Home theater has always been a hobby of mine. From buying, building, and installing surround sound systems, to exploring new media platforms-I love my PS3 Blu-ray player/videogame player/internet web browser/wireless media server-I've just about done it all! Something that I've never tried, though, is to use a tactile transducer. I've thought for years about various ways of using a tactile transducer-a truly creative method of keeping pets off of the furniture-but I've never gotten around to it...until now.

Tactile transducers work almost exactly the same way as speakers. The main difference is that instead of a motor (a speaker's magnet and voice coil) oscillating a cone and coupling with air, the tactile transducer oscillates the solid surface to which it is mechanically connected. Different applications apply this principle in different ways. For example, CNN mounts Clark Synthesis transducers to the glass storefront of their studios and use air to transmit the sound of a telecast to the passersby. Hasbro Tooth Tunes uses bone conduction to play music through a toothbrush using a transducer-my daughter's teeth have never been brighter or whiter!

For home theater, transducers fool the listeners' brains into thinking that what they're seeing is real by exciting deep tissue muscles (kinesthetic senses), skeletal nerve endings (haptic senses), and by using bone conduction. Our brains are pre-programmed to pay special attention to high-energy low frequency events. Think about the way you react to the first boom of thunder that announces a storm; now imagine movies with this extra element.

My primary goal for the Seismic Sofa was to transform my boring side-by-side recliner couch into more than just a place to relax; I wanted it to be part of my home theater experience and augment my subwoofer below 50 Hz. A secondary goal-and for you married guys, listen up-was to get my wife to agree to my madness. I accomplished this by promising to re-upholster said piece of furniture during the installation. Instant spousal approval!

Clark Synthesis transducers are used in military simulators (assuring durable, tough-as-nails longevity), and are widely regarded by drummers as the only tactile transducer accurate enough for work as a drum throne monitor. Also, the force-per-dollar ratio of their products is among the best in the transducer industry. So who am I to argue? My application was much tamer than those previously mentioned, plus I have a budget to consider, so the Clark Synthesis TST239 Silver transducer was a logical choice. Another advantage of choosing the TST239 was that a single transducer was recommended per seat. Less work is good.

For amplification of the Seismic Sofa, I chose the Dayton Audio SA240 240 watt subwoofer plate amplifier. Modification of the low frequency high-pass filter (present on most amplifiers) was made easy using the "Flat To" Responses table, located below the Boost Table, found on the product page at www.parts-express.com. Wiring two of the transducers in series yields an 8 ohm impedance. The SA240 supplies 120 watts, so 60 watts per transducer. This is a little lower than what Clark Synthesis recommends, but should be sufficient. In addition, a 24 dB/octave low-pass filter has been built into the amplifier. Clark Synthesis recommends running their transducers full range, but we'll call it a safety mechanism in case I start to notice people talking out of my nether-region.

In order to focus the energy transferred from the transducers to each chair (and maximizing power output) the chairs should be decoupled from the floor. Any energy transferred to the floor from the chair is wasted. To accomplish this, and answer my own personal curiosity, I compared rubber isolation feet versus the Dayton Audio DSS4 speaker spikes.

I began the construction phase of my project deciding where I was going to place the transducers on the sofa. Vertically mounting the transducers on the removable sofa backrests would have yielded the least amount of work, but reading the installation manual revealed that Clark Synthesis only recommends horizontal placement.

With the sofa backrests removed, I flipped the sofa for easy access to the underside of the seat cushions. Fortunately for me, each recliner on the sofa features a sturdy wooden frame. Clark Synthesis recommended adding a hardwood bridge to each recliner frame. Bridge material should be at least 3/4" thick and 6" to 8" wide. I had plenty of MDF on hand-where did that come from-but quickly decided against using it, as by itself the MDF would dampen the transducer and be counterproductive. So into the garage I went, where lo and behold...a 2 x 4 (actually 1-1/2" x 3-1/2")! That did deviate from Clark Synthesis' recommendation, but if you don't tell them, neither will I.

