Jump to content
 
 

Sign in to follow this  
Triticum Agricolam

Implementing Bracing

Recommended Posts

UPDATE! - I added a bunch of pictures as examples of bracing I've done, see page 3.
 
Bracing is a very important part of building a stiff and strong enclosure. There are lots of ways to do it, each with their own advantages and disadvantages. I have developed my own ways for doing bracing and they work well for me and I'll explain why, that doesn't mean there aren't other ways that work just as well though. Its up to each person to decide what works best for them. Bracing definitely has a personal preference component to it. There are some things that I see people do that I don't think work as well as they could and I'll go over some of those. Don't get butthurt if I pick on something you do, feel free to tell me I'm wrong if you think I am. Hopefully we can all learn something. I love seeing other builder's work, l learn new techniques and ideas from other builders all the time.

 

 

 

 

This post has two parts, first I'm going to talk about some general bracing strategies that I use and then I'm going to post the results of a experiment I did with single panel bracing. Once I started writing this I realized its going to be a huge post, so be prepared.

 

 

 

 

 

Bracing an enclosure serves two main purposes. The first is it adds overall strength to the enclosure by linking the panels together in more places. This helps transfer forces more evenly throughout the box to reduce high stress areas. The second purpose of bracing is to restrict panel movement in an effort to reduce panel flex and resonances, which can color the sound and reduce output. With this in mind, here are my general bracing guidelines that I try to adhere to:

 

 

1. Keep unbraced spans appropriate for material used. (Under 12" for 3/4" single layer plywood, under 10" or less for 3/4" MDF or thinner materials).

 

 

2. Brace across to opposite panels when possible, otherwise brace to adjoining panels. The more panels a brace joins together, the better. Use a single panel brace if nothing else will work.

 

 

3. Brace to the center of panels where movement is the greatest, avoid bracing in corners and near edges where it is unneeded.

 

 

4. Take up the least amount of internal volume and make bracing as acoustically transparent as possible.

 

 

5. Minimize disruptive bracing in high airflow areas.

 

 

6. Maintain as straight of a path of bracing material as possible between contact points.

 

 

 

 

 

Where it can be used, the most effective style of brace (IMHO) is the window brace. Here are some examples:

 

 

RQjgpAF.jpgJYJmlSe.jpg

 

 

The reason I like this style of brace is when its properly implemented it braces multiple panels together and provides strength in two dimensions. It does a good job of sticking to my guidelines by bracing across to opposite panels, supports the center of the panels, takes up little space, and maintains straight paths of material between contact points.

 

 

 

 

 

Some window brace implementation are more effective than others. I've seen some folks just make a square frame, this is certainly better than nothing, but it doesn't provide support in the middle of the panel where its needed most:

 

 

qTwQAhN.png

 

 

 

 

 

Other things I've seen people do is make a simple cross, this puts the bracing where it needs to be, but unless the pieces used are fairly wide it doesn't provide enough surface area to get a good glue joint:

 

 

dkfETi7.png

 

 

 

 

 

A proper window brace won't have either of the above issues:

 

 

E6Dqoi1.png

 

 

This is a good window brace, it has support where it needs to be and plenty of surface area for gluing to. This is how most window braces are done and this implementation very well. It only weakness is that it does have lots of material in the corners where it doesn't provide much benefit, so this style of brace does have room for improvement.

 

 

 

 

 

Here is an improved version:

 

 

mnBJTAY.png

 

 

This brace uses less material than the previous brace (and thus has more open area, making it more acoustically transparent), and it is stronger since the distance between support columns is less. Its more of a hassle to make though. I use my CNC router to cut out these braces, though they can be cutout with a router/jigsaw as well. They don't have to be pretty to be effective. They can also be made from just strips of material laid on top of each other and glued together, this is the most material efficient way to do it.

 

 

 

 

 

 

 

 

So what do you do if you need to put a brace somewhere but you have a sub motor or something else right in the way? That's where something like a donut brace can work well:

 

 

tsQHHao.png

 

 

 

 

 

One thing I see people do with window braces that is less than ideal is they place the support columns in a "X" pattern instead of a cross. Here is an example:

 

 

ZVqQT4X.jpg

 

 

It looks nice, but you aren't supporting the center of the panel where the strength is needed most. An "X" style window brace isn't really much better than the square frame brace in my first example.

