[randytsuch]

So, last week, I ordered the DS12 standard kit from Rythmik
http://www.rythmikaudio.com/DS12.html

And, I also talked to Rythmik, about building my own enclosure, or just buying this PE enclosure.
http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=302-810&CFID=5003256&CFTOKEN=48673314
He suggested I just buy the PE, so I would not have to go to the trouble of building an enclosure, and add some bracing to it.
AFAIK, the PE enclosure has one cross brace in it, that connects the two side walls.
He said to get a 2x2, cut to the length of the cabinet, and glue it to the middle of a wall (in this case, the top).  Do the same on the opposite wall (bottom).  Then, just add one more 2x2, to connect the middles of the 2x2 on the top and bottom.
I saw somewhere that it is best to brace the middle of the walls, which makes sense because this is the point farthest from a connection.  Adding this brace, in addition to the existing, should make this cabinet pretty sturdy.

In addition to that, I was thinking of adding some more 2x2's, on the front wall.  I think there is just enough room to fit a 2x2 between the speaker and the other walls.  I figured this would make the front wall stiffer.

So, in summary, my bracing stategy is to add 4 2x2's on the outside of the front wall, one in the middle of the top, one in the middle of the bottom, and one connecting the top and bottom.

Sound reasonable?

I will post further as I put this together.  Except for making holes for the amp and driver, and adding this bracing, there is not much to putting this together.

Randy

[ooheadsoo]

Good luck, Randy.  Let us know how the build goes and how it sounds asap!

[randytsuch]

I had a chance to make the driver hole today.


The hardest part was remembering how to use my rotary saw.  First time I have used it to make a hole like this.  Next time, I think it would be better, but the driver fits fine, so no problem.  The hole is a little big, it was supposed to be 11 3/16, and it came out to be 11 1/4  .  I guess I have to live with the 1/16 oversize.

Looking into the box, does not seem like my original plan will work.  The existing brace gets in the way of adding another brace. 

I am thinking about adding 2x2's to both sides of the brace, as well as the side walls.  Then, I will add the bracing 2x2's from the existing brace to the walls.

Randy

[jtwrace]

good job.  Let us know how it goes when it's done.  I use one of his (Rythmik) kits in my reference system.  They are great!!!

[ooheadsoo]

I would probably glue vinyl tiles (don't trust the supplied sticky backing) to the inside walls just for fun.  A cheap cop out on constrained damping.

[randytsuch]

I would probably glue vinyl tiles (don't trust the supplied sticky backing) to the inside walls just for fun.  A cheap cop out on constrained damping.

Hi Abe
I was thinking about trying to do something like that, or even something like whispermat, but then I did some searching over at diyaudio, and only found a couple times where they talk about adding dampening to subs.  Seemed like bracing is more important than dampening for a sub, because it is only working at very low frequencies.  That's why I want to add more bracing to my PE cabinet.  Of course, the tiles would be cheap, and couldn't hurt.  Something to think about.

Randy

[ooheadsoo]

Yeah, it's like $10 for a stack, and hopefully you have some good glue sitting around.  I can't get pieces of wood just the right length to be an effective brace, though.  I just don't have those skills.

[randytsuch]

Yeah, it's like $10 for a stack, and hopefully you have some good glue sitting around.  I can't get pieces of wood just the right length to be an effective brace, though.  I just don't have those skills.

The way I am doing it (based on the advice I got from Rythmik), the braces don't have to be exactly the right length.   I will put a 2x2 at each end of the brace, on the side wall and on the existing brace, and screw/glue the brace to the end 2x2's.  It may be clearer when I do it, and post pictures, I am not sure if I am explaining this very well.

Randy

[JoshK]

Just another idea for consideration...  I saw on the lambda forum where someone mentioned that they used steel rods for bracing and that they preferred it very much to window bracing or dowels.   I think they were referring to the threaded rods you can get at the big box, like we use in flexy racks although they needant be as thick.   

You can basically cut them and pressure fit them inside the box but if you want to glue them in place, I'd use a large diameter washer and nut on the end and tighten the nut so that the washer is pressed against the sides of the box...and use glue on the washer. 

The rods are quite stiff in their length direction and take up a lot less volume.  I really don't think you need to be concerned with them vibrating, because they vibrate at high frequency and this is a sub. 

[JoshK]

P.S. timely thread...I've been considering picking up a 3cuft box from PE for one of my avalanche 15"s to use until I can get the time to build my IB. 

