ScottG, check out this B&C 12TBX100 design - Page 2 - diyAudio
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Old 13th September 2006, 11:50 PM   #11
alexcd is offline alexcd  United States
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The concrete is definitely the most confusing part of the design. Thanks for the diagram of the sand but can you show the driver bafle?
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Old 14th September 2006, 12:04 AM   #12
ScottG is offline ScottG  United States
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Quote:
Originally posted by alexcd
..and I'll bust it over his head if he asks me to build one more thing for him.





Ok, here is a side view with the concrete (actually just cement) baffle.

The Key is the same except:

Light Grey = cement baffle. &,

The little bit of orange'ish color is actual still just mdf - this time however it is 1 inch instead of 3/4 inch mdf.

(..and note that 1 inch mdf isn't really a full 1 inch - this means that the air space that is to be filled with ultra fine sand should be almost exactly the same "thickness" as the actual dimension of the 1 inch mdf.)

I'll provide a view of that orange 1 inch mdf from another perspective in the next post.
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Old 14th September 2006, 12:10 AM   #13
ScottG is offline ScottG  United States
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Here is the "spacer" (orang'ish brown) portion of 1 inch thick mdf:

(..note that the ultra fine white sand is absent in the picture here.. its just the 1 inch mdf spacer on top of the 3/4 inch mdf "exterior" box panel. That same 3/4 inch mdf baffle would be on top of the cement baffle.)
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Old 14th September 2006, 12:14 AM   #14
alexcd is offline alexcd  United States
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Does the 1" MDF need to be square or will a circle work just as well?
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Old 14th September 2006, 12:17 AM   #15
ScottG is offline ScottG  United States
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Quote:
Originally posted by alexcd
Does the 1" MDF need to be square or will a circle work just as well?
A circle is fine as well - but its likely to be more work cutting the interior circle and then the exterior circle additionally.

Are things starting to look more identifiable?
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Old 14th September 2006, 12:30 AM   #16
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eh... the router would already be out.

I figure all this will add 250lbs per cab.
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Old 14th September 2006, 12:40 AM   #17
ScottG is offline ScottG  United States
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Quote:
Originally posted by alexcd
eh... the router would already be out.

I figure all this will add 250lbs per cab.
What do mean by the router being "out"? You'll need one for the circular cuts. You could get by with them using a saber saw, but I wouldn't recomend it! (i.e. beg, borrow, or steal one with a straight bit capable of more than 1 inch in depth.)

It might add that much weight, BUT you'll have a friend helping you with the sub inversion and placement after you have finished filling it from the bottom. (..obviously you'll only fill it *very* close to where you'll be placing it.)
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Old 14th September 2006, 12:49 AM   #18
alexcd is offline alexcd  United States
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I meant that I'll have my router out to cut that center circle anyways.

I'll ask him about the weight.

Which side do you suggest I fill it from? I can cut a hole in the base and plug later if that's the best option.
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Old 14th September 2006, 12:55 AM   #19
ScottG is offline ScottG  United States
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Quote:
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Which side do you suggest I fill it from? I can cut a hole in the base and plug later if that's the best option.
AH!

Time to go back and read the instructions *carefully*. You don't need to cut a hole in anywhere for the filling. The bottom exterior box panel is attached last AFTER filling with sand.

Remember, while the construction is very easy (except for the cement baffle - which is not what I'd call difficult), the key is planning your build!
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Old 14th September 2006, 01:19 AM   #20
ScottG is offline ScottG  United States
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Urgg.. I just did some analysis of the port size needed for the additional power.

Now I'm *NOT* sure that air velocity and *actual* power work out correctly in WinIsd.

When I modeled Shins it was based on 64 watts which should provide plenty of gain considering a supposed 1 watt/ 1 meter in room nearing 87 db at 20 Hz. (..in other words at 64 watts there is a power factor increase of X6 = +18 db theoretically).

If I up the power to 256 watts AND the vent diameter to 5 inches then the program calls for 61 inches of vent length to comply with its max velocity spec.. This would make for a very high (almost 6 foot) box that is quite "thin". (..or it would require some pipe bends, or perhaps an exterior pipe.)

Again though, I'm not really sure what's happening with the power requirement vs. acoustic output. If indeed because of the impeadance vs. phase the sub is basically "p!ssing" away power - does this mean that the power vs. velocity "holds up" for the max velocity vent diameter requirement? That I can't tell you.

But hey, since RonE is more technically astute than I am - why not ping him for the answer?
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