Topic: at851/at853 mics and WAV form question

[rsimms3]

I have been using a set of at831s and at853s recently and have noticed something with the WAV forms.  The bottom half of the form has more gain than the top half.  I know nothing about acoustics, the mics, or more of the technical stuff but was wondering if someone could explain why this is with the mics.  In both set ups, mics almost straight forward pointing on the sides of my hat, and at a 90 degree angle coming out the top of my hat, I got this type of WAV form.  Is this just a property of the mics?  Am I not positioning them right?  I am going SP-CMC-4 > battery box > AD20 > JB3.  Any explanation or pointing me in the right direction is appreciated.  I did go through several pages in a search for at853 in this forum but didn't see anything.

[jeromejello]

i know nothing, but it looks like one mic is like 3-6db off the other.

[rsimms3]

Sorry, that is only the right channel, both channels look like that with more gain on one side of each channel.  What I am asking is, why from center on each channel is the top shorter than the bottom.  I do have issues with my right channel have some extra gain that I will have to adjust with the battery box volume sliders.  I had thought it was the mics until I got the 853s recently and come to find out that it wasn't the issue of the mics not being matched, but my battery box wasn't giving me the same output with both sliders set at the same level.

[lordbelial]

Same thing happenst to me.

Maybe it's something with the pressure of the sound that came into the mics? When placed in hat, sound coming from above may be different presure than coming from below, so that may cause the waveform to be not exactly the same

[Humbug]

I've seen this effect occasionally.

I'm guessing here, but is the diaphragm moving more in one direction than the other, ie its either over-damped, or the SPLs are high enough to overcome the damping?

ps I know nothing about how microphones actually work

[rsimms3]

I am seeing it consistently and makes bringing the volume up on recordings a bear because I have less room to work with because of this.

[lordbelial]

I am seeing it consistently and makes bringing the volume up on recordings a bear because I have less room to work with because of this.

I've send the picture to a sound technician friend of mine, hoping that he has seen something like this before.

Let's wait and see what does he says.

[kgreener]

that my friend would be "asymmetrical clipping", as explained to me by Doug Oade.  I know this well now...please see my posts about this same experience i had about 10 days ago.  bottom line, you need to back off your levels, and might possibly need some attenuation in your signal path.  Hope this helps!

http://www.oade.com/Tapers_Section/Forum/dcboard.php?az=show_topic&forum=100&topic_id=3406&mode=full&page=
http://taperssection.com/index.php?topic=53054.0

[Humbug]

that my friend would be "asymmetrical clipping", as explained to me by Doug Oade.  I know this well now...please see my posts about this same experience i had about 10 days ago.  bottom line, you need to back off your levels, and might possibly need some attenuation in your signal path.  Hope this helps!

rsimms3 wave forms look very different to yours, which look pretty clipped. His are just off centre.

[kgreener]

and they look very similar to me. 

whatever.  just trying to help.

[lordbelial]

that my friend would be "asymmetrical clipping", as explained to me by Doug Oade.  I know this well now...please see my posts about this same experience i had about 10 days ago.  bottom line, you need to back off your levels, and might possibly need some attenuation in your signal path.  Hope this helps!

rsimms3 wave forms look very different to yours, which look pretty clipped. His are just off centre.

I don't really know if those waves could be really "asimetrically clipped" or not. I recorded a band few weeks a ago and the recording came out the way you are showing us, and with the same mics (at853 (cmc-4) with SP-SPSB-1 and NJB3).

The wave does not seem to be clipped because the sound is great! but I don't really undestand the behaviour of the wave...

[Humbug]

and they look very similar to me. 

whatever.  just trying to help.

Apologies, being a bit blunt, wasn't intending to be rude. The pics on your link look like someones drawn a ruler over the wave, whereas rsimms3 don't look so clipped. Perhaps they would look like that if the time frame was longer. Someone with some expertise please step in..

[kgreener]

no problem dude, i'm still waking up over here and could use another cup of coffee   actually, you just mentioned what i was about to write...the screen shot of my waveform is of an entire 700mb+ waveform, and not just a small snippet such as what rsimms3 posted.  i do notice clipping above 0db in some places in his screen shot, and i think if you were to look at a screen shot of his entire waveform of the recorded show, it might look even more like the screen shot i posted.  if i were to take a screen shot of just a snippet of my waveform i think it would look a lot more like what rsimms3 posted.

rsimms3, maybe post this over on the Oade board as well, Doug is usually great about posting a response in a timely fashion.

peace.

[rsimms3]

I had the gain on the battery box around 50%.  I had the AD20 set to 0.  I have only been using this set up for about 6 shows so I am trying to get the right balance between gain on the battery box and the AD20.  I have posted a full picture of the WAV.  It is Audioslave from last Sunday.  I know I didn't use enough bass roll off, no doubt about that.  I was also using a stealth hat that I made very similar to the one over at SP, but with mine I pushed the caps out for full exposure.  My WAV form looks a lot like yours, but I seen to have more random spikes above the general line that you do.  I want to figure this out so I can correct it.  My reasoning for using the gain more or the battery box is that I can set it and forget about the levels getting too far off where as with the AD20 I have to adjust and the knobs are just so small and I don't really want to be pulling out this brick sized piece of equipment during the show to do adjustments as I stealth 99% of the shows I attend.  Here is an mp3 sample:
http://home.comcast.net/~simms3/AS_Sample.mp3

[Humbug]

Sample sounds good, typical for a mid size venue - I'm guessing 4,000 capacity, half way back? Try a little bass cut in post and see if it works - don't go over the top though.