• LEDE – Live end, dead end room designs
  • Diffusion – breaking up high frequency energy
  • Absorption – controlling sound and resonance
  • Combined approach – controlling directional frequencies

 

The concept behind the Flexifuser came from trying to find an affordable way to disperse high frequency energy. High-end diffusers like the Razorblade are extremely expensive to produce and therefore are usually only found in high-end rooms. By combining simple diffusion with absorption, the Flexifuser delivers exceptional performance. 

 

LEDE – Live end, dead end room designs

The question is simple: Why diffuse energy in the first place? Why not simply absorb it? Well, way back in the dark ages of recording (circa 1960) many studios were entirely treated with absorptive materials making them sound dead and listless. Engineers quickly realized that listening in an artificial environment results in recordings that did not translate well into the ‘real world’.

Sometime in the 1970’s a new studio design concept came about that treated half the room with absorptive panels (dead-end) while the other half was totally untreated (live-end). This became known as the LEDE or a ‘live-end, dead-end’ room design. The intent was to allow the engineer to make critical decisions such as special placement by eliminating the ambience in the dead end, while allowing sound to reflect at will in the live end. Although better than an ‘anechoic chamber’, problems still persisted.

Diffusers began to find their way into studios during the 1980s as a means to help eliminate flutter echo and eliminate powerful primary reflections. Over the years, the LEDE concept evolved to where today, most rooms tend to have a greater degree of absorption at the source end of the room, while the receive end is left relatively live with the aid of natural and artificial diffusers.

 

Diffusion – breaking up high frequency energy

There are many types of diffusers and they pretty much have one thing in common: they feature some form of irregular pattern designed to reflect energy back into the room at various angles by breaking up directional energy.

Some diffusers such as the Razorblade are designed in such a manner to ensure all frequencies are broken up evenly via a carefully designed phase trap. These are painstakingly difficult to produce and end up being quite expensive. At the other extreme are products like the Radiator that employ a basic grid design that cause sound arriving at oblique angles to randomly spread into the room. These are easier to build, not quite as effective but are considerably more affordable.

The Flexifuser sits in between. It employs a series of variable pitch slats that can be rotated so that sound can be deflected away from the listening position. This increases the sense of space or air in the room. The simple design is particularly cool because you can optimize the dispersion pattern to suit the seating position.

variousdiffusers3

 

Absorption: controlling sound and resonance

Where the Flexifuser differs is that it combines diffusion with absorption. Think of it like a two way speaker where high frequencies are generated by a tweeter and lows by a woofer. In this case, highs are dispersed by the variable pitch slats and the lows are absorbed by the acoustic panel in behind.controlling-sound

The acoustic panel itself is a custom cut 2″ thick Broadway panel. Because it is offset from the wall with an air gap, the low frequency performance is extended by about an extra half octave. This means that it will be 80% effective down to 250Hz putting well below what most consider to be the directional frequency zone (above 300Hz). Any high frequencies that get past the slats will be absorbed and any sound that gets trapped behind the slats that could potentially cause resonance will also get taken out.

 

Combined approach: controlling directional frequencies

As mentioned above, acousticians generally agree that sound tends to beam or be directional above 300Hz. The task of a diffuser is in fact to diffuse this energy. Since high frequencies contain less energy than their lower counterparts, they are much easier to manage. Therefore, diffusing high frequencies above 1000Hz is not difficult. Where things get to be a challenge is down low. By using simple quarter-wavelength calculations, you need a device that is 8″ deep to diffuse 400Hz.

It is important to note that without mass, sound will pass right through. For instance a plastic bag will not contain sound even though it can contain air. It is for this reason that the Flexifuser in made from a heavy, wood composite; when sound hits the slats, most of it will reflect back into the room.

Basic math will tell you that a 4″ deep device will diffuse energy above 800Hz or one octave above. But to effectively diffuse energy down to 200Hz, one would have to produce a diffuser that is 16″ deep which is impractical. This is why the Flexifuser is so cool. Instead of trying to diffuse the energy below the directional frequency, it is absorbed using the acoustic panel.

And at less than half the price of a Razorblade, you truly are getting exceptional value for your dollar!

Diffuser Depth (inches) Low frequency cut-off (Hz)
1″ 3.2k Hz
2″ 1.6k Hz
3″ 1.2k Hz
4″ 800 Hz
6″ 600 Hz
8″ 400 Hz
12″ 300 Hz
16″ 200 Hz
24″ 150 Hz
This table shows the anticipated cut-off point of a diffuser using quarter-wavelength calculations. This assumes a relatively hard surface with sufficient mass to reflect energy back into the room. Some diffusers are designed to be grouped to create larger wells to lower their effective range. This table assumes a single device.