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Deirdre · Posted: Tue May 10, 2011 12:48 pm Post subject: Bleeding Waveform

I've recently begun using my RE 27 in my LA recording space and I've noticed an odd phenom in the wave form. Rather than a fairly even wave above and below "the line", sometimes the waveform hits zero on the bottom while the upper part looks moderate.

Sometimes it looks like dripping paint.

None of my other mics do this. What gives?

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captain54 · Lucky 700 Joined: 30 Jan 2006 Posts: 744 Location: chicago

I had that problem once and it turned out to be a bad cable, or bad connection somewhere in the chain. Maybe something got jostled when you switched back and forth between mics

Frank F · Posted: Tue May 10, 2011 2:20 pm Post subject:

Mic placement is also a factor D.B.

First check the cables and check the setting for DC Offset (make sure it is OFF on your sound card - if it is there at all).

After a look at the cables, check where and how you have the microphone diaphragm or capsule in relation to your luscious lips, Too high and offset will oftentimes show a waveform representation as you reveal in your post. Too low and offset will give the opposite effect where the "upper" level of the waveform will oftentimes be heavy in relation to the lower side.

This situation deals with the response of the capsule and strength of the air vibrating past the input circuit and is also related to the "proximity effect" of microphones.

So the short answer is: move the darn microphone around a bit until you see a better looking (more "even") waveform - after checking cables.

Frank F
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Deirdre · Posted: Tue May 10, 2011 5:09 pm Post subject:

I will see what that does!

I've used an RE20 all my broadcasting life, so I will see about positioning this one the same way.
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Mike Sommer · Posted: Wed May 11, 2011 2:13 am Post subject:

Some might call this DC Offset, but if you look closely at your waveform it is not really DC Offset, just asymmetrical waveform caused by high harmonic content.
DC Offset looks like this, with the top line being 0 DC:

You'll notice that your track is on center, but at certain spots it just becomes aysemetrical.

Note that while one half is 'lower' of the center line, the other half is 'wider' especially at 4:19 of your image. The areas of the two halves are probably equal, which means they are the same energy on both sides of zero, just a different distribution. The 'lower' part is quick while the 'short' part lasts longer.

There is not much to worry about, asymmetrical waveforms are quite common. One tends to see this a lot with brass instruments and electric guitars. The RE27 could be causing some harmonics with your DBX 286a's preamp section, and or the compressor maybe adding to it. Try backing off the compressor. If you are using any Aphex processing try backing off of that too-- Big Bottom and Aural Exciter are all Harmonics.

A quick fix is to apply a Hipass filter above 20 Hz. So a 75 Hz Hipass will do just fine. Once you do this bounce your file, and check your waveform.
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todd ellis · Posted: Wed May 11, 2011 6:33 am Post subject:

Reading this on my phone I read ... hip ass filter. I would love to have a hip- ass filter!

That is all.
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Deirdre · Posted: Wed May 11, 2011 10:10 am Post subject:

NO APHEX.
I am not fond.

I will tone down the bit of compression I an using. I don't think the RE27 needs any but I am just trying to get enough gain to make it from A to B. The Mic gain is nearly cranked to +60.

I think I will try a different cable.
I will straighten out the placement of the mic.
I do have a hip ass.

Thank you Everyone.
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Mike Sommer · Posted: Wed May 11, 2011 10:45 am Post subject:

It could be a dynamic problem between the Preamp and the mic, or form the pre to the interface.

If you are using the makeup gain form the compressor that could be doing it too. Sometimes summing pres can cause this problem in the analog world.

Sometimes a dirty power line can cause it too, especially if everything is plugged into the same circuit-- laptops are highly prone to this.
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dwpthe3rd · Posted: Wed May 11, 2011 4:40 pm Post subject: I'm interested in this thread

because I notice varying amounts of "weight" below or above the middle, and notice its in part dependent on the mic in use (my Audio Technica at4033 stays above the middle and my Sony c-48 remains pretty neutral). I do notice applying plug-ins has a much greater bearing on the situation.

Also of note, this situation does not to my ears affect the sound quality, however has the potential of limiting maximum volume if one half of the wave form achieves 100% well in advance of the other.
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