Stereo Speakers With Synched LED Lighting

This is a step by step guide to building a pair of two-way stereo speakers, with LED's synched to the audio. The LED's can be shut off when music without lighting is desired. In these speakers, clear acrylic is used so the entire interior can be viewed (along with the LED's).

My intention is for this instructable to be more of an inspirational guide rather than a strict series of steps. Of course I'll give the basic steps that it took for me to build mine, but with projects like speakers, a lot of variation is possible. I want to give you as much freedom of creativity as possible.

This Instructable is to build ONE SPEAKER. For a pair, simply repeat the process. I would recommend reading through the entire instructable before starting. The instructable is going to be split into three main parts: The Enclosure, The Circuitry, and The Assembly.

Another awesome instructable for speaker building can be found here:
https://www.instructables.com/id/Build-A-Pair-of-Stereo-Speakers/

This is my first instructable, so any and all feedback would be extremely helpful and appreciated.

If you have any questions at all, feel free to message me and I'll do my best to help.

Step 1: What You'll Need

Here's what you'll need for ONE SPEAKER. Just double and repeat for the second.

Tools:
Dremel and Bits
Power Drill and Bits
T-Square
Ruler (T-square works)
Level (T-Square)
Knife
Scoring Pen (T-squares usually have one hidden inside)
Wood Glue
Drawing Compass
Soldering Iron & Solder

For the Enclosure (Note, sizes vary depending on what drivers you choose):
3/4"x3/4" Pine Beams
1/4" Oak Wood Boards
1/4" Acrylic sheets (I used Lexan�)
6 Angle Braces & wood screws
8 Bolts and Lock Nuts
6 Furniture Pads

For the Circuitry:
1 Woofer
1 Tweeter
16 LEDs (I used two groups of 8 LEDs each, but you can mix colors if you want!)
2 NPN Transistors (I used 2n4401)
1 Speaker terminal
Insulated wire, 3' per speaker should be fine, but it'll vary depending on how big your speakers are
Speaker wire (12 gauge should be fine)
*Various wire coils
*Various polypropylene capacitors
*Various low-inductance resistors

*These parts are for the Cross-Over (Which separates the high and low frequencies of the audio), the L-Pad (which adjusts the volume of each individual speaker), and the Series-Notch Filter (Which controls the peaks at the resonant frequency of the drivers). Alternatively, you can just buy a pre-made one (which as it turns out, is usually cheaper).

Step 2: Selecting Drivers

The first step of any project is planning. When it comes to building speakers, there are many factors to consider. Essentially, however, it all boils down to driver selection.

I bought my drivers and other parts from Parts-Express (http://www.parts-express.com/home.cfm). I highly recommend Parts-Express. The shipping is very fast, the prices are good, and you can get very good technical advice from them.

Wherever you buy your drivers from, per speaker you're going to need:
1 Woofer (low pitch driver)
1 Tweeter (high pitch driver)
1 Wire Terminal Plate
1 Crossover

When looking at drivers, you should consider the impedance (how much resistance the driver offers), the sound pressure level (SPL, how loud the driver is), and the frequency range.
Ideally, you want your woofer and tweeter to be of the same impedance, with similar SPL, and with overlapping frequency ranges. The crossover splits the input from the audio source into high and low frequencies for the individual drivers, but the split is gradual. With a larger overlap, its easier to find a crossover at a frequency that's in the middle of the low-end of the tweeter and the high-end of the woofer.

You should also consider getting an L-pad. L-pads vary the volume of each driver independently, so if you wanted more bass and less highs, then you could adjust your L-pad to do that for you.

All of these parts are available at partsexpress
http://www.parts-express.com/speaker-building.cfm

Anyways, here's what I got:

$36.82 EA Goldwood GW-8PC-30-4 8" Heavy Duty Woofer 4 Ohm
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-312
$11.00 EA Goldwood GT-525 1" Soft Dome Tweeter 8 Ohm
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=270-182
$1.21 EA Square Speaker Terminal
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-297
$22.95 RL Speaker Wire 12 AWG Clear 50 ft.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=100-112

Notice that the woofer has an impedance of 4 ohms while the tweeter has an impedance of 8 ohms. I was a bit careless when I ordered, so I had to correct for that in my crossover. I would recommend choosing tweeters and woofers with matching impedance.

