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Author Topic: A little help re: Lawson microphone  (Read 2656 times)

jeremyjdonai

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A little help re: Lawson microphone
« on: October 10, 2013, 11:44:33 am »

Hello,

I'm not an expert in the field of sound engineering, but I was wondering if someone could help with an issue I am having. 

I have a Lawson L47 FET microphone (which I had at my prior institution and loved) connected to a Focusrite Saffire Pro 40 mixer (basically for pre amp).  I am getting a low frequency (approximately 8-10 Hz) artifact.  I plugged in a Shure microphone from around the lab and it is not there with that microphone. I checked to be sure there weren't any wires crossing to create any crosstalk (my word, not sure if its the technical term)...

I have wav files of both that I could email if someone is willing to try to help.  I do speech perception research and need the highest quality signal possible. 

Thanks

Jeremy
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Dinogi

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Re: A little help re: Lawson microphone
« Reply #1 on: October 13, 2013, 06:18:00 am »

8-10 HZ?? Being that those frequencies are well below the threshold of most systems, how are you noticing them? What is your recording system; digital, analogue? Can you not simply use a high pass filter to remove them? Is the Shure microphone you are using for comparison a condenser or a dynamic? The frequencies you mention can be generated by resonance in an air conditioning systems ductwork. Is it possible that your'e seeing that on your waveforms. I assume your seeing them on the waveforms because you're certainly not hearing them unless you have one amazing speaker system. Even then, your ears can't perceive frequencies that low. Feel them in your bones maybe, but not hear them.....olduncledino
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I'd trade everything I own now for a good sounding room and a bucket of 57's.

Fletcher

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Re: A little help re: Lawson microphone
« Reply #2 on: October 14, 2013, 09:18:29 am »

8-10 Hz isn't a usual problem range... as previously mentioned, look at something environmental rather than electronic.

Best of luck with your hunt.

Peace
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CN Fletcher

mwagener wrote on Sat, 11 September 2004 14:33
We are selling emotions, there are no emotions in a grid


"Recording engineers are an arrogant bunch
If you've spent most of your life with a few thousand dollars worth of musicians in the studio, making a decision every second and a half... and you and  they are going to have to live with it for the rest of your lives, you'll get pretty arrogant too.  It takes a certain amount of balls to do that... something around three"
Malcolm Chisholm

jeremyjdonai

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Re: A little help re: Lawson microphone
« Reply #3 on: October 18, 2013, 11:33:47 am »

I amplified the signal a bit in audacity and what I notice (which is what I think I am hearing) is this high frequency signal superimposed on the low frequency modulations.  It is extremely low level, but is present.  I can send a wav file if someone provides his/her email address....I do appreciate the help.

Jeremy
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Fletcher

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Re: A little help re: Lawson microphone
« Reply #4 on: October 18, 2013, 12:06:40 pm »

All due respect mate -- you're not hearing 8-10Hz, you may be hearing an upper harmonic of those frequencies, but you're not hearing those frequencies.

Have you thought about adding a high pass filter to your signal path?  A 24db/octave filter at 30Hz will take care of any kind of ultra low frequency information your microphone may be hearing in an unwanted manner.

Peace
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CN Fletcher

mwagener wrote on Sat, 11 September 2004 14:33
We are selling emotions, there are no emotions in a grid


"Recording engineers are an arrogant bunch
If you've spent most of your life with a few thousand dollars worth of musicians in the studio, making a decision every second and a half... and you and  they are going to have to live with it for the rest of your lives, you'll get pretty arrogant too.  It takes a certain amount of balls to do that... something around three"
Malcolm Chisholm

Dinogi

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Re: A little help re: Lawson microphone
« Reply #5 on: October 27, 2013, 08:00:02 am »

high frequency signal superimposed on the low frequency modulations. 
The plot thickens... When you say high frequency, what exactly are we talking about? I only ask because as you know, the frequencies contained in the human voice are rather limited, and it would seem that you could simply filter out the 8-10hz stuff because it wouldn't fall into the voice produced frequencies. Now you mention a high frequency component which if in the range of the human voice could indeed interfere with your research. How did you first notice the artifact as you call it, and how is it impacting the recording you are making? Can you get your hands on another condenser microphone and try to duplicate the anomaly? oud
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I'd trade everything I own now for a good sounding room and a bucket of 57's.
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