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Psychoacoustically Pleasing

Polyphonic Perception

The last several weeks we have been searching for a sound stage that really takes us “to the show.” These days, this might be the only show we will be hearing! So let’s make the best of it, and add sound stage depth to the equation.

How do we create an image in our mind’s eye that allows some musicians or effects to honestly seem to come from far behind the speakers? How can the drum kit sound like it is 20 feet behind the singer and 8 feet up on a riser? Read on to find out! (and read all the way to the end for a special bonus!)

What Mechanism Provides This Illusion?

Stage depth is created by adding treble range early reflections that bounce off the front wall. Rounded corner boxes let this happen. Dipoles also provide this feature.

However, bass range front wall reflections cause time delay phase add/cancel effects at the listening position. This is a bad thing!

The Solution?

Add bass traps that are faced with treble range diffusers.

The bass range phase add/cancel problem goes away while treble range stage depth reflections are created.

What amazing acoustic product combines these two features?

• TubeTraps
• ?????

What type of TubeTrap do this the best?

• Isothermal 13″
• Isothermal 16″
• Standard 13″
• Standard 16″

What is Really Going on Here?

When TubeTraps are stacked along a wall and sound is traveling toward the wall, some of the upper treble is back scattered by the curved reflector. This is specular diffusion.

But the narrow beam that passes between the TubeTraps reflects off the flat wall. Because is is a long narrow reflection, it expands to the sides. This is diffractive diffusion.

At the listening position, the direct signal from the speakers “fuses” with early diffuse reflections off the front wall which places the image floating in space beyond the wall. It seems like magic, but it is just physics and psychoacoustics. OK, let’s agree that it sounds magical!