Here is an introduction to the few main parts of a speaker:
This includes the woofer and tweeter. The woofer vibrates at a low frequency to create bass while the tweeter vibrates at high frequencies to create treble. more on how speakers work
This is a specially designed piece of circuitry that separates incoming audio signals into high and low frequency pass. All the low frequencies are sent to the woofer and the high frequencies are sent to the tweeter.
This is the box that holds the woofer, tweeter and crossover unit. It will take up the majority of the instructable.
This is my first instructable! Please leave comments. I am not an expert on this topic but I'll try my best to answer questions.
To get started, we need to decide which speaker drivers and crossover unit to use.
Step 1: Choosing the Drivers
- where you intend to use the speakers
- what you intend to power the speakers with
- how much space you have or how big you want them to be
- how much money you have to spend
In my case, i will be using them in a relatively small college student room and power them with a 100 watt per channel receiver that i found in someones driveway (they were throwing it out and yes i did ask if i could have it). I have about 200 dollars to spend on the whole project.
I need something not too big but will produce a good amount of sound and came up with the following drivers:
WOOFER: Dayton DC250-8 10" Classic Woofer $26.20 x2 (one for each speaker) more
This woofer can handle 70 watts RMS and 105 watts max which is good enough for my needs. Its Frequency Response is: 25-2,500 Hz and with an Xmax of 4mm and SPL of 89 decibels should produce a good about of bass. Remember, the larger the woofer, the larger the enclosure will need to be.
TWEETER: Goldwood GT-525 1" Soft Dome Tweeter $9.50 x2 (one for each speaker) more
This tweeter can handle 50 watts RMS and 100 watts max which matches the woofer. Its frequency response is: 2,000 - 20,000 Hz and has an SPL of 92 decibels.
CROSSOVER: Dayton XO2W-2.5K 2-Way 2,500 Hz $23.07 x2 (one for each speaker) more
This 2-way crossover unit separates incoming frequencies at the 2500 Hz mark. So any sound with frequency less than 2500 Hz will be sent to the woofer and vice versa for the tweeter. This means you need to chose a woofer and tweeter with overlapping frequency responses so no frequencies will be lost while in operation. It is also possible to make your own crossover but i will not go into that.
The total cost of the woofers, tweeters and crossovers came to be $137.06 which is relatively cheap considering how expensive they get. I bought my drivers and crossover from partsexpress. They are very reliable as i've used them numerous times in the past.
Hopefully this step will help you chose the best driver for your needs. The next step will describe how to design your speaker enclosure (the box).
Step 2: Designing the Box: Part 1: Type of box and its volume
Type of Box
There are two kinds of boxes we could construct: A sealed box or a vented box. A sealed box is completely airtight and allows for a smaller total volume and a decent bass response. A vented box has ports allowing airflow out of the box. These usually have larger volumes and a better bass response. These are more complicated to construct because finding an ideal port requires more measurement and calculation. Because I don't have much space (and I'm lazy :P) i will be constructing a sealed box speaker.
Finding the Volume
First we need to determine the most ideal volume of this box. It is quite important construct a box with a volume suited for the woofer. A volume excessively small or large will cause the speaker to sound "loud" or "hollow." This table gives approximate box volumes for corresponding woofer sizes:
Woofer Size........Enclosure Volume
4"...........................0.25 - 0.39 cubic feet
6"...........................0.35 - 0.54 cubic feet
8"...........................0.54 - 0.96 cubic feet
10".........................0.96 - 1.80 cubic feet
12".........................1.80 - 3.50 cubic feet
15".........................3.50 - 8.00 cubic feet
I have a 10" woofer but since space is an issue, I'm going to make my boxes as small as possible. The volume of my box will be slightly less than 1 cubic foot. here is a more detailed guide for finding enclosure volumes
The next step is to design the box in complete detail.
Step 3: Designing the Box: Part 2: Dimentions
10.0" across X 10.0" deep X 16.0" high = 1600 cubic in or 0.926 cubic ft
This is an over estimation because the walls of the box have thickness. Ideally the box should be slightly larger, but for my situation, i am not trying to make the most perfect sounding speakers, but the most convenient. Its close enough to 1 cubic feet for me.
