‘Home theater’ was once a television, a surround sound receiver and some speakers. Its goal was modest – a decent movie experience without driving, paying for tickets and popcorn, or sitting next to giggling teenagers and behind a basketball player. Today, home theater enthusiasts aim to put the cinemaplex experience to shame.

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Custom leather recliners with ergonomically-correct lumbar support and built-in remote controls, curved 122′ screens with a 2.35:1 native aspect ratio and motorised multi-masking 7.1 surround sound systems, high-definition DVD players and media servers with terabytes of digital storage, 1080p HD projectors with anamorphic lenses, even gaming systems with complex interactive Internet capabilities – all modern technologies that reflect the fact that maximum emotional response, immersion and impact are tools no longer exclusive to media magnates.

Is this technology both user-friendly and lifestyle compatible?

Although amazing technologies are now available in the home, often one or more challenges preclude widespread adoption. Space, cost, room dimensions, aesthetic preferences, and usability of equipment all play a significant role when determining the feasibility of a premier home theater. Even the best equipment is not practical if no one can use it without tech-support on speed-dial. Even if cost is no concern, visual design can be restrictive; spouses often find it difficult to match technical performance with aesthetics.

Can we achieve magnificent impact without hulking boxes? Can we retain sound quality with hidden, in-wall speakers? Large subwoofers might be impractical. Can we achieve personalised immersion without relegating ourselves to headphones or separate viewing rooms? Can we get jaw-dropping FEEL without endangering our children’s hearing?
Solutions that enhance the experience

One area of significant technological improvement has come in the form of bass impact without sound. Tactile devices have been developed to increase immersion and impact by augmenting traditional loudspeakers with the complementary ‘feel’ of low frequency sound and motion.

In the real world, humans experience sound and motion through two primary paths, namely the air and the ground. Waves that move through air pressure create audible sound by vibrating our eardrums. Ground-borne waves in the form of low frequency sound and infrasonic frequency motion are felt primarily through our haptic senses which include both kinesthetic (muscle) and touch (cutaneous) senses*.

Although both transmission paths have some natural frequency overlap, one without the other results in a sensory experience that at best, is only partially accurate. Experiencing air-borne and ground-borne waves in harmony delivers what we would describe as a ‘realistic’ sensory experience.

While loudspeakers produce air-borne waves for our ears, tactile devices introduce ground-borne waves, so we can experience sound and motion together. Without tactile devices, viewers may sense that something is missing, regardless of the perceived ‘quality’ of the audio/video system.

Propagation of air-borne and ground-borne waves

Almost everyone knows at least one ‘bass junkie.’ That is, someone who revels in sound pressure levels others may find annoying. Home theater retailers share ‘horror stories’ about customers that ignore safety warnings to ‘crank up’ subwoofers past recommended listening levels. Custom installers charge good money to calibrate sound systems, only to find that customers bypass the settings in order to get a little extra ‘oomph’ out of their subs. Unfortunately, this often annoys neighbours, wakes babies, muddies sound fields, and prescribes a ‘one-size-fits-all’ volume for the entire room. These customers are demanding ‘more physical involvement’, but seeking it in the wrong place.
How tactile and motion devices work – from shakers to actuators

There are two basic types of tactile devices, namely linear actuators and inertial shakers.

Inertial shakers, offered by companies such as Guitammer, Clark Synthesis, Aura, Earthquake Audio and Sonic Immersion Technologies, employ a mass which swings back and forth within an enclosed housing. The inertial forces of the swinging mass are transferred to the housing of the device and then to the object to which it is attached. These devices can be attached directly to the frame of a chair or to a platform under the chair. Shakers are triggered by specific sound frequencies delivered customarily by a home theater receiver via an audio file or soundtrack and are meant to enhance the audible bass with a ‘shaking’ or ‘rumble’ effect.

Inertial Shakers from Guitammer, Clark Synthesis, Aura, Earthquake Audio and S.I.T.

Linear actuators for home theater, offered by companies such as d-Box and Crowson Technology, are designed to push against a rigid surface. Replacing the static ‘feet’ on a chair, linear actuators drive directly against the ground through expansion and contraction to reproduce natural ground-borne waves. Rather than swinging a mass via push-pull and transferring energy to an object, linear actuators directly lift and drop the chair.

