Dahlquist DQ-1LP crossover owners

I used a modded DQ-LP1 for better than two decades and wish I hadn’t sold it. I’m not certain if a 5dB boost at 20Hz is enough for what you need, but the DQ-LP1 does offer that, via it’s EQ setting. Mentioned under, "controls and adjustments" on page 3 of the manual. If you need the entire Bass level increased, you could adjust in favor of the bottom, via the Level settings, which offer 15dB of gain.  Manual here: (https://sites.google.com/site/mpbarney/home/dahlquist-dq-lp1)

Good thought, rodman, but what f456gt is in need of is not a set boost of 5dB at 20Hz (or any other single frequency), but rather a 6dB/octave slope to counteract the dipole cancellation of his subs, adjustable for different x/o frequencies. THAT is exactly what the dipole "shelving" circuit in the Rythmik plate amp provides. The only separate x/o I know of that provides that is the special version of the First Watt B4, made especially for open baffle speakers, which also of course exhibit dipole cancellation with decreasing frequency.

Got it now.  Kinda like a Bose 901 EQ does(at both ends of the spectrum), but- not at as high an order.   Then again: I've seen Tympani Bass panels, used with different mains(ie: QRS) and a DQ-LP1, with great results.   WHEW(that's been a few decades)!