Build a Pair of Custom Speakers

Hi all,
Here's an Instructable on how to make a pair of custom speakers. These speakers use a pair of Dayton Audio Sound Exciters that can turn virtually any surface into a speaker.
I did this because I still have 2 weeks to go before I return to college. I thought this would be a good idea to kill some time and do something productive, and I must say the results are pretty good. This will be my first Instructable so comments for improvement are welcome!

Here are the materials you'll need for ONE of these speakers (x2 if you want a pair):
   Two 1/2" square rods(11 1/2" long)
   One 1/2" square rod (9" long)
   One wood board/block (2 1/2" x 1/2" x 10")
   One Acrylic Sheet (0.080" thick, 8" x 10"
   One Dayton Audio Sound Exciter
   Four Bumpers
   Two nails
   Two wood screws
   Elastic string (a lot)
   Aluminum Tape
   Wood Glue
Here's a list of tools that may/will come in handy:
  Scissors
  **Dremel (with mini-saw attachment)
  **Hand Saw
  Power Drill
  Hand-Powered Drill
  Drill bits (1/16",  3/32" and 5/32")
  Screwdriver bit
  Hammer
  Pencil
  Permanent Marker
  Triangle/Right angle tool
  Lighter
**-tools used for cutting the wood pieces to the right size.
Note: There are a number of items on this list that aren't absolutely necessary, especially the tools. The ones listed here are the ones that I used when making this particular pair of speakers.

Step 1 - Before we begin

Dayton Audio Exciters (also called audio transducers) are namely used for applications where you don't want the actual speakers to be visible or in plain sight. You can purchase these here:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-375
There's a product video on there that demonstrates a guy using them on his jet ski.
As you may have already guessed, the performance of audio transducers can vary significantly, depending on what type of surface they're vibrating. You will really want to test out different surfaces with the transducer before jumping in and using acrylic as I have. These transducers are meant to be permanently affixed to whatever surface you apply them on, so do some testing and choose wisely.
Personally, I've tried using them on my desk (wooden), but  you have to crank up the volume on the amplifier significantly (because of the sheer mass it has to vibrate). I've also put them on my wall, and at max volume, you can hear it on the other side pretty clearly. Foam project boards also work pretty well too.
The main reason I chose acrylic is because of looks, but the choice is yours.
Note: The best way to test these is to use double sided tape on top of the adhesive protectors, that way when you remove it, you'll still have the adhesive protector on the transducers.

Step 2 - Prepping the Materials

To prep the raw materials for this project, you'll probably want a ruler or measuring tape and the triangle or a right angle tool to help you with marking. Here are the marks you will need to make:
For the 1/2" square wooden rod 9" long:
Using a pencil, mark a hole 1 1/2" from one end of the rod. Mark holes 1 inch apart until you have a total of 7 holes. This should leave the last hole 1 1/2" from the opposite end. Holes should be marked along the middle of the rod.
For BOTH the 1/2" square wooden rod 9" long:
Using a pencil, mark a hole 1 1/2" from one end of the rod. Mark holes 1 inch apart until you have a total of 9 holes. This should leave the last hole 2" from the opposite end. Holes should be marked along the middle of the rod.
For the wooden block (2 1/2" x 1/2" x 10"):
Using a pencil, mark a hole 2" from one end of the 2 1/2" x 10" face. Mark additional holes 1 inch from each other until you have a total of 7 holes, leaving the last hole 2" from the opposite end. Each hole should be 1/2" inches from the long edge (10" long edge).
For the acrylic sheet:
Using a permanent marker, mark holes along the edge of the sheet. These holes should be spaced 1" from each other and 1/2" away from the closest edge. The corner holes should be 1/2" from the corner edges. This should yield 32 holes in total. Make sure you keep the protective film on the acrylic when marking the holes.
Done making marks!

Step 3 - Building the Wooden Frame

To assemble the speaker frame, do the following:
   1. Drill holes that are 3/32" in diameter though both 1/2" square rods where you marked in the previous step.
   2. Drill holes that are 5/32" into the wood block that's 2.5"x0.5"x10" where the markings were drawn. You will also need to drill a hole 3/32" in diameter perpendicular to the 5/32" holes to meet the 5/32" hole, forming a sideways T shape inside the wood. (Where the top of the T is the 5/32" hole, and the veritcal part of the T is the 3/32" hole)
   **3. Glue the two 11 1/2" square rods to the front two corners of the wood block. This may require the wood screws. The edge of the square rod that is 1 1/2" from the nearest hole should be at the bottom, and the edge that's 2" from the nearest hole should be at the top
   **4. Glue the 9" square rod to the top. This may require some nails.
   5. Attach the bumpers to the bottom 4 corners of the wood block.
**-When gluing the pieces together, make sure that all of the 3/32" holes are facing the front.
Let the wood dry overnight for best results or a few hours for quicker completion.

