Professional Vocals Don't Have Mono Image!

[scrubs]

I checked the video, they did use two mics for vocals on the black album... Who knows though, maybe they are panned very slightly..., I'll just go with the reverb idea, it sounds more traditional. Thanks for the help guys.

Although I've never been in a pro studio, I would guess that miking a vocal track with 2 (or more) mics (or at least using the sound from both mics on the recording) is relatively uncommon. Certainly, vocal tracks are often doubled (separate takes are blended to produce a thicker sound), but using more than one mic on a single take seems difficult and silly. The vocal is the focal point of most songs and you usually want it to be as pristine as possible. Complicating it with phase/comb filter problems is unwise.

I do remember reading that David Bowie would occasionally use 2 mics. One would be up close, while the second one was much further away (maybe 8-10 feet). The second mic had a gate on it so it only opened during the louder parts of the vocal (chorus, etc.) which would beef up the sound and add a natural reverb/delay because the second mic was further away and picked up more room. He worked with great engineers in great sounding rooms, however.

 

[MadAudio]

I do remember reading that David Bowie would occasionally use 2 mics. One would be up close, while the second one was much further away (maybe 8-10 feet). The second mic had a gate on it so it only opened during the louder parts of the vocal (chorus, etc.) which would beef up the sound and add a natural reverb/delay because the second mic was further away and picked up more room. He worked with great engineers in great sounding rooms, however.

Actually, that was for "Heroes."

 

[freak1c]

if you've ever seen a phase trace of any spaced pair technique (like running it through the phase trace on S.I.A. smaart) ,um.....I'll be using xy thank you.
I wont be micing overheads spaced pair much anymore.

 

[boingoman]

Well I've read an article by Robert Dennis about micing a guitar amp with two mics. One close and one distant, (about 6 - 12 inches back.) If it is safe for guitar amps, I don't see why it's not safe for capturing vocals. The only difference with the guitar method though is you end up panning the mics to different spots in the stereo field later. With the vocals, I don't know the application for panning as I said earlier.

That's true. People do it all the time. But no matter what, there is some cancellation or reinforcement. The second mic is placed so it captures a good sound, but with an ear towards keeping the comb filtering to a minimum, or in a frequency range that is less important.

There is a point where humans cannot hear comb filtering, because the notches are very narrow, or very shallow.

The distance between the mics determines which frequencies will be affected.

As an example:

100hz is about 11 ft. long.
If you place one mic 1 foot from a guitar cab, and another 5.5 from the first one (half of 11), when both tracks are played back, 100hz will cancel out, as the two signals are 180 degrees out of phase.

1000hz is about 13 inches long. Place one mic an inch from the grille, and another about 6.5 inches back, and 1000hz will cancel.

Place a mic at the exact wavelength of a frequency from the other mic, and that frequency will increase in volume on playback, as the waves add together.

This is in an ideal world.
In an actual room, the second mic is picking up reflections from the walls, floor, etc. These reflections have their own delays, causing more or less cancellation as well, depending on their arrival times and levels relative to the direct signal.

 

[jake-owa]

...so I guess I'll stick with offsetting the one side a millionth of a second or so....

You mean thousandth of a second...and probably a couple or few rather than one.

Milli=thousandths

FYI

 

[freak1c]

comb filtering can be good, try this-mic a guitar cab with 2 sm-57's,right next to each other with one 57 a capsule length behind the other (about an inch). This creates a comb filter, will cancel out some frequencys that wont be missed, no need to carve em out with eq this way. in other words it sounds good and a bit fatter.
formula for figuring comb filtering is 1ft.=1khz.=1ms., it's not exact, but close enough unless you like using a calculator.
a 1khz. comb filter will have cancellations of 500hz.,1500 khz.,2500 khz.,3500 khz.,etc.
bad comb filtering wich is noticeable at concerts and shows sometimes because of speaker misalignment (relative distance of multiple speakers creates comb filtering just like relative distance of mics), like when the bass player is playing a line but you only hear a few notes of it while other notes are cancelled. it's all math and relates to musical scale as well, the first, 3rd, 5th, and 7th of a scale get cancelled, what key it happens to is dependant on speaker distance (multiple arrivals) example- a 500 hz. comb filter (1/2 a foot) kills A#, 10 feet (10khz. comb filter) kills G, etc., you'll hear the root note but not harmonics.
speakers have latency issues (the speaker itself, not talking about multiple speakers and multiple arrivals) because different frequencys exit the speaker first (highs leave first), unless the speaker design compensates for this like many high end monitors do. If ya got a sub on yer system try placing the regular speakers a little behind the sub, experiment and you will notice a difference in sound.In a live sound setup with line arrays and subs for instance, the p.a. is delayed back to the sub, and the front fills and drum fills are delayed back to each other.so speaker distance and mic distance both produce comb filtering (when dealing with multiple arrivals).
Can go on and on with this subject, quarterwave theory, etc. live sound deals with these issues more than studios but it's all applicable and affects the sound.

