For sale FDeck HPF-Pre Series 3

This HPF actually has a 24dB per octave curve.

It’s a lot more effective than the Broughton HPFs in my opinion.

Thanks for the clarification, Joe. You are correct. The Broughton looks like it cuts 12 Db/octave below the filter, the Fdeck is what the designer calls, "12 + 12." Per the website:

"The "12+12" filter curve is two filters in one. The first filter has a fixed corner frequency of 35 Hz, and 12 dB/octave slope. The second filter is adjustable from 35 to 140 Hz, and also has a 12 dB/oct slope. Thus it always has 24 dB/oct slope below 35 Hz. I designed the Series 1 and 2M filter (same circuit in both) for double bass amplification, to tame the infrasonic "thump" produced by the acoustic instrument, which interacts poorly with the low frequency excursion behavior of ported speakers. Interest in a 24 dB/oct filter came from electric bassists who are experimenting with the latest high-performance speakers, to avoid driving the system at frequencies below the port tuning frequency."