Subwoofer box and lots of 5/16 hardwood dowels. - Woodworking Talk - Woodworkers Forum
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post #1 of 29 Old 04-30-2016, 06:22 AM Thread Starter
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Subwoofer box and lots of 5/16 hardwood dowels.

Hi, What do you think about this? I made a speaker box using 3/4 MDF. It has bracing and the panels are about 19"x15". its a big box that holds a 15" subwoofer driver.

Want to joint every edge by using 5/16 hardwood dowels. which would requiere about 80 5/16 dowels (1.5" long). Its ridiculous putting a dowel every 1.5" ? or is it just okay because the enclosure is big and the subwoofer is very powerful, "about 1000watts". Need to use dowels because don't trust using screws on MDF, if my box was made of plywood, then I could simply use screws, but need to use 5/16 dowels. Or should I even use more quantity?

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post #2 of 29 Old 04-30-2016, 06:31 AM
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Using dowels ever 1 1/2" is overkill. If you glue the joint together a dowel ever foot is more than sufficient.
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post #3 of 29 Old 04-30-2016, 06:43 AM
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A thousand watts? Where will this speaker be used? In the super dome?

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post #4 of 29 Old 04-30-2016, 07:30 AM Thread Starter
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Originally Posted by Steve Neul View Post
Using dowels ever 1 1/2" is overkill. If you glue the joint together a dowel ever foot is more than sufficient.
I can't imagine the walls being joined just by a 5/16 dowel every 1 foot, I mean, I was expecting at the very list 1 dowel every 3 inches. I want guaranties that the box won't take apart no matter what (regular but heavy use), so for that reason I saw a big number of dowels. remember that 5/16 is not too thick, just perfect for 3/4 mdf I thought. I am still doubting, please more opinions about this, although I am expecting going with once every 2", yeah, too much drilling, and glue and dowels, but that will guarantee a "perfect join".

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A thousand watts? Where will this speaker be used? In the super dome?

George
It's primordially for car audio, for cars like vans. Surprise to hear that there are subwoofers around 2K watts.

Last edited by Johanx3; 04-30-2016 at 07:33 AM.
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post #5 of 29 Old 04-30-2016, 07:31 AM
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No need for dowels, screws placed at the same interval will be stronger. For a box that size bracing is more crucial than doweling the joints.

Many audio people talk in max terms, 1000 watts sounds like a max number, what are you driving the sub with amp wise? Is this a sealed box or ported?

Did I mention you don't need dowels? :)
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post #6 of 29 Old 04-30-2016, 07:42 AM
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I have built speaker boxes before and screws work fine.
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post #7 of 29 Old 04-30-2016, 07:44 AM
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1000 watts really isn't that much for a subwoofer, however it is still plenty to rattle a car. So I have 2 suggestions.

1. Get rubber washers for your license plate.

2. If you are really worried use finger joints.

I would strongly recommend making a ported box, with a folded driver, angled inside. For subs to be effective they need space. It's takes around 22 feet to create a full sound wave at 80hz.

Not that you can't just do what ask the car audio people do, its loud, it works, just my thoughts. My day job is in live production so I am a little biased.
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post #8 of 29 Old 04-30-2016, 08:22 AM
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Glue and screws is all that is needed.( I've built them and have seen then built ) and the screws are just to hold it together while the glue dries.
Corner block it if your concerned.


bmarshall is right
" For subs to be effective they need space "

Knot Stumped ...just confused once in a while.
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post #9 of 29 Old 04-30-2016, 10:36 AM
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Quote:
Originally Posted by Johanx3 View Post
I can't imagine the walls being joined just by a 5/16 dowel every 1 foot, I mean, I was expecting at the very list 1 dowel every 3 inches. I want guaranties that the box won't take apart no matter what (regular but heavy use), so for that reason I saw a big number of dowels. remember that 5/16 is not too thick, just perfect for 3/4 mdf I thought. I am still doubting, please more opinions about this, although I am expecting going with once every 2", yeah, too much drilling, and glue and dowels, but that will guarantee a "perfect join".



It's primordially for car audio, for cars like vans. Surprise to hear that there are subwoofers around 2K watts.
Keep in mind that MDF is just a sheet of paper, the same kind of paper that grocery sacks are made of. How well do you think glue would adhere to paper? I think you would run into monumental problems trying to drill dowels 1 1/2" apart. The more dowels you put in a joint the more chances you will have getting one a little off. Putting dowels 1 1/2" apart you are asking for a bunch of dowels to be a little off. Then when you go assemble it the dowels will prevent the parts from going together. A better method for what you are doing would be to put a spline in the joint. This would give you 100% coverage instead of every 1 1/2". I also agree with these guys you could glue and either nails or use screws to assemble the box.
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post #10 of 29 Old 04-30-2016, 01:34 PM
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My side business is building subwoofer enclosures and as mentioned glue with screws in the appropriate sized pilot holes works fine (if you use nails be sure to clamp it as nails will not pull MDF tight enough to create a solid glue joint).

http://s29.photobucket.com/user/MrMa...?sort=3&page=1

Built this one for my El Camino and powered it with a true 1000 watts rms

Trujeepr likes this.