 

[jake-owa]

Or the simplest version, just turn the mic off axis a bit...filtering made easy. I EQ at the source with axis response, works like a friggin charm.
Ed-Sonusman-Rei showed me this once and it sounds great. We pointed the mic at the outer edge of the cone of a small amp and turned it away from the center of the speaker till it sounded right. It looked stupid but it sounded great.

 

[freak1c]

as far as aligning speakers making a difference in sound (besides comb filtering) it tightens up the mix, can get the same effect in pro tools by nudging tracks (especially drums) in line with each other and delay compensating for latency from the plug ins. it just tightens it up.

 

[Farview]

Or the simplest version, just turn the mic off axis a bit...filtering made easy. I EQ at the source with axis response, works like a friggin charm.
Ed-Sonusman-Rei showed me this once and it sounds great. We pointed the mic at the outer edge of the cone of a small amp and turned it away from the center of the speaker till it sounded right. It looked stupid but it sounded great.

For a nasally Marshall thing I have 2 57s right next to each other. One pointed straight in and the other at a 45 degree angle. I hit the phase button on one of them and mix to taste.

 

[corban]

I think you are off on this one.

"The distance between mics should be at least three times the mic-to-source distance (Again, see Figure 2). For example, if two mics are each 4 inches from their sound sources, the mics should be at least 12 inches apart to prevent phase cancellations."

It's all about mic-to source distance.

Given the definition, it is physically impossible to apply the 3:1 rule to two mics on the same source, unless they are both the same distance from the source. Think about it for a second. If you have one mic one foot away from a guitar, and another four feet away from a guitar, they need to be twelve feet apart to follow the rule.

http://www.prosoundweb.com/install/spotlight/bartlett/phase/phase.shtml

The 3:1 rule tries to keep the level of the indirect source in the mic around 10db less than the direct source.


Two mics on one source need to be the same distance, or some comb filtering will result if they are played back at the same volume. It's just physics. Playing with the distances or reversing polarity just minimizes the effect, like with a room mic on a drum kit.

Some people advocate the 3:1 rule when stereo micing, but it doesn't seem to make sense there either.

If you stereo mic a choir from 10ft away, then your mics would have to be 30ft apart.

A while ago I did a search on this site for the 3:1 rule because it didn't make sense to me for one source. I came up with people saying completely opposite things, but the arguments that made the most sense convinced me that it is for two sources, and that article confirms it. Maybe there should be a sticky on this site or something to counteract the bit of misinformation that is going around on that subject.

 

[Lionel_Hutz]

I've read, never mic one source with more than one mic, but I also read about guitar-amp recording applications involving two matched mics recording the same source, so right there is a contradiction.

Just keep this in mind, keep the 2nd or 3rd, etc., mic(s) 3 times the distance away as the mic closest to the source soundwave(s). Whether it be the same sound source or two, three, etc., different sources. And if something is still out of phase later on, just invert the culprit track in your DAW.

From my understanding, phase cancellation is the EXACT SAME soundwave reaching more than one mic at different times. So for a close and distant mic application, the distant mic's soundwave will be recorded a bit later in time than the closer mic. So as a result, one soundwave will be behind the other soundwave a few milli seconds or so creating a thin sound. Why thin? Well go here and look at the purrty phase pictures to understand.

http://www.kevinkemp.com/homerecordingtutorial/micing.htm

Understand what he's talking about? If I understand correctly, in order to get a stereo image from the same sound source means some phase cancellation must occur. In fact any sound considered stereo is out of phase to a degree, of course manual double tracking the same source makes the out of phase content more sporatic and keeps the track moving and not so consistently out of phase as a double miked single performance.

 

[boingoman]

Just keep this in mind, keep the 2nd or 3rd, etc., mic(s) 3 times the distance away as the mic closest to the source soundwave(s). Whether it be the same sound source or two, three, etc., different sources. And if something is still out of phase later on, just invert the culprit track in your DAW.

.

You are still missing the fact that this is not right.

The 3:1 rule doesn't apply in a near/far mic situation of the same source.

 

[Lionel_Hutz]

It does apply to a small degree since a mic further away will pick up different frequencies stronger than the closer mic. This will reduce phase cancellation on certain frequencies would it not?

 

[boingoman]

It does apply to a small degree since a mic further away will pick up different frequencies stronger than the closer mic. This will reduce phase cancellation on certain frequencies would it not?

It's the distance between the two mics that determines the frequencies which will cancel or reinforce, because all the different freqs have different wavelengths.

All I'm saying that for a near/far mic situation on a single source, there is no rule to follow, no magic ratio. You need to use your ears to determine where to place the mics to get the best sound, where the comb filtering is minimized or in a freq range that either doesn't matter, or gives some beneficial cancellation or reinforcement.

When you flip polarity and it sounds better, for instance, all you have done is change the freqs where comb filtering happens, not removed it.

