Infinite Baffle subs build in the Bat Barn

[Shockabuku]

Hi all. I thought I'd start a new thread in the subs forum to detail my infinite baffle build that I've been covering in my DIY build thread (link in my sig). There don't seem to be very many IB builds here in the UK, so I hope this might be of interest to some of the bass heads on here .

No prizes for guessing that forum member Nimby put me onto the idea of infinite baffle sub designs. From there, I spent a lot of time scouring the Infinitely Baffled forums for builds ideas, and finally I'm now building my very own own monsters of sub-bass

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1. The room
I'm nearing the end of converting the upper floor of a ~200 year-old detached barn into a dedicated home cinema. The room measures 31ft x 15ft x 14ft max (vaulted ceiling). Here's how the room started out...

..and here's how it's looking at approx 80% completed...

2. The subs
A room this size was always going to stuggle with "conventional" subs, and I really don't have the budget for 4 x PC-13s, so for about the price of a single PC-13, I'm building two IB enclosures, each of which will house two 18" Fi Audio IB specific drivers. Fi are pretty much the only company on the planet currently making IB specific drivers, and as such they're not the easiest things in the world to obtain! After a few months of trying, mine are finally on a boat from America, and are expected to arrive in the UK next week . You can see details of the drivers HERE.

[Shockabuku]

3. The manifolds
The ground floor of the barn is of course a similar size to the upper, with an approx 8ft ceiling. My plan is to mount the two manifolds to the ceiling of the ground floor, firing up into the cinema room. Obviously, this will involve cutting holes in the floor of the cinema room, which in fact is the next job on my list .

As of today, I've built the manifolds & other than some priming and painting, they're pretty much ready for the drivers. I'm following the recommended build from the Infinitely Baffled sub nerds, which involves a double-skin box, 18mm ply laminated to 18mm MDF.

Here are some images detailing the build process. First, putting the MDF panels together...

Ply panels going in...

MDF base in place...

Interior joints filled...

And here are the manifolds, awaiting some attention from a router...

Next comes the hole cutting. First, I marked out the widest point with a low budget compass...

A woodworker friend of the family came around with his router to help out. Here he's making a circle cutting jig...

Luckily we've had some respite from the rain today, so we could make the dust outside...

First a recess in the MDF, half an inch deep...

Next, change router bit & cut out a 16 3/4" hole through the MDF & Ply...

And here they are, all cut & sanded down...

They certainly weigh a lot less now, although that'll change when 64lbs worth of drivers are inserted into each manifold .
Here's a shot of the bottom of the barn, where the manifolds will be mounted...

The manifolds will be fixed to these beams. As you can see, they'll need a bit of sorting to get them nice & level, and I suspect some expanding foam will come in handy to ensure a good seal between back & front of the subs...

Fingers crossed, the subs should arrive next week sometime, and then the real fun starts. In between now & then, I need to think about cutting some holes in the floor .

[suniil]

Now that's something serious

Glad you picked the right choice of driver! Shame, I'm in discussion wtih Scott (FI Car audio) and thinking of getting the stuff in sea pallet to reduce the freight. We could have imported together

Anyways looking forward to see the progress pictures, and you would be the proud owner an IB with dual 18" drivers

[AngelEyes]

That barn is gorgeous, what a fantastic cinema room. Thanks so much for sharing and do keep it coming

Out of interest have you chosen your positions for the IBs? I assume at this stage you have some flexibility so it would be worth doing some calculations to get the best positions to avoid room modes... having said that the vaulted ceiling will probably inject a whole new dynamic, hopefully positive

What amps and EQ are you planning to use?

When can wee come round for a listen

Adam

[AngelEyes]

Originally Posted by suniil

Anyways looking forward to see the progress pictures, and you would be the proud owner an IB with dual 18" drivers

I think he will have 4 drivers in total, 2 in each enclosure, right?

[Russell.Williams]

Just when you thought it was safe to go out again.....

To echo Adams thoughts, what a fantastic room. Puts me in mind if the house we bid on and lost last year.

Originally Posted by AngelEyes

That barn is gorgeous, what a fantastic cinema room. Thanks so much for sharing and do keep it coming

Out of interest have you chosen your positions for the IBs? I assume at this stage you have some flexibility so it would be worth doing some calculations to get the best positions to avoid room modes... having said that the vaulted ceiling will probably inject a whole new dynamic, hopefully positive

Just what I was thinking. I'd have thought the quarter points were the place to start, but with so little actual wall, I'll bet it measures pretty damn well anyway. It would be easy enought to find out as a DF sub placed on the floor would be very close to mimicking the upward facing manifold. I'd certainly be interested to see how it measures currently.

I'm also interest to know why you settled on a 2x2, rather than 1x4 manifold.

Lucky sod.

Russell

[cribeiro]

Gorgeous!

I'd be worried about possible structural damages, though, if those beams are really 200 years old

[AngelEyes]

Originally Posted by cribeiro

Gorgeous!

