TubeTrap, the original, archetypal bass trap, dating back to 1984, are set up in the corners of the room where they act like sonic shock absorbers. The bass trap part of the TubeTrap damps out excessive build-up of bass energy in the room and the built-in diffuser backscatters slap back, converting flutter echo into fine grained lateral ambience.
The TubeTrap was developed through acoustical engineering principles and voiced by the consensus of golden ears. It was the first full bandwidth sound absorber/diffuser (abfuser) and has become synonymous with quality listening and performing spaces. TubeTraps quickly became the worldwide defining icon of high performance audio room acoustics, and remains so to this day.
TubeTraps are used to make music from the beginning to the end of the audio chain. In the recording studio TubeTraps are used to control the acoustics that surround the talent and mic and the creation of audio tracks. Later in the process TubeTraps work to create crystal clear mixing environments. Then TubeTraps are used to create the mastering rooms where the recording studio master tape is turned into a commercial album.
Then, TubeTraps are used to create reference listening rooms for the manufacturers of audio equipment, great demo rooms for the equipment dealers and fantastic playback rooms for the audiophile listener, rooms which help audio gear turn great recordings into great sounding music. TubeTraps are very busy at work, from the making of music to the playback of music...or as we like to say.....from music to music.
ROOM ACOUSTICS AND TUBE TRAPS
Modern loudspeakers and subwoofers in high performance audio playback settings produce dramatic amounts of bass energy. Professional recording studios have always used built-in bass traps to absorb this bass so that it does not build up and overpower the rest of the sound in the room. When high power audio is played in rooms constructed for residential or retail demonstration use, no accommodation has been made to handle the build-up of excess bass energy. And so the uncontrolled sound pressure builds up inside the room, which not only is unpleasant for the listener, but it additionally shakes the walls, floor and ceiling, windows and doors of the room.
These shaking surfaces act like giant uncontrolled loudspeakers that bother the neighbors and additionally ruin the quality of sound in the room. High power audio playback at home or in commercial spaces is no different than what goes on in recording studios. Bass traps mixed with treble range absorption and diffusion is the only way quality sound can be heard, regardless of how expensive the speakers and amps may be. The TubeTrap is a self-contained, broadband bass trap, a reactive acoustical circuit that is energized by and works off of sound pressure. It performs best when placed at locations in the room where the sound pressures are the highest, which is typically in the corners and against the walls of the room.
Because the TubeTrap only reacts to sound pressure it is sometimes referred to as a pressure-zone bass trap. Although the TubeTrap is a broadband sound trap, it can be modified by adding additional acoustic circuitry to give it an enhanced narrow band range of sound absorption in addition to its broadband bass trap properties. However, this is not to be confused with a "tuned bass trap" which is exclusively a narrow band bass trap and has no broad band properties.
For the most part the "tuning" of the TubeTrap is usually not done with internal circuitry but done by the room itself. When a room resonance is created, the sound pressures are always the highest in the corners of the room and in select locations along the walls. For tones that are not room modes, the energy in the room is diffuse which has a more uniform distribution of sound pressure throughout the room. Placing TubeTraps in the corners and at certain wall locations puts them in the high pressure zones of the room modes. The higher the pressure, the stronger the TubeTrap works. Properly placed TubeTraps in a room automatically ensures that loud, long lingering modes will be more highly damped than the more quickly decaying diffuse sounds in the room. This gives any room TubeTraps are used in a much more tonally balanced reverberant field.
HOW TUBE TRAPS WORK
Acoustic CircuitryThe bass trap component of the TubeTrap is an acoustic circuit. It acts just like a series RC circuit in electronics, a high-pass filter. The R part is the acoustical resistor, the wall of the TubeTrap, whose DC flow resistance equals the acoustic impedance of an acoustic wave, 460 Rayl. This is similar to what happens when a video technician terminates the unused leg of a video cable system. A 75 ohm terminal resistor is used to cap off the open ends of a 75 ohm coax cable transmission line. The C part of the acoustic circuit is an acoustical capacitor, the air cavity inside the TubeTrap. The larger the volume, the lower the roll off frequency in the response curve.
Covering half of the surface curved surface of the TubeTrap, end to end, is a perforated sheet of soft plastic, a limp mass. High frequency sound bounces off the surface of the reflecting sheet while low frequency sound passes right through the holes in the reflecting sheet. This is another acoustic circuit element, in effect it creates acoustic inertia, which is comparable to an electronic inductor, L. An inductor is a low pass filter.
These three acoustic circuit elements are connected in series which produces the effect of a bandpass sound absorber. The lower cutoff frequency is determined by the diameter of the TubeTrap, not its length. The upper cutoff frequency of the bandpass is determined by the hole pattern in the treble reflecting perforated sheet. Rotating the TubeTrap on axis changes the % of treble diffusion to absorption facing into the room between 0 and 100%. Rotating the TubeTrap is equivalent to adjusting the side scattered treble volume control. Tuned resonators can be installed inside TubeTraps to provide enhanced absorption at a particular frequency. Active TubeTraps are also available and they provide a very wide bandwidth of deep bass absorption.
Corner Bass Traps The TubeTrap is designed to absorb bass energy out of bass range sound pressure. The stronger the pressure the more energy is absorbed. Bass pressure is 4 to 8 times stronger in the corners of the room than out in the open parts of the room. TubeTraps are typically stacked floor-to-ceiling in columns in the corners of the audio room. Each corner acts like a giant megaphone in reverse, compressing incoming sound waves into the narrow volume at the root of each corner of the room. This corner compression of bass waves creates the perfect location for a pressure zone bass trap, the TubeTrap.
Not only do corners compress bass waves into pure pressure zones but standing waves and room modes also fully compress into the corners. Corner loaded pressure zone bass traps, TubeTraps, are extremely efficient at controlling bass throughout the whole of the room by extracting energy out of the corners of the room.
Sound is stored in the volume of the room and absorbed on the surfaces of the room. The bass range is best absorbed in the corners of the room. Small rooms have a fairly large percentage of their room volume tied up in the 8 corners of the room. Corner loaded bass traps, like TubeTraps, are perfectly suited to adding control to otherwise out of control build-up of bass energy in small but high power audio playback rooms.