Subsonic Filter


Bronze Member
Username: 3k_fx

Iowa United State...

Post Number: 20
Registered: Sep-05
Does anybody know where I can find a subsonic filter that rolls off between 15 and 20 htz. I'm looking perferably for something that comes before the amp to reduce wasted power output. I like the looks of the FMOD inline highpass filters, but they only come at 50 htz and higher. I'm looking for something that can reduce the signal fast enough to prevent over excursion of a ported subwoofer below 20 htz.

Do most EQ's with a subsonic filter have a high enough roll off to prevent over excursion? I'm not looking for something that costs a lot since I'm looking for a subsonic filter more as a preventative measure than as a needed feature of the sub.

I've seen plenty of plate amplifiers that have a built in subsonic filter, but most are situated around 30 htz, and I'd prefer to keep the lowest octaves; that is why I'm looking for a filter situated around the 20 htz range or a little lower.

Does anybody know a simple way to implement this?

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 6774
Registered: May-04

Subsonic filters are generally associated with turntables and phono inputs where a tonearm/cartridge mismatch or suspension glitch can result in frequencies in the 5Hz range driving the woofer's voice coil beyond its proper operating region and wasting amplifier power. If you aren't running a turntable, why would you require a filter that low?

Digital sources shouldn't have frequency response beneath about 15Hz, so there should be very little reason to filter a subwoofer if the sources don't have any truly "subsonic" frequencies. Overdriving the woofer at that point becomes an issue of where you set the volume control, not filtering the nonexistent frequencies.

Or, have I missed something here?



Bronze Member
Username: Southern_bass

Jacksonville, Florida U.S.

Post Number: 36
Registered: Dec-05
pretty much how it is
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