AES Europe 2026

Measuring the anechoic response of a loudspeaker system
requires space; facilities that are not commonly
available. The evolution of measurement instruments has
made it possible to visualize the time response of the
system under analysis, enabling the identification of
reflected signals; their elimination through time-gating
(windowing) of the impulse response. However, this comes at
the cost of a loss of resolution; characterization of
the system's response at lower frequencies. To correctly
characterize the system's response at the lowest
frequencies, the most widely used technique is the one
described by Keele in his AES paper "Low-Frequency
Loudspeaker Assessment by Nearfield Sound-Pressure
Measurement".
To obtain the overall system response, the appropriately
windowed far-field response; the near-field response are
combined, as described by Struck; Temme in their paper
"Simulated Free Field Measurements".
This operation is performed in the frequency domain, but
what happens when applied in the time domain?
The goal of this work is to use the near-field impulse
response to reconstruct the far-field portion of the
impulse response affected by environmental reflections. As
already stated, it’s quite easy to identify the first
reflection point on a far-field impulse response; this
can be used as a merging point to reconstruct the
reflections affected impulse tail using the corresponding
part of the near-field impulse measurement. Once the
far-field impulse tail is reconstructed, it is possible to
obtain the full-range frequency response of the system
under test while maintaining maximum measurement
resolution. The steps required to achieve a full-range
frequency response are fewer than those required for the
frequency-domain technique. For example, it is not
necessary to add the baffle diffraction step effect, as
demonstrated in the paper.