HTP-1 Installation and User Guide Release 1.8.1
The loudness curve needs to be calibrated against the volume in the room This is complicated by several
factors in a real situation, but HTP-1 allows you to calibrate by ear. The EQ page includes a “Loudness
Calibration” control.
The loudness calibration number corresponds roughly to the sound pressure level at which you want a
flat response. That would be the “normal listening volume”. A higher number means there will be more
loudness bass as the volume goes down. A lower number decreases the amount of bass boost.
The range is 50 to 90.
Bass boost matching the known curve is added slowly as you lower the volume. Hence there will be no
effect at high volumes with more and more bass added as you lower the volume. This graph shows the
frequency response at various levels:
A high-pass filter is included to avoid boosting the region below 20Hz. The relatively large bass boost
applied when the volume is low means that it is possible to hear a thump or a tick when turning the
loudness on or off.
HTP-1 User Manual
Page 74
V1.8.1