# Antimode 8033C Subsonic Filter



## bgarcia17 (Jan 8, 2007)

I bought one of these from CSS a while back, and am just now thinking about putting it in my system. So as I perused the manual, it brought up some questions. Manual claims that the subsonic filter is set at 10Hz, bu the fr chart showed it to be much higher. Having an IB, I wanted to be sure what it was so I emailed dspeaker. Here is the response that owners may already know. If not, definitely should know.

*"No, the subsonic filter can be defeated also when the Anti-Mode correction is on, it is simply enabled by default after the calibration. As the manual chapter 4.2.1 states: "This setting is automatically changed to Subsonic-Filter-Only after the first (main) calibration. You can override this and save the new setting. "

The exact -6dB point of the subsonic filter is at 14Hz on "flat" target."*

Still not clear on how to defeat subsonic filter in the unit, but I believe it's done by resetting the 'flat' eq setting. Manual isn't exactly clear on how to do that, only that the subsonic is automatically enabled after running the main calibration. I'd appreciate some help here if someone knows the answer. I'm a bit bummed that I can't use the Lift eq's without engaging the subsonic filter, but at least I can use the anti-mode corrections with it off.

I'm gonna have to run REW on the electronics to make sure the subsonic filter is acting as desired, else I'll either sell it or use it another room.


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## JohnM (Apr 11, 2006)

The instructions aren't entirely clear, but it might be that if you press the lift button until both LEDs are off then press and hold the button that might restore the flat setting as flat.


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## bgarcia17 (Jan 8, 2007)

That was my best guess. REW will help me confirm it, and whether or not is stays 'off' with antimode engaged.


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## Infrasonic (Sep 28, 2010)

Thanks for testing this bg! I'd like to be rid of the subsonic filter also.


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## bgarcia17 (Jan 8, 2007)

I have verified what we thought. I didn't check to see if the subsonic was in place after the initial calibration (with both lift lights completely off); I went ahead and pressed the lift button for three seconds before testing with REW. REW verifies everything the manual claims, other than the mistake that the subsonic frequency is set at 10Hz.

First, Bypass engaged. ALL signal processing is bypassed when BYPASS led is lit.
 

Here is the correction it would apply to fix my mock setup. Both Lift led's are dimly lit, indicating the subsonic filter is in place.
 

Here is the correction with the subsonic filter removed. Only the PWR led is lit.
 

Here is correction with Lift25 engaged.
 

Here is correction with Lift35 engaged.
 

Thank you REW!


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## Infrasonic (Sep 28, 2010)

Cool, so no lift lights and the filter is disabled. I wish it had the option to be disabled while the lifts are engaged but what can we do.

Thanks again for your help figuring this out!


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