Drum wave timing

[lebouche]

Upon closely inspecting drum takes I noticed the delay between mics...its small but would they sound tighter if I aligned them? If I did chose to align them and I was looking for a very tight beat (rather than one that was pushing or holding back) am I looking to align the peak of the wave or the bit before (not sure if thats what you call a transient)?
Many thanks,

[Fulcrum]

You don't want to go there.

Really, don't start lining the stuff up if you see a delay between tracks. You'll be there forever and at the end of the day you'll be wondering why it all sounds like ass-- it didn't use to sound so thin.

The issue of course is the phase, which will start to collapse when you start sliding tracks around.

The slight delay is what gives the drum sound its bigness.

Besides, if you were working on tape you wouldn't be able to do it anyway, and it wouldn't be an issue. Yeah?

[eagan]

You are quite fond of looking at how things look graphically, aren't you?


Alright. Well, you're kind of skimping on details of what all is involved there in regard to what you're working on.

In terms of what you choose to align on, if you want to play around with time shifting things visually/graphically, it doesn't really matter, except that whatever you focus on is the same point in the same sound source (albeit coming through diiferent mics and going to different tracks). The zero point at the beginning of where a wave is first appearing, the first peak of a waveform, whatever.

More important is this. The only rule and definite point of procedure is this.

Try it, then listen.

Did it sound better, or did it sound worse?

That's about all there is on that topic.

Otek might pop in and illuminate you in much more detail about what rapidly gets to be a hairy, complex subject. The short version is, anytime you have multiple mics in a room capturing a common source, stuff gets complex, and simply taking a track and shifting back and forth in time is not necessarily going to give you any magic fixes.


JLE

[lebouche]

I was just wondering because in mixermans diarys he compensated for delys between mics but that was with a whole band not drums...
I will leave this alone!
Say no more, say no more:Wink: :Wink: nudge nudge
Thanks


p.s yes I do look at things graphically too much. I've missed so many things that have been staring me in the face that I cant help investigating.

[Comte de St Germain]

Funny.

I never liked the way OHs or room mics sounded when slid forward.

I do however occasionally delay my room mics when I want more apparent ambience. It's an old trick and something that you really need to listen for to get right, but when it works, it really works.

[Mixerman]

I was just wondering because in mixermans diarys he compensated for delys between mics but that was with a whole band not drums...
I will leave this alone!
Say no more, say no more:Wink: :Wink: nudge nudge
Thanks


p.s yes I do look at things graphically too much. I've missed so many things that have been staring me in the face that I cant help investigating.

I can't remember what I compensated for in the diary. Probably the room mics pumped out after the fact from a PA. Is that what you're referring to?

You have to be careful about moving mics that are in close proximity. But room mics are typically far enough away that you can nudge them. I can't ever recall actually successfully nudging the overhead mics.

Sound travels at approximately 1128 feet per second (at sea level and 70 degrees farenheit). Let's round that down to 1000. That means for short distances, every foot is equivelant to 1ms in delay time. If your mics are 5 feet from the source there is a 5 ms delay, which is enough to make the drums feel on the back of the beat. But overheads are rarely more than 3 feet from the drums, and there is usually close mics invovled. So, the distance of your mics really shouldn't be too much of an issue.

It is possible that your room mics are considerably further away. But far away room mics are typically placed for that delay to make the drums bigger. On occasion, I'll move the room mics earlier in time, because that is an interesting effect to have the room reverb occurring immediately after the hit of the drum. But those mics need to be far enough away that eradicating the delay doesn't cause phase coherency issues.

Mixerman

[Goes211]

not specifically directed at you, lebouche...

but us DAW users...we need to MIX WITH OUR EARS...
and stop mixing with our eyes.

I've often got someone next to me who'll point at the screen and say something stupid such as "the green track is too loud"...
- Right. You mean the one that's muted ?
- It's muted ?
- Yup. You mean the blue track. Oh and BTW, the actual volume perception of the blue track is influenced by the yellow, the orange and purple tracks, too.

http://audiolink.dyndns.org/host/mixwithyourears.gif

[malice]

Yeah, there are no rules for me either in that matter.

It really depends on the vibe you seek. If you're talking "vintage" you wouldn't move them for sure, for obvious reasons.

