SVS AS EQ1 - Manual (Page 33)

AS-EQ1 Operator Manual
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Appendix A - Why EQ?
Despite efforts by speaker designers to provide a specific type of frequency response for their products, the
environment in which they are tested is typically anechoic (a room designed to absorb sound and eliminate reflec-
tive effects) or quasi-anechoic (ground plane). This test environment removes the acoustic effects of the listening
room, and allows the designer to specifically tailor the characteristics of the speaker to a desired set of criteria.
In many (but not all) cases the designer will try and achieve a “flat” response – e.g. very close to the same energy
produced at all frequencies covered by the speaker. The attached graph shows a plot of sound energy of a flat
subwoofer in an quasi-anechoic environment.
When a speaker or subwoofer is then placed in a non-anechoic environment (read – our listening rooms and
Home Theaters) the frequency response of the speaker/subwoofer is rarely close to that measured in the anechoic
environment, due to the reflection and absorption of sound waves off of hard and soft surfaces. This in turn causes
positive and negative reinforcement of sound energy and as such, the sound that then reaches our ears may seem
overly loud in some frequencies and muted in others – and definitely different than what the speaker designer and
recording engineer intended. The attached graph is an example of the effects of a listening room on our formerly
flat subwoofer.
Subwoofer Response in a Quasi-Anechoic Environment
FIG. 20