2242H Subs for Big Bass

[Mr. Widget]

Would enclosure walls of Plywood/MDF be a better choice for DIY speakers than veneered MDF? I'm thinking of using 1/2" veneered plywood glued to 1/2" MDF instead of 1" MDF. What's your opinion?

First of all, not all plywood is the same. Typical American plywood uses 5-7 layers of fir. More and more I am finding imported plywoods with a much lighter and less structural core material. If you use a veneered birch plywood (face veneered in the wood of choice with an all birch interior) you will have the best results. Basically you want a very stiff outer constraining layer. For the inside, I'd stick with 3/4" MDF. You will end up with a wall thickness of 1 1/4", but I think it would be worth the weight and extra size. If they are small speakers say L100 sized or smaller, then I suppose 1/2" MDF would be fine... still with adequate bracing.

Another question. My box program doesn't seem to make any adjustments to Vb to compensate for braces. Is this because the "virtual volume" created by the fiberglass stuffing offsets the volume taken by the braces? If this is so, it seems a little inexact to me. How do you compensate for the bracing?

I use BB 6Pro. It does allow for bracing as well as differing amounts of fill. It is still imprecise. All of these programs give you is a very good guess. Ultimately I measure the results and tweak. Of course a few years ago, before I had my Clio rig... I took the results from BB 6Pro and was satisfied.


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[scott fitlin]

They look much nicer in person... reducing the picture size to fit the forum messes up the look of the perf.


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Yeah, but even online, they look like they mean buisiness!

Mean looking!

Stepping in to the 2006 season, with heavy JBL artillery, MAKIN SOME BOOM BOOM!

[JuniorJBL]

Mr. Widget

What is the frame of the grill made out of ? How is it attached to the perf. And is your perf metal?

[Mr. Widget]

You want all of my secrets???



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[Mike Caldwell]

Hello
Having spent many hours at the table saw myself I can truly say
those are excellent cabinets! Nicely done with a pro finish.

Mike Caldwell

[JuniorJBL]

You want all of my secrets???



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No just some!!

I was just more curious then anything. I have some 5051 1/4 perf that I was going to make sub grills out of.

[Mr. Widget]

I was just more curious then anything. I have some 5051 1/4 perf that I was going to make sub grills out of.

I was kidding. It is a fairly thick aluminum perf (1/16" I think... I bought it a while ago.) with an aluminum extrusion frame. There is also an aluminum "U" channel that is in the center. The whole thing is pretty rigid and is screwed in to the cabinet on foam covered stand offs. I am also using rubber washers to reduce the likelihood of buzzing.


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[Mike Caldwell]

With perf screen you have figure on what the total open area is. The smaller holes closer together works out to be the best, less wasted area between the holes. While harder to get hex shaped holes offer the best open area. The perf on those subs looks to be about the size I use and that is in the mid 60% total open area.

Mike Caldwell

[JuniorJBL]

I was kidding. It is a fairly thick aluminum perf (1/16" I think... I bought it a while ago.) with an aluminum extrusion frame. There is also an aluminum "U" channel that is in the center. The whole thing is pretty rigid and is screwed in to the cabinet on foam covered stand offs. I am also using rubber washers to reduce the likelihood of buzzing.


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So you welded it to the back of your extrusion ? It is a very nice looking frame/grille.

Very nice work Mr. Widget.

[scott fitlin]

I love them already, can`t wait for them to get here!

[stevem]

First of all, not all plywood is the same. Typical American plywood uses 5-7 layers of fir. More and more I am finding imported plywoods with a much lighter and less structural core material. If you use a veneered birch plywood (face veneered in the wood of choice with an all birch interior) you will have the best results. Basically you want a very stiff outer constraining layer. For the inside, I'd stick with 3/4" MDF. You will end up with a wall thickness of 1 1/4", but I think it would be worth the weight and extra size. If they are small speakers say L100 sized or smaller, then I suppose 1/2" MDF would be fine... still with adequate bracing.

I use BB 6Pro. It does allow for bracing as well as differing amounts of fill. It is still imprecise. All of these programs give you is a very good guess. Ultimately I measure the results and tweak. Of course a few years ago, before I had my Clio rig... I took the results from BB 6Pro and was satisfied.


Widget

Thanks, Widget. My boxes are going to be fairly tall (about 5 feet), so I'll need the 3/4" MDF. Are you suggesting 1/2" ply on top of that? Now all I have to do is figure out how to attach the ply to the MDF without getting glue all over the place and keeping the joints nice and neat!

[Mr. Widget]

My boxes are going to be fairly tall (about 5 feet), so I'll need the 3/4" MDF. Are you suggesting 1/2" ply on top of that? Now all I have to do is figure out how to attach the ply to the MDF without getting glue all over the place and keeping the joints nice and neat!

Yeah that's a big box... I'd consider doing them like I did Scott's woofers with 3/4" Ply on top. When you rap your knuckles on the sides it is remarkably dead.

If you can't veneer the finished cabs, you'll need lots of clamps.


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[andresohc]

Mr. Widget, when you sandwich the MDF to the ply how do keep from getting voids between the panels (that would resonate). I have considered this technique but cant come up with a good solution.

Yeah that's a big box... I'd consider doing them like I did Scott's woofers with 3/4" Ply on top. When you rap your knuckles on the sides it is remarkably dead.

If you can't veneer the finished cabs, you'll need lots of clamps.


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[dieterj]

Great Project Widget!!!

I hope Scott tell us later about the Sound of this great looking Subs in his Place.

[Mr. Widget]

Mr. Widget, when you sandwich the MDF to the ply how do keep from getting voids between the panels (that would resonate). I have considered this technique but cant come up with a good solution.

The method I use requires that the speakers be veneered after construction or painted in this case. I use a ton of standard wood glue and a pile of Senco narrow crown staples. There are no voids... it is very solid.

With ingenuity and care, it would be possible to use clamps if you were to try to use pre-veneered plywood.


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