Assembling a box.....

[brettw22]

Ok, I have a question on how to put these things together.

A while back, Cody designed a box (thank you again) that will fit in my trunk but I'm a little unsure how to mount the side panels on these things and at what point to carpet everything (before or after assembly).

The main question I have is about the side panels. I can screw the top, bottom, front, and back and that's fine, but when I was at a Tweeter looking at some boxes, they said that in one of their boxes, the side panels aren't screwed down at all, but just wedged into place due to the carpeting. I guess if you're doing them en masse the process is much more streamlined, but I don't see how it's beneficial to have a panel just wedged there and not have it screwed into place.

Along with that, do I carpet the side panel and wrap the carpet around the sides to where it would go into the box itself or where should I be trimming all of the carpet to end? Edge where panels meet? around both corners and ending up in the box?

I have yet to cut the hole for the sub, but hopefully my dremmel doesn't completely screw that up or else i'm totally screwed......ha.

[Jstas]

No, a wedged panel is not a good idea and carpet does provide and adequate seal.

The best way is to cut dattos in the top, bottom and sides that the panel will fit in to and then assemble the top, bottom and sides around those side panels with glue and then nail or screw them into place also. If you are using MDF, use screws. The panels will be a bit recessed so make sure you compensate for the dimensions of teh internal volume.

Another way is to just butt-joint them right up against the ends and screw the panels to the ends of the top, bottom and sides of the box. However, for strength in this kind of design, I would use internal bracing.

Then again, I don't know what kind of box Cody designed so my advice might be useless.

[brettw22]

Since I don't have any power tools to do dattos, I'm going to have to butt them up at the ends. Here's the info from Cody on how it's going to be built (so you know what I'm building):

the side-view of the box is a (isosceles) trapezoid. exterior dimensions:
16" wide
~16.25" tall at the front
12.5" tall at the rear
14.375" deep

even though this box is much easier than the ported, it isn't really gonna be a breeze to make, there's a couple funny angles in there (specifically, it's about 12 degrees, i think). therefore, making the top piece will be a little tricky. the dimensions listed below are what you should cut it to, and i've left some leeway; you'll need it, because no tape measure will get you to the precise value you'll need. you'll have to stick it on top of the rest of the already-assembled pieces, and shave little slices off until it's right.

dimensions of pieces to be cut:
front: ~16.25" x 16"
bottom: 13.575" x 16"
rear: 11.75" x 16"
both sides: 12.825" on the bottom, 15.25" on the front edge, 11.75" on the back edge
top: 13.75" x 16"

to visualise how these pieces go together: start with the bottom laying on the ground. the rear piece goes on top of the bottom, at the rear (duh). the front piece rests on the ground, just in front (so when you screw it down, it's through the front into the bottom, just as the screws go through the bottom into the rear). the top piece rests on the rear piece, and just behind the front piece (same deal, you screw through the front into the top, but at a slight downwards angle). the sides can then be slotted into the frame. they're meant to be indented 0.25" each from the edge, in order to facilitate carpeting.

I didn't cut the pieces and took the MDF to a wood shop and they cut them out for me. The one slight alteration that we made was to the angle where the front piece and top piece meet.......rather than angle those two pieces to screw together, i had it cut so that the top sets directly onto the top of the front and the top of the back panel so there's as much wood thickness as possible without cutting the edge too thin making it more fragile for screwing etc. On his carpeting comment, I suppose I could just carpet the outermost side of the side panel, indent it slightly, then curve the carpet from the rest of the box into that slight overhang. My worry on that is that the small overhang is going to allow the carpeting to pull up........

I don't know I'm going to go about internal bracing because the sr subs are huge and any cross supports aren't gonna work based on the basket, right?

[brettw22]

As for bracing, are you talking just around the internal corners? Or more of a bottom of the back panel to the top of the front panel? Or just straight across the insidefrom front to back or side to side?

[MacLeod]

The best way to brace is to use a single piece from one side to the other.

The box should be big enough so that you can brace the inside of it without the sub hitting anything.

You should hit Sid up for some tips as well. He makes some very excellent boxes. Id even considered hiring him to build me something.

[Jstas]

Ok, for internal bracing, since that is the simplest question to asnwer, if you have a common chamber box it's easy. Cut another piece of MDF like you have for the sides. Only make it so that it fits inside the box when the top, front, back and bottom are together. Then, draw a fairly large line about 2-3 inches from the edge of said piece and go around the entire perimeter like that. Then get a drill, a jigsaw and a drill bit big enough to drill a hole that will let the jigsaw blade slide into the hole. Drill a hole on the inside edge of that line you just drew and cut that inside part out. Take some sandpaper or a fine file when done and round off the edges of the cut. Then slide it into the box so it is halfway down and screw it into place. You don't lose your common chamber and you increase the rigidity of the box by about at least 40% I would say.


