6 SPEAKER MEASUREMENT
With the DEQX connected into your system and DEQX-Cal
running, it is time to measure the speaker. This chapter walks
you through the first step of the measure-calibrate-configure
cycle, to measure a full range speaker in a typical listening
room. It assumes that the DEQX is connected for single-amp speaker configuration
mode e.g. as on page 23. (For bi-amp and tri-amp configurations, see Chapter 13.)
One of the vexing issues in speaker measurement is the presence of the room – it is
difficult to measure only the properties of a speaker, because reflections from any other
object (including furniture, floor, ceiling and walls) conspire to corrupt the
measurement. DEQX-Cal is able to remove these reflections from the measurement
when doing a speaker calibration (described in the next chapter).
While the reflections can be removed with software, a longer time delay before the first
reflection arrives at the microphone is still beneficial, because it enables correction to
lower frequencies. Figure 1 and the description on the next page describe how to
accomplish this in a typical listening room. Measuring outdoors on a raised platform can
provide a longer reflection-free time window, but excellent results can still be obtained
using the method described in this chapter.
To simplify the explanation, this chapter generally assumes that just one speaker is
being measured. This is a good choice if you are still becoming familiar with DEQX-Cal,
as modern hi-fi speakers (of a given model) are quite close to each other in response.
Once you have mastered the art of measurement and calibration with DEQX-Cal,
measuring and calibrating both speakers separately will provide the ultimate calibration
accuracy.
To obtain accurate speaker measurements, the measurement microphone must be
pointed directly at the speaker. While it is essentially omnidirectional at lower
frequencies, it becomes more directional at higher frequencies and is calibrated for a
flat response at high frequencies only when pointed directly at the speaker. If the
microphone is pointed vertically at the ceiling or floor, or anywhere but directly at the
speaker, your measurement (and thus calibration) will not be accurate at high
frequencies.
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