You have to be carefull, as Mixerman pointed, especially if it's a live recording with bleeding of other instruments, I noticed that you can fucked things up quite fast moving tracks because of the phase cancelation. Have in mind that when you fine tuned your sound during tracking, you did it without compensating delays.

Usually, I do this trick if I record drums alone and I put a distant mono room mic for a specific effect. But generally, I prefer my room mic close to the kit so ...

Lebouche, you are a goldmine for interesting topics. I'm going to increase your rep , hehehe ...

malice

[lebouche]

Thank you Comte,
Thanks once again evreyone.
I'm gonna try delaying my room mic ...sounds like something worth looking in to.
The rest of the time I guess that Curiosity killed the cat thng might come in to effect...:)

[lebouche]

Thank you Comte,
Thanks once again evreyone.
I'm gonna try delaying my room mic ...sounds like something worth looking in to.
The rest of the time I guess that Curiosity killed the cat thng
might come in to effect...:)
Mixerman...my mistake you just moved the amps to compensate..
"So we opened up all the doors, marked the mic placements and distances from each amp, moved the amps into the main room with the drums, and replaced the mics. We moved the amps because, if the bass amp and the guitar amps were too far from the drummer, Cotton would sound as if he were lagging. That’s because sound travels so slowly.

The rule of thumb is that sound will travel one foot per millisecond (it’s actually generally slightly faster than that, but the speed of sound changes according to temperature and this approximation is close enough for the distances that we deal with). Just five milliseconds can be the difference between the drummer sounding on top of the beat or in the pocket. Since the band wasn’t going to be playing with headphones, the players’ amps had to be a reasonable distance from the drummer."
Strictly speaking quoteing this without permission is copyright infringement...go easy I cant afford to even pay costs!

[otek]

Lebouche, when you quote other posts, please use the quote tags.

Like so


Thanks. :)

I found that you can sometimes use nudging to make the transients (which you so accurately guessed, is the "attack" part of a sound - not necessarily the loudest part) more clear, such as with ambience mics. This is because the time delay sometimes causes a bit of smearing.

The reason why Mixerman warned you about nudging the overheads is that they are in such close proximity that a nudge which is optimal for the snare, may be to the detriment of, say, the floor tom. This happens because you change the phase relationship between the mics, and those differences are often more dramatic the closer the mics are together.

Something which is usually far more beneficial to the close mics/overheads, is to check the polarity, using the polarity switch on the preamps, between all the mics when you're tracking (this actually goes for the ambience mics too). The way I do this is I often set out from the overheads, bring up one mic at a time, and compare the sound with polarity normal and reversed. I listen carefully, and determine which position gives me a fatter sound. The kick for example, 9 times out of 10 sounds better polarity-reversed, which is naturally a function of how I like to place my mics. The snare sometimes sounds better reversed, but not as often. Note that these results vary greatly depending on how you place your mics on a case-by-case basis, so there are no absolute rules. You always have to listen and compare.

[lebouche]

Lebouche, when you quote other posts, please use the quote tags.
.
Ok....I wasnt sure how too becuase it was from mixermans diary.

I've been doing the phase reverse test on the kick and the snare.
I remember reading somewhere that you minimise bad phasing on the overheads by reversing the phase on one and finding the spot where there is maximum cancellation and reversing it again.
Do you guys ever use this trick? I'm not sure I understand it..two overheads couldnt be that out of phase with each other unless they were somewhat facing could they?
Thanks

[lebouche]

Stupid question since deleted....whoops.

[Comte de St Germain]

Can we all agree that phase is not absolute and that we are looking for pleasing cancellations not just POLARITY FLIPS?

If in phase was THE WAY Jimmy Page would have sounded like everyone else.

Frequency depdendant = ear dependant.



http://audiolink.dyndns.org/host/mixwithyourears.gif

[otek]

Ok....I wasnt sure how too becuase it was from mixermans diary.

Fourth from the left in the toolbar above the post form is a little yellow speech bubble. Whatever piece of text you've highlighted gets wrapped with a "quotation" code.

I've been doing the phase reverse test on the kick and the snare.

Technically, it's a polarity reversal, but ok. :P (yeah, I'm a smartass!)

I remember reading somewhere that you minimise bad phasing on the overheads by reversing the phase on one and finding the spot where there is maximum cancellation and reversing it again.

