|
Construction Tips; Speaker Cabinets
|
I have been building speaker cabinets, rack mount units and road cases for years. The reasons for doing this are many, but my reasons were mostly because I had a specific need and I wanted to keep my costs as low as possible. I needed cabinets and cases that could take some normal wear and tear type abuse, and always look their best when in front of an audience.
When you build anything, always think about how to accomplish your tasks safely. Always wear safety glasses and keep your work area clean. If you don't how to use a particular power tool, ask someone who does to help you. You can do it - just take your time, measure everything twice and think your way thru every step.
Materials used to Cover Cabinets/Cases
The look of cabinets have changed over the years. When I first started building cabinets in the late 1960s, Tolex (the same stuff that is used to cover automobile roofs with, when you want that vinyl simulated leather look) was the big thing (It still is for some cabinets). These look great, except that over the years, the wood cabinets get beat up and the Tolex tends to look old and often is ripped in places. Some things really look good when covered in Tolex (or other vinyl covering), but if you build anything and cover them in this, you'll need to also make some sort of additional covers for their protection. Covers are a good idea no matter what, but if your budget doesn't allow it, maybe Tolex type cabinet covering is not the best choice. I did my Twin Reverb cabinet up in Denim (the same stuff your blue jeans are made of - looks ok, but this was a serious mistake - it has small tears and stains of all sorts all over it and looks like it needs a trip thru the wash).
In the early 1980s, people started covering cabinets and cases in outdoor carpeting. This is not the stuff with a rubberized backing, this is the stuff that is a low weave, tough outdoor carpet that was designed to be glued down to concrete steps and around swimming pools and hot tubs. Its between 1/8 and 1/4 inch thick and is made to be walked on and kicked around. It can still be torn and damaged, but it is infinitely stronger than Tolex. Done right, it looks exceptional and holds up. Its available in many colors, but most people use black, or some shade of grey. I've also used blue, and while this can look good, it looks out of place unless most of your cabinets are the same color. Its available in many colors, but, I reccomend that you use a darker shade of grey. Why? Because your cabinets will get dirty and this really shows up on black and light grey cabinets. I don't know about you, but I have better things to do than constantly clean of my cabinets to have them look good when you set your gear up for a gig.
 your cabinets up off the ground and, over the heads of your audience. |
If you already own speaker cabinets and cases that have this form of carpeting
on them, then it may be a good idea to try to match up things as closely as
possible. In general, as long as you have a mix of black and greys, they will
all look pretty reasonable together.
If you have no budget for covering your cases in anything, you can use Flat Black Spray paint. These will get beat up, but a quick zap of spray paint will make them look like new again. For small cabinets and cases, it may be far too much trouble to cover them - just paint them. Why flat black? because it doesn't show blemishes, and pretty much any brand of flat black spray paint will match what you used the last time you touched up the finish. Some cabinets that you build may require that they be capable of being suspended in on top of a stand. You will need to design your cabinets to allow for solid support of the stand adapter and you also need to know the balance point of the cabinet, so that it doesn't tend to fall over once put on the stand. You are also limited in the weight that the stand will support and your ability to lift the cabinet onto the stand. |
Cabinet/Case Materials (Wood)
For most road-worthy cabinets and cases, you will need to use 5/8 inch to 3/4 inch thick material. I have used 1/2 plywood for cases that are not exceptionally large - never use less than 5/8 inch material for speaker cabinets. The bigger the case, the more chance it has to get mangled by you or your road crew as it gets tossed into the trunk of your car or a van. If you end up with cases that give you a hernia moving them around, plan on using good quality hard rubber wheels on the base. If your cases and cabinets are to hold up, they need to be solidly built. 2 inch to 3 inch wheels on the bottom will save you a lot of effort during set-up and take-down on heavier gear.
Particle Board
Unless you are making fairly small cases and cabinets, don't use particle board. While particle board has the benefit of very solid sides and would never be troubled with voids inside the lumber (which can happen in plywood), the stuff simply doesn't hold up well on the road. If your cabinets are never going to leave your house, you can use particle board for everything. I have made the front part of a Speaker cabinet using Particle board with success - this is the part that the speakers are mounted to. I usually brace these with 3/4 inch square pine strips to add support. The fronts of speaker cabinets don't normally get much abuse, so, if you are careful with your cabinets, you might be able to get away with using it here.
