From the Desk of Art Noxon

Art Noxon is a fully accredited Acoustical Engineer with Master of Science degrees in Mechanical Engineering/Acoustics and Physics. A Professional Engineer since 1982, he is licensed in Oregon to practice engineering in the public domain with the specialty area of acoustics. A prolific inventor, he developed and patented the iconic TubeTrap, the original corner-loaded bass trap/treble diffuser, 150 other acoustic devices, and counting. Lecturer, writer, and teacher of acoustics, he has presented 7 AES papers, numerous magazine articles, white papers and blogs. He is president of Acoustic Sciences Corporation, the company he founded in 1984.


TubeTrap History

TubeTrap History

Arthur Noxon, Father of the TubeTrap bass trap, demonstrating bass trapping concepts at Recording Arts Center, Eugene, Oregon in 1985.


The TubeTrap is the world's first commercially manufactured corner loaded bass trap. Acoustic Sciences Corp. was founded in 1984 by Arthur Noxon to build and sell the TubeTrap. The TubeTrap was also the world's first portable bass trap, opening up an entirely new field in acoustics, namely audio acoustics. Coupled with recent new advances in audio speakers and solid state electronics, the necessary ingredients for explosive growth in high end audio were at hand.

Unlike any other bass trap, the physics behind the TubeTrap are based on a capacitive-resistive circuit. The acoustic capacitor (C) is the air chamber inside, the bigger it is, the more efficient the TubeTrap is at low frequencies. The acoustic resistance (R) is DC impedance matched to the radiation (LC) impedance of a freely radiating soundwave. Because of this design feature, the TubeTrap is another unique feature is the adjustable diffusion grid built into the TubeTrap. The specular diffusion panel that covers half of the TubeTrap is an acoustic choke (L) which is sized, ported and mass loaded to backscatter the treble range.

This diagram shows the acoustic circuit of a TubeTrap bass trap. This bass trap uses acoustic “time constant” technology to achieve high efficiency unlike membrane, Helmholtz and quarter wavelength bass traps.

Before The Beginning

Shortly after graduating in 1981 with a Masters in Engineering, Mr. Noxon had established a small acoustic engineering firm doing local projects in the Eugene, Oregon area. In the course of his work, he was hired to take care of a huge lecture hall at the University of Oregon. The lecture hall had a serious resonance problem at 125 Hz, not good for speech intelligibility. So he set out in search of a suitable bass trap.

Schematic of Ripple Tank, using speakers to generate the waves.

Mr. Noxon had always been interested in low frequency acoustics since his college days and endless hours observing wave theory using a ripple tank (see picture). As he researched the availability of bass traps, he found they only existed as custom units built for recording studios. As he pondered and searched, he was frustrated by the total avoidance of bass trapping within the acoustics field, as though it didn't matter.

In an epiphany, he could think back to his ripple tank days and "see" the acoustic waves. That led to the concept of the acoustic resistor, something that nobody had thought of until Mr. Noxon. Yes, bass traps existed, but they relied on membranes to deal with the pressure wave. Now it was time to test out Mr. Noxon's novel idea of applying a resistive-capacitive circuit to low frequency acoustic waves. Could he apply in practice this theory to the job at hand, the huge lecture hall at U of O?

Almost The First TubeTrap

Mr. Noxon searched for suitable materials for his bass trap, and knew he needed a porous walled cavity to experiment with. He found some 2" semi-rigid fiberglass duct board and experimented with it for a while. Then he found the circular fiberglass pipe wrap which became the basis for the familiar TubeTrap. The pipe wrap was easier to work with since the cavity didn't have to be made, it was already there. The problem was the resonance of the pipe wrap itself, the twang, would cause resonant dips at certain frequencies. After much experimentation, it was found that a wire mesh cage would muffle the twang, much like holding a bell muffles the ring.

So, now Mr. Noxon could place columns of his new TubeTraps in the corners of the U of O lecture hall, and fix the 125 Hz resonance problem. But as he looked over the test data of the lecture hall, he noticed that the numbers didn't check out for a room that size. Something wasn't quite right, the resonance at 125 Hz couldn't be caused by the room itself. So he went back to the hall to take a closer look. It turned out that the desk tops and the tiered design of the room were the real cause of the resonance, and the fix was to structurally strengthen the desk tops. The TubeTraps would have to wait for another opportunity.

The First TubeTrap

One day the phone rang and it was the local hi-fi shop getting ready for a remodel. They had Magneplanar speakers and they sounded awful in their demo room. The folks at Bradford's wanted something furniture-like, and Mr. Noxon figured maybe his TubeTrap might be the ticket. Sure enough, they made those Maggies sing, and Bradford's was thrilled. Now, 25 years later, Bradford's still uses TubeTraps in their demo room.

Mr. Noxon bought those first TubeTraps back from Bradford's, and replaced them with newer ones. The originals are now safely stored in the TubeTrap Archives for posterity, and Mr. Noxon recently showed them off.

At the time, Mr. Noxon's day job was as a sanitation engineer for the city, spending most of his time underground in the sewers. While it paid well, it wasn't all that much fun. Meanwhile, several speakers reps visiting Bradford's took note of the TubeTraps and really liked what they heard. Some time later, word reached John Dhalquist, a genius speaker designer famous for high end quality, that he should check these out.

Mr. Noxon gets a phone call from New York, it's John Dhalquist wanting to order 4 TubeTraps to "try out". Mr. Dhalquist liked them, but they were too dead in the treble range. So, along came the now familiar reflector (which originally was made of aluminum with holes drilled). However, there was more to it than everyday hi-fi tweaking. Mr. Dhalquist was getting ready to unveil his new DQ-10 speakers at the upcoming CES Show, and placed an order for 30 TubeTraps to be delivered at the show,

Finally, the TubeTrap was born.

The first Tubes, sold as a set of 8 that were 9" x 36", featured mated pairs with a unique built-in diamond base similar in shape to a "home plate" used in baseball. This gave the stacked Tubes a nice finished look and contributed to the "furniture look" that Bradford's wanted.

These first TubeTraps didn't feature the classic reflectors that create the now familiar live side/dead side found on all subsequent TubeTraps. These were the only TubeTraps made by Mr. Noxon prior to the formation of ASC, and once they became ASC TubeTrap, the reflectors were included.

As with the TubeTraps of today, these did feature a wire cage to add strength as well as to help dampen twang. The fabric covering, much like today, was a sleeve stretched over the cage assembly. The end caps were 1/4" plywood, and the base units permanently attached. The stacking feature relied on three dowels to keep the two Traps properly lined up and prevent toppling.

  

*This is the very first TubeTrap bass trap, then the only real bass trap that could be moved in and out of the corner, tuned with ease.

*The base plate shape for the original TubeTrap supported the bass trap in the corner while providing designer angles for the eye.