Now, if you already have your material cut, take the widest and tallest measurements of the box sides assembled and see if your sides fit over the whole end enough to give you enough material to seal it properly. If not, you'll either have to get more material cut or go with what you got.

Now Cody's plans say to place the panels on the sides on a slight indent. That will be fine if you want. Just cover the ends of the panels in glue. I would assemble the top, sides, bottom and back first id you can. That will allow you to slide the sides in straight down and see where you need to screw them in. Glue every joint that you can, even the brace. It's the joints that are the weakest part of the box so all the help you can give them, the better. Assembly should be fairly straight forward provided your measurements were on spot. Make sure that when assembling, you mark the spots where the brace is somewhere on the outside so you aren't trying to hunt & peck for the center brace with screws.

As for carpeting, it's easy. Get yourself a good deal of carpet. It's fairly cheap and you will likely have waste. Also, get yourself 3M General Trim Adhesive. The Super Trim Adhesive works fine too, it's just more expensive. Pep Boys or AutoZone has it. Also, razor blades, you don't need a holder, it's just going to get in the way and a staple gun with at least 1/4 inch staples and a ruler. Since the sides will be indented, do them first. Lay a square of carpet down that is about an inch and a half larger than the indented panel in all directions. Spray the adhesive on the MDF (be liberal and get it every where, even in the corners of the indent) and the stick the carpet on squarely. Give it about 5 minutes to set then use the ruler to shove the carpet into the corners of the indent. Let it sit and do the other side the same way. When the other side is done, flip it back over and take your razors and trim the excess off using the corner as your guide. Do that on both sides.

For the rest of the box, it's easier. Get a length long enough to go around the entire box, like you were wrapping a present. Make sure you seam will end up on the bottom of the box. Give yourself about an inch and a half to two inches of over hang on each side. Once the carpet is cut to the length and width you need, spray the top of the box with adhesive from edge to edge. Lay your carpet squarely down and even so the seam will end up on the bottom. This will ensure that the top, back and sides are unbroken lengths of carpet. Smooth it out to get all the wrinkles out. Used thee edge of the ruler like a squeegee to help out if you like. Don't shift the carpet around, just get the wrinkles out. Let that set for 15 minutes otherwise when you tug on the carpet to get it tight and crisp around the edges, it'll slide and get out of whack. Patience is a virtue here.

Next, with the box laying front panel down, spray the back panel with adhesive covering edge to egde. Pull the carpet straight out, tightly enough to just snug it around the corner and follow that nice, crisp edge. BTW, I hope you have all of your holes cut including your binding post hole. Once the carpet is down, do the squeegee thing again and make sure it is all stuck down. Let it sit for 15 minutes again.

When the back is dry, lay the box on it's back so the speaker holes are facing up. Follow teh same procedure as the back of the box to get the crisp edge and don't worry about the speaker holes or any other hole right now. Let that dry 15 minutes.

When dry, flip the box over on it's top and spray down the bottom, edge to edge. Take the front flap of carpet and stick it down, smoot it out and pull the ruller away from the front edge of the box. Once that is securely down, fold the rear flap over and smooth it out, pulling the ruler from the back edge of the box forward. You might get some over lap. That's fine, Just take a razor, fold the overlapping edge back until you can just see the edge of the front flap and cut along the inside edge of that crease. Once cut, stick it down and let it dry good. You might want to let the whole box set over night.

Now, the edges. You need your staple gun, razor and ruler. Since all the edges are probably buckling at the corners, you will want to relieve the stress. Take the razor, place a point at the tip of the corner and cut one side of a shallow V. Thee shallower the better. You can always remove excess material, you can't put it back. So cut a small V and test to see if the carpet will lay flat around the edges. If so, put a staple at the edge of each flap, unde the lip, as close to the corner as you can get. You shouldn't need adhesive but if you want to use it, it can get messy at this point. Do the same for each corner. When all the corners are secure, staple from the outside in along each edge of the box, alternating ends with each staple until they meet in the center. If you have buckling in the cent, cut small, shallow V's so that the edges will not over lap but lay flat. One last staple spanning the two edges will hold it.