Plywood
There are different grades of plywood. There are also different numbers of layers (plys) that make up the various choices that you will have for plywood. Since most hardware stores sell only structural plywood (ie. to build houses or kitchen cabinets with), there isn't a lot of thought given to the musical qualities of the lumber. Using indoor or outdoor plywood makes no difference to your cabinets - you shouldn't be planning to leave them anywhere that they will get rained on.
You need to look for at least 5 layer plywood (5/8 inch to 3/4 inch in thickness). The wood also needs one 'good' side (sanded smooth). There should be no exposed knot-holes in the plywood - you may see 'football shaped' plugs any place that a knot hole appeared in the actual log that the plywood sheeting was cut from; these are ok. The 'good' side will be what you glue your outside covering to.
It is very important to make sure that the one 'good' side is completely good. It is also important to look around the edges of the plywood and reject any sheets that have voids in them. These will be seen as open spaces in the layers. If you have these, your cabinet may buzz on certain notes - you don't want that if you can avoid it.
Plywood is made by scraping a thin layer of wood off of a log, with a consistent thickness. These are then layered where the wood grain alternates at 90 degree angles from each other. The layers are glued and pressed together to form a very strong and stable piece of lumber. The problem is that you cannot see inside of the layers - you can only see the 2 outside layers. Typically the cheaper grades will have holes and voids in the middle layers, so its really false economy to cut corners here. Looking at the edges of a sheet of plywood (and the others in the stack) will give you a good idea of how well these sheets are made. You may need to buy more than one sheet of plywood at a time for a project - try to use the sheets from the same batch when possible, mostly so that each part you cut out will have a consistent thickness.
You will probably be buying plywood in 4 foot by 8 foot sheets. Buy the best quality that you can afford. There is a grade called marine plywood, which is usually hardwood based and has much thinner layers with very few voids in it anywhere. I don't see it for sale in many places in the United States, so it may not be an option for you at all. You probably don't need this quality of wood, but if you feel that its what you want to use, it is an excellent plywood for musical purposes - its very hard to find and very expensive when you find it.
Pine - planks and furring strips
NOTE: Dimensional lumber - in this case Pine planks and furring strips - is labeled different than its real size. A 2X4 is not 2 inches by 4 inches - its 1 1/2 inches by 3 1/2 inches. A 1 inch thick piece of lumber is actually 3/4 of an inch thick. These inconsistencies in dimensions are not shared with plywood or particle board. Length is another area that tends to be correctly listed when quoting sizes of lumber. Keep this in mind when selecting your lumber. I always bring a pocket measure with me to verify the sizes of dimensional lumber so I know what it was I really bought. All sizes listed here are the measured size, not the listed size (ie. 3/4 inch thick means the board is really 3/4 of an inch thick). For those of you not working with inch measurements, 25mm is approximately 1 inch
You'll be needing 3/4 inch (or larger) square strips to screw your cabinet/case parts together with. You will need quite a few of these to build your cabinets since they are attached along the perimeter of the cabinet/case sides. For example, a square sheet of plywood 2 feet square, will need 4 2 foot strips - 8 feet of 3/4 inch square pine.
I normally buy 3/4 inch by 1 1/2 inch furring strips and saw them down the middle giving me 2 strips to work from. These are normally 8 feet long, and if you process all the material up front, you can have a large quantity of this material available in short order. You could also cut this from wider 3/4 inch pine planks - the end result is the same thing. Cutting the 1 1/2 inch furring strips will result in 5/8 inch wide by 3/4 inch strips - this is not going to cause you any problems.
For smaller cabinets and cases, you could build the entire thing out of pine planks. Many of the Fender amplifier cases (such as my 1974 Twin Reverb) have been made this way. It is very difficult to find good quality pine planks wider than 10 inches for a reasonable cost, so unless you are prepared to miter together planks to form wider pieces (or you have access to wood that this was already done to), I suggest using plywood.
Hardware
Wood Screws/Glue
You don't want this cabinet to come apart on the road. Some cheaper production cabinets and cases are simply stapled together. My experiences with this sort of design has been very poor and I prefer to avoid this 'quick assembly line' approach to building anything that will have to take some abuse in real life.
