Using two mics - out of phase?

[miroslav]

Of course, there would be extremely minimal filtering.

..............

We just want to minimize BAD phasing...when the comb filtering filters out frequencies we LIKE instead of amplifying them.


..............


again, I think that's what NY was saying.

Well...that's the bottom line..."extremely minimal".



And yes...that's the point of time-alignment, to get rid of the worst of the comb filtering (though not all will be bad all the time).



Not sure if NY and I misunderstood each other's meaning...but like I pointed out, I never suggested you could get them to be *100% perfect* (since they will never be 100% identical), I just said you COULD time-align them, he said you couldn't. Probably just a word thing.
I guess for me...time-alignment is about final sound quality. If it sounds better aligned...then that means you could align them for an improvement.

 

[cavedog101]

As long as you can flip the phase or are not adverse to dinking with the mic placements then all the physics, while still very important to understand, arent going to be much of a guide until you can get your brain around the why of it all. I'm for coincident and play with it till its right.

Trust me, I understand all the phase and comb filtering talk, its just that sometimes, the newbies get their heads all wrong and never can get it right.

Look at the capsule alignment more than anything and trust your ears with the phase switch.

Even better if you can vary the phase all of the 180degrees incrementally.

BTW Miro, Nice Hammerhead. We have the combo.

 

[pure.fusion]

Hmmmm. Well, I'm glad we all sorted that out!

I certainly got a lot from it. Especially the WAV files posted by Miroslav, thank you - it's quite a subtle difference, yet the difference is there and it was great to hear it.

Given that we're all now aware of a lot of the physics, what is the common way to address it.

On average, do you reckon people:-

- Don't address it at all
- Mic up and get a friend to move the second mic for testing
- Examine the wav files and drag one across visually so that the peaks match up.

At this stage, I'd say the easiest way is the last. Failsafe method?

Thanks for all the 'discussion'

FM

 

[Sonixx]

when I dual mic a cab I will often use this setup, post tracking, to achieve a mono mixed signal from the two recorded mics.

I often mic with a Ribbon and Dynamic and the ribbon is usually a bit farther from the speaker than is the Dynamic. But, it works very well for any two signals that are phase coherent.

I record a Stereo track and use these free plugins to create a pannable (100% one mic to 100% the other mic) mono track mix

Sample Delay - Alignment to taste. Works as an excellent EQ. Sample precision. One sample difference can make a significant difference
FreeG Stereo - Mixes the two tracked Mics
FreeG Mono - Mono Output that is Mixer Track pannable.

 

[miroslav]

Hmmmm. Well, I'm glad we all sorted that out!

I certainly got a lot from it. Especially the WAV files posted by Miroslav, thank you - it's quite a subtle difference, yet the difference is there and it was great to hear it.

Given that we're all now aware of a lot of the physics, what is the common way to address it.

You're welcome.
Sometimes it's easiest when you can see/hear the differences instead of just talking about math and techniques.

While even the aligned set is NOT ever going to be perfectly aligned for every peak (which I guess is what NYMorningstar was actually saying instead of the way I read it, that you couldn't align them at all... )
...simply sliding one of the tracks forward/back, you can audition which alignment position yields the best sound, which is kinda what you would do if you moved one of the mics around until you found a good combined sound.
But when you work/record alone...it's a PITA playing your guitar, moving the mics and auditioning the playback all at the same time!!!

My solution is to just put the mics where I want them individually ….and worry about blending them later on. Thing is, I rarely blend two mics for any one source.
Even if I put up two mics on my guitar cab...I'll usually end up using whichever one sounds better.
And THAT is the most simplest solution.
Find one mic and one position that gives you what you want.
I just don't see much need to toss up 2-3 or more mics on a single cab....unless...you *really* can't get what you want from any one single mic. But I think too often, multiple mics are just put up as an automatic SOP along with a blend SOP to then get them together into a mono sound.
IMO...if you want a mono sound, use one mic.
There’s nothing that says 2/3 mics will sound better than one.

Now...if you are going to put two mics on a single source, and then maybe pan them apart to some degree...that opens up other possibilities and may also remove some of the comb filtering issues even without time-alignment...though I would always try some time-alignment if going for a “mono” sound from multiple mics.

 

[miroslav]

BTW Miro, Nice Hammerhead. We have the combo.

Thanks.

I just got it about a month ago.
There was a music store down in Georgia permanently closing because the owner was retiring, so he was selling off everything at almost cost.

I got the head and cab for only $1300 shipping included.

I'm still breaking it in, it has a lot of tone options.