Step 3: Planning the Enclosure

The enclosure of course holds everything together. The shape and the dimensions of the enclosure are also important and impact the sound of the speakers, however. Supposedly, cube's lead to the greatest loss in sound quality while sphere's provide the best sound. To keep things simple, I stuck with a rectangular prism (like most speakers are).

The size of the enclosure should vary with the size of the driver. This nice table, found from http://www.homerecordingconnection.com/news.php?action=view_story&id=32 as well as the other speaker instructable I previously mentioned, gives approximate volumes for certain driver sizes.

Woofer Size --- Enclosure Volume
4" --------------- .25 - .39 cubic feet
6" --------------- .35 - .54 cubic feet
8" --------------- .54 - .96 cubic feet
10" --------------- .96 - 1.8 cubic feet
12" --------------- 1.8 - 3.5 cubic feet
15" --------------- 3.5 - 8 cubic feet

Alternatively, you could use a special calculator to help you determine the proper volume of the enclosure.
http://www.diyaudioandvideo.com/Calculator/Box

Designing the enclosure is pretty much an open process, and how you want it to look is all up to you. As long as you keep the total volume in mind, as well as the size of the front (make sure the drivers actually fit!), you should be fine.

I made mine 16"H x 10"W x 10"D = 0.926 cubic feet, which is on the larger end for an 8" driver. These are the exterior dimensions, however, so in actuality the volume is a bit smaller.

Step 4: Building the Enclosure

I found the easiest way to build an enclosure is by using 1" x 1" (or in this case, 3/4" x 3/4") beams for structure, 1/4" oak boards for panels, and wood glue to hold it all together.

Start by gluing down the beams onto a square so that it runs along the border, as shown in the 3rd picture.

Once those have dried, place a side panel flat and glue the bases onto both ends, as shown in the 4th picture. Don't forget to add the vertical support beams. As it dries, the sides may start to lean to one side or warp. To deal with this, I temporarily placed the opposite side panel on top (5th picture) and used the level on my t-square to make sure everything was level.

Next, you're going to need to cut out a hole on the back panel for the wire terminal plate. Mine required a circular hole, but not all terminal plates are the same. Of course, you should cut a hole that fits you're wire terminal plate. Do to lack of other tools, I used a dremel to cut out the hole. Pictures 6 through 14 document the process effectively.

When mounting the wire terminal plate, be sure to use metal screws (preferably with low resistance--mine measured to be about 2 ohms), and make sure they go all the way through and stick out on the other side of the board. We're going to use these as a convenient way to let electricity flow from the outside of the box to the inside. The LEDs are going to be hooked up to the exposed screws, and the power source in going to be hooked up outside. This way, its much easier to turn off the LEDs or to change the battery powering them.

Finally, once the wire terminal plate is mounted, glue the back panel onto the speaker and let the enclosure dry. You should now have a nice box with the front open and the wire terminal plate on the back.

Step 5: Cutting the Front

If you want you speaker to have a clear front, then follow this step using acrylic. If you want a normal speaker, then use wood. Either way, the process should be fairly similar.

When I bought my acrylic, was on a fairly tight budget and didn't fully understand the impact of gaps in speakers. I wanted to use Lexan because I knew it was extremely strong and durable (supposedly around 100 times more impact resistant than glass of similar thickness), but in order to get two 10" x 16" sheets, I had to buy one large, expensive sheet. To save money, I decided to buy two 10" x 8" sheets per speaker to form a 10" x 16" sheet. I would not recommend this, as it ended up causing more hassle than it was worth, and probably caused some loss in audio quality.

The process for cutting the holes for the drivers is very similar to cutting the hole for the wire terminal plate. Using a t-square, mark the centers of your circles. Keep in mind that the drivers need to be far enough away from the edges so that the acrylic doesn't crack and so that the drivers don't hit the wood frame (in my case, this means I needed at least a 1" border). After marking the centers, use a compass, set to the proper radius, to draw the circles.

You may notice that its hard to see the pencil lines, especially on the plastic cover over the acrylic. To make cutting easier, I used a scribing pen to trace the circles. This cut the protective plastic over the acrylic, allowing me to peel it off (picture 3).

Now that the circles are well-defined, use a dremel to cut out the circles (pictures 4-6).

