Elevate Your Audio Experience

In the early days electrodynamic and permanent magnets were in use but the concept was the same. Many things have been invented or evolved into something better but the loudspeaker is much the same. TBI Audio Systems is bringing much needed innovation to the industry that brings Transmission Line Subwoofer technology into the 21st century. 

Why is large size necessary?

Why do they have to be large? The frequency range for humans is 20-20KHz for young healthy individuals. The clear reason for size is to reproduce low frequencies! Natural sources of low frequency sounds typically have large surface areas and no boundaries. Early loudspeakers were large for this very reason and making them smaller was going against the laws of physics. Conventional Acoustic Transmission Lines are considered the Holy Grail for loudspeaker loading. The construction requirements for this esoteric design require large dimensions and complicated ducts to extend the bass deep. TBI has developed the Virtual Acoustic Transmission Line (VATL) to bring the advantages to smaller subwoofers and speakers. Low frequencies have long wavelengths and these are not compliant with small enclosures. The energy behind the driver has nowhere to dissipate the long waves so efficiency disappears. Typically low efficiency means higher distortion and little control over the compression that occurs. This is currently considered one of the biggest issues with loudspeaker design. This is a big concern however the observable issues occurring in the low frequency range are present  throughout the audio range. When high frequencies experience the effects of isolating the front of the diaphragm from the back distortion and harmful dispersion effects occur. The obvious problem is that the acoustic energy existing behind the diaphragm is not controlled. What you hear is a facsimile of that rebounding energy that was created previously. The driver is a piston typically executing a broadband audio output. The input signal determines the velocities that the diaphragm must follow for accuracy. The acoustic load presented to the diaphragm to achieve these velocities must be dynamic and responsive for program detail. If a load is favored for any particular range, detail is not maintained for other information. This is a very complex process not achievable by electronic means however the solution must remain simple in execution. The use of the VATL allows for real time instantaneous acoustic processing that must occur for all information present. The level and frequency must be processed in a way that a coherent diaphragm motion is achieved.

Is the room  getting in the way?

The conditions currently experienced by any driver are the cause of negative room interaction. A small room is insensitive to echo because the times of reflections are included in the initial sound. Rooms don’t become unfriendly to sound waves until large size introduces echoes. These echoes will be apparent for all sources of audio introduced into the room. Why is the loudspeaker the primary subject of small room acoustics? The main problem is that the loudspeakers' acoustic impedance varies considerably over the entire range. 

When considering the transfer of power from an electrical circuit to a load, those familiar with the amplifiers damping factor know how important this figure is. It is the ratio of its external load impedance to the amplifiers output impedance. If it’s low, the amplifier has a problem controlling the speaker. A high damping factor means the amplifier should always maintain control of the speaker load. The issue is that the speaker has poor acoustic impedance and is sensitive to low frequency room reflections. When the incoming signal creates pressure within the enclosure and it is not terminated at the end of its cycle it will negatively affect the diaphragms next work cycle. An acoustic cycle termination is the analog of an electrical ground! The information cannot be permitted to continue bouncing around until it naturally decays as is the current situation. Using a sound absorbent material within the enclosure will favor certain frequencies but will not terminate the internal reflections. Over damping and under damping will occur causing poor interaction with the ambient environment.

This issue has been referenced before!

Siegfried Linkwitz a revered audio engineer that invented the Linkwitz filter profile indicated on his website “issues with loudspeakers” there remains the challenge for an acoustic termination of the enclosed energy existing behind the diaphragm. This could be resolved with a hypothetical acoustic resistor that is frequency independent (non reactive) and responsive to the range of intensities experienced. He also said that all (engineers) would not agree with him and so far that is apparent. It is an observable common sense fact that cannot be ignored if natural sound qualities are to be obtained.

A real solution now exists!

We have met that challenge with the Loudspeaker Acoustic Adapter (LAA) and creation of the VATL, the result of discovery and heuristic development. Sometimes solutions have to come from non-traditional observation and new applications of physics principles. Isothermal viscous dissipation is the solution for coherent diaphragm motion! Currently loudspeaker technology is rooted in early 1950’s and reconciled with the TS parameters introduced in the 1970’s. Except for the impractical but effective Transmission Line there have been no attempts to create a frequency independent loading process benefiting dynamic loudspeaker pistons. Now with the VATL size is irrelevant as this patented TL process is the same for all dynamic audio drivers. While there have been many attempts to avoid these inherent issues using various new driver designs, the situation remains. Isolation of the front and rear of the driver is paramount. Maintaining detailed control of the resultant internal pressures is the solution for the idiosyncratic loudspeaker behavior.

Isothermal pressure modulation favors smaller enclosures for efficient accurate low frequency reproduction that is immune to room reflections. The VATL bypasses the Iron Law of physics allowing efficient and accurate low frequency reproduction.