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Author Topic: HPF and LPF  (Read 1183 times)

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Offline Geoff G

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HPF and LPF
« on: May 10, 2006, 01:21:52 AM »
Can someone help me understand when i would use these settings on mics, or boxes?  I'm borrowing a V3 next week, but am a little unsure about these switches. 

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Offline Brian Skalinder

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Re: HPF and LPF
« Reply #1 on: May 10, 2006, 01:39:49 AM »
HPF = high pass filter, aka bass rolloff.  It attenuates the low frequencies while passing through the high frequencies untouched, hence the name.  Frequencies affected and slope of attenuation vary by device.  See the Grace Design website's Support page for info on the V3's HPF.  I've never used the HPF on my V3, just haven't had a need to do so.  Unless what you're recording has massive chest-thumping, filling-rattling bass I don't think it's necessary.  But then again, I like a nice robust low end in my recordings.

LPF = low pass filter, opposite of HPF.

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Offline Nick Graham

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Re: HPF and LPF
« Reply #2 on: May 10, 2006, 02:21:26 AM »
Similar question, I understand HPF and LPF, but what about when it's a cut filter?

Aren't those the exact opposite of pass filters, i.e. a Low Cut Filter is the same thing as HPF.
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Re: HPF and LPF
« Reply #3 on: May 10, 2006, 03:14:57 AM »
Similar question, I understand HPF and LPF, but what about when it's a cut filter?

Aren't those the exact opposite of pass filters, i.e. a Low Cut Filter is the same thing as HPF.

A high-pass filter is the same thing as a low cut filter. A llow pass filter is the same as a high cut filter.

a band pass filter uses high and low pass filters..

Offline svenkid

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Re: HPF and LPF
« Reply #4 on: May 11, 2006, 12:19:34 AM »
Im not totally sure what Im doing, but I run the hpf thing on the v3 switched up to 1 in venues that give me a lame bass sound, and the bass sounds crisper when I do this, or at least not as schwag as before  :P
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Offline Kyle

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Re: HPF and LPF
« Reply #5 on: May 11, 2006, 01:28:58 AM »
I use the HPF 2 every once in a while - if I am right by the subs or if it is really windy, and sometime with the km140s in a boomy room...

I like good bass, but sometimes it helps (boomy room with wamr mics/adc)
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Offline Moke

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Re: HPF and LPF
« Reply #6 on: March 15, 2018, 06:24:24 PM »
OK,.... lets bounce an old thread up to the top.

Question,...
I've never used an LPFilter before.  I've recently found an oddity in a recording, an anomaly.  I have no idea what it is, but I do know its not musical.
With LPF, can I just set it at a specified frequency, and make that spike disappear?
Audacity frequency plot suggests 21.1khz peak.  But its down pretty far in the "mix". Still, would like to dump it.

Settings suggestion?

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Offline Gutbucket

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Re: HPF and LPF
« Reply #7 on: March 15, 2018, 07:13:57 PM »
Yes, assuming that peak is of long duration, a low pass filter is what you want for correcting this.  If its a single occasional peak, you should probably address the peak separately from the entire recording. 

I'd try setting the LPF for a corner-frequency of around 18kHz or 19kHz and it should knock it down nicely.  If your LPF also has a slope setting (how sharp the cut is, like the Q setting on a parametric filter), you'll probably want to use a slope steeper than 1st or 2nd order (6dB /octave, 12dB/octave).  A 3rd or 4th order slope (18dB/octave, 24dB/octave) will probably knock it down sufficiently without having to shift the corner frequency too low to be effective.  You could probably even go up to 8th order (48dB/octave). Higher order slopes are sharper, so they'll cut the peak more from a higher corner frequency, but the issue with higher order slopes is they can impart phase distortion.  Double check by ear, but it's doubtful you'll hear the filter having much if any audible effect.
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Offline Moke

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Re: HPF and LPF
« Reply #8 on: March 15, 2018, 07:36:43 PM »
Thanks, Lee.

I cannot hear it, even slightly, but, with my tinnitus being predominant, screaming "E" at 12khz,... anything above that gets buried in my head.
I was looking for something else when I found it. It surprised me to see it.  It is throughout the recording.
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