side is there anything much to setting those up? I don't have fancy software or calibration equipment.

Thanks.
If you really want a good method that won't require playing very loud and will have no room nulls at all, fire your IB subs into your seating. The bass is then immediately felt as it fires directly into your body. You won't need to crank it much because you feel it so aggressively and are fully satisfied.

I don't agree with above posters about wanting boxed subs for chest slam. You can get those effects with super cheap 8&quot; subs because those are the only frequencies they can play well. Your IB array will extend down towards 5hz and produce bass response normal boxed subs cannot handle. My center channel provides great chest slam. It doesn't make a good sub. I've gone to friends houses that are all excited about their subs and how hard they hit and they're the worst, boomy sounding PoS and I cant get out of there fast enough. IB is never boomy sounding.

Here is a sub array we built in a platform firing up into the couch. It has 2 18&quot; Fi's that hardly ever get cranked up because they push so much vibration into the main seating.



The amp is easy to set up. I just run speaker wires from amp to the subs and connect to avr then let the avr manage crossover.
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post #25 of 29 Old 07-22-2019, 02:32 AM
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Originally Posted by markmon1 View Post



If you really want a good method that won't require playing very loud and will have no room nulls at all, fire your IB subs into your seating. The bass is then immediately felt as it fires directly into your body. You won't need to crank it much because you feel it so aggressively and are fully satisfied.



I don't agree with above posters about wanting boxed subs for chest slam. You can get those effects with super cheap 8" subs because those are the only frequencies they can play well. Your IB array will extend down towards 5hz and produce bass response normal boxed subs cannot handle. My center channel provides great chest slam. It doesn't make a good sub. I've gone to friends houses that are all excited about their subs and how hard they hit and they're the worst, boomy sounding PoS and I cant get out of there fast enough. IB is never boomy sounding.



Here is a sub array we built in a platform firing up into the couch. It has 2 18" Fi's that hardly ever get cranked up because they push so much vibration into the main seating.







The amp is easy to set up. I just run speaker wires from amp to the subs and connect to avr then let the avr manage crossover.
I think you and I were more or less saying the same thing. IB at the front of the room doesn't provide chest slam but it digs deep with ease and without distortion. From a frequency standpoint chest slam comes from 60-500Hz. IBs do 5Hz-100Hz best. IBs have a very realistic sound so they sound great with music but also movies. If you want chest slam, the best way is with nearfield subs. With near field subs it's less about the frequency output and more about driver excursion. Of course an 18" IB sub under your a$$ is going to give you tremendous impact . I will tell you that a row of 12" subs firing directly into your chair also works (e.g. a riser isn't always an option). Where you and I differ is I also think large ported boxes at the front of the theater provide chest slam, and they dig somewhat deep, but you have to use a high pass filter just below tuning to protect the driver from over excursion. With a driver like the FiCar Audio IB3 used in a IB application, you just need to provide the right amount of power and it will never bottom out, yet make full use of it's 30mm Xmax all the way down to 0Hz (you wont hear it at those ultra low frequencies and the SPL drops rapidly but the sub still moves at full excursion). So to me it comes down to priorities. Do you want single digit extension? Do you want chest slam? How flexible is your budget? Are you able and/or willing to add extra subs now or later? I do not think a nearfield sub should be your primary subwoofer (boxed or IB). The muffled sound of a blocked driver is a great secondary subwoofer but the sound profile is too compromised to be the primary sub. If your goal is stealth appearance, great sound and great impact, then have multiple IB at the front, and a few nearfield subs to augment the impact (ideally the nearfield subs would be under your chair in a riser firing up into your bum). That would be the most expensive option but the best sounding. If your goal is to keep costs lower and you don't want to deal with nearfield subs, then start with one ported 18" driver and run it bridged on a 2 channel amp, then add a second identical ported 18" sub and run one sub off each channel. That way you only have to buy one amp. You would give up the ultra low frequencies but it would still sound better than anything you or your friends have had (especially if it's a DIY sub). If you go the latter route, do your research to figure out what driver you want, then get a flat pack to build the enclosure. Definitely don't go any smaller than an 18" driver (either IB or ported). That my 2¢.

