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View Full Version : When to use low cut filter on mic




puckhead193
Sep 10, 2009, 11:06 PM
My job has given me a consumer camcorder to tape stuff and an external shotgun mic (azden SMX 10) It has a low cut filter switch, what's the purpose of it? In what situations would i want it on/off? If i'm doing interviews outside would i want it on/off? If i'm inside in a small room, would i want it on or off? I'm not an audio guy and every place i've seen on the internet to explain it goes right over my head :p



ChrisA
Sep 11, 2009, 12:03 AM
My job has given me a consumer camcorder to tape stuff and an external shotgun mic (azden SMX 10) It has a low cut filter switch, what's the purpose of it? In what situations would i want it on/off? If i'm doing interviews outside would i want it on/off? If i'm inside in a small room, would i want it on or off? I'm not an audio guy and every place i've seen on the internet to explain it goes right over my head :p


If you are recording audio then you should have on a good pair of headphones. If you hear "rumbling" do to wind or whatever use the low cut filter

Actually if you are recording voice, there is no bass so you could leave the filter on. But you should e able to hear in the monitor headphones

zimv20
Sep 11, 2009, 12:05 AM
consider leaving the switch engaged all the time, unless you're recording a source that has those lower freq's you want to capture (e.g. the low rumbling of a truck as it drives by).

Pocket lint
Sep 11, 2009, 01:52 AM
Usually one uses the low cut when there is wind noise and/or close miking (speech) to avoid rumble and pops.

You should follow Zim's advice.

tomjscott
Mar 5, 2012, 05:27 PM
Usually one uses the low cut when there is wind noise and/or close miking (speech) to avoid rumble and pops.

You should follow Zim's advice.

I know this is an old thread, but I have to step in and say do NOT follow Chris or Zim's advice on the use of low-cut filter. I'm no audio expert, but in my attempt to produce better audio for my recent shoot, I bought a new $300 microphone and followed the above advice only to find out that my audio was tinny and echoy as a result. All the deep, rich sounding audio that I could have gotten with the filter off I didn't get. I must admit that it's partially my fault. I decided to test the difference between having the filter on and off, but didn't realize that both my mic AND my camera have low-cut filter switches. I flipped the mic switch on and off and got the same audio so I thought I was good to go.

Once I realized this, but only after wasting a 6 day shoot and 10 tapes worth of footage, I tried the test again with the filter truly off. Suddenly, I am getting rich, deep, excellent audio as opposed to the crap I got with the low-cut filter on. Now, I'm sure there are times and places where the filter would be beneficial, but I can tell you that if you're shooting people talking inside a building or something similar, do NOT turn that little filter on. You're audio will suffer greatly.

If you don't believe me then just e-mail me and I can provide an audio file to show you the difference. Or just give it a try yourself. The difference is pretty dramatic.

Jolly Jimmy
Mar 5, 2012, 06:16 PM
Of course it all depends on the cutoff frequency and slope, and what's being recorded. What is the cutoff on your mic? I wouldn't expect the use of a typical fixed high pass filter at 50-60hz to result in an overly thin sounding recording. Is the HPF on your mic much above that?

tomjscott
Mar 5, 2012, 06:26 PM
Of course it all depends on the cutoff frequency and slope. What is the cutoff on your mic? I wouldn't expect the use of a typical fixed high pass filter at 50-60hz to result in an overly thin sounding recording. Is the HPF on your mic much above that?

I have no idea. The manual doesn't say as far as I can tell. The camera is Sony HVR-a1u and the microphone is Sony ECM-673. However, I don't think it's my equipment. I discovered this issue when I saw someone doing a review on an Azden microphone with a completely different camera. In his youtube video, I noticed the dramatic difference in sound quality when he went from low-cut off to low-cut on. That's what tipped me off to give it another shot.

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Of course it all depends on the cutoff frequency and slope, and what's being recorded. What is the cutoff on your mic? I wouldn't expect the use of a typical fixed high pass filter at 50-60hz to result in an overly thin sounding recording. Is the HPF on your mic much above that?

Watch this video and listen to the difference when the guy goes from low-cut off to on. It's the same effect I had.

http://www.youtube.com/watch?v=JpiB_RKHdfc

ChrisA
Mar 5, 2012, 08:36 PM
I know this is an old thread, but I have to step in and say do NOT follow Chris or Zim's advice on the use of low-cut filter. I'm no audio expert.

My advice was to always use headphones if you are recording audio. Had you done that you'd hear the effect of the filter and not have to re-shoot. Get the best headphones you can afford.

tomjscott
Mar 5, 2012, 08:40 PM
My advice was to always use headphones if you are recording audio. Had you done that you'd hear the effect of the filter and not have to re-shoot. Get the best headphones you can afford.

I do have headphones and I heard exactly what I was getting. The problem is that I didn't know what I was getting was not what I was supposed to be getting.

You did actually say "Actually if you are recording voice, there is no bass so you could leave the filter on."

Not trying to be mean here, but that's what I was referring to as your advice. Yes, you said to have headphones, which I have, but I didn't realize I wasn't getting what was expected. Like I said, I'm no audio expert, but I ended up making a big blunder on this. No worries though. Because of this final snafu, we are re-shooting everything and it will turn out all the better. God knew what we needed.