The requirements for loudspeaker design now include miniaturization. The loudspeaker market has expanded well beyond the requirements of only 10 years ago. Currently the general consumer market is driven by multi-channel applications, multimedia computer applications, and mobile applications. This is in conjunction with the existing military, commercial and the smaller specialty high-end market.

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The various markets take very different approaches to product development. TBI Embedded Transmission Line Technology (ETL™) is applicable to all product designs for loudspeaker applications. The goals for entertainment and communications are different yet similar. The main differences are frequency response, dispersion and SPL requirements however the approaches to the product design can be consistent with results bringing advantages to products for all markets.

The consumer market is driven by miniaturization and is the initial focus for TBI product designs. The current emphasis is for small speakers that work as designed in the actual customer environment without the boxy sound character and with a linear dispersion allowing for more flexible seating positioning. The loudspeaker must be capable of location near walls without a negative impact on its sound. The changes in the driver radiation characteristics are the primary reason for sound variations in rooms. The dispersion pattern is also dynamically altered by program content when this occurs.

The internal standing wave pattern is a primary modifier of loudspeaker response and dispersion. Driver cone material has been the primary tool used by speaker designers to disrupt the internal standing wave pattern. This approach will cause changes in the sound but will not allow for different (better) sound on the front as opposed to the back of the cone. The cone must transfer the internal energy to the outside as the cone is of a single unit and cannot differentiate between the ambient air and the internal air mass. Even stiff cones must respond to the internal pattern. The smaller dimensions of the miniature speaker intensify the random internal standing wave problem to create the boxy sound character known to small speakers.

A single driver of small dimensions is the best candidate to improve the dispersion pattern. The small size is a requirement for high frequency reproduction and dispersion however the small driver has poor impedance match for lower frequencies. The result for existing designs is a grainy top-heavy sound with poor dynamic range and dynamically altered dispersion characteristics. The sound is worse when the listener sits close as with desktop sound monitoring. Two-way speakers create physical path differences to the ear and the need for a complicated lossy crossover network that cannot compensate for this.

TBI ETL™ eliminates the random standing wave pattern replacing it with an orderly pattern that dynamically assists the driver motion by moving the entire cone in real time with a dominating internal pressure. This results in a consistent impedance match for all frequencies even though the cone is small. This sound quality cannot be obtained using the existing enclosure type that has impedance match for a narrow range of frequencies. Close listening is improved as well as the dispersion pattern, which is not altered by the program content. The dynamic internal pressurization resists modification from room reflections allowing close placement to walls, ceilings and floors. This orderly internal air mass also improves the dynamic SPL of the speaker allowing for improved listening at low and high volumes.

Surround sound systems, which involve multiple speakers and near wall placement are of particular benefit for ETL™. The problems detailed above are multiplied when using many speakers in the standard room, which is generally of many reflective surfaces. The poor off-axis information from normal speakers causes a very confusing sound pattern to exist within the room. The need for neutral dispersion is highlighted by the ineffective methods currently employed for surround speakers. Existing high quality rear speakers use multiple drivers facing in opposing directions to diffuse the sound. The result is more drivers with poor dispersion making the acoustic result even worse and the product more expensive.

The center channel of multi-channel systems must be inherently neutral in its’ dispersion to allow for consistent quality of dialogue and other on screen sound information to be the same from any listening position. Multiple drivers as presently employed in more costly center channel speakers cannot create a frequency neutral dispersion pattern and will generally be less effective than a conventional single driver approach to disperse the sound information. It benefits the central listener but produces poor off axis sound.


1. Maintain a small size and minimum depth < 6". 2. Flat frequency response at all viewing positions standing, seated or floor. 3. Maintain dynamic sound at low and high volume levels. 4. Operate well with very modest amplification. 5. The ability to demonstrate the value of improved electronics. 6. Works well at close positions to the walls or ceiling. 7. Low cost for general-purpose application. 8. Attractive styling can be incorporated in the design to match the décor. 9. Flexible design in technology for multiple product applications. 10. Maintain this quality in different listening environments with no major variations. LISTS OF GOALS FOR AUDIO/VIDEO SUBWOOFER 1. Maintain a small physical size for easy visual integration into room. 2. Easy to integrate with main speakers with no separate subwoofer boom sound. 3. Must produce natural bass sound in different room types. 4. Must provide natural bass at low or high volume. 5. Has good musical sound while also having natural bass effects. 6. Must not require large power amplifier. 7. Must not require high cost for construction.