I use flat head countersunk phillips head (cross-point) wood screws. These are 1 1/4 inch long black wood screws that are sold in U.S. hardware stores by weight. You could buy a few boxes of these, or get 2 to 3 lbs of them in a paper sack - either is fine; you will be using many of these. The length is such that is you put the screw thru the 5/8 inch to 3/4 inch side material into the 3/4 inch pine cross strips, at least 1/2 to 3/4 inch of screw threads will be into the pine material. There won't be any sharp tips sticking out when things are tightened down (you can't appreciate how much damage you can do to your hands if you have screw points sticking out until you've done it once). You will be putting screws from multiple directions from both the inside and outside of the cabinet/case. Plan to use a lot of them. You will be using your hand drill to put these in with, hence the need for phillips head (cross-point) wood screws.
You can use Elmers White glue (or any brand of white wood glue), but I prefer the yellow carpenters glue. Both are water soluble and set up within 30 minutes. You'll be using this glue for both attaching wood pieces together and to attach the outer covering material to the cabinet/case. You will need a lot of it. I purchase this in the quart size (slightly more than 1 liter) containers. Start with a quart and see how far that takes you on your first cabinet, then from there decide how much more you will need.
Metal / Plastic Corners
|
The corners of your cabinets will take a beating. I prefer all metal
corners, but, the black plastic ones protect just as well. These are
available from many musician supply houses (mail order), and are often
available locally at music shops. There are different types. One is for the
front or back of cabinets that have removable sections. These attach using
screws to only 2 sides of the cabinet. The other type is for sealed cabinets
and cases where there are 3 sides to screw down to protect a corner.
It is unlikely that you will use many of the sealed cabinet/case corners, and use mostly 2 sided corners. You have a total of 8 corners required for each cube shaped cabinet/case that you build - keep this in mind when you go to buy/order parts. I rarely use anything but the 2 sided covers, and never keep any of the 3 sided corners on hand. If you use notched corners, the thickness of the side material is more critical. Notched corners expect 3/4 inch thick sides (5/8 if using 1/8 inch outdoor carpet, or 3/4 if using Tolex for finishing materials). |
  2 sided Plastic (top) and 2 sided metal notched (bottom picture) |
Handles
 
|
If you have small cabinets, you may want a simple pull handle. These are often used on the top of smaller guitar amplifiers and cases. If you have large PA cabinets, or cases that you haul your stuff around in, you might want a recessed handle or spring handle. Peavey sells a line of these in Music stores (as well as mail order). I suggest that you take a look at commercial cases and cabinets to determine the best selection for a given need. |
You need to decide what to use based on the size and handling requirements of your cabinets/cases. Recessed handles will require that you cut out holes, or use a router to recess the area that the handles go. Don't assume you don't need handles - their benefit will become obvious when loading/unload equipment and anytime you have something big that needs to traverse a flight of stairs.
Casters (Wheels) / Rubber feet
|
For lightweight gear, you only need rubber feet on the base of your
cabinets/cases. Once you start building things that have a bit of size,
mass or weight to them, you should consider placing good quality hard rubber
wheels (casters) on the equipment. It will greatly speed up set-up and
take-down times and you will exert substantially less energy moving things
around. My experience is that of the musicians being responsible for setting
up and tearing down after a show - the easier it is on me, the better. If
you don't put wheels on your gear, at least make a wheeled flat cart out of
2 inch by 4 inch wood.
