High Fidelity and Utility for Stuctural Loudspeakers
Author: Jan Plummer, TBI Audio Systems LLC
The Ideal Structural Loudspeaker (ISL) will open up a world of possibilities for this important application. This ISL will produce no acoustic energy in the ceiling structure and greatly reduce vibration while increasing dynamics and dispersion. The ISL distributes all of the drivers acoustic output into the room and is not affected by nearby reflection surfaces. The ISL must possess technology to assure elimination of diaphragm breakup and that the nearby wall reflections are the same as the on-axis output.
The ceiling-structural loudspeaker should produce sound only in the room desired. Unlike a flush mounted light, the conventional open back structural loudspeaker distributes its energy behind the ceiling as well as in the desired room volume. This structure borne energy prevents the use of the conventional ceiling loudspeaker as a true utility product. The origins of the ceiling mounted speaker is commercial PA and was not intended for high quality sound. ETL™ acoustic technology is now available to solve this and other inherent problems.
Typically the structure borne loudspeaker is considered a compromise solution for quality sound distribution. All drivers require a specific air volume to produce its sound as free standing speakers do however this is not possible with structure borne speakers. A practical enclosure is not an option with conventional structural loudspeakers because volume is required. The structural loudspeaker is designed to conserve space and conform to the available area within walls or ceilings. The energy from the rear of the loudspeaker will use the opposing wall, ceiling or floor to resound the energy which disturbs occupants of adjacent rooms or apartments. Enclosing the speakers to prevent this further degrades their character and is not considered an option if sound quality is a concern.
The ceiling loudspeaker is also compromised in its location relative to the surrounding walls. The fact is that a ceiling loudspeaker is supposed to be a part of the structure as any utility fixture and must accept any reflections from nearby walls as an enhancement to performance. This is not possible using existing ceiling system configurations as the driver(s) has poor dispersion and reflection properties. Typically acoustics teaches against quality sound from ceiling speakers. The ceiling loudspeaker should be useful for condominiums, hotels, apartments or homes without concern of quality variations or noise pollution.
The ceiling loudspeaker suffers from cone breakup and dispersion problems in most any driver format. The use of pivoting tweeters does not provide proper dispersion of high frequencies to multiple occupants. Ceiling loudspeakers for entertainment must produce the full range of frequencies in all directions to provide its benefit. The sound level must be distributed evenly if there is to be no location specific sound issues. The ceiling loudspeaker must use the rooms surfaces to enhance its sound quality as it must coexist with the structure.
THE IDEAL STRUCTURAL CEILING SPEAKER
The Ideal Structural Loudspeaker (ISL) will open up a world of possibilities for this important application. This ISL will produce no acoustic energy in the ceiling structure and greatly reduce vibration while increasing dynamics and dispersion. The ISL distributes all of the drivers acoustic output into the room and is not affected by nearby reflection surfaces. The ISL must possess technology to assure elimination of diaphragm breakup and that the nearby wall reflections are the same as the on-axis output. The ISL ceiling speaker should have the ability to respond to lower bass and higher treble frequencies simultaneously while dispersing the sound to the entire room. This level of performance will eliminate the need for unsightly wall speakers with solid depth, width and height imaging achieved from the ceiling.
The ISL should be capable of being mounted in any ceiling and if not to high right above flush mounted HDTV sets while clearly tracking the on screen sound. This will make the sound image bigger than the picture itself for truly wonderful involvement in the action. The ISL should be capable of providing excellent off axis imaging and the proper phantom for center image to all viewers. The center channel can be used in surround systems but phantom should be good even for this application. With a full 40-20kHz response, this would be the true solution for music and home theater integrated into a invisible system that won’t transmit sound into the surrounding structures. The ISL should be capable of being specified for any ceiling location with consistent natural sound for all rooms. Subwoofers must be an option with this speaker which should reproduce the full range of sound in its acoustic output. The ISL must produce dynamic levels over 100db and with an even diffusion of the sound this should result in less need for blasting it. One very important aspect of any speaker is the ability to resolve low level detail. This is the factual definition of dynamic range not how loud it gets and with the ISL you can maintain low levels and hear all of the dynamics, vocal and detail. With these abilities the designer can focus on the room aesthetics and not have to be concerned about unforeseen future hidden sound problems.
There are manufacturers stepping forward to produce this ideal type of structural loudspeaker such as TBI Audio Systems LLC of Marietta GA with its patented ETL™ technology. This serious limitation is surfacing everyday so it shouldn’t be too long before more manufacturers recognize this problem and their solution is sought in order to specify quality structural sound to all residential and commercial customers. It does require thinking out of the box.