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Imaging: Vertical Reflections

Published On: April 30, 2020Tags:

Refining the Sonic Sound Stage

The magic of 2-channel audio is in the imaging. Fidelity, clean bass, and dynamic performance-those can be delivered by single sound sources. But we have two ears, so an accurate playback environment has two sources. When the signals from these sources reach our ears properly, the result is a truly life-like sonic image.

In our continuing series on imaging, this week we’ll discuss the positive and negative effects of ceiling and floor reflections and your choice of listening seat. We’ll also briefly delve into side wall reflections.

Floor Reflections

A floor bounce lowers the image, but most high-end rooms use carpet and don’t experience image drop. What kind of carpet to use? Thick, Persian-style with woven pile and an open back. A substantial carpet pad (5/8″ or more) helps even more. Be sure to take care of the main reflection point, and then grow or shrink the overall carpet/rug size for a more hushed or lively room, respectively.

Ceiling Reflections

A ceiling bounce raises the image. For most, a raised image seems agreeable. After all, we imagine we are attending a show, sitting down in the audience, looking up at the stage. Wide, tall, and deep sound staging permits an effective “suspension of disbelief” for the astute listener to honestly perceive the instruments and musicians to exist on a phantom stage in front of them.

For nearfield critical listening or mixing, elimination of the ceiling reflection with a “cloud absorber” or more traditional flat panels will usually tighten up the imaging by matching the height to the width and depth.

Listening/Mixing Chair

Unless you do your listening/mixing in a 5.1/Atmos/etc surround sound environment, you want the majority of input to your ears to arrive from the front. Lengthy mixing sessions can be fatiguing when no ambience exists, therefore most mixing seats are of the “office chair” type with nothing directly behind the engineer’s head. But what about HiFi chairs?

HiFi Listening Chair #1

Many audiophiles like to listen in soft, high, wingback chairs. These chairs block and absorb reflected sound coming from the sides and back of the room. In this case the chair is casting an acoustic shadow on the listener. This is a good thing and helps imaging accuracy.

HiFi Listening Chair #2

However, vinyl or leather wingbacks create very early cross-talk reflections that are added to the direct signal. This creates a large, dim, foggy center image. Either get a shorter chair or a “softer” chair…or place pillows beside your head!

Extended Lesson: Side Wall Reflections

There are two early side wall reflections from each loudspeaker. The RR reflection simply moves the apparent speaker position towards the right wall. The RL reflection injects right ear signal into the left ear which completely kills imaging.

To widen your sound stage, leave RR untreated. To tame RL, place a mid/treble absorber on the left wall at the reflection point. You can also place a TubeTrap of proper height anywhere along the ray trace path to take out the cross-talk reflection. A wall of TubeTraps running from the listening position to the plane of the speakers is a fun, albeit extreme, experiment in holographic imaging.
Hover into Holographic Heaven

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