The mother of all subwoofers build

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Thanks. I hear Bruce Edgar built a sub for the army to simulate mortar rounds, etc. If I remember right they proposed 500 15 inch drivers. Bruce built a horn with 4 18 inchers. The test was done with Pink Floyd outside :). There are levels of grand daddies.

My plans are to build the box and listen to it, then finish it if I like what I hear. That way if something's not what I want I don't have so much into the build.

Grant.

Certainly not the silliest idea I have ever heard. I have seen some fancy finishes like the $20k sub where he spent something like >$3k on fancy jewel encrusted logos for the boxes.

The smart money like you say, would be to test it then make it pretty.
 
Both of those will result in the cabinet wanting to walk around at high levels.

Putting the PRs on opposite sides of the cabinet is the way to avoid this.

Chris

Last night I came full circle back to where I started...
Except instead of ply to make the centre section, I might build it using layers of 25mm thick ply.

If I make all four sides no bigger than 600mm x 600mm I could get 8 slices per sheet. So 5 sheets would be enough to build the cabinet.

Building the internal bracing into the same piece as the side walls would allow me to cut more elaborate patterns per layer, that I couldn't do with flat ply.

On the layers where there is no bracing I could use the big cut out pieces for other smaller speakers, like Russian dolls.
 

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I'm going to add that I really liked your 'number 4' graphic earlier. I'll explain why. -Triangles are natures strongest shape, unless you are talking circles and radial pressure.
-If this was made into a triangle, your glue joints would be larger in the corners.
-Your feet underneath would be in 3 spots and placed well out of the central weight of the drivers and mass. This creates tremendous stability.
-Bracing would be less of an issue with fewer panels to flex or vibrate.
-Even if just barely a hexagon by making the corners flat and such, I feel this would be a great approach.
-If nothing else, you've given me fire fodder that I might build one such as this.
Later,
Wolf
 
Personally I think the granite and the logos are over the top. It is $4k+ he didn't need to spend, but each to their own.

Interesting that he used MDF for internal bracing parts. If I am not mistaken the sides only look to be about 19mm thick. Would be very interested to know if the cabinet vibrates.
 
I'm going to add that I really liked your 'number 4' graphic earlier. I'll explain why. -Triangles are natures strongest shape, unless you are talking circles and radial pressure.
-If this was made into a triangle, your glue joints would be larger in the corners.
-Your feet underneath would be in 3 spots and placed well out of the central weight of the drivers and mass. This creates tremendous stability.
-Bracing would be less of an issue with fewer panels to flex or vibrate.
-Even if just barely a hexagon by making the corners flat and such, I feel this would be a great approach.
-If nothing else, you've given me fire fodder that I might build one such as this.
Later,
Wolf

Squares can also be very effective in bracing. The only problem with a triangle shaped sub is the size of the pieces when cutting from a sheet, then a square comes into its own.

Biggest issue I see with a triangle is moving it. You are probably talking few hundred kgs minimum. Really hard to get the centre of gravity over on a triangle, and you risk damaging a PR or driver on ever side.
 
If mine is the mother of all subwoofer builds, I found the grand daddy earlier...

4 x TC Sounds LMS 5400's, 8 x 18" TC sounds VMPs.

2 x Crown I-Tech 8000s (I am using 1 x I-Tech 9000HD)

Cost him $20k to build mine will be about $10k.

Sometimes things get a little out of hand... Wish you success with yours, looks like you have some good gear there to start with.

I haven't heard from Robert in a long time. That was quite the build he had.
 
So long as the bracing is open and the box has a reasonable aspect ratio, the air within the box will act as a simple spring. One you get towards high-aspect-ratio cabinets, transmission line effects start to come into play.

Your cabinet will be fine.

I'd go for PRs arranged opposite to each other, so there's force cancellation and the cabinet itself doesn't walk around. You're looking at over a kilo of mass vibrating around.

So, the conclusion is that your cabinet is fine. Just make sure the PRs are mounted on opposite panels when you build the thing. You could have main driver and one PR firing forwards, and one PR firing backwards, or PRs firing out of each side with the driver firing forwards, or...

You get the idea.

Chris

This.

The force of that much mass oscillating is not be underestimated. Adding bracing or additional enclosure mass will be ineffective at preventing the system from rocking. At one time I had pairs of every size of the TC VMPs. Make sure you use the supplied rubber spacers and torque the nuts down well.
 
Triangles are nature's strongest shape

I have been revisiting the idea... Can only get 5 pieces per sheet which would mean a minimum of 8 sheets if I make no mistakes possibly 9.

At around $100 per sheet for 25mm think ply it is doable, but not cheap.

I should be able to just do this on my CNC machine.
 

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Not sure why you are cutting 5 tops and bottoms out of a board when you only need two, unless you are translaminating the thing. Seems that you could cut 3 pieces with the proper angles, mate to 3 smaller pieces with the right angles, and then add your bracing. You would be out less material, not require translam style, and still be able to brace well with CNC'd bracing as you have pictured.

FWIW- Paradigm had a box shaped like this, and it was a doozy of a sub according to spec and reviews.

And yes- I know rectilinear prisms can also be well braced.

Later,
Wolf
 
Not sure why you are cutting 5 tops and bottoms out of a board when you only need two, unless you are translaminating the thing.

That is the plan, I count 46 pieces and if I get 5 per sheet, that's 10 sheets. The idea is to make the walls 50mm thick which means two 25mm top boards and two 25mm bottom boards. 1150mm high in total. Flat to flat side just under 700mm, so is a good size without being over the top. What I like about this design is the PRs and the driver are on the same plane, and top and bottom can be easily padded without getting in the way of the drivers.

Not sure why you are cutting 5 tops and bottoms out of a board when you only need two, unless you are translaminating the thing. Seems that you could cut 3 pieces with the proper angles, mate to 3 smaller pieces with the right angles, and then add your bracing. You would be out less material, not require translam style, and still be able to brace well with CNC'd bracing as you have pictured.

FWIW- Paradigm had a box shaped like this, and it was a doozy of a sub according to spec and reviews.

And yes- I know rectilinear prisms can also be well braced.

Later,
Wolf

Will have to see what Paradigm did with theirs to pick up some tips.

After some measurements and considerable thought I believe I have a final design. To avoid compilation and too much board juggling I have decided that if I get three pieces per sheet I am doing alright. I did multiple versions getting progressively wider / lower, and with only about 80mm difference in width, I can reduce the height by roughly 40%. At 770mm between the flats I don't want to go any wider. Funny enough going bigger and getting less pieces per sheet I still wind up using less sheets.
 

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By offset I was referring to cutting pieces out of the 1200mm x 2400mm sheet.

I built the CNC to be able to take a full 1200mm wide sheet in from the side (meaning I don't need to pre chop the full size board).

I don't currently have full 1200mm of X length (more like 1100mm) In the next round of modifications I plan to extend to 1200mm but for now if I chop from one side of the board I can get three pieces out of one side of the board with spares for future speakers.
 

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If mine is the mother of all subwoofer builds, I found the grand daddy earlier...
Not even close. A couple of years ago, a guy on AVS built a system with 32 18" drivers in a room not much bigger than mine (~52cu m). And I have 4 FTW21's and never go near their capacity.

Based on long term reading over there, I'd be tempted to build the 18Hz tune and add a Crowson for the really deep LFE.

It's also nice to see someone else build matrix cabs. I've been doing it ever since it came to my attention.
 
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