Ported enclosures are tuned to a certain frequency range which is determined by a combination of port area, port length, and net volume of the subwoofer box. This is the reason why you want to cut those frequencies out.Īs a general rule of thumb, if your sub is mounted in a sealed enclosure, adjust the subsonic filter to 25-35 Hz, to filter the extremely low bass frequencies your subwoofer is unable to play. Subsonic frequencies can potentially damage your subwoofer because they push it past its mechanical limit and make it play below the enclosure tuning. In a Sealed Box:īecause lower frequencies are harder to re-produce, the lower you set them, the more excursion a woofer is forced to take in order to play them loudly and accurately. 5Hz below what the box is tuned for… half (½) an octave below what the box is tuned for…etc. If you frequent any of the popular car audio forums, you’ll notice that there are many opinions about where to set a subsonic filter.
Subsonic filter on amp how to#
How to Set Subsonic Filter on Car AmpĪ subsonic filter is used differently in sealed enclosures than in ported. So, a subsonic filter isn’t mandatory, but it’s highly recommendable in some situations, specially when your sub is mounted in a vented box, or if you listen to heavy-bass music for extended periods of time. Because of that and because these frequencies are prone to damaging woofers, filtering them out is a desirable characteristic in subwoofer amplifiers. Is Subsonic Filter a Must?Ī subsonic frequency is very low, so low the human ear is incapable of hearing it, however your body can feel it. However, if you want a little less rolloff, you can opt for a lower slope such as 18dB, or 12dB. That said, if you’re looking for extreme protection of your subwoofer, then a higher slope is better. If it has a 12db/octave slope, then it will attenuate all the frequencies below the selected frequency at 12 decibels per octave. In other terms, if your subsonic filter has a slope of 18db/octave, then it will attenuate (make quieter) all the frequencies below the selected frequency at 18 decibels per octave. Taking into consideration that one octave corresponds to a doubling of frequency, if you set an 18 dB/octave subsonic filter to 40Hz, then at 20Hz it will sound 18dB quieter, and the 24 dB/oct would be 24dB quieter. Slope is expressed as decibels (dB) per octave, and the dB numbers (18dB, 24dB…) refer to the rolloff of the subsonic filter. It refers to the rate at which music notes will be attenuated to below the specified subsonic filter frequency. Speaking of “slope”, when talking about subsonic filters, you may hear that term thrown around quite often. Think of the filter as a slope, not an on-off switch. In fact, it’s safe to say that when a subsonic filter is set to 40 Hz, a frequency like 25 Hz notes will still get through and be quite audible, albeit much quieter than it would be if the filter was not set at all.
If you have an amplifier with a subsonic filter set at 40 Hz, this doesn’t mean, by any means, that everything below this is completely dead and gone. Most music doesn’t contain these frequencies for that very reason but sometimes even 30Hz can be hard on your subwoofer if it isn’t designed to dig down that low. So, if you send low frequencies below 20Hz to your subwoofers, you won’t be able to hear them anyway (you’ll mostly feel them). The human hearing ranges roughly from 20 Hz to 20000 Hz. I mean, think about it, if you have a custom built ported enclosure tuned to 31Hz, you don’t want to play frequencies that are way lower than that, otherwise you risk blowing your subs. Subsonic filter is a very important feature for vented enclosures, as it can significantly reduce the loud booming notes around the box’s resonant frequency. That said, it’s safe to say that a subsonic filter is nothing more than a high-pass filter with really low crossover points. It cuts off (to a certain degree) extremely low bass notes (often below the range of human hearing) that many speakers and subwoofers cannot effectively reproduce, thereby making the amplifier and the speaker, more efficient. Also known as an infrasonic filter, a subsonic filter is a feature that attenuates the intensity of low frequency notes.
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