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post #1 of 121 Old 01-05-2012, 09:20 PM - Thread Starter
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In the planning stages for my dual LMS Ultra.



A few questions about wood, glue, bracing and a proposed faceplate:



Wood: Baltic Birch, Arauco, MDF Which one to use?



Glue: Titebond, PL400, PL Premium Whats best, dependent on wood???



Bracing: This is my first attempt at designing some sub braces, need some critic, too much, not enough, not properly done???



Faceplate: I have an idea about constructing a faceplate made out of fiberglass and/or combination of wood and fiberglass to cover up the face of the box leaving only the cone and surround exposed (flush mount look). Much like the car audio guys do for show.



Question would a faceplate vibrate and be a bad idea?????



Are in red showcases roughly 2" lip were proposed faceplate would attach too sub box.



Box Dimensions: 22 wide, 44 Tall, 22 Deep



Rough Sketch, just an idea were Iam going

















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post #2 of 121 Old 01-05-2012, 11:34 PM
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faceplate: no, unless you're running dual opposed, it will not be happy. Just flush mount if you want that look.

wood: go with a ply, either BB or arauco is fine

glue: depends some on your woodworking equipment and skills. If you can create tight/flush cuts, you can use titebond just fine. Otherwise, you should use PL. I used PL anyway just because I like overkill, though it is messy and harder to work with.

bracing: little ridiculous, and the flat panel facing the subs may cause reflections. Are you sure the motor will fit ok in that setup?

As always, this is just my $0.02
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post #3 of 121 Old 01-05-2012, 11:39 PM
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Quote:
Originally Posted by notnyt View Post

bracing: little ridiculous, and the flat panel facing the subs may cause reflections.

I agree on the holes in the braces

Reflections not an issue unless he's going to run above a couple hundred Hz

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post #4 of 121 Old 01-06-2012, 05:03 AM - Thread Starter
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Could I get someone to help me design proper bracing to ensure a super stiff cabinet, weight is not an issue.
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post #5 of 121 Old 01-06-2012, 05:47 AM
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post #6 of 121 Old 01-06-2012, 07:10 AM
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Quote:
Originally Posted by bodhisafa View Post

Could I get someone to help me design proper bracing to ensure a super stiff cabinet, weight is not an issue.

3-4" wide strips of plywood from the main panel scrap placed every 6-8" from one panel to its opposite panel. Window bracing like what you show is a waste unless you are CNC'ing everything and want to expedite assembly.

NotNYT's bracing is a compromise between the strips and wasteful window bracing.

I think people put way too much thought into making some sort of super structure out of their bracing. This isn't a suspension bridge.

On the other stuff, I'd take NotNYT's advice. You are basically replicating his project. I'm sure you could do a fancy "faceplate" but I'm not sure it would be worth the effort. I'd just do a double thick baffle and recess the drivers. Roundover or chamfer the front edges and finish it.
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post #7 of 121 Old 01-06-2012, 07:33 AM
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Quote:
Originally Posted by bodhisafa View Post

Could I get someone to help me design proper bracing to ensure a super stiff cabinet, weight is not an issue.

Your braces are pretty much like those below left, which puts most of the material where it's least needed, in the cab corners. Below right makes the best use of material. A distance between connection points of 8 inches is OK with 3/4 inch panels, 6 inches is fine with 1/2 inch panels. There's no need for or benefit from making them one piece.


I'd also make two cabs rather than one. You can't control room modes by splitting a single cab.

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post #8 of 121 Old 01-06-2012, 07:52 AM
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Quote:
Originally Posted by notnyt View Post

click the link in my sig =]

This
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post #9 of 121 Old 01-06-2012, 07:52 AM
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+1 to bill, if you're only using two woofers, I'd split them.
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post #10 of 121 Old 01-06-2012, 08:51 AM - Thread Starter
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I will be using 4(drivers) total, 2 boxes.
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post #11 of 121 Old 01-06-2012, 09:05 AM - Thread Starter
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Something very similiar to this is what I had in mind for the faceplate:http://www.hometheatershack.com/foru...html#post17472

Attaching it to the box with allen bolts and using weather strip or foam to pad inner walls to eliminate vibrations.

It seems so far, according to recent replies, that it would not be a good idea.

Just wanted to do something different, specially considering these drivers come from the car audio world.
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post #12 of 121 Old 01-06-2012, 09:26 AM
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Quote:
Originally Posted by bodhisafa View Post

I will be using 4(drivers) total, 2 boxes.

Even then smoothing of room modes is best accomplished by having as many sources as possible. If it somehow turns out that two of the cabs sharing the same footprint gives the best result you can still do so.
Quote:


Something very similiar to this is what I had in mind for the faceplate:http://www.hometheatershack.com/foru...html#post17472

They look pretty, but at subwoofer wavelengths that's all they'll do.

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post #13 of 121 Old 01-06-2012, 09:38 AM
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If you want to add that faceplate, go for it. Do you have experience with composites? It is not a trivial task.

As far as vibrations, just make it rigid and heavy. Some isolation at the mounting points like the stripping you describe might help too.

Like Bill says it is strictly for aesthetics.
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post #14 of 121 Old 01-06-2012, 09:58 AM - Thread Starter
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^^^^I dont have any experience with fiberglass/resin. A local car audio shop would have to pitch in for that aspect of the build.

The "tic tac toe" bracing I can do, lay all the braces horizontal? or both vertical and horizontal?

I understand smoothing of room modes is best with multiple boxes, I just dont have the room for all them to be spread out, reason for dual stacked design.
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post #15 of 121 Old 01-08-2012, 11:09 PM - Thread Starter
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Iam I on the right track, better...worse.....vertical bracing???