Unlike shakers, linear actuators can accurately reproduce motion: kinesthetic frequencies from 0-30Hz, as well as higher ‘tactile’ frequencies. The technology to achieve this level of realism is uniquely complex and hence, linear actuators are often more expensive than shakers.

d-Box Universal Motion Platform
(two actuator system)

Crowson Stereo Tactile Motion System
(two or four actuator system}
Practical considerations for the employment of tactile devices

Aesthetics, performance, installation requirements and price all play an important role when considering any equipment, and in many situations, tactile devices offer a satisfactory solution to one or more common problems.

Although customers desire maximum impact, large and/or loud subwoofers are an often impractical solution. Tactile devices employ novel technology to deliver impact without negative sound field repercussions, without safety risk to fragile eardrums, and they can fit well within a discerning design aesthetic or dimensional constraints. Furthermore, tactile devices may be employed in individual seats so that each viewer can customise his/her experience by controlling the visceral impact.

When choosing between types of tactile device, customers should select products based on discerning need-to-performance analysis. Frequency range, flatness of frequency response and efficiency are all important considerations. Other factors include uniformity of motion, power requirements, gain and level control, interoperability with control systems, and cost.

If cost is a primary concern, shaker devices such at the Aura Bass-Shaker deliver a vigorous motion for a low price, although accuracy may be sacrificed due to aforementioned technical constraints. d-Box actuators can deliver incredibly low frequency motion with authority, but require proprietary motion content via a separate ‘motion controller’ and may not accurately reproduce frequencies above 100Hz.

When realism is a primary consideration, the best solution is provided by devices whose frequency range most closely corresponds to human tactile perception between 0 and 500Hz.
The future of home theater

One company, d-Box Technologies, has developed a proprietary Motion Code system which enables pre-programmed motion tracks to be played through linear actuators. These motion effects occur in synchrony with the standard sound and video files, with the intent of eliciting realistic visceral response. Motion programmers code each scene by hand, serving up motion codes for both new releases and classic movies as quickly as possible in order to meet customer demand.

As the concept of a discrete motion track becomes further adopted by movie producers and sound engineers, the ability to wield this new tool to improve immersion will become more widespread through both commercial and home theater. Additional applications of a discrete motion track include both console and PC-based gaming. Primitive examples of motion effects for gaming are well known. Who remembers sit-down arcade games like ‘California Dreamin’ which jostled you back and forth? Discrete motion track employment moves this concept a giant leap further, implementing actual motion recordings captured via motion microphones. Now the motion you feel is the actual motion you would feel in reality.

Imagine a racing car simulator whose motion track was actually recorded from the specific car that you had selected to drive, recorded on the specific track and location you watched on the screen? Not unlike the detail that we now see in visual design (note the meticulous accuracy programmed into each real-world stadium in Madden 2007). We may soon FEEL this level of accuracy as well.

The rapid rate of improvement in technology can boggle the mind. In just a few years we have collectively raised the bar such that the best home theaters far surpass the experience offered by your local cinemaplex. Keep in mind that a large part of the enjoyment depends upon personal tastes and desires, and that unlike the traditional goal of mimicking a cinema, the far more satisfying challenge is to craft a system which offers maximum immersion, personalized character, comfort, meets your design aesthetic and fits your budget.

Tactile technology promises to deliver personalised, realistic impact through aesthetically pleasing (hidden) design, and straightforward integration without jeopardising our family’s hearing.

*NASA, in the research paper ‘Challenges and solutions for Realistic Room Simulation’, Durand R. Begault, ASA June 2002) defines the frequency spectrum thus:
Touch: 0-1kHz.
Kinesthesia: 0-30Hz.
Audition: 0.20-20kHz: overlap from 0.02-1kHz.

Randolph Crowson is President and Chief Engineer of Crowson Technology, LLC, a US-manufacturer of the TES100 Tactile Motion Actuator and related accessories. Mr. Crowson holds multiple patents in the electromechanical field. He founded Crowson Technology in Santa Barbara, California in 2001.

John Yi is Executive Vice President of Business Development for Crowson Technology LLC.

Crowson products are sold worldwide by specialty home theater retailers and through Certified Integrated Seating Partners. International distribution points include Canada, UK, Belgium, Southeast Asia, Australia, and South America.

Aura, Clark Synthesis, d-Box Technologies, Guitammer, Earthquake Audio, and S.I.T., are all trademarks of their respective companies and no portion of this article constitutes an endorsement, sponsorship of or between any companies herein or licensing of their respective products or technologies.