Subsonic filter?

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Subsonic filter?

Postby hjf » Sat Dec 11, 2010 5:08 am

I'm going to make an active LPF for my sub (Which frequency should I set it to?), and I was thinking of adding a subsonic filter to ir. Do I really need it? I was thinking of making the filter a 4th order 20-120Hz bandpass. It's not much more difficult to add the subsonic filter to the circuit anyway.
hjf
 
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Re: Subsonic filter?

Postby llung » Sat Dec 11, 2010 7:30 pm

Definitely a good idea to have a subsonic filter if you have a vented box. At the port's tuning frequency, the driver will be barely moving. But below that, the driver is no longer loaded and it can easily exceed it's excursion limits. In your case, pump in 20Hz or 25Hz and you risk damaging your driver. With a sealed box, it's not as bad but certainly won't hurt to have a filter in place. Note that it's not so much a "subsonic" frequency that matters, it's the frequency that fits your design that matters. In your case, if your sub has an F3=40 (or whatever), don't set your filter to 15Hz because that's subsonic, set it closer to 30Hz to protect the driver.

hope this helps
-lou
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