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Gear / Technical Help => Microphones & Setup => Topic started by: Chuck on November 07, 2013, 03:11:35 PM

Title: On the microphone high pass switch setting for omnis?
Post by: Chuck on November 07, 2013, 03:11:35 PM

You guys that use the on board high pass filter on your mics to record PA systems with omni's...

What frequency do like to use for the bass roll off?

and...

What frequency do you wish you could have/use if you had a choice?

I'm moding an LD mic and while I'm in there I want to change the knee frequency of the high pass switch. Right now it's set at 106Hz. That may be good for close up instrument/voice recording, but I think it should be lower than that for typical PA system recording.

For me, most often I record with no low end roll-off on the mics or pre-amp. I then roll off around 60Hz while editing music recorded with my omnis. But, I suspect somewhere closer to 40Hz to 50Hz would be useful if I could implement the cut on the mics. Increased head room from not even recording the really low frequencies may be a benefit.

What do you guys think?

Title: Re: On the microphone high pass switch setting for omnis?
Post by: Gutbucket on November 07, 2013, 05:10:35 PM

Similarly I prefer to do it later, and even then I prefer fine tuning a shelf or peak filter, or a graphic EQ over doing a straight high-pass/low-cut chop. 

However, for your project I think it would be interesting and perhaps more useful to sort of emulate the low-end rolloff off a cardioid which you know to have a good response in such a situation.  Basically setup a relatively high corner frequency with a very low-slope (like 6dB) rather than a high-slope cut (like the typical 12 or 24dB) farther placed farther down.  Besides possibly being more 'musical' it would also probably be more 'reversable' with EQ after the fact if necessary.

Title: Re: On the microphone high pass switch setting for omnis?
Post by: Chuck on November 08, 2013, 02:23:40 PM

Good idea about mimicking the natural roll-off of a cardioid mic. That's pretty much what I want to do.

Title: Re: On the microphone high pass switch setting for omnis?
Post by: DSatz on November 11, 2013, 09:04:35 PM

Try 3 dB/octave below 50 Hz for starters. The bass rolloff curve of a properly designed cardioid will generally be less than 6 dB/octave.

Title: Re: On the microphone high pass switch setting for omnis?
Post by: Chuck on November 11, 2013, 10:28:01 PM

That figures.

6db/octave high pass microphone filter is easy. That's a simple, passive RC circuit.

3db/octave not as easy, but not impossible. I'm going to have to do some more research.  8)
 
Thanks for the input DSatz.

Title: Re: On the microphone high pass switch setting for omnis?
Post by: Chuck on November 12, 2013, 08:25:45 AM

I did read about band pass circuits. So it looks like I can still do it using a band pass filter before the high pass circuit. Thanks Jon!


edit to add...
Sorry I misunderstood.  :-[ Thanks for the tip.