 

 

 

 

 

 

 

 

 

 

 

After windows braces, my next most often used brace is a shelf brace. A shelf brace links panels together on up to three sides, and has at least one side that is open. Here is an example:

 

 

CEk9ZQ2.png

 

 

 

 

 

Since they don't extend all the way across the box, shelf braces can be solid. However you can skeletonize them to make them more acoustically transparent and to save weight. Here is a skeletonized version:

 

 

0FXP2b5.png

 

 

Like the window brace, this brace supports opposing panels, supports panels in the center, and has material in a straight path between contact points.

 

 

 

 

 

If you wanted to get fancy you could remove the material in the corners like this:

 

 

oWmPtM5.png

 

 

 

 

 

 

 

 

When bracing across to an opposing panel isn't possible, you can use triangle corner braces to brace to an adjoining panel:

 

 

aWxTAfj.png

 

 

 

 

 

These can also be skeletonized:

 

 

UUxoX9q.png

 

 

If possible you want the triangle brace to extend at least half way across the panels being braced so you provide support in the middle of the panel where its needed most.

 

 

 

 

 

Here is an example of a box where I used shelf, corner, and window braces:

 

 

r7Yvf9W.jpgcYOGdUy.jpg5sRGwYp.jpg

 

 

 

 

 

 

 

 

Some times bracing to an adjoining panel or an opposing panel isn't possible, in this case you can use a single panel brace. These can be just a strip of material meant to double the thickness of the panel in that area, like this:

 

 

488fBzK.jpg

 

 

 

 

 

Or they can be shelf braces like these:

 

 

fQ3Ewuz.jpg

 

 

Both styles work, but the shelf brace is MUCH more effective. Which leads me into my experiment......

 

Edited by Triticum Agricolam
  • Like (+1 Rep) 11

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

Share this post


Link to post
Share on other sites
The question:

The purpose of this experiment is to show how much strength bracing can add, and to compare a couple different bracing implementations. Since braced 3/4" material takes a LOT of stress to get it to deflect I'm using cheapo 1/4" plywood. The results should scale up with the usual 3/4" material.


For the testing apparatus I will be using my deflection stand from my material testing experiment, details on that are in this thread: http://www.stevemeadedesigns.com/board/topic/206653-an-experiment-in-box-materials/?st=0


I have four different panels I will be testing. A single thickness unbraced piece, a piece with a doubling strip brace glued to it, a piece with a shelf brace, and a strip with a skeletonized (crudely) shelf brace. Here are the pieces:

tUDRd96.jpg


As with my material test, I will be stressing these panel with 25 lbs of lead shot and will be measuring the deflection with a dial indicator. Here is the unbraced piece in the test apparatus:

Bi0nBSy.jpg

Its got a pretty good bend to it, I was a little concerned it might break under the weight, but it held.


Here is the panel with the shelf brace:

nK9whO4.jpg


The results:

Unbraced panel - .836" of deflection

Panel with doubling strip brace - .157" of deflection - 81% reduction compared to unbraced

Shelf braced panel - .010" of deflection - 98.8% reduction compared to unbraced

Holey shelf braced panel - .009" of deflection - 98.9% reduction compared to unbraced


Conclusion:

The reduction in deflection by any kind of bracing is very significant. The way test was setup probably increases the stress put on the panels since they are only supported on two sides, in an enclosure panels are going to be supported on three or four sides. None the less you can see how much difference bracing can make. The doubling strip brace made a big difference, but the shelf braces made a HUGE difference. I would like to point out that the shelf brace used exactly the same amount of material, and thus would take up the same amount of box volume as the doubling strip brace did, but it was MUCH more effective. Shelf braces are the way to go whenever possible, IMHO. The shelf brace with the holes in it performed virtually identical to the one without holes. It actually performed slightly better, but I attribute that to the measuring limitations of my test apparatus. The holey brace goes to show that you can remove significant material from that style of brace without compromising its effectiveness at all.


Hopefully this experiment has given you something think about when it come time to implement some bracing in your next enclosure!

  • Like (+1 Rep) 3

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

Share this post


Link to post
Share on other sites

Great info. I'll definitely be looking at this when designing future enclosures.

Share this post


Link to post
Share on other sites

Thoughts on wood bracing vs other options? I.e. threaded rods, or for serious ballers carbon/aramid tubes. Having done some stress testing I know composites have downright silly strength and stiffness, and usually not much weight.