Post count on a forum does not denote level of knowledge, skill nor experience

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post #11 of 29 Old 04-30-2016, 01:42 PM
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I don't think I'd use mdf...
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post #12 of 29 Old 04-30-2016, 05:45 PM Thread Starter
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Quote:
Originally Posted by Steve Neul View Post
Keep in mind that MDF is just a sheet of paper, the same kind of paper that grocery sacks are made of. How well do you think glue would adhere to paper? I think you would run into monumental problems trying to drill dowels 1 1/2" apart. The more dowels you put in a joint the more chances you will have getting one a little off. Putting dowels 1 1/2" apart you are asking for a bunch of dowels to be a little off. Then when you go assemble it the dowels will prevent the parts from going together. A better method for what you are doing would be to put a spline in the joint. This would give you 100% coverage instead of every 1 1/2". I also agree with these guys you could glue and either nails or use screws to assemble the box.
well, I cannot do the spline because the walls are now glued, just waiting for dowels or screws, anyway I had no tool for doing that, so this time my option is doweling or screwing. I found that 3/4 MDF is pretty strong and most speakers and subwoofers are built with it, problem is that it can easily split at the edges if you dont use the proper screws, to avoid disasters like mdf splitting, will simply use dowels, making straight holes is not a problem because I am going to use a drill bit guide. I think I will put a dowel every 2 inches.

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Originally Posted by Marv View Post
My side business is building subwoofer enclosures and as mentioned glue with screws in the appropriate sized pilot holes works fine (if you use nails be sure to clamp it as nails will not pull MDF tight enough to create a solid glue joint).

http://s29.photobucket.com/user/MrMa...?sort=3&page=1

Built this one for my El Camino and powered it with a true 1000 watts rms

Wow thats very nice.

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Originally Posted by Rebelwork View Post
I don't think I'd use mdf...
Most subwoofers are made of MDF, because the high quality sound you get with it, only critic thing about using MDF, if the care of screwing the edges, something you can solve with dowels or box joints, I mean, its a very interesting material, cheap and very strong.

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post #13 of 29 Old 04-30-2016, 05:57 PM
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Quote:
Originally Posted by Johanx3 View Post
well, I cannot do the spline because the walls are now glued, just waiting for dowels or screws, anyway I had no tool for doing that, so this time my option is doweling or screwing. I found that 3/4 MDF is pretty strong and most speakers and subwoofers are built with it, problem is that it can easily split at the edges if you dont use the proper screws, to avoid disasters like mdf splitting, will simply use dowels, making straight holes is not a problem because I am going to use a drill bit guide. I think I will put a dowel every 2 inches.



Wow thats very nice.



Most subwoofers are made of MDF, because the high quality sound you get with it, only critic thing about using MDF, if the care of screwing the edges, something you can solve with dowels or box joints, I mean, its a very interesting material, cheap and very strong.
So what do you expect the dowels to do in this instance? They have no compressive strength that will hold the box together like screws. They only have sheer strength the way you are installing them, and by removing 5/16 out of the MDF you are weakening it. As others have stated, the proper screws, installed properly, will be the best solution.

But it's your box, and it seems as though you have convinced yourself to use dowels, so I'm not really sure why you asked for advice?
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post #14 of 29 Old 04-30-2016, 06:58 PM Thread Starter
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So what do you expect the dowels to do in this instance? They have no compressive strength that will hold the box together like screws. They only have sheer strength the way you are installing them, and by removing 5/16 out of the MDF you are weakening it. As others have stated, the proper screws, installed properly, will be the best solution.

But it's your box, and it seems as though you have convinced yourself to use dowels, so I'm not really sure why you asked for advice?
There's no way I will use screws on the edge of a MDF board, I have made several tests, and found that it splits very easily, however I found that machine screws work better if you clamp the board while screwing the screw, but although it did not split it, I won't trust it won't eventually split it with a hard movement.

Take a look at this picture a took some minutes ago.

A - I screwed a #12 1.5" machine screw to a glued sandwich, it did not split although the screw went in so tight, not only because I pre drilled, but because it's very hard to split MDF on its face. To mention that I was near to the edge, but as I ran perpendicular to the fibers, nothing bad happened.

B - I attacked the edge with same screw used on A, I properly pre drilled and clamp the area with a clamp and two wood pieces, once I removed the clamp, it did not split, but just as I said before, I won't trust a screw inserted in that side.

C - Here I used a coarse wood screw, which even had a self drilling in the tip, anyway I pre drill with my drill before screwing. It split and ruined the mdf very easi and horrible, maybe because of that head type, that make even easier splitting.

