For truly effective room control, you cannot merely absorb mid and high frequencies; you must address all frequencies in a balanced fashion. For instance, if you remove all of the highs in your room, the mids and bass will be pronounced. This will lead you to compensate by reducing the mids and bass form your mix. When you take the recording out of the studio and listen to it in your car or home, you will likely find the results to be overly bright. A balanced solution is required. This is what we have managed to achieve with the FullTrap. Let's have a look at some basics so that you can best understand what we have done and why.

Sound absorption typically follows what is known as quarter-wavelength calculations coupled with good old common sense. Because high frequencies are more directional, strategically placing absorptive panels using simple vectors will solve many of the primary issues such as eliminating flutter echo, room chatter and standing waves. The deeper the absorptive panel, the lower the frequency it will take out of the room. As an example, a 3" thick panel will effectively remove 200Hz and above. The more dense the panel is; the greater the effectiveness. For instance, open cell acoustic foam is produced in varying densities; the most common as offered by a major manufacturer is a mere 1.3 lbs per cubic foot. (Primacoustic open cell foam is 50% more dense at 1.8 lbs per cubic foot!) The absorptive panel used on the FullTrap is made from 6 lbs per cubic foot fiberglass with roughly 500% greater density. Serious professional recording and broadcast studios employ high-density fiberglass panels for this important reason.

Truth is, high frequencies are easy to control while low frequencies can be very problematic. This is due to the wavelength. The lower the frequency; the longer the wavelength. For instance 1kHz has a wavelength of just over 1 foot long while 50Hz has a wavelength that extends to 22 feet! Once you get this 50Hz 'freight train' moving, it is very tough to stop it. (Speed of sound 1130ft per second divided by the frequency 50Hz = wavelength 22 feet). If you were to use simple quarter wavelength calculations to measure the optimum depth of a given bass absorber, you would take the low frequency wavelength (22 feet for 50Hz) divide it by 4 (quarter wavelength to get 5.5 feet) and then divide again by 2 for the angle of incidence (2.75 feet). This means your bass trap would have to be almost 3 feet deep to absorb 50Hz! Given the fact that most small studios or control rooms range from 12 feet to 16 feet long, giving up three feet of space to build a bass trap is often difficult, if not impossible to do.

During the development of the FullTrap, we considered all of this and came to the conclusion that we had to take a slightly different tactic. We had to find a way to control all of the frequencies down to the low bass without taking a lot of space out of the room. Furthermore, we had to find a way to make shipping cost effective. Big bass traps take a lot of space and if half the cost of buying one would be in freight, we knew this would not bode well for project studio owners on a budget. Finally, it had to both perform well and look professional so that it could be used in any type of facility. Considering most studio owners are not carpenters we also had to make it easy to assemble and virtually impossible to screw up. So this is what we did:

We started with the same premise as a 3-way loudspeaker whereby three components are combined into a single box to produce bass, mid-range and high frequencies. Only with the FullTrap, we are absorbing each of these using three different acoustical techniques.

First, high frequencies are absorbed using a high density, rigid fiberglass panel. This 3" thick face panel has been tested and will actually absorb sound from 200Hz and up.

Second, This is supplemented with a deep air cavity behind the panel that traps bass and controls the lower midrange. By increasing the air space behind the panel, we are basically adding depth without adding cost. This old trick has been used for years to extend the performance of rigid panels. By applying quarter wavelength calculations, we can quickly surmise that with over 8" of total depth, the FullTrap will easily extend well below 150Hz without yet considering our final, third treatment.

It is interesting to note that the 'science' behind sound absorption is actually called thermo-dynamics. Sound waves travel through mediums such as air, walls and even the ground we stand on. When they excite or penetrate the medium, it shakes in relation to the frequency. For instance when thunder roars and the walls and windows of your house vibrate, Mother Nature is compressing air particles that in turn cause things to vibrate. When they vibrate, they generate heat. As stated before, the lower the frequency, the longer the wavelength and the more difficult it is to contain the offending sound. High frequencies with their short wavelengths penetrate the minute fiberglass strands inside the face panel that are encapsulated behind the acoustically transparent fabric and micromesh causing them to vibrate. The rigid fiberglass panel itself will also quietly vibrate further converting sound into heat.

Thirdly, we have employed this same thermo-dynamic science to help control the deep low bass, only this time instead of controlling bass by vibrating minute fiberglass strands, we have pulled out the big guns and incorporated a dead-mass in the form of a heavy membrane. For fun, kick a sand bag. Other than hurting your toes, nothing will happen. Why? You are kicking a dead mass or if you wish, a substance that is not able to resonate as it has no rigid structure.

The dead mass in this case is a 1lb. per square foot membrane made from a barium impregnated PVC barrier that is loosely suspended like a diaphragm behind the fiberglass face panel. Powerful low frequencies with their long wavelengths first pass through the absorptive panel and cause the membrane to vibrate. Due to the dead-mass nature of the diaphragmatic membrane, a wide swath of low frequencies is absorbed. Because it is a dead mass, it does not resonate like a wall so therefore it does not create sound.

The result: Three acoustic principles are applied providing broadband absorption. This not only helps control excessive bass and room nulls, but will result in a tighter more consistent sound throughout the room. All of a sudden, the listening sweet spot is enlarged; troublesome standing waves are eliminated; intelligibility is increased; and listening fatigue is reduced. How cool is that?