You should always put good quality screw on rubber foot (3/4 inch diameter or larger) onto any gear that sits on top of the floor (unless it has wheels) or on top of some other gear. Bass notes tend to make things slide around - rubber feet will keep things from wandering around the stage on their own. On some gear that sees a lot of action on its sides (large PA Cabinets and cable cases), I add rubber feet to some of the sides - this protects it, and offers the option of you using the gear laying down on its side. Rubber feet can have a metal protector on the the base - this is for heavier gear. |
  Wheels can save you a lot of effort. Rubber and metal feet will protect your cabinet finish |
T-Nuts
| T-Nuts are a great invention. They will be used for securing handles, hinges and speakers to wood panels. Typically, you drill a hole out for them, then on the backside of where you will be attaching the handle (etc), you hammer a T-Nut in place and now you have a strong threaded insert for you to bolt to. You will use at least 4 of these per speaker (possibly up to 8), and 4 or more per handle. These effectively spread the load across a larger surface area - for some parts of the construction, you don't want screws that only hold into the wood sides - specifically handles and speakers. |
 Available in 4 or 6 prongs |
Tools Required
Circular Saw / Table Saw / Saber Saw
You can cut the 4 foot by 8 foot sheets of plywood down to size with any sort of power saw you have handy. A hand held Circular Saw or Table Saw is the fastest way to cut the wood material to size when all the cuts are straight. If you have never cut wood products extensively with these types of saws, you will find that you get your best cuts by adjusting the depth of the cut to 1/4 to 1/2 inch deeper than the material itself. I also find that a Carbide Blade saw cuts cleaner and longer (but it does make a wider cut in the material). You will need the Saber saw to cut any shape that is not straight, such as speaker openings, recessed handle cut-outs and cable connection holes. It is hard to get a long straight cut with a Saber Saw (also called a power Jig Saw), but it can be done if you take your time.
Power Drill
I have 3 power drills. You could get by with one, but let explain why I use all 3. My best drill (the one with the variable speed control) has a phillips head (cross-point) screwdriver bit in it. I need sensitive control of the drill bit when putting screws into the wood pieces. Then I have 2 cheap power drills. One has a 1/8 inch drill bit in it, the other has a small countersink bit in it.
When you are assembling cabinets/cases, you will be marking where holes go, drilling them out, countersinking some of them, slopping some glue on the parts then screwing the parts together. This all happens within a minute or so. If you have 3 drills, all set up and read to go, this all happens very quickly and effortlessly. You may put in 100 or 200 screws in the course of an hour. You can get by with less, but borrow any extra power drills if you need to to get you past this step. The rest of the building process can easily be accomplished with a single power drill.
Heavy Duty Stapler
I've often wanted to buy a power stapler, since my hands often cramp up after 2 or 3 hours worth of stapling the outside covering material to my cabinets - the reality of it is that I don't do this everyday and power staplers that can go thru indoor/outdoor carpeting are expensive. Even then, you can't use a cheap stapler - you will be putting in staples up to 1/2 inch long, and these require a solid stapler (my Arrow brand Stapler cost over $20.00, but its built very rugged). I use at least 100 staples when covering a cabinet or case - make sure you have a few boxes of staples handy before you start. Typically, for vinyl (such as Tolex) covering, you use 1/4 inch staples. For indoor/outdoor carpeting up to 1/8 inch thick, I use 5/16 inch staples. For 1/4 inch indoor/outdoor carpeting, I use 1/2 inch staples.
When applying the covering, you are constantly painting glue onto a surface, then pulling the covering over it, and then stapling. Cabinets/cases go together pretty quickly - you will be pumping 50 to 100 staples per hour into the wood/covering.
Screwdrivers
Get yourself at least 2 good quality phillips head (cross-point) screwdrivers that fit the screws that you are using. You should also have 2 flat blade (regular) screwdrivers handy to adjust the various tools with as you are working.
Router / Files
You will need to put a nice rounded edge on the outside of your wood cabinets/cases and you also need to remove any sharp edges that you might be pulling carpet or vinyl over. You need to use a router with a 1/2 inch inverse round cutter to do the outside (this is done after the cabinet is assembled). You also need to moderately round the edges of the rest of the assembly pieces. I have found that carpeting can tear when you stretch it tight against some of the cut edges of plywood and particle board. Slightly rounding these edges with a wood file will make a great difference.
Squares/Measuring tools
I find a small carpenters square a most useful tool to make sure that my angles (of the sides of anything I build) are at a true 90 degree angle from each other. These are not expensive and can save you a lot of time. I use yardsticks that I get from lumber yards (like Home Depot in the U.S.A) to allow me to measure up to 36 inches easily. Many yardsticks are actually 1 meter long (a bit more than 39 inches). When I am drawing pencil lines on long pieces of wood (such a plywood). I use the 8 foot length of the plywood as a straight-edge. Using a sheet of plywood, you can easily draw an 8 foot long straight line on another sheet of plywood.
