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Analog console hf comb filtering
Old 4 weeks ago
  #1
Gear Addict
 

Analog console hf comb filtering

Hello,

I'm having a problem mixing a record on a console, specially in the hf spectrum: drum cymbals have a weird phasing effect/washy comb filtered sound when they run through the console.

The drum kit has 2 overheads and 1 room mic as "ambient mics", the overheads are routed to 2 adjacent channels hard panned L/R with +3db of 10Khz boost on the channel's eq and then sent to the drum bus for compression togheter with the close mics. I'm also running a parallel drum bus but without the overheads in it, just the close mics, nevertheless some cymbal bleed is there as well.

If I listen to the recordings bypassing the console (and no parallel drum bus), directly to a stereo D/A the cymbals sound fine and there is more and clearer high freq. content (as always, that is usual in the setup that I'm using).

Anyone experienced something similar? Any advice?
Thanks
Old 4 weeks ago
  #2
Gear Addict
Is every track going from your DAW to the console? What happens if you do not parallel compress things?
Old 4 weeks ago
  #3
Gear Addict
 

Quote:
Originally Posted by shobud View Post
Is every track going from your DAW to the console? What happens if you do not parallel compress things?
Yes every track is going through the console. I'm not in the studio right now, I will be there tomorrow afternoon to try something (here is midnight and 30, Europe).

I thought about trying to remove the parallel bus, I also think that those drums are a bit overcompressed in general. Do you think that could be the cause, or one of the causes, of the problem?
Old 4 weeks ago
  #4
Gear Nut
 
TonyS's Avatar
 

Some kind of feedback loop would be my guess.
Old 4 weeks ago
  #5
Gear Addict
I think in general if you split a signal and eq only one of them and then combine them with relatively equal levels then you have the possibility of weird things happening...
Old 4 weeks ago
  #6
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Quote:
Originally Posted by shobud View Post
I think in general if you split a signal and eq only one of them and then combine them with relatively equal levels then you have the possibility of weird things happening...
Thanks, I will try to bypass the eq and also to take out the parallel drum bus.
I'm at my first approach at parallel compression, when "studying" about it I've read that in the analog domain there would be no latency problems of course but seems that I have to consider also frequency related phase shifts.
At this point I guess that some weird phasing is happening also in the lower frequencies and I don't hear it
Old 4 weeks ago
  #7
Gear Nut
 

Quote:
Originally Posted by shobud View Post
I think in general if you split a signal and eq only one of them and then combine them with relatively equal levels then you have the possibility of weird things happening...
pretty sure that shobud was on the right track with this one... EQing does shift the phase of the material in most cases/with most EQs.
Old 4 weeks ago
  #8
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Quote:
Originally Posted by xenosapien View Post
pretty sure that shobud was on the right track with this one... EQing does shift the phase of the material in most cases/with most EQs.
Sure. By the way it's not exactly that the parallel drum bus has an eq, the overheads were eqed and not sent to the parallel drum bus but just to the "main" drum bus
Old 4 weeks ago
  #9
Gear Addict
 

if the "close mics" are at the same level and pointing at your (rather above and pointing down) cymbals what you're doing is recording the swing of the cymbals (usually the ride and crash). this can also happen when the mics are set too close to the outer edge of the cymbals also catching the up/down motion. this is especially true of cymbals that ride very loose and have a large swing in motion.

g
Old 4 weeks ago
  #10
Gear Addict
 

Quote:
Originally Posted by gramps View Post
if the "close mics" are at the same level and pointing at your (rather above and pointing down) cymbals what you're doing is recording the swing of the cymbals (usually the ride and crash). this can also happen when the mics are set too close to the outer edge of the cymbals also catching the up/down motion. this is especially true of cymbals that ride very loose and have a large swing in motion.

g
The mics were placed properly, that phasing issue doesn't happen bypassing the console.
It must be because of the parallel compression, the eq and/or some stuff going on within the console itself.
There is always some high freq "air" loss when using this console
Old 4 weeks ago
  #11
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Drumsound's Avatar
Is the parallel compression ITB or with outboard? IF its ITB I'd check that your delay compensation is right.
Old 4 weeks ago
  #12
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Quote:
Originally Posted by Drumsound View Post
Is the parallel compression ITB or with outboard? IF its ITB I'd check that your delay compensation is right.
It's all outboard, drums sent to bus 1-2 and 3-4 for parallel, there shouldn't be any latency problems
Old 4 weeks ago
  #13
Gear Maniac
EQ on parallel processing not a problem!