I prefer staples in such a situation because it is my experience that the glue pulls up too easily. Staples won't pull up easily at all. The staples can be hidden easily enough. If the carpet is gray, get a black permanent marker and color the top of each staple. If it is any other color, go to the hobby shop and get a model paint for metal that is close to the color and a flat (like primer) or semi-flat or satin finsih. Then paint the top of each staple. If you have something like a suede brush, take that rub the carpet lighlty in a cricular motion over the top of each staple and it should muss up the carpet enough to make the staple unnoticable. If you have a visible seam anywhere, run the brush over that in a circular motion too and it should blend the seam together and make it almost completely disappear.

Now, the holes. Find the center of the hole with your finger. Take the razor blade and cut an X in the hole starting from the center and working your way to the edge. Then, when the X is cut, fold the flaps of carpet over the inside of the box and staple them down. Any loose flpas or pieces can get caught in motor structures and destroy your subs. Theye will be fine inside the box and actually help with dampening. Now, your box is carpeted!

Things that should be done before the box is carpeted and after initial assembly.

- Caulk all interior joints, even the ones for the internal brace. Let it dry for 2 days. Just run a bead in thee corner of each joint and smooth it out with your finger. Any silicone based caulk will do. My favorit is Permatex RTV Sealant. It'll stick to anything, it's cheap and comes in a tube that is managable insides the box. You can get it at ANY auto parts store and even Home Depot or Lowes.
- Cut all holes, even the terminal cup holes.
- All sanding if needed should be done.
- If you are soldering your internal wires to the cup, MAKE SURE YOUR LENTHS OF WIRE ARE LONG ENOUGH TO REMOVE THE SUB FROM THE BOX COMPLETELY. You don't want to have to dick around with wires that are too short to get to the binding posts easily if you are all pissed about blowing a sub.
- Also, measure the amount of polyfil you will need before you put the caulking or glue in. Then put it in a bag and put it aside.



To finish your box, install your gaskets on your subs and terminal cups, not the box. They won't stick to the carpet but they will seal to the carpet. Spray the inside of the box with 3m adhesive and stick your polyfil to the sides. If you are going to pack it full, the get yourself some light canvas remnants and place them between the back of the sub and teh ployfil so it doesn't get all wedged up in the vents and motor structure. Use a large enough square and it can be free floating. Install your terminal cups with the wires. Get some wire hold downs and secure the wire to the inside of the box so that as little of it is free floating as possible. The extra length to get the sub out will be OK. The stuff that gets screwed down inside will rattle around if it is not secured.

After all of that is done, I would let the box sit some place well ventilated for about a week so that all thee caulking fumes, glue fumes and even the carpet and polyfil fumes have a chance to dissapate. Otherwise, some of the oils and acids coming off that stuff can harm your speakers.

I know it's alot of work but that's what I would do with my stuff and I don't cut corners. You box should work out great and look even better if you take your time.

I hope I answered your question. Sorry it was so long but I did my best to make my points as clear as I could. Sorry for the delay in responding, your questions while seeming simple were not so easy to answer for me.

[brettw22]

Holy crap.........thanks for the detailed description....ok......I got most of that, but am unclear on a few points.

Paragraph 1 - Each of the 2 subs are going to have their own box. I don't have much room on either side of the sub to mount the type of brace you described. (basically, a 3rd side panel mounted center for support) If that's not an option, what other alternative would you suggest?

P2 - The side panels are going to fit within the top/bottom/front/back panels, and will be inset about 1/4".

P3 - Since the side panel will be basically within each of the other panels, I don't understand what "covering the ends of the panels in glue" would accomplish. I understand the purpose in gluing all joints as well as screwing them down, but the phrasing of the ends being glued doesn't make sense right now....

p4 - I'm under the impression that if I was to carpet the side panel before mounting it, I'd be doing the carpet and then having enough overhang to pull that around the edge and then staple or cut the excess off that would be within the sub cavity. I'm not sure if I'm understanding your description correctly, but it sounds like you're saying the excess of the side panel isn't going into the sub cavity, but instead lining the 1/4" lip and then being trimmed at the end of that 1/4" lip (or continuing on around to cover the 3/4" thickness of the MDF.......Or maybe I'm not understanding this part at all......lol...

p5 - p9 - After getting all the carpet glued to all sides and the drying times, when you're talking about applying the staples......are you stapling on the 3/4" sides of the panels or are you stapling at the 1/4" indent of the side panel? This kind of ties into the P4 question, but better to over specify than under.....

skipping down to trimming the carpet for the holes......Most of the premade boxes I've seen in stores had the carpeting trimmed off at the front panel without them running around the inside edge. Considering the terminal cup and the sub cutout are going to be gasket covered, would it be ok to cut off all excess at the front of each panel or is the purpose for pulling it around and within the sub cavity to line that hard edge so no scratching of the basket while installing the sub? (maybe not the actual purpose of that, but makes sense nonetheless).

