[chadci]

Hey guys,

I'm trying to iron out the details of my next IB build. Shortly after we moved I sold off my previous system planning to use the funds towards my new build, well, life happened and it did not work out that way... back to the drawing board.

I had planned on doing a 4 driver manifold. This past weekend I had to get up in the attic and went to the spot where the box will go... I'm not sure a manifold will be doable after all.

I still want to run 4 drivers. I plan to buy 2 soon and then 2 more down the road ( after the holidays)

What would happen if I invert 1 driver, meaning, the one driver would have the cone facing the room, the other driver would have it's backside facing the room. WOuld I still get the mechanical cancellation as I would with an manifold? The way I see it, the driver is about 8" top to bottom so by the time you figure in the width of the joist plus 2 ( or even 3) sheets of MDF / Ply etc it should be up enough that I don't have a magnet peeking through my ceiling. I plan to use an air return cover to hide the drivers.

After having had an IB I don't know that I can really be happy with a box sub again... My wife thinks I'm crazy for wanting to cut a hole in the ceiling and she hated the old IB. The movie The Mist literally made her cry, that organ music got SO low... she could not handle it :yikes: but when it was normal level music / movies she commented on how much cleaner and clear it sounded.

 

[tenzip]

So you're talking about putting them in the wall (an array), rather than in a manifold, correct?
If so, no, there would be no mechanical cancellation. The cones would still be moving in the same direction at the same time, regardless of which side the cone faces.
I know there have been many successful arrays, so don't let that worry you overmuch.

 

[chadci]

It will be an attic mount. I guess I'm confused, though. If one cone is facing up and the other down, they would not cancel each others vibrations?

I've seen plenty of arrays and to those that say it's too much vibration, I wonder just how loud they are listening... I'm not an over cranker upper, but, I don't want cracks in the drywall either.

I'm trying to figure out how to do a manifold... I was very happy with my last one... Still have it in the garage, maybe I should just mod it to fit... that's if I can get it up to the attic!

 

[thxgoon]

If so, no, there would be no mechanical cancellation. The cones would still be moving in the same direction at the same time, regardless of which side the cone faces.

Just be sure to wire the subs properly so that they still fire in phase with the room.

 

[chadci]

Are there any 12's that would work in an IB application? I could do 8... 2 per side of a manifold... My big issue is going to be how tall a manifold will have to be to support 15's or 18's.

 

[tenzip]

First, in an array, the drivers will all be mounted in the same plane, so regardless which direction the cone/basket faces, you need to have the cones moving in phase, that is, all in (to the room) together, so the moving mass of cone and coil will be moving the same direction even if you have one facing each direction. Clear? The only way that I know of to cancel the mechanical forces is to mount the drivers in a manifold, so when they both move in together, one is going thisaway-> while the other is going <-thataway.

Second, you can cancel some portion of the mechanical forces if you angle the sides in to each other a bit. The walls of the manifold should not have to be parallel to each other. My physics is rusty, but I believe if you made a right triangle manifold, with the base being the ceiling, you'd only get 75% of the mechanical force a 'normal' array would produce. Vectors were never my favorite. The closer to parallel the sides of the triangle get, the less mechanical force would transfer. Although I think it unlikely, you might get some weird bandpass or compression effects if you had a skinny 'A' shaped triangle manifold. I'd ask here and at the Cult, Thomas is Da Man for IB, IMO.

I'd go for it either way. Maybe if you take some pictures of the attic space, and have a piece of cardboard the size/shape of the manifold in place for scale, we can make some more suggestions.

 

[chadci]

Well, I'll get a shot of the attic up in a bit, it'll be the weekend before I can make it into the attic to really mark the spot. I will mark the spot in paint or something before posting.

That's for the assist, that makes perfect sense now that you put it in first grader terms :lol:

 

[tenzip]

Well, I'll get a shot of the attic up in a bit, it'll be the weekend before I can make it into the attic to really mark the spot. I will mark the spot in paint or something before posting.

That's for the assist, that makes perfect sense now that you put it in first grader terms :lol:

NP, these things can be counter-intuitive.

Paint would work, but I think a cardboard mock-up, or even a 2d cutout would help even more to picture your issues with the space. Just get a big piece of cardboard and cut out the size of your manifold, then it's easy to see where it or the drivers might interfere with framing, etc.

 

[chadci]

Great idea about the cardboard cutout. I might give that a go this weekend.