The aspect that many find difficult is knowing what to do with the
results. One of the main things we are looking for here is to combine
acoustic sources in different locations that, when summed, remove
frequency response dips. Combine two speakers with the same dip and
you are stuck with it. Combine two speakers each with a dip in a
different place and the other counteracts it. Where all sources are
in-phase, they will sum as shown.
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SPL response Summed for two speaker with major dips
You can see that where both speakers have the same level and are
both flat, they gain a 6 dB increase in level combined. When one of
them has a dip, the speaker with the dip simply fails to contribute as
much, and the result is that the dip tends to be smoothed. In some
cases the dip has very little effect. You can use this to your
advantage by selecting positions that cancel out the dips.The
measured response of speakers in a room is quite complex, so
predicting the combined response is not quite as simple as one might
expect.
The main priority is to avoid dips. The peaks at this stage are less of
a concern as they can often be tamed with EQ later in the process. If
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