Subsonic Filter

[bose301s 5,000+ posts]

Is using the subsonic filter a must? I do not have mine set at the moment, and I am afraid that if I do set it I will lose my lowest notes, as my understanding of the filter is that it rolls off everything below where it is set so as not to damage the drivers in a ported box. Any help on this is greately appreciated.

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[Immacomputer 10+ year member]

It's not always necessary but it really depends on the enclosure, subs, power, and what you listen to.

If you set the subsonic to like 20hz, you really won't be losing any musical content. And no, you do NOT set the subsonic filter at the tuning frequency of the enclosure.

 

[blackbonnie 5,000+ posts]

x2^^^

 

[bose301s 5,000+ posts]

Ok. I learn something new everyday, I'm glad I asked this question because otherwise I would have never know how to actually set the ssf and whether to use it or not.

 

[Electrodynamic 10+ year member]

It's not always necessary but it really depends on the enclosure, subs, power, and what you listen to.
If you set the subsonic to like 20hz, you really won't be losing any musical content. And no, you do NOT set the subsonic filter at the tuning frequency of the enclosure.

X3 ^^^^^

Setting the filter at the tuning frequency of your enclosure is going to limit your output at/near tuning significantly. Xovers start rolling off the response slightly before their selected frequency, as some of them try to hit the -3 dB point at the selected frequency, not begin (i.e. 0 dB) at the selected frequency. So if you have your enclosure tuned to 30 Hz, setting your subsonic filter to 25 Hz will be just fine. What you want to avoid is having your subs "unload" below tuning and start moving in excess, which can potentially damage the drivers. If you want a quick visual, open up WinISD (it's free and most people have it) and open up any driver in a ported alignment. Now take a look at the response followed by cone excursion. Notice how below tuning excursion skyrockets as SPL plunges? Setting your subsonic filter correctly eliminates the excursion demands on the subwoofer(s) below tuning and could provide you with years more service from your system.