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Discussion Starter #1 (Edited)
http://www.hometheatershack.com/forums/ib-infinite-baffle-subwoofer-build-projects/48481-dayton-ib385-8-15-sound-quality.html ....(this link will take you to my thread "Dayton IB385-8 sound quality?" which is a precursor to this IB Fi18 build, it explains how I derived at these drivers)





Here's my IB sub build almost done, still doing the finishing work now.
Just wanted to get some pics up as soon as I could, will add more pics and more writing soon:

IB sub in attic, 2 FI IB318 drivers.

SUB BOX BUILD:
-dimensions,, exterior is 22.5" on all sides
-double layer of OSB
It's not a very pretty box, the only tools I had was an electric drill, a circular saw, and a sawzall. I didn't care too much about it's looks because I plan on covering the opening with fabric.
Normally a 24" box is made to sit on top of the rafters, but my attic doesn't have enough room to accommodate a box this size to be moved around. So I had to cut a hole in the living room ceiling the width of the rafter spacing (22.5") and push the box up into place.

AMPLIFICATION/WIRING:
-450w from ATI AT1506 amp
-2 drivers wired in series
Before firing the new system up, I was just going to use the ATI amp temporarily, I didn't think 450w feeding 2 drivers would be enough. But after the calibration I found that to get proper SPL levels, the LFE gain control (LFE volume) in the Onkyo AVR only had to be set to 0 (neutral). So 450w is obviously enough power. Also, having my main amp control the sub works well because it is always on when the system is being used. Both of my older subs that have built-in amps with auto on-off circuitry have trouble staying on when getting lower volume signals.

EQ/SETUP:
-Rane ME 60 graphic equalizer (1/3 octave, 25-20KHz)
-Audyssey MultiEQ
-main/center speakers crossed over at 80hz
I placed the IB sub at the center of the room (ceiling). This location gave me the most equal SPL readings around the room. Placing the box toward the side wall (where the blue "X" is on the ceiling) would have yielded alot of room gain and would have been very impressive sounding at the listening postion, but the SPL's dropped off significantly when listening toward the opposite side of the room. I am into proper/accurate/level sound, so the middle of the room was the best placement for me. Now I can walk around anywhere in the great room and it mostly sounds the same (I definitely could not say that when using my old subs).

EVALUATION:
Of course it sounds great and accurate. There is a huge difference in sound and feeling between this IB sub and my other regular boxed subs. I would have to say the IB sub is a little less exciting, it has a great feeling of sound pressure with light rumbling. The regular boxed subs have great rumbling and add much more drama when watching movies. Much of the difference is because the IB sub has 2 drivers facing each other, cancelling out most vibrations. The regular boxed subs have single drivers facing the floor and they really shake/vibrate everything, no need for butt-kickers on the couch with those. Musically, the IB sub really shines.
But this isn't to say that I am disappointed with the IB sub. I am very happy and will not go back to the regular boxes.

...More info at posts #4 and #5...
 

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Looking good.:T

The regular boxed subs have single drivers facing the floor and they really shake/vibrate everything, no need for butt-kickers on the couch with those.
Maybe you now have better placement for sub and it doesn't cause same room modes around listening position. Usually it's room mode peaks that makes things rattle.

Or you can have some dips with IB, caused by placement.

Any measurements before vs after?

It could be that you are now evaluating more two different placement than two different subs.
 

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Discussion Starter #4
Maybe you now have better placement for sub and it doesn't cause same room modes around listening position. Usually it's room mode peaks that makes things rattle.
Or you can have some dips with IB, caused by placement.
Any measurements before vs after?
It could be that you are now evaluating more two different placement than two different subs.
When I got more time I was going to talk about placement and eq'ing.
PLACEMENT: the new IB sub is definitely in a better place for more even sound around the entire room. If you noticed the blue "X" on the ceiling near the wall, that was another optional placement area. That area closer to the wall would've given much more gain at the listening position, but also the SPL's dropped off very fast when listening a the opposite side of the room. So the placement I chose, in the middle of the room, gives very equal SPL's throughout the entire room, best for all listening positions.

MEASUREMENTS/EQ: I don't have REW set up yet but I do use a SPL meter, test tones, and outboard eq to level out the freq band. As far as room modes and nodes, obviously there are with both of the new and old sub setups. The old subs had much bigger modes/nodes outside of the listening area. But I can tame those at the listening position with the eq and the couch still shook much more with the old subs.
With all subs being eq'd, if you stand next to the old subs, the floor vibrates and shakes. Put your hand on the ceiling next to the new IB sub and you don't feel much of anything.
Also the feeling of the sound pressure wave that hits your head is different and much more intense with the IB sub.
 

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Discussion Starter #5
Good work Glen, have you fired it up yet?
Yes, I'm watching movies instead of finishing the screen to cover the opening.
The first movie I compared was Thor. I just happened to watch Thor the night before installing the new IB sub, then Thor was the first movie I watched after setting up the new sub.
Watching Thor and Master&Commander first gave me a bit of doubt at first. The new IB sub didn't give me the same intense rumblings and vibrations that the old subs gave. I kept thinking maybe my eq setup was wrong, and 3 times I went back and re-checked the freq response with my equipment, it always measured flat, exactly the same as the old subs. I figured this just must be that clean sound of "hearing the bass not the box."
Then I listened to music with low freq instruments that I know how they should sound. Well, all those bass freq that I thought were low or missing when watching Thor, came alive with music. Pipe organ, string bass, electric bass, kettle drums, double bassoon all represented themselves perfectly.
For movies with the IB sub, I guess now I'm hearing/experiencing more of how the bass was meant to be presented. Maybe the old subs added extra stuff with the sound of the boxes and the extra shaking and vibrating.
I'm very happy now.
 

