Dimensions of manifold opening

[iansr]

OK some other questions if I may.

1. One of my (2) manifolds will be near a corner of my roof space. I will be using 2 drivers in each manifold. if I mount the drivers opposite one another as recommended then the back of one of them will only be a few inches from a wall. I assume that is not a good thing. I could however mount them at 90 degress to one another (so they are mounted on adjacent panels of the manifold) and they would then be both backing into open space. In that orientation would you still get the vibration cancelling effect? If both options are compromises, which is the better one?
2. The recommendation is to use a combination of MDF and OSB. Is that for CLD purposes? (Given that OSB is not that much more expensive than MDF and is stronger, I was wondering about using 2 layers of OSB instead.) Comments invited.

TIA

[ThomasW]

Jan 4, 2011 9:35:44 GMT -7 iansr said:

In that orientation would you still get the vibration cancelling effect?

No

If both options are compromises, which is the better one?

The one that provides the most clearance for the driver

2. The recommendation is to use a combination of MDF and OSB. Is that for CLD purposes?

No

(Given that OSB is not that much more expensive than MDF and is stronger, I was wondering about using 2 layers of OSB instead.) Comments invited.

Per the the Generic Deisgn/Build/Install FAQ page, OSB provides strength, MDF machines nicely.

You can use 2 layers of OSB but understand it splinters and chips easily.

[iansr]

OK thanks. Having them at 90 degrees is going to provide the most space behind the drivers, so I sacrifice the vibration cancelling benefit. So that prompts the thought, why complicate matters with a box manifold, why not just install the 2 drivers as a line array but in the ceiling rather than a wall? Or am I missing something??

[ThomasW]

As discussed on the main FAQ page, the pull of gravity shortens the life of horizontally mounted drivers

[iansr]

Thanks. I can't help but note your pointed comments re the FAQ etc. I would just like to assure you that I have read all the generic infomation several times, but you should appreciate that there is a great deal of information on this site to assimilate, so I ask for your forebearance.

[iansr]

Re earlier comments on horizontal mounting: I intend to use the JBL GTO1514 drivers (others have been well satisfied with them and I can get them for £65 each). I've done the sag calculation and it comes out at 2.7% So I'm going to mount those 2 firing down from the ceiling.