Step 4 - Assembling the Acrylic Panel/Sound board

Drill through each of the holes marked along the edge of the acrylic sheet. For this procedure I used a hand drill so that I could stop myself faster if I saw the sheet crack or beginning to crack.
(Optional) Place two strips of aluminum duct tape on the sheet. For mine, they were placed 1 1/2" inches from the long edges, but this is up to you. These are more for aesthetic purposes.
Mount the Dayton Sound Exciters in the center of the acrylic sheet. The easiest way, I found, to get them centered was to mark the center of the acrylic sheet and then attaching a piece of radial graph paper on the opposite side of the Sound Exciters to mark the center circle for the Sound Exciters.
** My set of Sound Exciters were pulled off my table, so the original adhesive wasn't there anymore. I replaced it with mounting tape (for the edges) and glued the cone to the acrylic using a special glue used to replace foam rings on your typical speakers. Follow whatever mounting instructions come with your sound transducers for best results.
The Acrylic Panel is done!

Step 5 - Putting It All Together

Place the Acrylic Panel in the center and begin threading the elastic thread through the holes. I'm not exactly sure if this thread pattern has a specific name, but I guess it can be analogous to threading one end of a shoe lace.
A few tips about doing this:
Tip 1: It may help to use a binder clip to keep one end of the string from moving while threading with the other.
Tip 2: When threading the bottom portion, you first need to put the string through the 3/32" hole that was drilled in the front. Using a needle or some other pointy object, push the end of the thread up through the 5/32" hole by pushing the needle up from the bottom of the 5/32" hole.
Tip 3: You may consider doing an opposite threading pattern on your second speaker if you decide to make both left and right speakers. I did it so that they had more symmetry.
Tip 4: Be careful of how tight you decide to keep the acrylic sheet at. If you make it too tight, it could be harder to pull together. If it's too loose, then the sheet could swing around if the speakers are moved.
Tip 5: When using the thread, if one end is frayed, you can use a lighter to lightly melt the end so that it looks better and will be easier to thread.
Once you've finished threading the elastic thread, twist the to ends and pull them back. Hold the thread in place and put a piece of aluminum tape around it.
The speaker is fully assembled!

Step 6 - Testing the set up

To test the speakers, I used a Sonic Impact Amplifier. Box specs says the amplifier is rated at 15W x 2 as shown below. If I'm not mistaken, this means that the speakers will be over powered, which may explain some of my findings as you'll see.
I went to http://www.audiocheck.net/audiotests_frequencychecklow.php to check the frequency response of these speakers. I maxed out the volume  to see how it would perform. Looks like there's a pretty good low frequency response at around....BUT, as you tell from the video, there's an annoying buzzing noise that occurs. From what I can tell, it's because of the way the transducers are designed or possibly the overpowering from the amp. I think it could also be related to the mass of the item you attach it to, because it could be vibrating much more than it should be since turning the volume down stops the buzzing noise from occurring. When I had these attached to my table, I never heard the buzzing noise, but I had to turn the volume up all the way to get good sound.
[[Video(http://www.youtube.com/watch?v=WBx84ifnZx8) ]]
Below is a video of the speakers in operation. The speakers have a boxy noise to them, but then again the performance of these speakers does depend greatly on where they are situated (since it's not an enclosed box/confined volume).
Now....Michael Jackson's Thriller. Enjoy!
[[Video(http://www.youtube.com/watch?v=P4KM1Go0rXg)]]

Step 7 - Closing Thoughts and Other Ramblings

This is my entry for the back to school contest.
A few comments on what I would do differently if I did this again:
0. Match the amplifier to the Audio Exciters better. I bought these two a while back as a sort of amusement toy. I didn't completely understand the significance of matching power back then.
1. Test out more materials. The audio transducers create the buzzing sound at max volume, and I would like to test if heavier materials really will help reduce it, as I am guessing, or if the buzzing is due to the transducer quality.
2. Create a better design on the acrylic panel. I don't have the artistic confidence/experience to try anything fancy, nor do I have a laser cutter. I think it'd look pretty neat to have some cool etchings on the acrylic sheet.
3. Add some sort of LED lighting to the acrylic sheet. Maybe this is a bit of a stretch, but I think it'd be awesome if the panel changed color with the beat. The added etching would look even better too!
4. Find a better way to assemble the pieces. My tools were limited and the joining of the wood pieces definitely could have been done better.
5. Do more legitimate tests on the speakers to measure the sound quality.
Thanks for viewing!
Also, tell me what you guys think!  I'd love to see other designs as well!