I have drawn up some diagrams that show dimensions of the boxes that will be constructed. They are a bit small when viewing them in instructable's photo viewer so here are links directly to the jpg images.
Front View ............................... Side View ............................... Top View ............................... Complete View
Either click to zoom or Press ctrl and scroll up or down with the mouse to zoom in or out (this shortcut is very useful in many other apps too) It may be a good idea to open them up in a new tab/window for easier viewing (right click -> open in new tab)
My diagrams were made using adobe illustrator which worked like a charm. I recommend drawing diagrams like these for your speakers because it helps to clarify exactly what pieces (sides) you need and how big each needs to be.
In my case there will be 4 different sizes:
1) The front piece: .......................... 10.0" X 16.0"
2) The back piece: ......................... 8.50" X 14.5"
3) The top and bottom pieces: .... 10.0" X 9.25"
4) The two side pieces: ................ 9.25" X 14.5"
0.75" thick particle board will be used for all pieces. We are now ready to go out and buy some particle board. (Make sure to get a piece big enough to be cut up into all the smaller pieces)
In the next step we will cut each side to its corresponding dimensions and route the holes.
Step 4: Preparing The Sides: Part 1: Sawing
1) The front piece: .......................... 10.0" X 16.0" ........... (2 total, 1 for each speaker)
2) The back piece: .......................... 8.50" X 14.5" ........... (2 total, 1 for each speaker)
3) The top and bottom pieces: ..... 10.0" X 9.25" ........... (4 total, 2 for each speaker)
4) The two side pieces: ................. 9.25" X 14.5" ........... (4 total, 2 for each speaker)
Using a table saw is probably the fastest and most ideal way to cut these pieces. But don't worry, if all you have is a hand held circular saw (like me) here is an alternate method to cut the wood. (if you have a hand saw or you don't have a saw, you might be screwed)
1) Find a long, straight piece of wood to use as a guide for the saw.
2) Draw out the line in which you need to cut along.
3) Find the distance from the saw blade to the edge of the actual saw. (only have to do this once)
4) Draw a line parallel to the first line, at the distance in step 3.
5) Clamp the wood guide, from step 1, along this line.
6) Cut the wood! The saw should glide along the wooden guide and make a perfectly straight cut.
Make sure all your measurements are very precise! Also don't forget to consider the thickness of the blade while cutting. The above method is tedious but can provide very accurate cuts.
It really doesn't matter how you cut the wood, as long as you end up with all 12 pieces at the end.
Next we need to cut the holes on which the speaker drivers will be mounted.
Step 5: Preparing The Sides: Part 2: Routing
To construct a jig:
1) Find a relatively skinny piece of wood about 3" by 10" by 0.25" (see photos).
2) Cut a hole at one end, large enough for the router bit to fit through.
3) Drill holes and find screws to fasten the wood to the bottom of the router.
4) Make sure the screws don't stick out the bottom by hollowing out the top of the holes.
On with the routing:
Next, measure the radius of your woofer. You will want a small gap between the edge of the woofer and the wood so add 1/16 of an inch or so to the measurement. This will be the radius of the first cut.
With your homemade router compass attached to the router, measure the radius: from the edge of the bit (not the center) to the point on router compass where it will revolve around. Drill a small hole at this point (on the compass) and also drill a hole on your particle board at the center of the woofer hole. Screw your router and compass to the particle board. (see pictures to clarify if all this seems confusing)
Check to make sure the router will cut in the correct location by lowering the router to the wood. Set the depth constraint on the router so it will make a cut half way though the wood. (The depth of this cut depends on your woofer). Finally we are ready to cut the wood, just turn it on, plunge and move it in a circle.
The previous cut creates the shelf on which the woofer's edge will sit upon and be screwed to. Next we have to make the actual hole. Repeat the above process except with a smaller radius and with the depth constraint set deeper, so the bit goes all the way through the wood.
Repeat all of the above for the tweeter hole. From here we will start to assemble the box.
