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Post by stevessti on Jan 5, 2014 0:15:07 GMT -7
First off hello and thanks for the time that anyone gives me. My room is 15"6' x 18" with 8" ceilings, Right now I have 2 10' in a ported box down firing from my attic over the top of my TV. they are on a QSC amp with 500w at 4ohm witch I will use on the 18's, they are very loud but no low frequency output. My questions are, Will the 2 18s be big enough for the size of my room or should I build the box for the potential of installing 2 more 18s in the future? If I use 2 Fi IB318 in the same place as my subs are now will I still need the 10's or will the 18's play up to 80Hz? Is there a certain size that the box needs to be, also I saw a box that the was big enough for 4 18's bit it only had 2 and they were not directly across from each other,does that matter? Added pic of box in question. Thanks  |
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Post by ThomasW on Jan 6, 2014 7:21:21 GMT -7
A pair of 18"s should be adequate for your room. That said IMO it's always a good idea to build for potential expansion when possible.
Regarding the picture I think he did that to get the drivers closer together so the box wasn't too long. Symmetry of design/construction is what helps cancel the most vibrations.
No I wouldn't continue to use the 10"s, they'll just muddy up the sound.
Of course the 18"s will play to 80Hz, actually they'll play much higher than that but it's not a good idea to do so
Per the FAQ the box only needs to be large enough to accommodate the drivers, so 4-18"s can be shoe horned into a cube roughly 22" or so on a side
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Post by stevessti on Jan 6, 2014 10:48:50 GMT -7
So if I build the box say 13'1/2 to fit between the 2x6 rafters by 36'W x 48'T that should be a big enough box? Also I was going to mount one of the subs with the basket out and reverse the polarity if you think that is OK. Thanks for the help
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Post by ThomasW on Jan 6, 2014 14:43:28 GMT -7
Not sure why it would need to be so tall?
If you're starting with a pair of drivers, one/side the box only needs to be 22" or so taller than the joists.
If you're going to build it wide enough for 4 drivers 2 per side but start with 2 you'll need a partition to seal off the 1/2 of the box that isn't being used. We want the sound to exit the drivers and go immediately out the opening into the room. We don't want it bouncing around a 1/2 empty box.
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Post by stevessti on Jan 6, 2014 15:15:03 GMT -7
Sorry I said rafters instead of joists you were right on that, When I got home I measured the joists and they are 2 x 8 I at least need to be 9' to 10' above the sheetrock to mount the speaker. But I do understand what you are saying is to make the box as small as possible. One more thing is 1' MDF overkill because I see some boxes with two layers of wood? Thanks again
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Post by ThomasW on Jan 6, 2014 16:44:04 GMT -7
Per the design/build/install FAQ, 1.5" sandwich made from a layer of MDF laminated to OSB is intended to obtain strength and mass not available in either material alone
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