is this what you mean (from here)?
-- filter
filter_fc = { type="control", controlspec=controlspec.new(10, 12000, 'exp', 1, 12000, "Hz") },
filter_fc_mod = { type="control", controlspec=controlspec.new(0, 1, 'lin', 0, 1, "") },
filter_rq = { type="control", controlspec=controlspec.new(0.0005, 8.0, 'exp', 0, 2.0, "") },
-- @fixme use dB / taper?
filter_lp = { type="control", controlspec=controlspec.new(0, 1, 'lin', 0, 1, "") },
filter_hp = { type="control", controlspec=controlspec.new(0, 1, 'lin', 0, 0, "") },
filter_bp = { type="control", controlspec=controlspec.new(0, 1, 'lin', 0, 0, "") },
filter_br = { type="control", controlspec=controlspec.new(0, 1, 'lin', 0, 0, "") },
filter_dry = { type="control", controlspec=controlspec.new(0, 1, 'lin', 0, 0, "") },