I think that's it mostly...........I'm about to start measuring out the holes for my terminal cups and sub......hopefully start doing some assembling and whatnot this weekend.

Thanks again........

[Jstas]

Holy crap.........thanks for the detailed description....ok......I got most of that, but am unclear on a few points.

Paragraph 1 - Each of the 2 subs are going to have their own box. I don't have much room on either side of the sub to mount the type of brace you described. (basically, a 3rd side panel mounted center for support) If that's not an option, what other alternative would you suggest?

If they are going to be in seperate boxes then don't worry about bracing at all. It won't be necessary. I probably should have read better but most of my reading happens at work with all the commotion.

P2 - The side panels are going to fit within the top/bottom/front/back panels, and will be inset about 1/4".

OK, then leave them that way and just assemble the back, top and bottom like I said so you can slide the sides in with glue on them and screw them down. BTW, regular old Elmer's wood glue will work fine. It doesn't have to be necessarily waterproof wood glue but get a big bottle because you want to be liberal with it. If you get drips, wipe them up immediatly with a damp rag. You shouldn't have to clamp them if you use wood screws to hold the sides together.

P3 - Since the side panel will be basically within each of the other panels, I don't understand what "covering the ends of the panels in glue" would accomplish. I understand the purpose in gluing all joints as well as screwing them down, but the phrasing of the ends being glued doesn't make sense right now....

Strength. Since they won't be datto'ed in (a trench cut in the wood to allow the panel to fit inside so it doesn't move), the sub actually has enough pressure to be able to push them out. Besides that, MDF is not as structurally strong as plywood or solid wood and screws alone create stress points as the MDF expands and contracts in temperature changes. Even with wood glue, teh screws will still create stress poinhts but theglue will help keep everything together. Besides, with modern glues, they tend to be stronger than nails at holding a joint together. Also, whenever I'm not sure what to do of whether I should do something or not, I think of what Norm Abrams would do and follow his lead. The guy is a master carpented with about 35 years of experience. He would glue every joint so I do too.

p4 - I'm under the impression that if I was to carpet the side panel before mounting it, I'd be doing the carpet and then having enough overhang to pull that around the edge and then staple or cut the excess off that would be within the sub cavity. I'm not sure if I'm understanding your description correctly, but it sounds like you're saying the excess of the side panel isn't going into the sub cavity, but instead lining the 1/4" lip and then being trimmed at the end of that 1/4" lip (or continuing on around to cover the 3/4" thickness of the MDF.......Or maybe I'm not understanding this part at all......lol...

No, the side panels get trimmed right at the corner joint. The big piece you wrap around the whole box has the extended edge pieces which will get wrapped around and stapled. You want the side panels to have a little extra so you can trim the right up to the corner.

It's all about neat and clean and it's the attention to detail that gets you points. That's what I'm trying to go for here. Long, uninterrupted expanses of carpet will make the box look clean and sharp. Making the box strong and solid is part of that too. If somebody rapps thier knickles on the box, you want them to feel like they are hitting carpeted stone. It's a mark of quality to have that solid feel and uniform look. That's why Lexus, MB, BMW and so on are held in such high regard, fit and finish. The cookie cutter boxes in the stores look OK but why do you want a cookie cutter look when you have a custom design? I mean, it may be a common shape but it's still a box you built yourself. Take some pride in it and make it look like you're proud of it. These sub boxes aren't rocket science to assemble. Cody did the hard part of getting all the measurements done for you.

p5 - p9 - After getting all the carpet glued to all sides and the drying times, when you're talking about applying the staples......are you stapling on the 3/4" sides of the panels or are you stapling at the 1/4" indent of the side panel? This kind of ties into the P4 question, but better to over specify than under.....

The 1/4" indent. If you look at the side of the box, the 1/4" lip creates an overhand around teh entire side of the box. So if you are looking at the top of the box from the side, you want the staples to go into the underside of the overhang so they are hidden from view. The staples will hold the carped around teh edge of the overhang without peeling back.

skipping down to trimming the carpet for the holes......Most of the premade boxes I've seen in stores had the carpeting trimmed off at the front panel without them running around the inside edge. Considering the terminal cup and the sub cutout are going to be gasket covered, would it be ok to cut off all excess at the front of each panel or is the purpose for pulling it around and within the sub cavity to line that hard edge so no scratching of the basket while installing the sub? (maybe not the actual purpose of that, but makes sense nonetheless).

