Topic: weird split omni problem, diagnostic help needed

[Thom Joad]

I ran split omni's at moe.down on Sun. night, for moe.'s set. I'm not really sure what happened, and would appreciate any help figuring it out. Here's the deal: I ran 4060's, about 7.5' high (the left may have been 6" lower than the right), split 8', left was DFC (right was 8' ROC, duh), directly in front of board.  Rest of gear is microdot/XLR adapters>Aerco MP2>D10ProII.  First tune, check the levels, I notice the left channel is stronger than the right. Adjust as much as I can, on the fly, with the wheel, boosting the right while lowering the left. Still didn't get it even, but close enough where I said I could fix the rest with Wavelab. Awesome show ensues!!
 
Transfer to Wavelab. Immediately notice a large difference when looking at the waveform, with the left channel being significantly bigger than the right. Put the phones on (and here's where the fun starts), the stereo image (for lack of a better term), is shifted way over to the right! I listened to just the left, there's music there, it's just missing some parts that the right has. Bust out the frequency meters in Wavelab, find out there's significant drops in the levels, in a curve form, around 170Hz and 2.6kHz. I used the Q function to give the left a boost at these frequency ranges and it sounds better, but still not as great as I thought it'd be.
 
My question being, how can the waveform and levels, that represent the left signal, be so much bigger than the right, but the right be favored so much more in actual sound? I was thinking along the lines that the left mic. may have been in a bad position, whereas the two frequencies I mentioned that were low, were somehow cancelled out by opposing waves, creating a sonic blindspot of sorts, but that doesn't explain the extremely strong looking left signal, on paper. Then I got to thinking, maybe there was some sort of ultra low frequencies coming in to the left that made the levels look higher, but couldn't actually be heard. Not sure about this either, since I can hear about equal kick drum in each channel. So that leaves me with equiptment failure. Which is a possibility that I'm going to explore, however, all of this gear worked a couple of weeks ago, when I taped The Wilder's with it.  Used split omni setup there too.  Any idea's?

[Brian]

sounds like some phasing issues.....whether it was in your setup or in your cables remains to be known.

brian

[shaggy]

Sounds like one of those DPAs went 'kaput'.

If it is that noticable, run them side by side about a meter from a speaker with radio white noise, record that and transfer it to the HD.  Look at the sample in Wavelab 'freq plot' feature and note difference in curve.

[Scooter]

I had something similar happen to me a couple days ago.  Split Omni's 7ft-ish, centered though, not off to the side.  Left chan was way hotter than the right, so had to lower left while boosting right to get levels in the ballpark.  Get home and image is pulled to the right cause the left side is pretty muffled compared to the right.  TONS of low bass in the left chan, lots in the right too, but not as much.  When you look at the waveform, the left is hotter, but your ear pulls to the right cause it percieves the brighter chan as the louder one, even though it's not true.  I still don't know what caused this, either equipment or placement, or PA issue.  Doing some testing tonight to try and figure it out.  I'll prolly do something similar to what Dwonk suggested to rule the mics/cables out.  Good luck w/ your troubleshooting...

[Jason R]

Sounds like placement.  I've had this happen a few times.  Next time running Omnis try to get them as centered as possible, stand at each mic and listen.  Sometimes there is a noticeble difference like explained above/ one brighter than the other.  Don't worry what the levels look like, adjust to how it sounds.  I don't like using headphones, but this is one time they are useful in the field.  I doubt this is an equipment problem.  Also try lesser spreads,  My favorite outdoor tape I made this sumer was 4 ft.

[Scooter]

doesn't seem to be equipment, it all checks out.  Guess it was just a placement issue, I'll keep your advice in mind...

[Brian]

Sounds like placement.  I've had this happen a few times.  Next time running Omnis try to get them as centered as possible, stand at each mic and listen.  Sometimes there is a noticeble difference like explained above/ one brighter than the other.  Don't worry what the levels look like, adjust to how it sounds.  I don't like using headphones, but this is one time they are useful in the field.  I doubt this is an equipment problem.  Also try lesser spreads,  My favorite outdoor tape I made this sumer was 4 ft.

as jason has pointed out......

try splitting 6 feet or less to minimize on phasing issues like this one.  kind of a rule i always follow personally, ymmv

[wbrisette]

try splitting 6 feet or less to minimize on phasing issues like this one. 

Even 6 feet is a bit too far in a lot of cases. The "hole-in-the-middle" problem along with "phasing" and other issues start creeping up the further and further from 1 metre that you get.

There is some great information about this in "On Location Recording
Techniques" by Bruce Bartlett, Jenny Bartlett. This book has a lot of information in it that in my opinion would help a lot of tapers.

Wayne

[Brian]

try splitting 6 feet or less to minimize on phasing issues like this one. 

Even 6 feet is a bit too far in a lot of cases. The "hole-in-the-middle" problem along with "phasing" and other issues start creeping up the further and further from 1 metre that you get.

There is some great information about this in "On Location Recording
Techniques" by Bruce Bartlett, Jenny Bartlett. This book has a lot of information in it that in my opinion would help a lot of tapers.

Wayne

definitely true my friend!  i merely meant 6 feet as the MAX i'd go.  it really all depends where you are located and far apart the PA stacks are.

[hexyjones]

I ran split omni's at moe.down on Sun. night, for moe.'s set. I'm not really sure what happened, and would appreciate any help figuring it out. Here's the deal: I ran 4060's, about 7.5' high (the left may have been 6" lower than the right), split 8', left was DFC (right was 8' ROC, duh), directly in front of board.  Rest of gear is microdot/XLR adapters>Aerco MP2>D10ProII.  First tune, check the levels, I notice the left channel is stronger than the right. Adjust as much as I can, on the fly, with the wheel, boosting the right while lowering the left. Still didn't get it even, but close enough where I said I could fix the rest with Wavelab. Awesome show ensues!!
 
Transfer to Wavelab. Immediately notice a large difference when looking at the waveform, with the left channel being significantly bigger than the right. Put the phones on (and here's where the fun starts), the stereo image (for lack of a better term), is shifted way over to the right! I listened to just the left, there's music there, it's just missing some parts that the right has. Bust out the frequency meters in Wavelab, find out there's significant drops in the levels, in a curve form, around 170Hz and 2.6kHz. I used the Q function to give the left a boost at these frequency ranges and it sounds better, but still not as great as I thought it'd be.
 
My question being, how can the waveform and levels, that represent the left signal, be so much bigger than the right, but the right be favored so much more in actual sound? I was thinking along the lines that the left mic. may have been in a bad position, whereas the two frequencies I mentioned that were low, were somehow cancelled out by opposing waves, creating a sonic blindspot of sorts, but that doesn't explain the extremely strong looking left signal, on paper. Then I got to thinking, maybe there was some sort of ultra low frequencies coming in to the left that made the levels look higher, but couldn't actually be heard. Not sure about this either, since I can hear about equal kick drum in each channel. So that leaves me with equiptment failure. Which is a possibility that I'm going to explore, however, all of this gear worked a couple of weeks ago, when I taped The Wilder's with it.  Used split omni setup there too.  Any idea's?

Wow - I think omnis are more subject to lopsided channels - but the frequency deficiency you cite is the wierd part. What were the conditions? Was it possible that you may have had some water condensation on one mic? I know on some cool evenings everything can get a thin layer of dew on it as sun goes down...

Could some bozo have spashed something on one mic?

The frequency thing makes me want to think equipment - did one channel have a bass pad on by mistake? Anything on the D10 to bump? (not sure if you going in analog, or dig...?)