Finally, place the drivers in the holes (or behind them, if they're mounted that way) and mark where screw holes should be. Again, use your ever helpful t-square to make sure everything is level. Once the holes are marked, carefully drill them out. Smooth everything down now and file down any rough/sharp edges.

Step 6: Building the LED Circuitry

To make the LEDs light up in sync with the speakers, we're going to use transistors. Transistors act as electrical gateways. When a small amount of current flows into the middle pin (the base), current is allowed to flow from one pin (the collector) to another (the emitter). We're going to use the current from the audio to open the gate, letting electricity to flow to the LED. Whenever a sound is produced, the LEDs will light up. Each driver will have an LED light unit attached to it, so the lighting for the bass and treble will be independent. In my speakers, I used blue LEDs for the bass and green LEDs for treble.

To build this, you will need LEDs, transistors, and wires. www.ledshoppe.com offers good LEDs at very reasonable prices.

To build an LED light unit, start by taking 8 LEDs and bending apart their leads (picture 2-4). Make note of which terminal of the LED is positive and which is negative, as it it more difficult to determine which lead is longer when they are not next to each other. In most LEDs, the smaller half in the actual LED is positve, while the larger part where the light is emitted from is negative.

Once all the LEDs are ready, gather them together into a bundle, making sure the leads are all pointing in the correct direction. Using electrical tape, tape together the leads. Repeat this process for the other 8 LEDs. Now you should have two bundles on LEDs.

Once your LED bundles are ready, take an NPN transistor and carefully bend the leads apart. The transistor in the picture is flat-side up. Using a soldering iron, solder the transistor, LED bundle, and wires together as shown in pictures 10-12 (if you need any tips on soldering, either message me or search for tips online). Afterward, use electrical tape to make sure all exposed metal is covered. Repeat the process for the second LED bundle.

Step 7: Adding the Crossover

A crossover is necessary to split an audio signal into two parts, a high and a low.

If you decided to build a crossover, then it needs to be tailored to fit into the overlap range of your tweeter and woofer. A very helpful tool can be found here:
http://www.diyaudioandvideo.com/Calculator/XOver/
By entering in the relevant information, this calculator will create a schematic for you and list all the necessary parts. If you do decide to build your own, I would recommend using a 3rd Order Butterworth.

When buying and building a crossover, it is important to remember that to add resistors and inductors, put them in series. To add capacitors, put them in parallel.

If you decided to buy a crossover, you need to make sure that its in the overlap range of the tweeter and woofer. Details for use of specific crossover units should be included when you purchase them.

Step 8: Assembling the Speakers

In order the mount the acrylic, I decided to use angle braces with furniture pads. As shown in pictures 2-4, place a piece of furniture padding onto one side of the angle brace and cut off the excess. Place the mounts where you want them to be on the enclosure (without the acrylic in between). Without compressing the padding, mark on the enclosure where the screw should go. Drill the pilot holes for the screws now.

Now carefully move the crossover into the enclosure. It's probably a good idea to secure the crossover so it doesn't shift around when the speaker is moved.

Now take your LED systems and hook up the wires as shown in picture 6. The signal wires should be in parallel with the drivers they correspond to. The two LED systems are powered from the same source, so take the power source positive wires and solder them to one of the bare screws of the wire terminal plate. Next, take the power source ground wires of the LEDs and solder them to another screw. Tape the screws with electrical tape for safety (picture 7). Now mount the LED bundles inside the enclosure however you like. To power the LEDs, apply a current across the screws (that have the wires on the other side) from the outside (picture 9).

Now the speakers are almost done! Simply use the bolts and lock nuts to mount the drivers onto the acrylic sheet, and then connect the drivers to the crossover.

All that's left now is to close the box. This might be a bit tricky, so its helpful to have someone help you here. Carefully lift the acrylic plate up and line it up to the rest of the enclosure. While someone holds it there, take the angle brace mounts you made and, using wood screws and the pilot holes that were previously made, secure them to the speaker. The furniture pads should be tight and compressed, and the acrylic sheet should be securely fastened between the mounts and the rest of the enclosure.

Congratulations! You're done!

Wait, no, not yet. Test your speakers one more time and make sure everything works. If not, unscrew the mounts and try to find what went wrong since the last time you tested the system. Once you have that cleared up, screw the mounts and the acrylic back on and test again. If everything works...

Congratulations! Now you're done!