I'd be worried about possible structural damages, though, if those beams are really 200 years old

They don't build em like they used to, I wouldn't give it a second thought

Also interested in the rest of the kit, it looks such a large space for those standmounts to fill, however I must confess I don't know what they are

I really am impressed with the project, this really epitomises Home Cinema for me, glorious building with bags of character and seriously mental kit

Very jealous

Adam

[suniil]

probably, for structural safety . I'm sure mark has borrowed nimby's brain too for 2x2

Originally Posted by russ.will

I'm also interest to know why you settled on a 2x2, rather than 1x4 manifold.

Yes, my bad reading!

Originally Posted by AngelEyes

I think he will have 4 drivers in total, 2 in each enclosure, right?

[Shockabuku]

Thanks guys, I'm certainly having fun with this part of the project . Regarding placement, I've done the "sub at the seating position, crawling on the floor" trick, and actually I found the room to be fairly flexible in this regard. I also have to consider the aesthetics of holes in the floor - and safety - I have a young daughter. So, they'll be located in between the main LR speakers and the centre speaker, which will keep things tidy.

I went for two manifolds of two drivers each, rather than 1x4 following some discussion on the Infinitely Baffled forum. There are potential issues with delay due to the drivers lower down the stack, but I don't think there's a lot to decide between the two really, but two just made more sense to be, and I think should provide more chance of an even sound signature for all listening positions. I also prefer the aesthetics of two smaller boxes, and my back was weeping at the thought of a single huge manifold with 4 drivers!

To be honest, I think the barn will definitely be the weak point in the whole setup...based on what I have read about similar IBs, I suspect I could do some damage if I turn the gain up a litle too much . I'm just hoping I can turn it up high enough to enjoy before things start breaking .

Ah yes, amplification. I have a T.Amp TA2400 MK-X, which will feed 1200w max into each manifold...

I also have a Behringer BFD which I'll be using with REW to calibrate the setup once installed.

The vaulted ceiling is indeed a bit of a head-scratcher, acoustically. Following a recommendation from a knowledgable forum member, I've done a load of acoustic panels to absorb some of the stray reflections up there. Obviously it won't have much if any effect on sub-bass, but in theory should improve the higher frequencies...

[AngelEyes]

Originally Posted by Shockabuku

Thanks guys, I'm certainly having fun with this part of the project . Regarding placement, I've done the "sub at the seating position, crawling on the floor" trick, and actually I found the room to be fairly flexible in this regard. I also have to consider the aesthetics of holes in the floor - and safety - I have a young daughter. So, they'll be located in between the main LR speakers and the centre speaker, which will keep things tidy.

I went for two manifolds of two drivers each, rather than 1x4 following some discussion on the Infinitely Baffled forum. There are potential issues with delay due to the drivers lower down the stack, but I don't think there's a lot to decide between the two really, but two just made more sense to be, and I think should provide more chance of an even sound signature for all listening positions. I also prefer the aesthetics of two smaller boxes, and my back was weeping at the thought of a single huge manifold with 4 drivers!

To be honest, I think the barn will definitely be the weak point in the whole setup...based on what I have read about similar IBs, I suspect I could do some damage if I turn the gain up a litle too much . I'm just hoping I can turn it up high enough to enjoy before things start breaking .

Ah yes, amplification. I have a T.Amp TA2400 MK-X, which will feed 1200w max into each manifold...

I also have a Behringer BFD which I'll be using with REW to calibrate the setup once installed.

The vaulted ceiling is indeed a bit of a head-scratcher, acoustically. Following a recommendation from a knowledgable forum member, I've done a load of acoustic panels to absorb some of the stray reflections up there. Obviously it won't have much if any effect on sub-bass, but in theory should improve the higher frequencies...

The crawling around 'myth' won't really tell you a great deal, so I would ignore any advice based on that little gem.

Room EQ wizard should be the order of the day along with Russells suggestion of using DF subs in the proposed locations to give some idea of room response.

It may sound like a 'faf' but all that effort in construction resulting in a hideous room response at the seating position will be a lot worse There is after all only so much a BFD can do to help.

From what I have gathered the vaulted ceiiling should actually help quite a bit but you won't actually know until you run some sweeps.

Not sure on your aesthetic tastes but there is nothing stopping using some sturdy grates/grills to cover the IB vents so they are safe to walk over. The only real issue you have to worry about then is how it impacts on the floor below

Adam

[Russell.Williams]

Originally Posted by AngelEyes

Also interested in the rest of the kit, it looks such a large space for those standmounts to fill, however I must confess I don't know what they are

Sonus Fabers mate. Beautifully crafted Italian speakers designed for the highest quality accurate reproduction. Nothing that would interest you then.

Russell

[AngelEyes]

I am guessing you have a Sony Projector there, and forgive my ignorance but 2.35:1 is the more common 'cinema' ratio right? Do you need an Anamorphic lens for that?

If I were to have a dedicated room I think I would opt for a true 'widescreen' option rather than 16:9. Any negative issues with this kind of setup?

Sorry for the questions, you ahve just rekindled my interest again

Adam

[AngelEyes]

Originally Posted by russ.will

Sonu Fabers mate. Beautifully crafted Italian speakers designed for the highest quality accurate reproduction. Nothing that would interest you then.

Russell

Silence wuffian

Don't tell anyone but I have been considering demoing some 'non' M&K speakers

Adam

[AngelEyes]

Originally Posted by russ.will

Sonus Fabers

They do look rather lovely, not the model you linked to though, these look front ported?

Adam