D - Same test as C, just clampling the area with 2 more boards and C clamp, the damage was minor, but it split the edge.



You see guys? I think that you can use screws on mdf, but not in a edge. Dowel with get its compression once the glue expands and dries.
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post #15 of 29 Old 04-30-2016, 07:19 PM
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I use screws in the edge of MDF all day long with no problems. In this picture I put a screw only a half-inch from the edge, another one three quarters of an inch away and another one 2 inches away with no splitting.

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post #16 of 29 Old 04-30-2016, 07:33 PM Thread Starter
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I use screws in the edge of MDF all day long with no problems. In this picture I put a screw only a half-inch from the edge, another one three quarters of an inch away and another one 2 inches away with no splitting.
I think that the problem comes once you tight the screw to recommended torque. I have to say that I made a mistake in my test, specially with that wood screw, that head makes disaster if touches directly the edge, in real application that head should be placed in the face of the mdf board, so maybe I wont have that problem screwing my speaker box, but because I don't want to risk my two big boxes, was planning using the screws as if it were dowels, I mean, if they are 6mm counting the threads, my pilot hole its going to be 6mm, that way it can be inserted without stressing the mdf fibers, but what about the fixation? I will put wood glue in the hole and on screw, and that with make the magic. I did this before, what do you think? I am using a woodglue which is harder than wood.
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post #17 of 29 Old 04-30-2016, 07:44 PM
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If you drill a pilot hole for the screws and countersink it, screws shouldn't split the edge of MDF.
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post #18 of 29 Old 04-30-2016, 08:06 PM
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Originally Posted by Johanx3 View Post
well, I cannot do the spline because the walls are now glued, just waiting for dowels or screws, anyway I had no tool for doing that, so this time my option is doweling or screwing. I found that 3/4 MDF is pretty strong and most speakers and subwoofers are built with it, problem is that it can easily split at the edges if you dont use the proper screws, to avoid disasters like mdf splitting, will simply use dowels, making straight holes is not a problem because I am going to use a drill bit guide. I think I will put a dowel every 2 inches.



Wow thats very nice.



Most subwoofers are made of MDF, because the high quality sound you get with it, only critic thing about using MDF, if the care of screwing the edges, something you can solve with dowels or box joints, I mean, its a very interesting material, cheap and very strong.
You sure? My four MTX AAL212's all made from Pb running on an old Pioneer with 125 wpc. I mean I turn off the BOSE when its time to run mice off and dust the rec room walls son. My daughters MTX sub in her car is pb from the manufacturer.

When I was asked in the early 80's to make subs for a local audio deal I declined because they required pb and I thought it was a waste of time. Little did I know subs were the future
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post #19 of 29 Old 04-30-2016, 08:09 PM Thread Starter
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If you drill a pilot hole for the screws and countersink it, screws shouldn't split the edge of MDF.
I countersink it, and anyway happened, as I mentioned it, what I did not do, was to make the countersink in the board which fibers are not running parallel (I mean, in the corner of a box attacking 2 pieces), but I don't know, I made a test with a machine screw and a big washer, thinking that if all head pressure falls on the washer and therefore cover more mdf area, it won't split, but it did it. Is it ok using #10 screw on 3/4 MDF? or should I use #8? I think for this time only going to dowel the screws with glue and drilling a same diameter hole. Next time will think in using plywood or even particulate board, which dont have this problem. I decided to use MDF, because had planned using some 2x2 timbers at every corner, that way I was supposed not to screw on any MDF edge, but plans changed and needed to get rid of the 2x2 timbers and now need to do what I said.
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post #20 of 29 Old 04-30-2016, 08:26 PM
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Originally Posted by Johanx3 View Post
I countersink it, and anyway happened, as I mentioned it, what I did not do, was to make the countersink in the board which fibers are not running parallel (I mean, in the corner of a box attacking 2 pieces), but I don't know, I made a test with a machine screw and a big washer, thinking that if all head pressure falls on the washer and therefore cover more mdf area, it won't split, but it did it. Is it ok using #10 screw on 3/4 MDF? or should I use #8? I think for this time only going to dowel the screws with glue and drilling a same diameter hole. Next time will think in using plywood or even particulate board, which dont have this problem. I decided to use MDF, because had planned using some 2x2 timbers at every corner, that way I was supposed not to screw on any MDF edge, but plans changed and needed to get rid of the 2x2 timbers and now need to do what I said.
Again, as others have clearly stated, no issues with the correct screws, properly installed screws, your test is flawed.

Regardless, I think you should do what you want to do, as we wont convince you otherwise. There are DECADES of experience on the forum, that have all indicated screws will work. Your inexperience is making you think they wont. So this will be like raising kids, you have to let them take their own path sometimes, and find out if something works, or doesn't. It's just odd you ask for advice, and then wont take it.

And, you might do some research on the type of screws to use with MDF, I think you will find some interesting info...

Last edited by shoot summ; 04-30-2016 at 08:34 PM.
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