Well, yeah, it helps with scratching the sub but you'd really have to bang it around. It helps sung up the fit of the sub in the hole too. But mostly, if the carpet glue on the face of the box fails, the carpet is still pulled around inside the box and it will keep it from peeling up from under the sub and sliding out and looking like ****. I mean, it's unlikely it will happen but if you are moving back to a warmer climate like Arizona, that heat down there can melt a polymer based adhesive like 3M Trim Adhesive and cause it to fail. The wood glue will be fine though so don't worry about that. Fit and finish again. You can probably get away with the terminal cups being trimmed flush but the pieces are so small and aggravating that you will like just leave them and pound that terminal cup in there and screw them down. Most of the stuff I do that seems anal is from experiences I had and found a way around it. I don't like messy installs. If anyone besides Bill and Noel took the time to take a look at the inside of my truck at Polkfest, you'd see nothing until I started to point stuff out to you. If I lived close enough, I'd come over and show you how to do it all the way I've done it. The same anal stuff I'm telling you to do is what we did with Antny's truck and he was tickled pink with the results and they looked damn good.

Are you going to have a Polk Audio show car? No. You can't live with that every day. Just because it's a daily driver though, doesn't mean you can't take the extra time to trim up and make it look good or make sure something is secure. Besides, the tighter the tolerances are and the higher a standard you hold your build quality to, the better they will sound. They will also likely outlast your desire to keep the car they are in. I have a sub box I built 12 years ago that has outlasted 4 subs and been installed in 3 different cars. I can stand on it, I can throw it across the yard, I even rested my Ranger on it for a few moments when it fell off of the jackstands. It's as solid as ever because I took the time to attend to the details. Of course it's made from 3/4" thick birch veneer plywood and glued together with waterproof wood glue and 2 inch brads every inch and a half with silicone caulking on every joint. It's over built for sure but it sounded great with every sub that was in it. I wouldn't do all that abuse with MDF though, it doesn't take impacts quite as well! ;)

[brettw22]

I'm down with all that......

I misspoke on the P3 question. I don't know what you're describing when you say "cover the ends of the panels in glue." Are you talking about layering a bunch of glue around the 3/4" edge that's next to where the 1/4" inset is? I don't understand how doing that would strengthen anything because the only thing going over that 3/4" edge is carpeting that's on it's way to being terminated at the 1/4" inset.

[Josh]

Okay..okay...I think our server is full now. Do you have any fingertips left?

[MacLeod]

LOL! I was just thinking the same thing.

My attention span is way too small to be reading any of that!

But no denying, our boy knows his stuff.

[Jstas]

I'm down with all that......

I misspoke on the P3 question. I don't know what you're describing when you say "cover the ends of the panels in glue." Are you talking about layering a bunch of glue around the 3/4" edge that's next to where the 1/4" inset is? I don't understand how doing that would strengthen anything because the only thing going over that 3/4" edge is carpeting that's on it's way to being terminated at the 1/4" inset.

Sorry dude, you don't have to cover the 3/4" edge with anything. The staples holding the dge to the 1/4" lip will hold it over the edge just fine.

[brettw22]

On the staples on the lip, how far apart do you space them usually? I don't want to have a lot of shiny (albeit sharpied colored) staples around the edge if i can keep it minimal.

[Jstas]

It depends on the installation. If you leave enough excess on the edges to pull over so that you don't have to stretch the carpet real tight, you can get away with very few of them. Remember, it's easier to take away excess than it is to add material back on. Be patient and take your time. What you can do is use some of the 3M glue on the underside of teh lip also. However, I would not rely on the 3M stuff solely because it will pull up. There is not enough matrerial to grab the glue well enough. Staples and glue will keep it in place for a good long time.

Also, check Home Depot or Lowe's. You should be able to get staples coated in vinyl for electrical installations. They are coated in vinyl to keep teh metal edges of the staples from cutting the insulation on the wire. You might be able to get them in a color that would be close to your carpet color. Then you won't have to worry about shiny staples.

[exalted512]

umm, I didnt design that....
-Cody

[brettw22]

Brain fart......

David/Neo designed it..............my bad.

[exalted512]

lol. Its ok. I saw this thread and was trying to remember what I had designed for you, then i saw the word isosceles and I was like....ummm, that def. wasnt me:D

That, and if the front baffle is touching the ground, the rear one is also touching the ground if I design it.
-Cody

[vinkalmann]

New to the board. Thanks VERY much for the write-up. Maybe random, but I HAD and LOVED my Polk C4 sub (had it for 10 years) until it was stolen last week. Looking to build my own box now and this seems like a great place to start :)