I think that would be a sure-fire way of driving yourself nuts. :D Especially since you would find that the optimum position would be something as close to mono as you could make it.

Though checking in mono is always a good thing.

You can look at it like this: The least favorable position when it comes to phase accuracy is when both mics are "hearing" the same thing, but at different points in time - in practical terms, if both mics were on an identical axis, facing the same spot, but from different distances. If the mics are facing each other, they are looking at the kit from different aspects, and are likely hearing some of the same frequencies, but the complex entirety of the sound and the surrounding reflective surfaces will be different.

[lebouche]

You can look at it like this: The least favorable position when it comes to phase accuracy is when both mics are "hearing" the same thing, but at different points in time - in practical terms, if both mics were on an identical axis, facing the same spot, but from different distances. If the mics are facing each other, they are looking at the kit from different aspects, and are likely hearing some of the same frequencies, but the complex entirety of the sound and the surrounding reflective surfaces will be different.
Thanks...
I'm not taking in this last bit v well...have read it three times.
Are you saying ths mics facing each other would sound better than two pointed at the same spot from diferent veiwpoints?
Whoooshhh over my head with the overheads! There are many parallels with the theory of relativity...space time and phase. Shame I don't really get that either!
P.S Ive never tried that ovehead techniqui when you put the two mics together making an x shape, I suppose thats a different kettle o fish..

[archtop]

Thanks...
i when you put the two mics together making an x shape.

We call that an XY configuration

and it's my go to placement for heavy fisted drummers.

( I don't actually make an X but more like a --- \/ ----)

[lebouche]

I wonder y its called an xy if its closer to a v than an x or a y?
hhhmmmm...
I guess you use it on heavy handed drummers because it places less emphasis on the center of the kit and more on the outer parts. I could see that coming in useful because sometimes I have soo much snare coming through the overheads, I find I cant introduce much of my 'Sculpted' snare sound because its too loud already.

[otek]

Are you saying ths mics facing each other would sound better than two pointed at the same spot from diferent veiwpoints?

All I am saying is that phase cancellation will be the most dramatic when the mics are on the same axis and pointing in the same direction at a sound source.

Thus, ex. 1 in the picture below will be more succeptible to phase problems than ex. 2, because the mics are hearing almost the same thing* at different points in time.


*this is a simplification, there will be plenty of differences.

[lebouche]

Wow thats blown my narrow knowledge out of the water!!
I always thought mics set up like ex 2 would have more problems but I guess you can just reverse the polarity...maybe I'm just thinking of it in above and below a snare terms....is that different? i.e. on fig two if there is no skin dividing the two mics will they be in phase? I suppose also that if sound waves are different lenghs according to frequency then while one frequency might be in phase, the same set of mikes might find others to be out...is that a correct assumption?

[Mixerman]

Thank you Comte,

Mixerman...my mistake you just moved the amps to compensate..
"So we opened up all the doors, marked the mic placements and distances from each amp, moved the amps into the main room with the drums, and replaced the mics. We moved the amps because, if the bass amp and the guitar amps were too far from the drummer, Cotton would sound as if he were lagging. That’s because sound travels so slowly.

The rule of thumb is that sound will travel one foot per millisecond (it’s actually generally slightly faster than that, but the speed of sound changes according to temperature and this approximation is close enough for the distances that we deal with). Just five milliseconds can be the difference between the drummer sounding on top of the beat or in the pocket. Since the band wasn’t going to be playing with headphones, the players’ amps had to be a reasonable distance from the drummer."


That's different than moving waveforms of mics that are different distances from the source. In the situation you quoted from (above), the band is no longer using headphones. This means, the further the amps are from the drummer, the later he's hearing the other band member's instruments. These are apples and oranges to moving microphones earlier in time that are in close proximity to one another.

Ola spoke about flipping polarity, and this is a good way to determine the severity of your phase coherency issues. If you put a mic facing up from the bottom of the snare, and you put a mic facing down from the top of the snare, you will have severe phase cancellation between those two mics, and switching polarity on the bottom mic will magically reveal low end to your snare.

Other scenarios aren't so obvious, and in many cases, there is not right answer. If you flip your overheads as compared to your close mics, you might find such a move positively affects your kik drum, but negatively affects your snare drum. That's because you are dealing with degrees of phase coherencey, and flipping the polarity on your overhead, is merely flipping the point of cancellation.

