Reply To: I just need one HPF for my aux-fed subwoofer

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The OP wants to reduce level between 20 Hz and 35 Hz.

Close, but not exactly. I wanted to cut everything below 35Hz, with a steep 4th order (24dB/octave) Linkwitz Riley slope.

Are you saying that there is content below 20 Hz that is not being filtered out?

Yes, many movies have extremely low (useless) frequencies < 10Hz, that instantly put my amp into protect-mode. The driver’s resistance goes below 2Ω with these subsonic frequencies, triggering the amp’s protection circuit. I use my mixer for everything, including my “home theater”, so I can get my money’s worth from it.

The OP didn’t want to reduce level between 20 and 35Hz, he needs to cut everything below 35Hz (which totally makes sense since this region isn’t recognizable by our ears and simply eat power from the Amp and force sub speakers to extraordinary movement, except you have subsonic-able speakers, then you can feel this inside your body…).

Thank you! I see all kinds of people on the home-theater forums chasing the < 20Hz dragon, and it seem so futile. They give up so much efficiency, and claim it makes all the difference for their listening pleasure. I won’t even mention my 35Hz x-over point on those forums, because they wouldn’t even begin to understand. They have huge threads with waveform pictures touting the merits of movies that go as low as 5Hz – I put an alien movie from their list on my video-monitor and instantly regretted it. My woofers surpassed their physical limits and my amp went into protect-mode, within the first minute of that movie.

I got a DriveRack PA+ for $219 delivered, on closeout, because they’re discontinued, which was the pièce de résistance of my rig, in effect. 99% of its functions are already covered by the Qu-16, but I really needed that 1%, so I bought the thing. The newer, replacement, the DriveRack PA-2, adds wireless iPad control, so people can ring-out their monitors from the stage and so forth, but I can already do all that with the Qu-16, so I didn’t need any of the cool new features, and saved a grip on the deal. I’m basically just using it as a crossover with subsonic filtering at this point, but I still like it.