# Need help with box



## auburnu008 (Dec 21, 2006)

I am wondering if someone can comment on the box I have planned. I am about to build 2 boxes housing 8 MJ18's. Each box will be 40"x48"x20" (length, height, deep) I am limited on those measurments with my back wall. I was going to mount the drivers the way the pics are and was wondering if I would get any kind of phase problem or anything else. I picked this way so the 2 subs on the front will be firing below the screen into the section covered by AT fabric and the 2 subs on the side will be firing next to my mains. I know it is best to mount the drivers in opposite directions to eliminate movement, but they would be firing right into my screen. They would also be firing right into my screen if I made a wall of them firing frontwards. Does anyone see anything wrong with the way I have planned? Each box will be roughly 16 cubic feet. I appreciate any help I can get! Thanks alot.


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## Darren (Apr 20, 2006)

It is hard to tell from the drawings but be sure your drivers have at least 12" of clearance to breathe. I'd want more clearance but that would be my minimum. It's the ones in back that I'm worried about.


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## JCD (Apr 20, 2006)

I agree with Darren.. also, I think it may be better anyway if you put the two pairs of drivers on opposite sides of the box rather than adjacent sides like you have it.

I'm also assuming the internal volume of the boxes is correct.

JCD


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## Sonnie (Apr 11, 2006)

You stated 2 boxes to house 8 drivers, but I only see 2 per box shown in your drawings.

Have you modeled the drivers to make sure the box size is appropriate?


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## brucek (Apr 11, 2006)

> It is hard to tell from the drawings but be sure your drivers have at least 12" of clearance to breathe.


Can you expand on that Darren. 

I've read conflicting information on this, and am interested since I have my Servo-15 sub in a corner facing a side wall with about 4" of clearance. 

Surprisingly, It seems to produce the best response while avoiding exposing the business end of the driver to toys thrown by my grandson.  

How would you account for sonotubes that have the driver mounted horizontally and upside down with about 4" to a bottom plate?

I don't think this is off topic, as I think it plays directly into what auburnu008 wants to know... hopefully Darren or others can answer.

brucek


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## JCD (Apr 20, 2006)

I have to admit tha I was thinking of ports when I said "I agree".. I still think it would be better if the drivers were located on opposite sides of the box though.

JCD


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## Darren (Apr 20, 2006)

brucek said:


> Can you expand on that Darren.
> 
> I've read conflicting information on this, and am interested since I have my Servo-15 sub in a corner facing a side wall with about 4" of clearance.
> 
> ...


I ain't got no evidence  Just advice I picked up from others along the way. I don't think it is a huge issue but basically what I'm concerned about is the force generated from the pressure wave bouncing off of the opposing wall interfering with the travel of the cone a bit.

As far as the downfiring subs... I had one and it was about 5" from the floor like you describe. It worked well, had plenty of room to breath out the sides so it may be a moot point. Dunno. I do know that it behaved very differently when I oriented the driver forward on that particular sub. In my case the downfiring configuration was beneficial.


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## Darren (Apr 20, 2006)

Sonnie said:


> You stated 2 boxes to house 8 drivers, but I only see 2 per box shown in your drawings.
> 
> Have you modeled the drivers to make sure the box size is appropriate?


 
He's got two out the sides and two out the back of each box.


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## Sonnie (Apr 11, 2006)

Darren said:


> He's got two out the sides and two out the back of each box.


Okay.... yeah... I see now that you mention it.


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## auburnu008 (Dec 21, 2006)

Thanks for the help guys. I am leaning towards having all the drivers face forwards. Would this interfer with the screen (making it shake, ect)? I could either have them all face the screen or all face the back wall. If they were facing the wall, the clearence would only be about 3". Thanks again.


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## 1Michael (Nov 2, 2006)

As a general rule of thumb if you can have 2 feet space around the speaker that is ideal, however that is usually not always practical or possible so put them where you need to.


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## Rodny Alvarez (Apr 25, 2006)

auburnu008 said:


> Thanks for the help guys. I am leaning towards having all the drivers face forwards. Would this interfer with the screen (making it shake, ect)? I could either have them all face the screen or all face the back wall. If they were facing the wall, the clearence would only be about 3". Thanks again.



I think if you fired the subs down it will be the best choice, little bit more work but you don't have to worry about the screen moving because of the subs being so close to the screen. 
Is the screen perforated?
How much room do you have behind the screen?

:bigsmile:


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## Fred33 (Sep 4, 2007)

Never knew about the two foot rule. Learn something new everyday.


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## Guest (Sep 10, 2007)

This setup leaves only 4cuft per driver.. Unless you use a linkwitz transform or very heavy eq, it will have poor bass extension despite all these drivers.... such as -15db or -18db @20hz (V/S).


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