Work Area
When you build cabinets and cases, the better organized you are, the simpler the task will be. When I draw up the lines to cut on sheets of plywood or particle board, I also number everything and indicate which side its for (top, bottom, back, front, left, right) and which one its for (in the case of PA cabinets, you are usually making one for each side, so I mark each part with a 1 or a 2. If you are making more than one set, you might mark them 3, 4, or higher. This is especially important if you are trying to optimize your cuts on a 4 foot by 8 foot sheet of plywood - that one piece may contain parts for 6 or 7 things). I tend to also mark things on the inside surface area of the cuts. This way, when I'm assembling things, all the numbers are facing the inside, and will be visible even after I cover them.
Cutting plywood sheets
You will need a space for the power tools that you are currently using, and a place to stack the parts in groups of what they will be used for. You might be having the plywood cut at a friends house if they already have the power tools set up and ready to go. Typically you will need at least as much space in your garage or work room that you would need to park a car in. Once the wood is cut, and you have all the pieces for a compete assembly, then you can work in a much smaller space. I highly suggest cutting everything at one time - get it over with, but also make sure that you measured correctly before cutting and that you allowed for the thickness of your cutting blade when you measured. You need to wear safety glasses when ever you cut wood with any power tool.
Assembling the Cabinet/Case
You will be dripping glue and dropping screws on the floor, so the area you do this should not be carpeted. You will need a workbench of some sort to work on and you will be working on completing single case/cabinet at a time. if you have to adjust anything, it will be simpler if the glue is not totally dry when you try to do it. You will need a place to stack the completed boxes as you finish them. You will be laying them down with any open sections facing up. This will eliminate any stress on glue joints that have not set yet. Once you have glued everything together, you will let the whole thing sit overnight, so you need to have space for all the assembled cabinet/cases that you will be building. You might want to put newspaper down on the floor to catch any dripping glue.
You will be switching power drills frequently as you drill holes, glue and screw down panels. Make sure that it is well lit and you have enough power outlets. This task works well when 2 people help each other.
Routing / Rounding edges
You cannot do this step until all the glue joints are fully set. You'll need the same amount of space as when you assemble the cabinets. The router will throw wood chips all over the place. You need to wear safety glasses when ever you use a router. You will use a wood file to slightly round the edges of all other areas that you plan to cover with vinyl (Tolex) or outdoor carpeting. Make sure that all the parts fit and keep all parts of an assembly together. You will also need to clamp down the boxes as you pull the router over the edges. Having someone hold the boxes while you do this is very helpful if you have no way of clamping things down effectively.
Applying the outside covering
Do not attempt to do this until all the glue joints are fully set and all the screws that appear on the outside of the panels are flush with the wood surfaces. I find that I am on my knees all the time that I do this, and that a carpeted floor is nice. You will also be spilling glue on many things and putting in hundreds of staples. If you have a section of carpeting that you can work on that won't matter if you stain it, that would be your best bet. You will need the same amount of space that you needed of assembling the cabinets. Take inventory on how much glue you used when you complete covering the first cabinet. This should help you decide if you need to buy any more, and how much you will likely use.
Have water and paper towels handy to clean up any spills - you don't want this glue on the outside covering material on your cabinet/case.
NOTE: Some people use contact cement to attach the covering with. While it does work, it has a few bad things about it. For one, the fumes are toxic. The second problem is that if you make a mistake with contact cement, you can't take the covering off and correct it - you only get one chance to get it right.
Sources of parts
You can the tools you need in most well equipped hardware stores. Some additional sources are:
- Indoor/outdoor carpeting - Home Depot (hardware store) or a local carpet supply house
- Your local music shop - they often sell corners, handles and speakers. These are already oriented towards professional music systems and you won't be dealing with consumer quality goods. They will also know more about what works best for specific applications.
- Parts Express Source for Audio components and cabinet hardware.
- Hundreds of on-line Electronic Components and hardware suppliers
- Your Local Radio Shack - They have a book on designing and building speaker cabinets. While this is directed more at their own speakers, it has a lot of good information about design and it is easy to find. Very few of Radio Shacks speakers are appropriate for high powered audio - some of their piezo horns will work fine, but not much else. Parts Express also sells books and software programs to aid in Speaker cabinet design.
See also: Finding Materials
Questions? Comments? .
Return to Shavano Music Online home
page
© 1997 Shavano Music Online