Thinking Outside the Box -- Listening Outside the Room or the Bouncing Sound

This may seem strange. But, a good test of how well a speaker and a room are matched is listening from Outside-the-Room (OtR). By listening through an open door while standing where you cannot see the speakers, you will learn a lot about the room/system interaction.

You lose all imaging qualities. In this OtR test, an excellent stereo (or home theater) system should sound very similar to an excellent mono system. So, this is not the only test you must do before choosing the right speakers and their proper placement. The sound you hear with OtR will have bounced around the room a bit. Losing the imaging qualities makes it easier to hear the energy response of the system/room combination.

What do I mean by energy response? We all understand that frequency response is the output at one frequency compared to the output at all other frequencies. Speakers are usually tested at just one point in space or over a typical listening area. Energy response is averaging these responses from all directions. That is the energy response of the speaker. The speakers’ placement in the room affects the overall energy response as reflections add and subtract from each other. By listening OtR, you can hear the average of the bouncing sound inside the room.

When you are inside the room, the information coming directly from the speaker to your ears is crucial to what you perceive as the musical content and imaging. The reflections off the floor, ceiling and walls contribute more to your sense of the room than the information from the recording. A room with a lot of glass, tile floor and unupholstered furniture will sound very different from a room with heavy drapes, thick carpets and large upholstered furniture. The higher frequencies will sound more pronounced in the first room.

Your brain/ear listening system is very good at distinguishing sonic events from room reflections. It does this by recognizing a reflection as a slightly delayed repeat of the same information. If the delay is very long, the second signal will be perceived as an echo. If the delay is very short, the second signal will be integrated into the original signal, thus distorting the perception. We have lived with the floor bounce our whole lives and it has a long enough delay to be recognized as a bounce and be used for imaging cues; but not long enough to be heard as an echo. When you listen from outside the room, the bounces and their time delays are all mixed together and lose their imaging information. You hear only the sonic balance of the combined room and speaker interaction effects.

A system with a flat frequency response in its “sweet-spot” will often sound dull when listening OtR since treble is usually much more directional than bass. To get a flat frequency response when listening OtR, the speakers total energy output must match with the absorptive/reflective characteristics of the room. With OtR, you are evaluating both the room and its match to the system. If the room is very “dead” and absorbs much of the highs, you will need more treble energy to sound balanced from both outside and inside the room. If the room has mostly hard surfaces and little sound absorbing material, you will need and want less treble when listening either inside or OtR.

If you are auditioning in a showroom, OtR is often a valuable test since it is a reasonable assumption that the dealer has optimized the system for the sweet spot which may or may not be compensating for the showroom or for unusual dispersion patterns.

If you are auditioning in your home, you can use this OtR test to evaluate room energy balance with different placement of the same speakers or of different speakers.

Like a Jack-in-the-Box, this Outside-the-Room test may surprise and entertain you – and, unlike the Jack-in-the-Box, it will also inform you.

See you on the 15th. Until then,

Enjoy & Good Listening,

John

John Strohbeen Author

John Strohbeen was the President and Chief Engineer of Ohm Acoustics from 1978-2023.