# Is Subsonic filter same as a PEQ filter?



## PoorSignal (Jul 23, 2009)

Can you use 1 filter on the BFD to implement a subsonic (high pass) filter?


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## ironglen (Mar 4, 2009)

To the best of my knowledge, no. That's why many of us pick up a reckhorn or elemental designs hpf. One (or more) more capable and pricier behringer products can do it along with full range eq capabilities.

Subsonic filter will pass greater than 20hz (usually variable 10-30hz, depending on model) to the sub while peq is typically used to smooth in room response by minimizing peaks or boost nulls in the freq response between 20hz and 20khz.


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## PoorSignal (Jul 23, 2009)

Yes I suppose a ssf is more discrete but I think a filter down low maybe can pull down signal enough to avoid damaging the driver also?


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## ironglen (Mar 4, 2009)

The bfd has enough cut to do the job, but it can only do >20hz, and not one way. It works as a bandpass filter, such that it affects a designated bandwidth, not as high pass or low pass. Were you to try it, you would attenuate output in freq perhaps 0-40hz, which probably is not what you want for sub use, eh?


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## PoorSignal (Jul 23, 2009)

I see, I had thought the BFD can put filter at any hz even below 20
Forget my idea then, I guess I will have to buy a reckhorn.


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## Wayne A. Pflughaupt (Apr 13, 2006)

A lot of people seem to be concerned with getting a high pass filter with a DIY sub seemingly as a matterof course. However, in reality you only need one if you are driving the sub to its limits and it's overloading, or perhaps if the amp is clippling trying to generate ultra-low signals that the speaker can't reproduce. If that's not happening, there's no need for one.

Regards,
Wayne


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## Moonfly (Aug 1, 2008)

A HPF will not allow anything below it to be output, so with a 20hz cut off, nothing below is played as its all filtered out. A PEQ doesnt do this, it attenuates part of the frequency response, is centred on a specific frequency, and has a width of effective range determined when its set up. If the PEQ has a 20 hz width, and is centered on say 40 hz, then it will apply the cut at 40 hz, and the effect lessens either side of the attenuation, in this case 10 hz either side of the centre point of the cut. In this case the PEQ would be having little to no effect on sub 30hz tones, and these could still hurt your driver.

You could implement the BFD's PEQ to act as protection to your driver as a pseudo HPF, but if might have negative side effects. IIRC, the lowest you can go with its PEQ filters is 20 hz.

A wayne says, the HPF might not be needed depending on your subs design. I run my DIY sub with no HPF and Ive never had any issue with it whats so ever.


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