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post #16 of 121 Old 01-09-2012, 05:55 AM
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You still have contact points closer to the corners, which don't need bracing at all, than to the center of the box, where it's needed the most. Top to bottom bracing is just as important as side to side.

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post #17 of 121 Old 01-22-2012, 07:42 AM - Thread Starter
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Iam having a bit of trouble figuring out the vertical bracing for my boxes. These drivers are big and dont allow much room behind them for vertical bracing, unless I offset the bracing further back which puts the brace closer to the back wall. According to Bill I need these more towards the center "middle" of the box.

Also I have been told the vertical brace sitting behind the driver can cause reflections.....so how much bracing can I have before this becomes a problem.
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post #18 of 121 Old 01-22-2012, 10:04 AM
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Quote:
Originally Posted by bodhisafa View Post

Iam having a bit of trouble figuring out the vertical bracing for my boxes. These drivers are big and dont allow much room behind them for vertical bracing, unless I offset the bracing further back which puts the brace closer to the back wall. According to Bill I need these more towards the center "middle" of the box.

Make them V shaped.

Quote:


Also I have been told the vertical brace sitting behind the driver can cause reflections.....so how much bracing can I have before this becomes a problem.

Up to 1/4 wavelength across.

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post #19 of 121 Old 01-22-2012, 10:08 AM
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This is why I used double plates for the top and bottom and no vertical bracing in mine. You can use some heavy dowels, but they'll end up so close to the corner it wont really help you any.

Some 2-3" strips of ply between the horizontal bracing on the back/sides will work fine. Some may say the bracing in my cabs is overkill, but works quite fine for me as the cabs are very solid/inert.

EDIT: as Bill said, you can go diagonal as well, from the middle of the top at a 45' angle or so to the back, and that should clear the motor structure.
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post #20 of 121 Old 01-22-2012, 11:50 AM - Thread Starter
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Ok gentlemen, this is what I have so far. Implementing Notnyts bracing (really the only thing that fits given size constraints). Box is 44" tall 22" wide and 22" deep. Still contemplating faceplate idea, that would add another 3" to the front as shown in model. All bracing is 1.5" wide, 3/4" thick wood.

Vertical bracing in RED, using dowel square rods or similiar product.












The middle window bracing




The V goes in between the A cutout

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post #21 of 121 Old 01-22-2012, 04:15 PM
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Looks good. You've still got a lot of transverse bracing on the panels, which does very little, while adding weight and build complexity. If the extra weight and work isn't a concern go for it. If you do keep them don't cut the braces whole from plywood, cobble them together in place in the cab from plywood strips.

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post #22 of 121 Old 01-23-2012, 07:46 AM - Thread Starter
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Whats the name of the program that shows you how to cut a 4x8 sheet with all your measured panles...getting ready to cut wood.
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post #23 of 121 Old 01-23-2012, 09:17 AM
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Whats the name of the program that shows you how to cut a 4x8 sheet with all your measured panles...getting ready to cut wood.

cutlist.

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post #24 of 121 Old 01-30-2012, 10:36 AM - Thread Starter
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Question regarding brad nails for this project...how long of brad nails should I buy. The Auraco I purchased is 3/4 in.
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post #25 of 121 Old 01-30-2012, 12:34 PM
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Question regarding brad nails for this project...how long of brad nails should I buy. The Auraco I purchased is 3/4 in.

1 5/8" paneling nails.

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post #26 of 121 Old 01-30-2012, 01:53 PM
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Don't get me wrong, but your bracing, while very pretty, could be simplified greatly. Take Bill F. advice and glue up a series of ribs to the insides of your panels. Make each rib 3-4" tall, and glue it all the way along its edge. Then add cross-ribs between the first ribs you installed. The ribs are simple, 3/4"x3.5"x?? long. Essentially you are trying to make a torsion box (sans the inner skin), or if you want to go really crazy, add panels to the inside as well.

Also, keep in mind that the holding power of glue is much stronger than screws or nails. While a screw may have 200#'s of holding force, it is concentrated at only one 1/8" spot. Glue on the other hand may have 1/10th the holding power (making these figures up as example) for the same 1/8" spot, but once you add up all of that contact area that the glue has, the glue will out-hold the screws by a wide margin. Screws and nails are used to hold the cabinet together while the glue sets up.

Like I said, your design is pretty, but it just looks like a lot of work that may not be worth the extra effort involved over simple ribs glued to the inside of the cabinet. You may want to keep it simple.
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post #27 of 121 Old 01-30-2012, 02:12 PM
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[quote=urapnes1;21572027Also, keep in mind that the holding power of glue is much stronger than screws or nails.[/QUOTE]

glue has no clamping power though

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post #28 of 121 Old 01-31-2012, 08:04 AM
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B&W Matrix was the best bracing, bar non... By far. I was working on a bracing system that involved 1/2" dowels top to bottom, front to back and , sides to side.... Maybe its time to revisit and post a thread. They were spaced about 2" apart, hold in place with stiff wire and coated with PL at the end....

Large basket drivers pose a real challenge in this area. What would be perfect is to build a perfect cube, totally cross braced and mount the driver firing into the box and out of phase so the cone moved backwards, but they were not meant to move backwards
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post #29 of 121 Old 01-31-2012, 12:35 PM
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... so the cone moved backwards, but they were not meant to move backwards

? cones always move backwards and forwards

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post #30 of 121 Old 01-31-2012, 01:30 PM
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Quote:
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? cones always move backwards and forwards

So, why not bolt the speaker to the hole where it ususally drops in. No question you can brace the box front to back, side to side, top to bottom...with no attention to the basket protruding to the inside of the cabinet.

So wiring it out of phase and firing out through the basket as its primary direction isnt a problem....
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