How to build a tactile Transducer
The materials that you will need to make a TT are as follows:
An Exacto Knife.
3-4 tubes of 5-minute epoxy.
A piece of steel (I used 1 3/8” wide, 14 gauge (which is about 1/16” thick).
Weight that can be adjusted during tuning (I used a slab of lead that I cut into strips).
Zip ties, or hose clamps to attach the weight to the steel.
A test CD that goes from 20 Hz - 200 Hz is nice to have for the purpose of “tuning”.
Assembly of the TT is quite easy.
Step one: Cut the cone away from the dust cap, and frame. Be careful not to cut the wires that connect to the base of the dust cap (they conduct the signal to the voice coil). The cone is removed because you do not want the TT to produce sound by itself. This allows you feel only vibrations that are produced by the voice coil, and which are transmitted to the fabric in your couch, and thence to thine rear end.
Step two: Put several thin layers of epoxy on the dust cap. Take your time here, and do several thin layers, not a single heavy one. The epoxy strengthens the dust cap so it does not tear apart from the strain that will be placed on it.
Step three: Cut your steel to the appropriate length. The steel that you choose must be stiff enough to keep the lead weight from sagging. The thickness of steel that I used at a 10 inch length would be able to hold about 4 lbs before sagging. I was lucky enough to be able to mount my steel to the lip of the basket. Depending on the driver you use, you may have to attach the steel to the basket arms. If you have to do this, bend the ends of the steel up to comform to the angle of the arms. You want the steel to hover just over the dust cap. You do not want the steel to press down on, or rest too far above the dust cap. Make a mark on the steel that is directly above the dust cap. Drill a hole approximately 1/2 inch in diameter through the steel. This hole will be used in step five to drip epoxy through to the dust cap, and to glue the steel strip to it.
Step four: Attach the steel to the basket by drilling holes through the steel, and basket. Then use nuts and bolts to secure. My TTs vibrated the nuts right off the first couple times I tried them, so make sure you use lock washers. Do not overtighten the nuts. This will result in bending the basket, causing it to change shape. [click here to see photo.]
Step five: Make sure you are on a level surface so the dust cap centers itself. Drip epoxy through the holes of the steel so the steel attaches itself to the dust cap. MAKE SURE THE DUST CAP DOES NOT MOVE. If the dust cap gets out of alignment, the voice coil will rub, causing it to make an aweful noise. Make sure you are generous with the epoxy. The stronger you make the connection to the dust cap, the better the TT will perform.
Step six: Apply about 2 pounds of lead weight to the center of the steel. You can use lead sinkers from a fishing shop. I found slabs of lead at a Mom-and-Pop hardware store, and I was able to cut them up with a hack saw (the lead, not Mom and Pop). If you use lead sinkers, place them in a old sock, then use duct tape to wrap them up tightly so they do not rattle. If you look at the close-up shot of the lead, you’ll notice that I placed a piece of rubber between the lead and the steel. If you don’t do this you will experience a rattling noise. I used zip ties to attach the weight to the steel. [Click here to see photo.]
By adding weight, you are essencially lowering the Fs, and “tuning” the TT. I do not have the equipment necessary to measure the Fs of my TTs. I just used a test CD until I got the best vibes at approximately 30 Hz (sort of like tuning by the seat of your pants!) Weights can be added or deleted until the TT is “tuned”. [Click here to see photo.]
Step seven: Mount them to whatever you want to vibrate. I mounted mine to the wood frame of my couch. I wired them in parallel so I would achieve a 4 Ohm load, and used a piece of rubber to cushion each of the mounting points on the couch. If you don’t use a piece of rubber in between the wood and the TT, you will experience a rattling noise.
I am sure that my design can be improved upon. This kind of DIY project offers many opportunities to use your imagination to make it better. You will find your bass will seem much tighter, and well defined. The spousal acceptance factor (SAF) will also be through the roof! I think you will find that this will be about the biggest bang-for-the-buck improvement for your home theater. You will have to tweak the setup until you get the desired effect, but once you have it dialed in, you WILL love them as much as I do.