Quote:
Originally Posted by xenosapien View Post
pretty sure that shobud was on the right track with this one... EQing does shift the phase of the material in most cases/with most EQs.
EQ shifts the phase of the actual waveform not the start of its cycle or its frequency. So in my experience EQ on a parallel buss doesn't cause "phase" issues.
Just been testing this and I have zero phase issues. HiHats with parallel distortion and shed loads of EQ on both. Sounds great! No phase issues even when the levels are matched. Works when collapsed to mono and with the distortion bypassed too.
Old 4 weeks ago
  #14
Gear Nut
 

Quote:
Originally Posted by Carl Freeland View Post
EQ shifts the phase of the actual waveform not the start of its cycle or its frequency. So in my experience EQ on a parallel buss doesn't cause "phase" issues.
Just been testing this and I have zero phase issues. HiHats with parallel distortion and shed loads of EQ on both. Sounds great! No phase issues even when the levels are matched. Works when collapsed to mono and with the distortion bypassed too.
I´m glad you have no problems with your gear, but what you just said doesn´t make too much sense in itself I think...
phase issues of course come from shifted phases, shifting the start (!) or the frequency would either be called latency and/or would alter the perceived pitch... totally different beasts.

(unless I COMPLETELY misunderstood you... in that case: sorry ^^)

and yeah, not all EQs and not every amount of EQing will cause phase issues...

but i´m no expert on this either, so maybe somebody with a bit more solid knowledge can correct us.. ?
Old 4 weeks ago
  #15
Gear Maniac
Quote:
Originally Posted by xenosapien View Post
I´m glad you have no problems with your gear, but what you just said doesn´t make too much sense in itself I think...
phase issues of course come from shifted phases, shifting the start (!) or the frequency would either be called latency and/or would alter the perceived pitch... totally different beasts.

(unless I COMPLETELY misunderstood you... in that case: sorry ^^)

and yeah, not all EQs and not every amount of EQing will cause phase issues...

but i´m no expert on this either, so maybe somebody with a bit more solid knowledge can correct us.. ?
Its nothing to do with my gear. Its physics. Try it. I am making absolute sense.
Yes all non FIR regular EQs will shift the waveform within its own cycle but not so much that its polarity becomes negative. So EQ on a parallel buss does not in itself cause phase "issues" exactly because the cycle of the waveforms are starting together.

Now if one of the signals is delayed or has an amount of opposite polarity you will have "out of phase" artefacts.

This is regular audio engineering. Basic stuff really.

Last edited by Carl Freeland; 4 weeks ago at 12:17 PM.. Reason: typo
Old 4 weeks ago
  #16
Gear Nut
 

Quote:
Originally Posted by Carl Freeland View Post
Its nothing to do with my gear. Its physics. Try it. I am making absolute sense.
Yes all non FIR regular EQs will shift the waveform within its own cycle but not so much that its polarity becomes negative. So EQ on a parallel buss does not in itself cause phase "issues" exactly because the cycle of the waveforms are starting together.

Now if one of the signals is delayed or has the opposite polarity you will have "out of phase" artefacts.

This is regular audio engineering. Basic stuff really.
alright, fair enough.
I´ll chalk it up to language differences, I read/understood your previous post differently.
Old 4 weeks ago
  #17
Gear Maniac
Quote:
Originally Posted by xenosapien View Post
alright, fair enough.
I´ll chalk it up to language differences, I read/understood your previous post differently.
No problem. If you think about it if phase was an issue with parallel processing nobody would do it. Everything should be fine if the cycles of the waveform start together. The phase relationships between the two parallels do change if you EQ or distort but only in terms of tonality. Not like the effect of a delayed cycle at all.

