Universal Audio UAD POWERED PLUG-INS ver.6.1 - Manual (Page 520)

UAD Powered Plug-Ins Manual - 520 - Chapter 52: SPL Transient Designer
Figure 172 on page 520 shows the difference between Env 1 and Env 2 that
defines the control voltage of the VCA. The shaded area marks the difference
between Env 1 and Env 2 that controls the control voltage of the VCA. The am-
plitude of the attack is increased if positive ATTACK values are set. Negative
ATTACK values reduce the level of the attack transient.
Figure 173 on page 520 displays the processed waveforms with maximum
and minimal ATTACK to compare against the original waveform in diagram
1.
Figure 172. SPL Transient Designer Attack Control Voltage
Figure 173. SPL Transient Designer Processed Attack