I a recording a guitar amp using an Golden Age active ribbon mic and am getting a strange asymmetric clipping on the waveforms. Levels are quite high and i am using the -10db pad on the mic and fairly low gain settings and pad on the A-D interface (Saffire pro 40).
 
Whilst recording a symmetric waveform is shown on the DAW (X1) but when the waveform plots properly the top side clips and the bottom side doesn't. I am also recording the same sound with another mic and this is normal so its not any peculiarity in the sound source. Recording vocal or acoustic sound at a lower level produces a normal result
 
Any ideas?????

Asymmetrical waveforms usually indicate that the signal is rich with odd ordered harmonic distortion.

The little chips in active stuff are real good at making odd ordered distortion.

If you like the sound... great!

If you don't like the sound... use the lower levels.


The figure 8 pickup pattern also hears sound much differently than other patterns, so consider that also when comparing to your other mics.


best regards,
mike

Ribbons usually need tons of gain to get a reasonable signal recorded.

I'd check your entire chain and make sure it's gain-staged properly from start to finish

careful Colin - you're offering advice which could be considered "silly practice bordering on misinformation" according to someone....

There was a mention that the other mic was working fine.

And that the ribbon mic was getting hammered... hence the -10dBpads and the level settings. 

It all makes too much sense.


I'll bet moving the ribbon mic back away from the guitar amp another 11" will seem helpful.

Sometimes I "face" it at a 30* to 45* degree angle so that wind blast coming off the speaker cone doesn't over load the ribbon by hitting it square, but more often than not I just move it back enough so that it doesn't get blasted. Probably about 15" maybe a little more, for starters.

That is for a regular ribbon mic. 

If it is an active ribbon mic you may need to move it back another 13" as the mic may simply have to much gain for close mic'ing on a loud amp.


best regards,
mike

 

edit spelling

Or maybe the ribbon has gone slack and needs to be retensioned. 

Thanks for your replies. I had already pulled the mic back quite a bit, prob about 24in from the cab, but still the same effect. We haven't had the ribbon long and are just getting used to its peculiarities.

We are recording the cab in a 6ft sqr booth to get separation. The booth is reasonably well conditioned, but i had wondered if the asymmetry was something to do with using a fig 8 pattern in a confined space. Was interested in your comment mike.

I had read that ribbons were happy with high sound pressure levels, but may be thats not so much that case with active ones.  My main worry is that the mic is defective in some way.

Yes the sound is acceptable and any distortion isn't obvious due to the slightly overdriven source material. Lower SPLs such as voice produces no clipping and a super smooth sound. So overall happy with the results we are getting.

bitflipper


Or maybe the ribbon has gone slack and needs to be retensioned. 

Dave, just saw your post after i finished writing. The ribbon is new so wouldst expect it to need that. Maybe i should be contacting the manufacturer.

Just found this thread with exactly the same thing on the same type of mic

http://www.gearslutz.com/board/so-much-gear-so-little-time/470550-strange-waveform.html

Asymmetric waveforms are very common when recording drums and some mic’s exacerbate the effect more than others (at least in my experience).  For example, if I run a side-by-side comparison of an EV RE20 and an AKG D112 on my base drum, the lopsided or asymmetric effect is more prevalent in the waveform generated by the EV RE20.

From a practical stand point, the bass drum sounds as it should, but the lopsided waveform presents processing issues.  If I apply a compressor to the track, it appears as though the threshold is governed by the peak values on one side of the waveform yielding a less than optimal result.

I too have read over the years that the effect is the result of:

even-ordered harmonics
odd-ordered harmonics
out of phase harmonics
air pushing on the diaphragm

… but I have yet to find a published study systematically evaluating the effect (just people quoting other people from gearslutz).

The guy in this video that was posted about a year ago does a really good job of systematically eliminating electronic artifacts and ascribes the origin of the effect to a lopsided sound source (it is worth watching and the text is transcribed for you).

http://www.youtube.com/watch?v=-a8-ULhmz_4