Since I had open access only to the front and rear sections of the frame, I chose to install the bridge longwise. Careful consideration was made to ensure that the bridge contacted the maximum frame surface area while still being able to drop into place. Prior to installation, I moistened each contact surface with water and applied a layer of Gorilla Glue polyurethane glue and then screwed two 2-1/2" wood screws into place on each side of the frame.

The most important part of the installation was checking for clearance. This is usually the part where I say to myself, "I know what I'm doing" and then gloss over the actual tolerances. During the installation, however, I had an audience-my son and wife. Lots of pressure on me for this to work correctly the first time. Clark Synthesis advises placing each transducer at the bridge's center, but I noticed a brace bar occupying that space. In fact, the only place I could mount the transducer was off-center on the front third of the brace. Didn't seem like a bad compromise because that's where most of my tush ends up when reclined, anyway!

Clark Synthesis didn't omit anything hardware-wise. No less than four installation methods are included, and I decided to use the Unimount brackets in order to simplify installation. After screwing the bracket into place, I mounted the transducer onto the threaded stud. Be sure you follow the instructions when it comes to tightening transducers to the threaded stud, a slight resistance is adequate; jam nuts are included to lock the transducer in place.

With the transducers in place, it was time to mount the amplifier. The center console of my sofa has a sub-frame that happened to allow the SA240 amplifier to be recessed on the backside without additional work...hooray for me! While my wife watched, I carefully cut away the fabric stretched over the frame. The amplifier dropped into place as if it had been made to mate with my sofa. Once the amp was screwed into place, I proceeded to wire the transducers in a series configuration. Before making any connections, I measured the total recliner travel in order to decide if additional wire should be added to the 36" pre-installed transducer wire lead. I found that the only additional wire needed for this installation would be to complete the series loop when connecting the positive from one transducer to the negative of the other.

Red (positive) from the left transducer was spliced to the red (positive) lead from the amplifier. Black (negative) from the right transducer was spliced to the black (negative) lead from the amplifier. The remaining red and black transducer leads were spliced together to form the series loop. My home theater receiver's LFE output was connected to the SA240's signal input. Two RCA splitters (single male to dual female) were used, the first of which divided the signal between the SA240 and the HSPA500 that powers my 15" Dayton Audio Titanic MkIII subwoofer (nothing wrong with a little overcompensation). Because I've noticed a slight difference in output power when providing both input channels of an SA240 with signal (your mileage may vary), a second RCA splitter was placed at the output of the first for a stereo RCA run. A 50 ft. stereo RCA patch cable was on hand and installed as well.

The installation was completed by testing the differences in sofa feet: stock, spikes, and rubber. I cued up The Flaming Lips' "Yoshimi Battles the Pink Robots, Pt. 1" on my iPod and sent the signal directly to the SA240. With the stock feet still on the sofa, I immediately noticed a nearby air vent trying to play along. I tested again using the speaker spikes, but they just localized the vibration to the dishes supporting the spikes on my wood floor (hypothesis disproved). When the Clark Synthesis TI-100 rubber feet were installed, I found my solution. My sofa was effectively isolated from the floor, and I could even detect more energy focused on the seating area.

I spent a couple of hours tweaking my system to integrate the transducers correctly. Special care needs to be taken to be sure the tactile effects match speaker output-too much and it feels grossly exaggerated, too little will have you wondering if they're even on. Once dialed in just right by using the opening scene from Swordfish, I noticed more impact than I had previously experienced with my subwoofer by itself. Gunshots seemed crisper and clearer, thunderclaps produced raw, visceral sensations, and my entire home theater experience was taken to another level-I was part of the movie, not just an observer. My biggest thrill was that I could turn off the subwoofer completely, throw on a set of Sennheiser HD555 cans, and get lost in a movie while my family slept.

If you haven't experienced tactile transducers, I suggest you give them a try. My wife and kids enjoyed them as much as I did, if not more! By the way, my wife loves the new look. I may be onto something here: we do need a coffee table.