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post #26 of 29 Old 07-22-2019, 02:40 AM
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Originally Posted by krholmberg View Post
I think you and I were more or less saying the same thing. IB at the front of the room doesn't provide chest slam but it digs deep with ease and without distortion. From a frequency standpoint chest slam comes from 60-500Hz. IBs do 5Hz-100Hz best. IBs have a very realistic sound so they sound great with music but also movies. If you want chest slam, the best way is with nearfield subs. With near field subs it's less about the frequency output and more about driver excursion. Of course an 18" IB sub under your a$$ is going to give you tremendous impact . I will tell you that a row of 12" subs firing directly into your chair also works (e.g. a riser isn't always an option). Where you and I differ is I also think large ported boxes at the front of the theater provide chest slam, and they dig somewhat deep, but you have to use a high pass filter just below tuning to protect the driver from over excursion. With a driver like the FiCar Audio IB3 used in a IB application, you just need to provide the right amount of power and it will never bottom out, yet make full use of it's 30mm Xmax all the way down to 0Hz (you wont hear it at those ultra low frequencies and the SPL drops rapidly but the sub still moves at full excursion). So to me it comes down to priorities. Do you want single digit extension? Do you want chest slam? How flexible is your budget? Are you able and/or willing to add extra subs now or later? I do not think a nearfield sub should be your primary subwoofer (boxed or IB). The muffled sound of a blocked driver is a great secondary subwoofer but the sound profile is too compromised to be the primary sub. If your goal is stealth appearance, great sound and great impact, then have multiple IB at the front, and a few nearfield subs to augment the impact (ideally the nearfield subs would be under your chair in a riser firing up into your bum). That would be the most expensive option but the best sounding. If your goal is to keep costs lower and you don't want to deal with nearfield subs, then start with one ported 18" driver and run it bridged on a 2 channel amp, then add a second identical ported 18" sub and run one sub off each channel. That way you only have to buy one amp. You would give up the ultra low frequencies but it would still sound better than anything you or your friends have had (especially if it's a DIY sub). If you go the latter route, do your research to figure out what driver you want, then get a flat pack to build the enclosure. Definitely don't go any smaller than an 18" driver (either IB or ported). That my 2¢.

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The latest Fi IBv2 series is pretty good. The 15's are about as aggressive as the 15's now and are rated at the same db efficiency (they use to be 3db lower).

I also had an IB array of 12's firing into my seats. It was great. I disagree that you get any muffled sound in this configuration. IB in platform firing into seating is the best feeling and sounding sub I've ever heard and beats my front behind screen IB setup. Although, if I crank the volume up more, I can get about the same tactile feeling from the front subs.

IB subs do great from 0-100 like you said. In my opinion, it's not the sub's job to do 100-500hz. Those are very directional frequencies. Good center/left/right fronts should be able to provide authoritative chest slam in those frequencies. I know my center does, although it's really not cheap. But I've heard DIY centers, JTR, others that do it well also.

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post #27 of 29 Old 07-22-2019, 07:16 AM - Thread Starter
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Originally Posted by markmon1 View Post
The latest Fi IBv2 series is pretty good. The 15's are about as aggressive as the 15's now and are rated at the same db efficiency (they use to be 3db lower).

I also had an IB array of 12's firing into my seats. It was great. I disagree that you get any muffled sound in this configuration. IB in platform firing into seating is the best feeling and sounding sub I've ever heard and beats my front behind screen IB setup. Although, if I crank the volume up more, I can get about the same tactile feeling from the front subs.

IB subs do great from 0-100 like you said. In my opinion, it's not the sub's job to do 100-500hz. Those are very directional frequencies. Good center/left/right fronts should be able to provide authoritative chest slam in those frequencies. I know my center does, although it's really not cheap. But I've heard DIY centers, JTR, others that do it well also.
Thanks for your input here, it has given me much to research and look over. I am tired this morning from a weekend of pulling wire and installing RISC clips.

I think I am leaning towards the following set up with input from this thread and other research:

- two IB subs set up at the front of the room in an array with space to add two more in the future.
- Locate the array horizontally near the floor using a double OSB board attached to the backside of a 2x4 stud screen wall, studs at 24" O.C.
- Add additional horizontal braces around each of the four sub openings, glue and screw everything together.
- Add conduit and wire for future under seat sub configuration (BOSS)
- Quit over analyzing and just build it!

My next need to is to determine what amp to get. I am planning getting a 9 channel Denon receiver (5.2.4). I would like something expandable, but provides a good bang for the buck.