I spend time flipping the phase switch on diferent mics on the kit to see just how much of an issue phase coherencey is. If it's a problem, the best solution is to move the mics. After a while, you have a good sense of what works and what doesn't work, but there is still a hit-or-miss component to mic placement on a drum kit. Ideally, you want to find the sweet spot for any given mic, and it's the relative axis rotation of the mic that will adjust your phase coherency issues. But you are at all times compromising the placement of one individual mic to how it is affected by the aggregate of all the mics.

No matter what you do, there is cancellation of frequencies when mics are in close proximity of one another. The trick is to get that cancellation to work the way you WANT it to work at the time you're getting your tones. This is one big reason why moving the overheads earlier in time in relation to the song (not delaying them as you suggested), doesn't typically work. If it does, you are fixing something that wasn't right to begin with. It is prudent to make your compromises BEFORE your record. Not after.

Since moving room mics that are some distance away from the drums will likely not affect the overall phase coherency of the drums, moving the waveforms earlier by 10-20ms isn't typically a problem. If you delay the room mics (as you stated in another post), they are going to sound even further away. You need to make them happen earlier in time, and thus move the room mic waveforms to the left.

On 2" I was able to do the same thing, come mix time, by playing the two room mics off the sync head (which is the record head and which is physically earlier that the playback head) while the rest of the tracks were set to play off the repro head (which is the playback head). The time gap between the record and playback head at 30ips is in the neighborhood of 50-60ms, which is considerably more than the 10-20ms delay caused by the distance of the room mics from the drums. This means, that the rooms playing off the sync head were actually sounding off BEFORE the drum hit. So the next course of action was to run those room tracks through a delay to adjust for the ~40ms discrepancy, and thus achieve the effect of room mics reverberating simultaneous to the close proximity drum hit. It sounds like more of a pain in the ass than it actually is.

Enjoy,

Mixerman

[ajcamlet]

I wouldnt move the OH's around. I have moved the snare track a bit and listened to its relationship to the OH's, sometimes its tighter, sometimes not

[Comte de St Germain]

"Much easier is to delay the two ambient mics by a few milliseconds, which moves them out of the haas effect (the delay range where delays affect sound quality and localization rather than being perceived as ambience) and into the range of perceived ambience."

I found the above quote attributed to Steve A.

The technique is something Glyn and Andy Johns use(d).

Sometimes I do.

[otek]

I always thought mics set up like ex 2 would have more problems but I guess you can just reverse the polarity...

I admit using the snare drum in the pic was perhaps adding to the confusion (it could have been a Bassoon, or a concrete mixer). The point is that, since the mics are facing the same point from different directions, they will have a more or less simultaneous pickup of the compression/rarefaction of the sound wave, making their pickup of the sound source in phase - the sound would take the same time to travel to both mics.

If the two mics in ex. 1 were exactly equidistant from the source, they would be essentially in phase (they could naturally not exist in the same space at the same time, so they would have to be placed side by side, giving each of them a slightly different aspect of the sound source). The fact that one mic is placed further back than the other, gives it the time delay that introduces the phase error.

maybe I'm just thinking of it in above and below a snare terms....is that different?

It is different because the bottom head would move towards the bottom mic at almost exactly the same time that the top head would be moving away from it, and vice versa. When the stick strikes the top head, it moves downward, then springs back up, so does the bottom head, but because the bottom mic is facing upward and the top mic downward, they register the opposite movement. This would be causing the phase problem.

I suppose also that if sound waves are different lenghs according to frequency then while one frequency might be in phase, the same set of mikes might find others to be out...is that a correct assumption?

Phase cancellation would never work equally at all frequencies, something which a polatity reversal can. With phase cancellation, some frequencies remain in phase while others cancel to different degrees. This is commonly referred to as comb filtering. A phase cancellation involves time displacement, whereas a polarity reversal only reverses the positive and negative swings of the waveform.

[eagan]

Mix with your ears?

What madness is this? Now you're talking crazy, man!

:lol:



OK, seriously....

You see, lebouche? I told you it gets complicated.

Anytime you start talking about "phase" there's huge potential for deep confusion, depending on what you know and don't know.

Let's put something this way as a quick example.

Let's say you have multiple drum tracks from a set of mics.

