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Post by fireanimal on May 5, 2007 6:10:04 GMT -7
Well after looking around on this site over the past week, I am hooked, and already started the ball rolling.
I have purchased a Crown Xti 1000 Amp, and have been in touch with Scott at Fi for 4xSSD-18 Subs. I will also be getting a BFD to EQ the room.
Originally I was going to install two manifolds with two drivers a piece into the ceiling, but after measuring my Attic opening, I realized that the Manifold opening size would have to be around 50" Long just to have an equal area as the 18's.
So I decided that I would do a Line Array on a Baffle Board.
I have a cathedral ceiling in my room, and want to balance the drivers evenly from the peak, on the left and right side. But because of space problems in the attic, I can only put 1 driver per baffle board per Truss Space. So what I will have is two drivers each on its own baffle board on the left and right side of the peak. The first will be installed 2 ft from the front speaker wall, and the next around 3ft from the front speaker wall.
The ceiling is 9ft at the walls and 12ft at the peak, so it is not to steep, but I am worried that I will have problems because the drivers will be firing at angles into the room.
If anyone has any suggestions, or recommendations please let me know.
Thanks
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Post by ThomasW on May 5, 2007 7:28:42 GMT -7
You can use a manifold, the opening doesn't need to be 50" long. If you look in the gallery you'll see the picture shown below. This is a manifold with 4-18"s mounted in a box roughly 24" square. And the drivers in that picture have significantly more Vd than the Fi SSD-18"s. You could also use two smaller manifolds, each containing 2 drivers.... Regarding your question about the angles of the installation you propose, bass waves are so long the differences in angles make no difference.
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Post by htnut on May 5, 2007 9:32:46 GMT -7
Perhaps you could provide additional room for a manifold by putting a flat across the ceiling where you want the IB sub. You could even mimmick that flat at other points along the ceiling to look like structural beams.
When I look at the SD for an 18 inch Mach IXL the square opening to prevent compression is 26 inches. For the Fi 18s it is 27 inches.
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Post by fireanimal on May 5, 2007 9:40:26 GMT -7
Oh, I was under the impression that the opening had to be the same area as the drivers that you are using, or you will be reducing the output.
For example, if I used a manifold it would have a internal dimension of W15"L22"H22" for an opening area of 330sq/in. The diaphragm area of 2 SSD18 would be 372sq/in approx, thereby loosing the potential of 42sq/in of area.
I may be wrong in this assumption, or that little amount may not matter, I just want to make sure that I use all the driver that I am paying for ;D
Thanks
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Post by ThomasW on May 5, 2007 11:07:54 GMT -7
In the FAQ I willfully error on the side of recommending too large a opening just to compensate for the all too frequent requests for WAY to small an opening.
A somewhat smaller opening doesn't decrease the output, it changes a different parameter, but you don't need to be concerned with that if you use an approx 24" cube.
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Post by fireanimal on May 5, 2007 14:35:19 GMT -7
My problem is I can't use a 24" cube, that is the size I was originally planning, but to be able to get it in the attic, my max opening size would be 15"x22".
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Post by fireanimal on May 5, 2007 14:58:53 GMT -7
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Post by ThomasW on May 5, 2007 15:29:39 GMT -7
My problem is I can't use a 24" cube, that is the size I was originally planning, but to be able to get it in the attic, my max opening size would be 15"x22". Do two manifolds with that size opening.
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Post by fireanimal on May 5, 2007 20:02:49 GMT -7
Here is a drawing of the manifold that I would have to build if I go that route. I understand the benift with the manifold is the mechanical cancellation of the drivers, but I am still unsure why I should proceed with the manifold versus the line array? Thanks
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Post by chrisbee on May 6, 2007 0:46:25 GMT -7
Manifolds reduce the opening required in the ceiling (or wall or floor).
If covered with screens manifolds become invisible to WAF concerns. It depends whether you (or a partner) want to see your drivers.
Do not underestimate the vibration cancellation benefits of opposed driver manifolds. From my own experience with my modest 4 x 15" I would never build another array. The reduction in vibration going from an array to a manifold is quite simply unbelievable. As is the massive increase in output I have obtained. Particularly at the bottom end which I could never lift by electronic means or structural stiffening around my array. I can't imagine fighting with four longthrow 18" drivers in an array. The house would probably have collapsed from the mechanical vibrations! The manifold solved all my problems with a single sheet of 3/4" plywood and few hours making sawdust out in the sunshine.
It is galling to think how much time I wasted trying to improve my array. When I could have been enjoying my present performance from day one.
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Post by kadiddle on May 6, 2007 5:55:38 GMT -7
My problem is I can't use a 24" cube, that is the size I was originally planning, but to be able to get it in the attic, my max opening size would be 15"x22". I had the same problem with my manifolds. Build it in the shop but do the final assembly in the attic so that you can get the parts through your small attic opening. kadiddle
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Post by fireanimal on May 6, 2007 6:56:22 GMT -7
Looks like manifold is the way to go. I would prefer to assemble in the garage and then just install the drivers in the attic.
Is the manifold drawing, with that size opening acceptable, for the two SSD18's.
Thanks for everyones help.
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Post by htnut on May 6, 2007 9:01:20 GMT -7
That design should be just fine.
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Post by chrisbee on May 6, 2007 12:07:17 GMT -7
Double check your exact joist spacing at the installation site(s) before you start work on your manifolds. (you never know)
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Post by fireanimal on May 6, 2007 14:25:48 GMT -7
Here is the final design. If you see any problems with the measurments please let me know. The second picture shows the Ceiling joist, which I will be adding extra 2x4's to for extra support. The fine line in the center is the peak of the ceiling. Thanks for the help.
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Post by ThomasW on May 6, 2007 16:43:16 GMT -7
The design looks fine.
Don't assume the joist spacing is perfect or identical. Go up and measure each position before building the manifold.
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Post by fireanimal on May 6, 2007 18:13:52 GMT -7
Already confirmed the joist spacing, and have left 1/8" spacing from manifold to joist on each side. Thanks
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Post by ThomasW on May 8, 2007 7:14:50 GMT -7
You need to make sure there's adequate clearance for the magnets on the woofers.
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Post by fireanimal on May 8, 2007 12:38:06 GMT -7
The magnets will be running parrellel with the truss, lots of room!
Got the wood, and started to assemble the boxes. I tried to place my order with Fi so I can get my drivers on there way, but there is some problem with their email. Hopefully it won't be too long, those drivers will have to travel a long way to Canada!
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Post by fireanimal on May 9, 2007 17:35:57 GMT -7
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