Thank you.
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post #28 of 29 Old 07-22-2019, 07:20 AM - Thread Starter
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Originally Posted by krholmberg View Post
I think you and I were more or less saying the same thing. IB at the front of the room doesn't provide chest slam but it digs deep with ease and without distortion. From a frequency standpoint chest slam comes from 60-500Hz. IBs do 5Hz-100Hz best. IBs have a very realistic sound so they sound great with music but also movies. If you want chest slam, the best way is with nearfield subs. With near field subs it's less about the frequency output and more about driver excursion. Of course an 18" IB sub under your a$$ is going to give you tremendous impact . I will tell you that a row of 12" subs firing directly into your chair also works (e.g. a riser isn't always an option). Where you and I differ is I also think large ported boxes at the front of the theater provide chest slam, and they dig somewhat deep, but you have to use a high pass filter just below tuning to protect the driver from over excursion. With a driver like the FiCar Audio IB3 used in a IB application, you just need to provide the right amount of power and it will never bottom out, yet make full use of it's 30mm Xmax all the way down to 0Hz (you wont hear it at those ultra low frequencies and the SPL drops rapidly but the sub still moves at full excursion). So to me it comes down to priorities. Do you want single digit extension? Do you want chest slam? How flexible is your budget? Are you able and/or willing to add extra subs now or later? I do not think a nearfield sub should be your primary subwoofer (boxed or IB). The muffled sound of a blocked driver is a great secondary subwoofer but the sound profile is too compromised to be the primary sub. If your goal is stealth appearance, great sound and great impact, then have multiple IB at the front, and a few nearfield subs to augment the impact (ideally the nearfield subs would be under your chair in a riser firing up into your bum). That would be the most expensive option but the best sounding. If your goal is to keep costs lower and you don't want to deal with nearfield subs, then start with one ported 18" driver and run it bridged on a 2 channel amp, then add a second identical ported 18" sub and run one sub off each channel. That way you only have to buy one amp. You would give up the ultra low frequencies but it would still sound better than anything you or your friends have had (especially if it's a DIY sub). If you go the latter route, do your research to figure out what driver you want, then get a flat pack to build the enclosure. Definitely don't go any smaller than an 18" driver (either IB or ported). That my 2¢.


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This is great info and I appreciate your input. I do want to phase in the sound system over time, so I like your idea of starting upfront and moving to nearfield over time if needed/desired.

Thank you.

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post #29 of 29 Old 07-22-2019, 07:29 AM - Thread Starter
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The backchamber of a IB is basically the inside of a huge sealed sub, not impossible but needs good planning and execution to minimize LFE transference.
Your on the right track.

My utility room is my backchamber, it's lined with 9" pink fluffy all the walls, and I did my best at sealing so the wave would not leak out.
Honestly at "normal" HT listening levels , -15db MV, it totally works can't really hear it on main floor.
However when you run say -3db or 0db MV it does transfer upstairs thru the home.




No matter what, containing LFE is not practical unless your room is a sealed concrete bunker, only a few I know have done that.


Read this on SBA
https://www.avsforum.com/forum/19-de...ter-build.html


If I had a re-do on my home, I'd have put the HT under the garage, and fully encased the 4 walls with engineered foundation walls with a 30" IB chamber up-front and use (4) 24" SI drivers and then 36" deep rear for absorption depth.
engineered foundation walls have studs 24" on center which helps absorb above 20hz energy.
For my HT, I used 2x6 and offset stud construction, so all 4 my walls have drywall on 24" centers.


Going the IB route, if you choose a line-array on the bottom that helps by anchoring it to the floor and also having braces from your wall front to the back wall.
Or, using a IB manifold will allow cancellations of speaker cone movement.

Consider how you will get into your IB backchamber to install/service.
Wow, great real world experience and thoughts here. I appreciate it. Your room is awesome and I appreciate the work it took to take out concrete to open up the back of your array.

I can see how a concrete bunker would be the best to start out with, but most folks don't get that opportunity. My room is full of compromises as it is an odd shape (open concept) and is multifunctional. I am trying to best I can and all the input from you and others from AVS are a huge help.

I think I am heading down the IB route, so I will keep in mind the anchoring and future access.

One question on lining the space with insulation, how is that mounted/hung from the walls? I am not sure how to do that.

Thank you.

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