 

[SouthSIDE Glen]

NYMorningstar was right. The 3:1 rule has absolutely nothing to do with multiple miking of a single source. It is simply a rule of thumb for how far different mics on different sources should be from each source in order to minimize *bleed* from the adjacent sources that can cause phase issues.

And no, there is nothing magical about the 3x distance, it is simply a general rule of thumb as a minimal distance ratio to keep the bleed down. IOW, it's *generally recommended* that two adjacent mics be at least 3x the distance from each other's source as the maximum distance of each mic from it's own sound source. Microphone face placement, polar pattern and relative loudness of sound sources are all variables that can affect the actual necessity of the 3x (or greater) distance.

As far as multiple miking of a single source, there are no rules as far as distance or placement. There's always going to be *some* frequencies that fall out of phase at any given distances, and some frequencies that reinforce themselves by being *in* phase. But neither of those are always a bad thing or a good thing; you simply have to pick placement by what sounds best to your ear, taste and needs.

And there's no magic or need for flipping polarity on multiple mics on a single source *unless* they are two mics on different sides of a moving diaphragm that's causing the sound (e.g. the top and bottom of a drum skin or the front and back of a loudspeaker.) In such cases you need the polarity flip because the two waveforms will be 180° out of phase at all frequencies.

Otherwise, a polarity flip will - on average - throw as many frequencies out of phase at it will throw in phase, which gives you - on average - about a 50/50 chance of whether the flip will actually sound better or not. It's probably easier and better to just properly place the microphone and not worry about the polarity in such cases.

G.

 

[NYMorningstar]

Miro I see your point with it being easier than moving mics when working alone but its just another way of fixing it in the mix that I try to avoid. Keep in mind what would happen in a live situation where you have limited space and sometimes unavoidable bleed from other sources(like drums). Then it would be even worse moving the tracks post recording as you would be creating most likely unwanted artifacts.

 

[bozmillar]

There's nothing I hate more than the 3:1 rule, because ever single person has a different definition, and almost none of them are correct. I don't know who started it or how it turned into the ugly beast that it is today, but it's one of those things that all engineers should just purge from their minds because it hasn't caused anything but confusion.

 

[cavedog101]

I rarely use both mics on a single source except for guitar bed tracks and at that point I will use two mics that are complimentary to each other and hard pan them. Its this situation where you want your phase to be correct since , if its not, they will cancel each other at the center of the pan. For something like a lead, I find I never use both mics, I simply pic the best sounding one and , of course, the one that sits in the mix better.

 

[miroslav]

Keep in mind what would happen in a live situation where you have limited space and sometimes unavoidable bleed from other sources(like drums).

Well...then you have bleed.
Moving mics around won't really solve it either...so you STILL have phase issues.

Like I said, I'm not big on multiple mics on single sources...so I don't get into time-alignment of tracks too often...but I know many folks do it with everything, and they have found that DAW capability of big plus. They like everything hitting at the same mark....with no "delay smear".
I tend to prefer the delay smear to a point, as that is what gives you a sense of depth/dimension...plus, when you line up too many things "on a mark" you have a greater chance or those peaks summing to a high/clip point.
When there is a just a bit of delay smear...it softens the total peak point.

But it's all on an individual basis...I mean we try this we try that...and we go with what works for our situation.

 

[NYMorningstar]

Originally Posted by NYMorningstar
Keep in mind what would happen in a live situation where you have limited space and sometimes unavoidable bleed from other sources(like drums).

Well...then you have bleed.
Moving mics around won't really solve it either...so you STILL have phase issues.

So what happens when you have bleed from other sources like drums and you try to time align your 2 mics on your guitar amp?

 

[miroslav]

So what happens when you have bleed from other sources like drums and you try to time align your 2 mics on your guitar amp?

There's never going to be a perfect solution with multiple mics...you try stuff and see how it lays out.
But look...if you have two mics on your guitar cab, and the drums are bleeding into them...
....the distance from the drums to mic 1 and mic 2 is already NOT the same, so there is already a time delay issue...right?
So if you move one of the mics to get a different sound, you also change the time-alignment between it, the other mic and the drums...which is not much different than changing that time relationship in the DAW by sliding tracks…right?
But again...neither method is a perfect solution.

Heck...even IF I spotted my mics where they sounded good out on the floor...I might STILL see how they sound if I messed with their time-alignment in the DAW.
I just don't see any reason NOT to try moving things around in the DAW if you don’t like the blended tones.

If it doesn't gel.....[UNDO].

