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Old 30th October 2009, 09:22 PM   #1
asiquis is offline asiquis  Canada
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Default Sub box shape an issue??

Designing an entertainment unit that will also house my sub box.
Room is long and narrow 50 X 12 ft and 7.5 ft high (basement)
Amp: BASH 500 watt with 12.9hz high pass
Driver: Exodus Audio Tempest-X 15"

Looking at an "L" shaped box:
24" H X 26" depth X 24" width (the driver will face the corner of the room about 4 feet from the corner on the face of the box that measures 24"H X 26"D) however, I would like the box to have larger volume and I have enough room to continue the next 24" of width at 15" H and still 26" of depth.
So, overall 48" wide and 24" high and 26" deep with a notch out of the one side with the back of the Tempest X toward the notched part of the box.
Will use 3/4 inch baltic birch plywood.

I could run sealed as I do not think I will have enough volume with a big port in there but will have little room gain.
Will the shape make a difference?
Might you see any flaws in this approach?
Should I mount the driver midpoint or closer to the floor?
Suggestions?
Thanks
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Old 31st October 2009, 10:25 AM   #2
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There is only one main rule to box shape for subs: The longest dimension of the box must be less than one quarter wavelength at the highest frequency the sub will be used at. If the box is "L" shaped, add the lengths of the two parts of the "L" together.

In your case, the longest dimension appears to be 48 inches.
You'll have a resonance problem at about 72 Hz.
(longest dmension, times 4, divided into speed of sound in feet per second.)
You need to make the box shorter if you can.
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Old 31st October 2009, 11:31 AM   #3
breez is offline breez  Finland
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Stuff it with damping material and the 72 Hz resonance won't be a problem.
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Old 1st November 2009, 03:10 PM   #4
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Let's not get into debates about stuffing.
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Old 1st November 2009, 03:43 PM   #5
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Quote:
Originally Posted by asiquis View Post

I could run sealed as I do not think I will have enough volume with a big port in there but will have little room gain.
Will the shape make a difference?
Might you see any flaws in this approach?
Should I mount the driver midpoint or closer to the floor?
Suggestions?
Thanks
This driver would not be a good choice for a vented design so sealed is the way to go. I believe you will want to keep the volume of the box to 250 litres or less (I'd make it 200L) and stuff it well. Going with a bigger volume will cause excursion problems, especially with a high power amp. As it is, this driver runs out of linear excursion in a 250 litre box at 500 watts for 40Hz and lower.
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Old 1st November 2009, 10:51 PM   #6
asiquis is offline asiquis  Canada
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This from the website:
Exodus Audio Tempest-X Application Guide 5
Copyright Ó 2007 Exodus Audio. All Rights Reserved.
200L (7 cubic feet) Sealed with 100% poly-fillI love large sealed subs like this, great extension, musical, good transient response and it reaches deep with a reasonable amount of power. The F3 is just under 26Hz but the rolloff below that point is shallower . Can you tell I’m a big fan of large subs?  Nothing really more to say, load it up with about 100oz. of poly-fill, brace it good and you only need the 500W PE amp to get this baby cooking.
I’d remove their subsonic filter or push it low as possible. You have plenty of protection provided by the acoustic high pass nature of the box as long if you stick with the 500W amp. Going up to 1000W is not needed.

How does the damping affect things (100 oz suggested)?
The F3 is just under 26 with this 200 liter box will I get any rooom gain with the size of room 50 x 12.5 X 7'5 (ft)? I was hoping to get down to 16-17 hz for organ music hence the thought of going ported, but this driver seems to like a big box!
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