[randytsuch]

Just another idea for consideration...  I saw on the lambda forum where someone mentioned that they used steel rods for bracing and that they preferred it very much to window bracing or dowels.   I think they were referring to the threaded rods you can get at the big box, like we use in flexy racks although they needant be as thick.   

You can basically cut them and pressure fit them inside the box but if you want to glue them in place, I'd use a large diameter washer and nut on the end and tighten the nut so that the washer is pressed against the sides of the box...and use glue on the washer. 

The rods are quite stiff in their length direction and take up a lot less volume.  I really don't think you need to be concerned with them vibrating, because they vibrate at high frequency and this is a sub. 

Thanks for the idea.  I will take a look into that.  I just did a few calcs in a spreadsheet, to figure out how much space I would lose from my bracing.  Turns out the box is a little bigger than the advertised 2 cu ft, which is good for me. 

If I add four 1x2's on the front wall, around the driver, along with a couple 1x2's along the side walls, to make those stiffer, then add a few steel rods (I did not account for the volume of the rods, figured it was in the noise), then the box ends up to be almost exactly 2 cu ft in volume.

If I have time today, plan to stop at my local HD, and see what I can find there.  I was thinking about using hardwood for the 1x2's, but I have a feeling that they would be too expensive.

Randy

[ooheadsoo]

Great idea, Josh!  I think I'll do that next time I build a sub.

[JoshK]

I also read an idea about how to test for good location of bracing. 

Face the sub with the side under observation facing up and lightly spread sand on top of the entire surface.  Then play test tones up and down the freq spectrum you wish to use the sub at, going up at least on octave higher than xo.  Watch the sand dance.  Then you can temp'y place a brace where you think it will help the most and repeat. 

You don't have to have fancy test equipment either.  You can usually find test tones on the 'net and use your soundcard's analog out into your sub amp. 

[randytsuch]

So I went to HD today, to see what they had, a research trip.  It's on the way to work, so it is easy to stop by there.

They have many sizes of threaded rods, but I already knew that.  I just have to decide which size to use.  I know any reasonable diameter will be strong enough, I just want to a large enough size, so the nut is big enough to give some adjustment.  If the nut is smaller, then the rod length is more critical, and I have less room for error.  The only drawback to the larger size rods are they cost a little more, and take up more volume, but the volume difference is negligable, and these are fairly cheap. 

I am going to add a small piece of hardwood at each end of the rod, so the rod/nut will not attach directly to the walls.  I want to spread the pressure from the brace over a larger area, so I will glue the hardwood to the walls, then install the rod brace.  I will use the rod brace as my "clamp" for gluing the hardwood.  I will also drill a hole in the hardwood for the rod to go into.  This will give me even more play in the rod length.

The more I think about the treaded rods, the more I like the idea.  With boards, I would just attach them to the walls, for the brace.  With rods, I can turn the nuts, to apply pressure against the side walls.  This will let me stress the walls, and bow them out slightly, which will make them stiffer than if you installed a brace that fit exactly to size.

For the front wall, I am now thinking about using angle iron.  All other things being equal, a piece of a angle iron will be stiffer than a flat piece.  Same theory behind ibeams.  HD had some 1/8 thick, 1x1 angle that I might pick up, and use for the front.  I had been thinking about adding something else to the side walls, but my current thought adding a couple braces on the unbraced wall will make those walls stiff enough.  I may add another brace on the walls that already have one brace, to help it out a little.

Josh,
The sand in another interesting idea.  But, making the angle braces for the front wall will take a little work, will take a look at that once I get there.

Randy

[randytsuch]

Hi Guys
So, over the weekend, I bought a 1.25 x 1.25 x 1/8 L angle bar, some threaded rods and assorted hardware.  I cut the angle down to 4 pieces, to make a box around the driver on the front wall.  I drilled and tapped some holes in the angles, to screw down the angles to the wall.  Eventually, I will use 2 ton epoxy, and the screws to hold the angles to the wall.  I also have 4 aluminum blocks, which will go into the corners, to hold the angles together, and turn it all into one solid piece.

I also bought some 8-32 size T nuts.  I am using these to screw down the driver.  My driver hole turned out to be about 1/4 too large, so in some places only two of the three tongs in the T nuts hit wood, but I think they will be fine.  I decided to use T nuts to hold down the driver better than standard wood screws.