 

[NYMorningstar]

But look...if you have two mics on your guitar cab, and the drums are bleeding into them...
....the distance from the drums to mic 1 and mic 2 is already NOT the same, so there is already a time delay issue...right?
.[UNDO].

That's not necessarily true when your drumkit is adjacent to the amp. When you have bleed, changing the position of the mics is not the same as sliding the timeline in your DAW. Using the mic method reduces the artifacts you would introduce by changing the time relationship between sources. Anyhow, experimenting is good.

Peace

 

[miroslav]

Point taken.


I try to stay as far away from drummers as I can!

 

[SouthSIDE Glen]

I try to stay as far away from drummers as I can!

And banjo players.

I'm curious as to why everybody assumes the mics even have to be different distances from the git amp?

l almost never put more than one mic on a guitar as I almost never see a reason for it, quite honestly. If the guitar sounds good, a single decent mic will work just fine. If the guitar doesn't sound good, then there's no point in putting any mic on it.

But, there have been a small handful of times where the mic selection I had available to me was wanting, and I had to blend two mics to get a serviceable sound. But at those times I much prefer to just stick both mics on the cab. No phasing, no 3:1, no dealing with idiotic forum threads, just two sounds to blend like a nice blended whiskey.

G.

 

[miroslav]

And banjo players.

I'm curious as to why everybody assumes the mics even have to be different distances from the git amp?

l almost never put more than one mic on a guitar as I almost never see a reason for it, quite honestly. If the guitar sounds good, a single decent mic will work just fine. If the guitar doesn't sound good, then there's no point in putting any mic on it.

But, there have been a small handful of times where the mic selection I had available to me was wanting, and I had to blend two mics to get a serviceable sound. But at those times I much prefer to just stick both mics on the cab. No phasing, no 3:1, no dealing with idiotic forum threads, just two sounds to blend like a nice blended whiskey.

Exactly....one mic is all you need most times.
I spent a good deal of time screwing around with multiple mics on cabs (more=better ) and came to the conclusion the one correctly chosen mic yielded better results than summing two (for mono tracks).

The only reason I stuck the two mics at 2' apart in my examples was for the sake of the discussion....I never do that. Like you said...if I was going for two mics, I would probably put them at equal distances from the cab and next to each other, and maybe just aim them a little differently, but no real need to even do that especially if you use two different types of mics.
Maybe if I was going to try and capture the room ambience…and stuck one at the cab and another like 10-15 feet back….but that’s different.
And I have never bothered with mics on front AND back of cabs (or top/bottom of drums).

I think a lot of that multi-mic stuff comes from 1.) Not really being sure how to mic the cab in the first place, and 2.) hedging your bets by trying to cover all possibilities so you can mix-n-match later on.

Someone here recently said they read somewhere about Slash using 40 mics on one cab....
... I would love to have been a fly on the wall during the editing/mixing session!!!

 

[DrewPeterson7]

Man, sorry for opening a can of worms, guys. :lol:

I kind of understand the multiple mic thing - it makes sense when you're either 1.) only recording a single track of guitar (say, a blues trio, tracked live) and either need a fuller tone than a single mic allows, or for whatever reason want to track the guitar in stereo, 2.) are using a second mic that tonally compliments the first (say, a dark mic that fills out a bright one), or 3.) intentionally want to use phasing to get a particular tone.

That said, I almost never bother. I record instrumental guitar music - the last thing I need is a whole bunch of really "big" tones fighting for space in a mix.

 

[SouthSIDE Glen]

I think a lot of that multi-mic stuff comes from 1.) Not really being sure how to mic the cab in the first place, and 2.) hedging your bets by trying to cover all possibilities so you can mix-n-match later on.

And don't forget: 3.) the over-hyped, over-priced engineer who wants to camouflage the fact that all he's really doing to get "that $200/hr sound" is an SM57 and just a little bit of 4k EQ. Which naturally segues right into...

Someone here recently said they read somewhere about Slash using 40 mics on one cab....

The irony is Slash actually knows how to play guitar; 98% of his "tone" comes from his fingers. You could tape a lav to his cabinet and it would sound great. 4 mics, let alone 40, is little more than a PR stunt, IMHO.

G.

 

[Sonixx]

why I almost always mic with two mics

significantly more tonal options at mix time. one mic can always be used as the fall back. there is nothing to loose but a lot to gain with two mics

phasing two mics EQs in ways impossible with conventional EQ devices

often I'll mic two different speakers and/or speaker models and use two dissimilar mic types.

flexibility