If everything from these different sources was perfectly "in phase", when you flipped polarity on a track, a whole bunch of stuff would simply disappear completely! (assuming the levels were the same)

And, of course, in the real world, it never works that way. It just sounds different, maybe better, maybe sucking fiercely.

It comes down to this, in terms of what has to be a homework assignment for you.

Read and study, and learn the basics of waves and fundamental relationships between:

-time
-frequency
-wavelength
-distance
-phase

On the one hand, understanding this will make a lot of things much clearer, and on the other hand, understanding this will make you understand that there are many situations where you can't just figure out exactly what's happening. All you can do is listen to results, and have enough of a general concept of what's going on to make reasonable guesses on what to do.


JLE

[otek]

I wonder y its called an xy if its closer to a v than an x or a y?

I find it a bit silly to discuss semantics like this but ok: I think it has more to do with a description of different axis.

Be that as it may.... It's a very common technique and it works. It's also called a coincident pair.

I guess you use it on heavy handed drummers because it places less emphasis on the center of the kit and more on the outer parts.

I'll leave it up to Archtop to explain that, but let me say this: A coincident pair, if anything, places more emphasis on the center of the kit because it tends to give you a narrower image than a spaced pair (the mics separated to the left and right over the kit.

And by the way, they also call that an A/B configuration, and don't ask me why it's not called an I/I configuration, even though it looks like that. :Roll eyes:

I have soo much snare coming through the overheads, I find I cant introduce much of my 'Sculpted' snare sound because its too loud already...

Considered the possibility that maybe you don't need it? :Wink:

[aframe9999]

I spend time flipping the phase switch on diferent mics on the kit to see just how much of an issue phase coherencey is. If it's a problem, the best solution is to move the mics. After a while, you have a good sense of what works and what doesn't work, but there is still a hit-or-miss component to mic placement on a drum kit.
Mixerman

As a Noob/Hack, I'm following this thread with great interest..... When checking for phase coherence, and especially switching polarity from mic to mic, do you do this the the kit panned? or do you do all your checking in mono with everything panned right up the middle? I would also assume you would do all of the checks, mic by mic with all the channels open (i.e. OHs, snare, kick, toms,) in the context of the entire kit, no?

AF

[Mixerman]

As a Noob/Hack, I'm following this thread with great interest..... When checking for phase coherence, and especially switching polarity from mic to mic, do you do this the the kit panned? or do you do all your checking in mono with everything panned right up the middle? I would also assume you would do all of the checks, mic by mic with all the channels open (i.e. OHs, snare, kick, toms,) in the context of the entire kit, no?

AF

Different combinations.

I want to know how the snare works with the overheads. Remember, level is imprtant too. You can discover a lot about your phase coherency by flipping polarity, and then adjusting fader levels. If your snare drum starts to go up in level as you pull the snare fader (I combine my bottom and top mic into one channel), Houston, you have a problem!

I listen in stereo. Occasionally, if I'm not sure about a problem, I'll pop the board in mono and check, but this is all done by listening and experimenting with polarity. Sometimes this can also be confusing, because switching polarity on a mic doesn't make it better or worse, it just makes it different.

For instance, switching polarity on your kik drum could change the low end "crossover" (wrong term, but we'll go with it here) of the drum. With the phase reversed, your kik might have much more sub 60 hz explosion to it. With the phase normal, your kik might have more of a 100hz thud to it. Which is better? Depends on what you're loooking for.

Mostly though, you're looking for problems. And ideally, you want to find problems before you commit to tape.

Mixerman

[otek]

For instance, switching polarity on your kik drum could change the low end "crossover" (wrong term, but we'll go with it here) of the drum. With the phase reversed, your kik might have much more sub 60 hz explosion to it. With the phase normal, your kik might have more of a 100hz thud to it. Which is better? Depends on what you're loooking for.

Excellent point.

I guess the reason for why I most often flip the kick is, I never seem to get enough subs for the way I mic otherwise.

Mostly, things are fine with some adjustment of the mic position.

[lebouche]

I found the above quote attributed to Steve A.

The technique is something Glyn and Andy Johns use(d).

Sometimes I do.

Nice one! Gold dust!
Is that Guy who produced Ryan Adams, Ethan Johns related to those guys? Someone told me he might be.
I love that hollywood boulavard song..