I also bought some 1/2" threaded rod.  Size is overkill, but I already had one rod this size.  I also cut up some pieces of hardwood I had (think it is Jocobo or something like that), to 1x4x4 size pieces.  One will go on each end of the rod, with a hole in the middle for the rod to enter.  The wood will be glued to the walls, then I will torque the rod nuts to apply force to the walls, to expand them out a little bit.

I am going to use 2 rods on the unbraced wall, 1 on the braced wall, and one from front to back wall.

I will post pictures later, and this will make more sense, but I am on a business trip right now, in Iowa.  I get back home late Thurs, so project is on hold for a few days.

I do have one concern right now.  The angle bars are slightly magnetic.  I think their magnitism is too weak, and they are too far away from the drivers to effect them, but it does bother me some.  I don't think I would use them if this was not a sub, but my sub driver has some big strong magets in it, so I don't think it will matter.

Randy

[randytsuch]

Made some more changes since I posted last.
Will describe with the following pics.

Here is a tnut, that I was going to use to mount the driver.  Now, I am only using a few of them.




A couple of the tnuts installed




On diyaudio, someone suggested I use threaded rods to mount the driver.  It would mount the driver, and help make the baffle to rear wall more rigid.

Here is a picture from the front, showing the threaded rods which will mount the driver
The rods will stick through the front by about 3/4".  There will be a nut/washer to hold the driver down, and another set behind the front wall.






I am gluing blocks of wood down to hold the rods to the rear wall




I made a hole with a forstner bit, then hammered a nut into the hole

You can't see this nut, it is on the back of the block of wood after I glue it down.  I will also put another nut on the top of the block, so the rod is held to the block on both directions.

Randy

[ooheadsoo]

Wow, Randy.  Cool stuff.  You have lots of patience.  I'd want to get it done quick and dirty and be listening, already.

[randytsuch]

Few more pics.
I am still adding the angle iron to the front baffle, to make it more rigid.

I was going to screw it down, but I decided to just clamp and glue.  I used two ton epoxy, here is the clamps from the front.




And here is an angle that was already glued down.  You can see a couple of tapped holes I made, but did not end up using.



Next, I need to finish glueing down the blocks to the rear wall, that hold down the driver rods.
Then, I will add some rod braces for the side walls.

Randy

[randytsuch]

Hi
So, I am finanlly basically done.

In the last set of pics, there were the #10 rods that I installed for mounting the driver.  To those, I glued a 7/16" rod.  I used gorilla glue, and tie wrapped them while the glue was drying.  It is the vertical rod in this picture.
The horizontal rod is a 1/2" threaded rod that goes from side to side.  All the rods that go to the side walls end into blocks that are around 4x4x1.  I used nuts to push out against these blocks.  The blocks were glues against the side walls, and I used some locking nuts, and thread lock, to keep the nuts from coming loose.




Another pic of the inside.
I painted the inside, because I read about MDF breathing, and it is better to seal it with paint.



I positioned the braces to try to make them intersect as much as possible.  Then, I used gorilla glue to hold them together.  Now, they are very stiff, you can push on them hard, and get almost no deflection.  The #10 rods used to deflect easily, maybe 3/4" from side to side, before I reinforced them.



One more, from the back.  I added three rods on each side wall, and there are 5 rods going from front to rear, that also hold the driver down.


I installed some spiked feet from PE, but I forgot to take pictures of them.  Only problem here was when I drilled the front holes, I hit the L bracked I added to the front wall, so I had to move the feet back a little, and had to fill the holes with sealer.

Sub is put together now, sitting in my HT.  I set it up this morning, and calibrated it, but I want to play with the settings after I let it break in a while. 

Won't be able to comment on the sound for a week or two, after I put some time on it.

I do have a couple things left I would like to do.  Rythmik suggested I put some 1-2" thick polyfill sheet on the walls.  Said I could buy from auto upholstery place, but I found this stuff
http://www.mcminone.com/product.asp?catalog%5Fname=MCMProducts&product%5Fid=LS00916

I was going to buy a couple packs, and put on the walls where I can.

I also want to add some sealer where the rods meet the rear of the front wall, to make sure I am getting a good seal here.  I already put in sealant in the spike holes, and in the driver holes where I am using a tnut/screw.  Want to make sure there are no air leaks anywhere.


Randy


http://www.audiocircle.com/image.php?id=12064