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Glad to hear your starting to enjoy a new style and setup of subs i'm fixin to do an install with 4 of them bad boys and can't wait for the results.:yikes:
Great job!:T
 

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Great work Glen. I think you may well find things change in the rumbling stakes once run in. My IB certainly has a lot more kick now than when first installed.
 

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Discussion Starter #9
This week I did boost the 40-50hz range on the eq by just 1 or 2 db and that made a difference. Really enjoying this.
Enjoying this a little too much as I still haven't finished the covering for the hole, although I have made more progress. Almost finished last weekend but found the magnetic strips weren't strong enough to hold the cover in place. The wife brought home some Velcro so will try that very soon.
Then I will snap some more photos and add them to the first post with the other photos.
 

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Discussion Starter #11
Actually I finally got the cover screen in place recently. It still needs a little more finishing work to look perfect, but it's up there. I used a white aluminum frame screening kit with some white muslin cloth since I couldn't find actual white speaker cloth ( http://www.wikihow.com/Make-a-Window-Screen ).

I've been busy changing stuff up a bit with a new plasma tv and downsizing equipment by taking the external equalizers out of the system. I'm on vacation this week and hopefully can get some new pics in here.

The amplification is still the same with a single channel from my ATI amp feeding 450w to the 2 drivers in series. This set up is working very well and I don't feel any need to change it.

I love the sound of the IB subs and my earlier descriptions still apply today. With the IB sub, there is a greater feeling of pressure but there is slightly less physical rumbling compared to the old sub boxes. Both of my old sub boxes had downward facing drivers which would physically vibrate and shake up and down with alot of action. The IB sub has 2 drivers facing each other which causes the physical back and forth shaking to cancel out, making for a vibration-less box.

If I ever have to move to a different house, I will make sure the living room is an area that will accommodate an IB sub.
 

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Is the cabinet size the same size as your rafter spacing? No structural bracing was required?
 

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Discussion Starter #13
The cabinet fits snugly between the rafters and is secured to them, so no extra bracing needed.

Many IB installations make the width of the sub box the same as the rafter so the sub box sits on top of the rafters, but my attic is so cramped that the box could not have been brought into the attic and then moved into place, so I had to cut the access hole in the living room ceiling and push the box up between the rafters at it's mounting position.

Maybe I can get some pics of the attic space.
 

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The cabinet fits snugly between the rafters and is secured to them, so no extra bracing needed.

Many IB installations make the width of the sub box the same as the rafter so the sub box sits on top of the rafters, but my attic is so cramped that the box could not have been brought into the attic and then moved into place, so I had to cut the access hole in the living room ceiling and push the box up between the rafters at it's mounting position.

Maybe I can get some pics of the attic space.
Thanks, I had a feeling that was why there was no bracing involved in the build.
 

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Discussion Starter #16 (Edited)
Upper bass (120hz) is no problem for the IB with 18's. Sounds very good.

Before installing my IB 18's, I had the same concerns, thinking of some elaborate setup involving an added 12" driver and crossover that would direct upper bass to the smaller 12 and then direct lower bass to the bigger 18's. But after listening to the 18's, they handle upper bass surprisingly well and evenly. No need for a smaller driver.

As with my old normal sub boxes, I still think the mid/upper bass performance is slightly better with my main speakers (JBL Studio S312), so I usually use a crossover setting of ~50 or ~60 hz, always experimenting. The only time I can hear that the main JBL S312's sound better is when listening to material that is specifically made to test the performance of the bass region, such as solo electric bass guitar or upright string bass. With normal full range content, the difference is not noticeable. If I had less capable main speakers, I would have no concerns with using a crossover of 80hz or even slightly higher, the 18's can handle it adequately.

Thoughts about lower sub bass (using 2 or 4 drivers):
The physical layout of my ceiling and rafters limited my IB box to using 2 drivers instead of 4. The 2 drivers definitely are adequate for the majority of listening, but some soundtracks would definitely benefit from using 4 drivers. Some soundtracks (Tron 2, Thor, The Hunger Games) use such low frequencies at such high volumes (and where the sub bass is alone and not mixed in with higher frequencies), that the 2 drivers are working very hard and you can actually hear the drivers working. 4 drivers would help to lessen the work needed by each driver.
 

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i remember the first time i heard an ib sub.similar to this a few large drivers in wall.it was an awesome experience.i bet you sure are enjoying yours.
 

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Discussion Starter #18
I'm enjoying it immensely. Hopefully my neighbors are not annoyed by it immensely.
That reminds me that I need to do a sound check by playing super loud bass and going outside to make sure it is not escaping the attic too much.
 

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I'm enjoying it immensely. Hopefully my neighbors are not annoyed by it immensely.
That reminds me that I need to do a sound check by playing super loud bass and going outside to make sure it is not escaping the attic too much.
i just noticed your location.thats where my sister lives.
 
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