All that stuff ITB can be a nightmare though and one of the main reasons I am OTB.

Sounds like the OP has an issue with the console or a cable.
Old 4 weeks ago
  #18
Gear Addict
 

Quote:
Originally Posted by Carl Freeland View Post
No problem. If you think about it if phase was an issue with parallel processing nobody would do it. Everything should be fine if the cycles of the waveform start together. The phase relationships between the two parallels do change if you EQ or distort but only in terms of tonality. Not like the effect of a delayed cycle at all.

All that stuff ITB can be a nightmare though and one of the main reasons I am OTB.

Sounds like the OP has an issue with the console or a cable.
Cables are ok, what kind of console issue it could be?
Old 4 weeks ago
  #19
Gear Nut
 

Quote:
Originally Posted by Logima View Post
Cables are ok, what kind of console issue it could be?
again a "half-educated shot in the dark" type of guess on my side, but based on what Carl just explained to me:

I remember having some cheapo piece of gear (something with a transformer in it, I think) that was somehow wired incorrectly internally and would flip the phase on its output.

if I had mixed that back into whatever the original program material was, it would have cancelled out/phased for sure...

maybe one of your channel´s outputs has its phase flipped?
or one of your cables has Pin 2 and 3 reversed (on XLR)?


could that lead to what he is experiencing, Carl?
Old 4 weeks ago
  #20
Gear Maniac
Quote:
Originally Posted by xenosapien View Post
could that lead to what he is experiencing, Carl?
Yeah all that stuff could be to blame. Faulty Op Amp? A power rail on on one side not performing etc etc.

This is where you need to do an actual test. Get a sine wave split it off with an aux to another channel and simultaneously record both back into the DAW on separate tracks at the exact same level and see if the waveforms look the same. Probably best to look at a phase meter RTA like in Span too. It should be solidly to the right. If it is flickering there is a problem with the hardware.

When you add the same signal to itself at the same level you should be able to measure a 6dB increase in level exactly.

You could also bypass the EQ you are using and see if that is the problem. Just mock up the same connections but without the EQ.

OK so I am going to contradict myself here but if the EQ unit is rubbish or partially broken it could be that. Generally though there should be no problem with doing what you are doing. Test.
Old 4 weeks ago
  #21
Gear Guru
 
Brent Hahn's Avatar
 

It would help to hear what's going on, which I reckon we won't. But I'm guessing the issue is pretty simple.

Even with just stereo overheads you'll get some cancellation on cymbals because the two mics can't be equidistant from every cymbal. Introduce snare and tom bleed into that and it can get a lot worse. Compress the whole thing and you get a cancellation cluster****.
Old 4 weeks ago
  #22
Gear Maniac
Quote:
Originally Posted by Brent Hahn View Post
It would help to hear what's going on, which I reckon we won't. But I'm guessing the issue is pretty simple.

Even with just stereo overheads you'll get some cancellation on cymbals because the two mics can't be equidistant from every cymbal. Introduce snare and tom bleed into that and it can get a lot worse. Compress the whole thing and you get a cancellation cluster****.
Yeah he did say he thought the drums were over compressed. Could just be mix mush.

Phase differences can sound great on cymbals. That swooshy thing is sort of right sounding sometimes. Like a natural phenomena we experience in everyday life.

To add to the test idea I posted above. Once you have recorded the signals back into the DAW invert the phase of one of them then collapse the mix to mono. You should hear practically nothing.
Old 4 weeks ago
  #23
Gear Guru
 
Brent Hahn's Avatar
 

Quote:
Originally Posted by Carl Freeland View Post
Phase differences can sound great on cymbals. That swooshy thing is sort of right sounding sometimes.
I get that. It's something that's been around for long enough that it sounds normal. On pianos, too.