  • Like (+1 Rep) 1

Share this post


Link to post
Share on other sites

Thoughts on wood bracing vs other options? I.e. threaded rods, or for serious ballers carbon/aramid tubes. Having done some stress testing I know composites have downright silly strength and stiffness, and usually not much weight.

Lmao I just had an image of the "Aliens" meme guy pop into my head saying "Carbon nano tubes".

Share this post


Link to post
Share on other sites

Thoughts on wood bracing vs other options? I.e. threaded rods, or for serious ballers carbon/aramid tubes. Having done some stress testing I know composites have downright silly strength and stiffness, and usually not much weight.

Threaded rods can work well, though I don't use them myself for several reasons. They are more expensive than using wood and are just another material that has to be bought, they can be prone to causing leaks, they only brace in one dimension, and I think they are ugly. If you do use threaded rod its important to tighten them down so there is some preload tension on the rod. They can't provide much strength in compression, so the preload tension is important to get the most strength out of them.

Another alternative that I should have mentioned in my original post would be large wood dowels. Like threaded rods, dowels only brace in one dimension, but they are cheaper and can provide strength in both tension and compression. The important thing when using dowels is you CANNOT just glue them between the panels inside the box, you MUST drill a hole the diameter of the dowel through the panels, smear glue everywhere, and then drive the dowels in. The ends can then be trimmed flush and sanded down after the glue dries. The problem with trying to just glue them in without drilling holes is you have very little surface area for glue contact and the endgrain of the dowel will wick glue away from the joint. The glue joint will fail almost every time. If you drill holes and do it the right way though there is a lot more surface area and you aren't gluing to then end grain of the dowel, they are strong as hell when done this way.

  • Like (+1 Rep) 3

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

Share this post


Link to post
Share on other sites

Good read


On 3/28/2014 at 4:22 PM, KyLar96 said:

Its all about the music anyway..... Do a proper install, something your happy with, Fuck everyone else...... improve in time, where you can..... its not rocket science...

Tiburon build //www.stevemeadedesigns.com/board/topic/174059-97-hyundai-tiburon-build-from-ramming-to-slamming-slow-5k-build/

2000 Mountaineer build http://www.stevemeadedesigns.com/board/topic/186736-2000-mountaineer-build-from-ramming-to-slamming-part-iislow-5k-builddc-audio-americanbassxspowersingerarcaudiostingershcavideo-on-pg7/

2000 Mercury Mountaineer: Electrical:Singer 340 alt, Big 4 double run 1/0 SHCA OFC, 4 runs 1/0 OFC SHCA,xs d3400 uh, 4 XS D3100s HU: Pioneer deh80prs interiors: Skar sk85.4 on sb acoustics neo dome tweeters Mmats sq4100 on 4 silver flute 8s(4ohm) SUB Stage: 2 DC5K [email protected] on 6 ascendant audio mayhem 12s d1.4s fully loaded

Share this post


Link to post
Share on other sites

love it!!! honestly speaking,i´m having major issues with my wall, it has threaded rods and 2x4s inside the sealed chamber and a few 2" poles on the ported chamber, i was thinking about ditching all that and maybe use the shelf braced panel idea wth some iron angles????? opinions? or maybe using a bunch of wood braces instead of the angles


I´m the SPL Gains topic creator!! wanna get louder?? check this: SPL Gains. Panamenian 2009 & 2010 & 2014 Bass Race 149.9 Champion!

2 15" subs and a 2K wired at 1 ohm, http://www.stevemeadedesigns.com/board/topic/167788-fecupe2001-2-15s-on-a-2k-video-on-page-3/

8 Massive 15" subs and small power, http://www.stevemeadedesigns.com/board/topic/179296-fecupe2001s-8-15s-4th-order-bandpass-wall/

Share this post


Link to post
Share on other sites

awesome info, thanks


'08 Honda Fit
SSA 15"
Banda
Nendo 800.4
Evil 6.5 and Tweets
WINSTONNN
Singer
Knu Koncpetz Wire/Deadener

'01 Dodge Stratass Sealed Trunk Build Log
2008 Honda Fit Sport Build Log

On 3/12/2014 at 7:09 AM, Gunnem said:

it was fun pretending his build is mine
I can feel the loudtown farm fresh girls getting hot from my bass vibrations

On 10/3/2013 at 10:00 AM, ROLEXrifleman said:

Anyone who says they knew everything they wanted out of life at 19 can go suck a bag of dicks cause they are lying to themselves or brought up in a cult.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...