 

[mrface2112]

i think we're missing the point here. if it sounds good and works in the context of the mix, what does it really matter if there's massive amounts of phase cancellation or not? sometimes that ultra-thin sounding track which sounds like shit when solo'd is exactly what the doctor ordered when it's stacked in the mix.

i almost always record amps with 2 mics--usually a shure545 (or senn 609) on the cone, midway between the edge and the middle, and almost always at 45 off-axis. then i typically put an LDC 6, 12, 18in back, depending on the sound i'm looking for. position them right and it's a recipe for a very nice sounding track.

it just seems to me that some folks are over-thinking and placing mics by looking rather than listening. who cares where the mics are placed and whether it's "right" according to someone's textbook as long as it sounds good? :-D


cheers,
wade

 

[Lionel_Hutz]

The further away you put the mics, the lower the frequencies are phased out. So I'll bet the three to one rule is a default setting that ensures you only cut the less important frequencies, therefore it does apply. Any closer together mic placement would entail an experienced engineer who knows what he's doing.

I've read this just recently which I found helpful in understanding mic placement and frequency cancellation....

The Comb Filter

When you have a 50/50 mix of a direct and delayed signal, the delay time puts the delayed signal out of phase with the un-delayed signal at some frequencies. These frequencies will disappear from the mix and other frequencies will be noticeably reduced. At short delay times (less than 20 ms) the noticeable reduction of level occurs in frequencies easily heard. At medium and long delay times, the noticeable reductions happen at frequencies too low to hear (below 20 Hz or below the lowest frequency of most instruments).

 

[boingoman]

The further away you put the mics, the lower the frequencies are phased out. So I'll bet the three to one rule is a default setting that ensures you only cut the less important frequencies, therefore it does apply. Any closer together mic placement would entail an experienced engineer who knows what he's doing.

I've read this just recently which I found helpful in understanding mic placement and frequency cancellation....

The Comb Filter

When you have a 50/50 mix of a direct and delayed signal, the delay time puts the delayed signal out of phase with the un-delayed signal at some frequencies. These frequencies will disappear from the mix and other frequencies will be noticeably reduced. At short delay times (less than 20 ms) the noticeable reduction of level occurs in frequencies easily heard. At medium and long delay times, the noticeable reductions happen at frequencies too low to hear (below 20 Hz or below the lowest frequency of most instruments).

The thing is, 20ms= 22 feet. Two mics closer than 22 feet is a short (less than 20ms) delay. Therefore, the comb filtering is well within the audible range.

Plus, I don't buy it anyway. Wave cancellation is wave cancellation. Distance doesn't matter. Where did you find that?

Give up on the 3:1 thing. Read that article on ProSoundWeb, and Mrface's post.

 

[Lionel_Hutz]

Wave cancellation is wave cancellation? You just said earlier that different frequencies have different wave lengths meaning distance does matter. Where did you hear that 22 feet equals 20 ms? Sounds about right though, I'm trying to find out which delay times work best so I can do it manually in my program rather than placing mics. Oh, by the way, the reason I'm doing this is because professional vocal recordings have slightly out of phase vocals and not a mono image. Soooo, if anybody has set delay times for vocals, or anything else let me know, I'm looking on google now as well.

 

[corban]

i think we're missing the point here. if it sounds good and works in the context of the mix, what does it really matter if there's massive amounts of phase cancellation or not? sometimes that ultra-thin sounding track which sounds like shit when solo'd is exactly what the doctor ordered when it's stacked in the mix.

i almost always record amps with 2 mics--usually a shure545 (or senn 609) on the cone, midway between the edge and the middle, and almost always at 45 off-axis. then i typically put an LDC 6, 12, 18in back, depending on the sound i'm looking for. position them right and it's a recipe for a very nice sounding track.

it just seems to me that some folks are over-thinking and placing mics by looking rather than listening. who cares where the mics are placed and whether it's "right" according to someone's textbook as long as it sounds good? :-D


cheers,
wade

That's a good point. The 3:1 rule is used to guarantee that you won't have to worry about phase when recording two sources. If people use it for one source recording, they're going to assume it'll be fine and possibly not pay as much attention to phase.

 

[jake-owa]

Wave cancellation is wave cancellation? You just said earlier that different frequencies have different wave lengths meaning distance does matter. Where did you hear that 22 feet equals 20 ms? Sounds about right though, I'm trying to find out which delay times work best so I can do it manually in my program rather than placing mics. Oh, by the way, the reason I'm doing this is because professional vocal recordings have slightly out of phase vocals and not a mono image. Soooo, if anybody has set delay times for vocals, or anything else let me know, I'm looking on google now as well.

You are talking about proximity effect when you say that low frequencies are "phased out" the further away you get.

That is a totally different thing man. He was saying the distance between the two mics does matter and it is the main factor in comb filtering along with reflective surfaces etc.

All sound dissipates or radiates out the further you get from a source. Low frequencies actually travel further because they are less likely to get interference from small objects.