Best way to brace a box?

Goblenator · December 6, 2015

Ok i'm looking to brace my sub box and i was wondering what the best way to brace a box is. All opinions welcome so are pics. the box is a 4.2 cu box with 2 12's facing forward and an aero port between the subs

kirill007 · December 6, 2015

https://www.youtube.com/watch?v=IOnbkyjfQOI

Triticum Agricolam · December 7, 2015

Yay, bracing!! Is it sad that is probably one of my favorite topics? Its also an area that I don't think people put enough effort into when designing/building boxes. Here is my basic bracing guidelines:

1. Keep unbraced spans appropriate for material used. (Under 10"-12" for 3/4" MDF/Plywood)

2. Brace across to opposite panels when possible, otherwise brace to adjoining panel.

3. Minimize bracing in corners where it is un-needed.

4. Take up the least amount of internal volume as possible.

5. Minimize disruptive bracing in high airflow areas.

So for bracing, there are lots of ways to do it while following the guidelines above. One way is using dowels. The advantage of dowels is they are cheap and really easy to use, the disadvantage is they only brace along one dimension. When you are using dowel you MUST drill a hole through the panels and then drive the dowel (with glue) into the holes. If you try to just glue the end of the dowel to the panel, the glue joint will fail.

In addition to dowels, there are also window braces. These are my favorite. They are also something that a lot of people do incorrectly. Here are some pictures, I'll start out with the wrong way to do it:

This is the way I see a lot of folks try to do window braces, it looks good but it accomplishes nothing since there is no material linking the middle of the panels together. Seriously, the only thing this brace does is take up space.

This is another bad way to do window braces, while it has the material where you need it, to link the middle of the panels. There isn't enough surface area for glue to stick to. The panels will pull away from the brace.

This is a good window brace. It has material where it needs to be, and it has lots of surface area for glue to stick to. It can be improved upon however.

Winner, winner, chicken dinner! This is the best way to do window braces, it has all the right stuff in all the right places, but without any unneeded material in the corners of the box where it doesn't do anything. You can make this brace out of leftover strips of material, it doesn't have to be cut from one panel, and it uses less material than the previous brace. There is nothing wrong with making them out of one panel if you prefer, it just takes more time and material.

In addition to window braces there are also corner braces and shelf braces, here is an example of a corner brace:

Like the window braces, these can also be easily built out of strips of material:

Here is a shelf brace:

Typically you see these used on the back side of the baffle between the subs, like what is shown in the picture. They need to be at least 4" wide, in my opinion, to provide a worthwhile benefit.

There are lots of other ways to do bracing, these are just the methods I use the most.

Joe X · December 7, 2015

Ok i'm looking to brace my sub box and i was wondering what the best way to brace a box is. All opinions welcome so are pics. the box is a 4.2 cu box with 2 12's facing forward and an aero port between the subs

Bracing needs (for subs) will depend on the amount of energy you are dealing with and the shape of the box, in your case if you are using something like SA-12s you won't need any additional bracing, the port in the middle itself will act as very effective bracing.

Goblenator · December 7, 2015

Thanks Triticum Agricolam that's a great post. gives me some good ideas.

Goblenator · December 7, 2015

Ok i'm looking to brace my sub box and i was wondering what the best way to brace a box is. All opinions welcome so are pics. the box is a 4.2 cu box with 2 12's facing forward and an aero port between the subs

Bracing needs (for subs) will depend on the amount of energy you are dealing with and the shape of the box, in your case if you are using something like SA-12s you won't need any additional bracing, the port in the middle itself will act as very effective bracing.

It's an aero port so that won't work

SlamminBeats · January 11, 2016

i planned on using the tic-tac-toe board window brace using .75 in MDF. Is 1in big enough or do i need to move up to 2in? It will be a monolithic piece as well.

Katt · January 11, 2016

5/8 all-thread is what I use. Or wooden dowels fiberglassed in.

reedal · January 11, 2016

i planned on using the tic-tac-toe board window brace using .75 in MDF. Is 1in big enough or do i need to move up to 2in? It will be a monolithic piece as well.

What do you mean by 1in or 2in?

I used this bracing on my enclosure I just built, and I'd recommend it. My enclosure is wide, so there was a lot that was unbraced, and just tapping on the front panel was a very hollow sound. Made that brace and slid it in snug, tapped in the center of each respective side of the brace and no more hollow sound.

audiofanaticz · January 11, 2016

For me it all depends on the panel size.

All thread only works decent if you go through both sides of the box to prevent it from flexing not only inwards but outwards, but it typically looks ugly with bolts sticking out of your enclosure.

wooden dowels is not a lot of surface area and your relying on the screw to do the bracing due to such small surface areas on both ends for glue ups.

Not to mention its wood and thin so is prone to flexing at the woods resonance making it almost useless.

Now for pics, just a few that I could quickly find pics of that I did

Im still working on improving more and more now that I have a router lift and it makes things quicker and easier.

However Im still using things like a roll of tape for a jig for the router bearing to trace lol