Step 6: Assembling The Box
I will be using an alternate method which consists screwing rather than gluing. For this method the two materials needed are 5/4" wood screws and plenty of 1" by 1" which we will cut to appropriate lengths.
Basically what we will do is wedge lengths of 1" x 1" into the corners of the box and then use screws to hold the sides together through the 1" x 1". Here are specific steps:
1) Cut the 1" x 1" into lengths that fit along the corners of the inside of the box.
2) Drill screw holes into each piece. Usually 4 (2 at each end, perpendicular to each other on adjacent sides). The size of these holes should be big enough for the screws to slip.
3) Clamp the box together as it should be when assembled. Lay the lengths of 1" x 1" into their appropriate positions then mark where to drill into the particle board. You can do this by poking a skinny pencil through the holes already drilled into the 1" x 1".
4) Take away the 1" x 1" pieces and drill the holes marked on the particle board with a smaller bit which allow the screws to grip.
5) Put the 1" x 1" pieces back into their same positions then screw together the box.
Do not worry if the sides don't match up perfectly or if there are slight gaps in the joints; we will deal with this in later steps. If the steps seemed confusing refer to the pictures to clarify (I'm a visual learner so pictures help me a lot).
Step 7: Sanding, Filling and more Sanding
First, sand any edges that stick up. A power sander makes this much easier but still takes lots of time so be patient. I used 60 grit sandpaper; for this part, the more coarse the better.
After all edges are flush with one another, fill in the gaps with wood filler. Use a putty knife to lay down the filler and let it dry. Do this for all the little holes that appear on the edges of the particle board too.
Sand the whole box again with a finer grit sandpaper. I used 220 grit for the second time around. If you find any more holes that need to be filled, repeat the last step.
Sand it again with even finer sandpaper such as 320 grit and finally 600 grit. The surface should feel completely smooth. Be sure to sand the corners a bit, rounding them to your liking.
The box is now ready to be painted.
Step 8: Priming and Painting
After the box has been sanded, it is ready to be primed. There are a couple different primers available to use. One is spray paint primer and the other is brush on primer. I used both.
First set up an a painting area with a ground cover such as newspaper. Just a warning: spray painting can leave a residue on surfaces in the room but can be wiped off. Also, wear a mask to prevent inhalation of fumes and paint; you might find yourself with colorful snot if you don't.
Spray paint both boxes with primer and leave it to dry for a few hours. This layer doesn't need to be very thick. After It has dried, use a brush to paint on a layer of canned primer. This layer will be a lot thicker than the spray paint.
I found this method works well for a few reasons:
If you use brush on primer directly on the sanded particle board, it lifts up many small fibers and the finishing surface is rough. Using spray primer only, seemed to give a layer that was too thin. Therefore i sprayed first, to prevent fibers from being lifted, then used the brush on primer to give it some substance.
Leave this to dry overnight. The surface may be slightly rough after priming. To prepare it for the next layer, lightly sand down the box using fine 320 grit and then 600 grit sandpaper (or similar).
Spray the first layer of the final color of your choice. I chose a navy blue glossy finish.
After letting the paint dry for 24 hours, apply the second coat.
WARNINGS: let the paint dry for 24 hours, do not paint in excessively hot/cold or humid/dry weather, do not spray the paint on too thickly. Something went wrong with my second layer as it started blistering and drying patchy. I had to let it completely dry, sand it down and then reapply primer and paint.
Step 9: Decorations
Use stencils to spray paint designs onto the box. I had absolutely no experience in this area (not a big art person) so if there is anything i should do differently, let me know.
First, find an image you would like to put onto the speaker. Something simple will make your life a lot easier. I chose a hibiscus flower for the front, simple logo for the bottom and a couple others. Print out this image and then glue it to a stiff piece of paper using rubber cement.
Use a knife to cut out the stencil.
Glue the stencil to the speaker where you want the image to go using the rubber cement. This prevents spray from going under the stencil. (don't worry the rubber cement comes off easily).
Wrap the rest of the speaker in a bag and tape a large piece of paper around the stencil to prevent any spray from reaching your nicely painted box. Then spray paint the stencil.
