Audio Engineering Associates RP48Q Operating Manual - page 7
Figure 4: Response of LF Filter
LF filters tame proximity effect and reduce other unwanted low-frequency noise, such as air-condition-
ing rumble, traffic noise, “P-pops” and breath-noise noise. However, a fixed-frequency, constant slope
low-cut filter cannot handle all situations effectively. The RP
48
Q offers a flexible LF filter that can be
tailored to satisfy the varying and critical demands of both speech and music.
Pushing IN the LF Filter switch (ref. #5) inserts a - 20dB (maximum) low-cut shelving filter. The tun-
ing control (ref. #6) adjusts the -3 dB break-frequency of the filter. Setting the filter is easy: push in the
LF Filter switch and adjust the tuning control until you like the sound. Then toggle the LF Filter switch
quickly to compare the result against the original. When the offending noise is reduced sufficiently but
the low-frequency content of the program remains unaffected, you have achieved your goal.
Using the Curve-Shaper and HF Gain
The RP
48
Q features a unique Curve-Shaper circuit that enables you to add a little extra “presence” or
“air” to the pickup to compensate for high-frequency losses that are inherent to most ribbon micro-
phones, the result of distant mic placement, or an overly “dry” acoustical environment. This circuit
functions similarly to a conventional parametric shelving boost, but with a significant difference: the
slope varies as both the Curve-Shaper and HF Gain controls are adjusted.
Once the Curve-Shaper switch (ref. #7) is IN/ON, adjust the continuously variable Curve-Shaper
control (ref. #8) to tune the filter to the +3 dB break-frequency at and above which you want to intro-
duce the boost. Then, dial-in the amount of boost you desire with the HF Gain control (ref. #9). The
two controls are interactive, so as with the LF filter, listen carefully to determine at what frequency and