I don't usually do it on my own stuff; for me the musical solidity and power of a mono overhead trumps the stereo ear-candy. But I know I'm in the minority.
Old 4 weeks ago
  #24
Gear Addict
 

Quote:
Originally Posted by Carl Freeland View Post
Yeah all that stuff could be to blame. Faulty Op Amp? A power rail on on one side not performing etc etc.

This is where you need to do an actual test. Get a sine wave split it off with an aux to another channel and simultaneously record both back into the DAW on separate tracks at the exact same level and see if the waveforms look the same. Probably best to look at a phase meter RTA like in Span too. It should be solidly to the right. If it is flickering there is a problem with the hardware.

When you add the same signal to itself at the same level you should be able to measure a 6dB increase in level exactly.

You could also bypass the EQ you are using and see if that is the problem. Just mock up the same connections but without the EQ.

OK so I am going to contradict myself here but if the EQ unit is rubbish or partially broken it could be that. Generally though there should be no problem with doing what you are doing. Test.
I'll try this tests. I don't think it's a channel opamp, I'm going in the console through the inserts to bypass the channel preamp stage, maybe it's a problem of the bussing
Old 4 weeks ago
  #25
Gear Addict
 

Quote:
Originally Posted by Brent Hahn View Post
It would help to hear what's going on, which I reckon we won't. But I'm guessing the issue is pretty simple.

Even with just stereo overheads you'll get some cancellation on cymbals because the two mics can't be equidistant from every cymbal. Introduce snare and tom bleed into that and it can get a lot worse. Compress the whole thing and you get a cancellation cluster****.
You want to hear it? I can post a few seconds clip.

I'm not recording myself, I have to work for a band. Some things like a mono overhead for metal is not something I would do, I already know it will not be liked by the drummer. They are not used to hear mono overheads.
I'd also like to use concert toms more often, but it's "weird"
Old 4 weeks ago
  #26
Gear Guru
 
Brent Hahn's Avatar
 

Quote:
Originally Posted by Logima View Post
You want to hear it? I can post a few seconds clip.
Great, if it's okay with your client.
Old 4 weeks ago
  #27
Gear Addict
 

Quote:
Originally Posted by Brent Hahn View Post
Great, if it's okay with your client.
Ah, you're right, didn't thought about that in the rush. Let me ask them first
Old 4 weeks ago
  #28
Gear Guru
 
Brent Hahn's Avatar
 

Quote:
Originally Posted by Logima View Post
Ah, you're right, didn't thought about that in the rush. Let me ask them first
I can see how that might turn out:

"Can I post a bit of the drums online?"

"Why?"

"So people can tell me what I did wrong."

"And what might you have done wrong?"

"Umm... oh... never mind."

"No, really. What's wrong with the effing drums, Steve?"

Completely understandable if you change your mind about asking them.
Old 4 weeks ago
  #29
Gear Addict
 

Quote:
Originally Posted by Brent Hahn View Post
I can see how that might turn out:

"Can I post a bit of the drums online?"

"Why?"

"So people can tell me what I did wrong."

"And what might you have done wrong?"

"Umm... oh... never mind."

"No, really. What's wrong with the effing drums, Steve?"

Completely understandable if you change your mind about asking them.
Ahaha, no I've already asked them and they just said it's okay.
I've already talked to them about this thing and also said that it's no big deal because bypassing the console it doesn't happen, and I also thing it's solvable even using the console.
If it happened in tracking that would have been a problem
Old 4 weeks ago
  #30
Gear Addict
 

Quote:
Originally Posted by Brent Hahn View Post
Great, if it's okay with your client.
Here is around 10 seconds instrumental of a moment in which that cymbal phasing is very evident, listen to the china, it sounds like it has a phaser.
In the itb version this doesn't happen, sounds fine, it was not tracked this way.

This is premaster and the mix is yet to finish, I know it sounds too dark, dirty and overcompressed, this is how it should be.
I want it to be suffocating and "covered in tar", the guys in the band are also fine with that. I just want to figure out that cymbal problem
Attached Files

NM oh.wav (2.01 MB, 251 views)

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