Take the stencil off after a few minutes and let it dry. Use a piece of masking tape and lightly stick it to the paint to remove excess bits that may have resulted from the rubber cement.
The above process can provide very good results but takes practice as with most things.
Step 10: Preparing The Back Panel
to screw it down once everything is done. Drill holes large enough for the screw to slip in the particle board then drill corresponding holes in the 1" X 1" thin enough grip the screw.
Construct and install the terminals
It is possible to buy finished terminals then all you would have to do is make a hole in the back panel to mount it. But since they are so easy to make, might as well just make it.
The first thing to do is drill a large hole (minimum 2 inches in diameter) into the back panel. An easy way to do this is with a circular sawing drill bit (see pictures). Next we need 2, 3" by 3" or more of a solid, flat, firm piece of plastic, acrylic or metal etc. Drill two holes in each piece for mounting the electrical terminals. Then glue the piece to the back of the hole and make sure it is airtight. I used epoxy but silicone or other glues will work just fine.
There you have it, the back panel is finished. If you want you can put a final layer of paint on it but since its at the back, its hardly seen.
Step 11: Preparing The Insides: Part 1: Crossover Unit and Drivers
First we need to mount the crossover unit. I chose to mount it on the bottom of the box. All you have to do is drill a few holes into the bottom of the box and screw it down. I recommend placing some rubber between the crossover unit and the bottom of the box to prevent rattling. If you have a blown bicycle inner tube, those work perfectly, else rubber can be found in many places.
Next mount the speaker drivers. Get some machine screws and nuts that fit the mounting holes in the woofer and tweeter. Drill corresponding holes along the little shelf we routed out in the particle board and then bolt down the drivers! To enhance the look of your speaker, spray paint the screw heads a different color!
The wiring is VERY simple to do. Two wires for the positive and negative leads enter from the terminals and connect to the crossover unit. Two wires (positive and negative) leave the crossover unit and connect to the woofer. And lastly two wires leave the crossover unit and connect to the tweeter. See the wiring diagram for clarification. You will need a soldering iron and solder for this.
Some new stuff (added august 4th): Zobel Network!
Since the woofer is quite large, its impedance rises due to self inductance. The crossover does not take into account this higher resistance. This in turn causes the woofer to sound 'loud' at frequencies close to the crossover frequency. If your woofer is large like this, consider installing a Zobel network across the terminals of your woofer to improve sound quality. The Zobel network will help to restore the impedance to a lower value allowing the crossover to preform correctly. Here is more on Zobel networks. This network consists of a resistor and capacitor placed in series between the terminals of the woofer. For my speakers a 100V non polar electrolytic capacitor and a 10 ohm 10 watt resistor should do the trick (partsexpress has them for pretty cheap). I haven't actually added this in yet but am planning to in the future.
Step 12: Preparing The Insides: Part 2: Sound Insulation
One common method is to place a bunch of fiberglass into the box and seal it up. Fiber glass is pretty rough and messy stuff so i decided to line the sides of my box with carpet instead.
Cut out rectangles and squares of carpet using a knife. The most important place to put the carpet is on the back wall of the box. I put a bunch here and a few strips on the other walls but remember: this material takes up volume too so don't use too much. Use epoxy or a staple gun or both to fasten the carpet to the walls. Make sure they are securely fastened to prevent rattling.
A very last optional thing to do:
Line the edge of the back panel with a bit of rubber. I glued some bicycle inner tube down to help keep the box airtight. If your pack panel fits perfectly you probably wont have to do this but make sure the enclosure is airtight.
WE ARE FINISHED! don't screw the back on yet, its time to test it out!
Step 13: Test It
This is the second pair that i have made. I was very pleased with my first, they were just lacking in the lower frequencies slightly. (woofers may have been to small/not powerful enough).
Here is a video of them in action. Audio is obviously lower quality than how they really sound. The volume was turned up quite a bit too :P
I definitely found that all the time and effort put into this project paid off. The speakers are used almost every day and i am extremely satisfied with the quality of the sound they produce. With 100 watts of power this pair can produce plenty of noise (perfect for those parties you know?). If you like to build stuff and need an audio system this is a very suitable project that i recommend!