Drum Kit Room Mics

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gavintheaudioengineer
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Drum Kit Room Mics

Post by gavintheaudioengineer » Tue Oct 02, 2012 8:12 am

I seem to be having problems maintaining definition on my kick drum when employing room mics as part of the drum sound.

I have 2 PZM mics up on the wall facing the front of the drum kit, about 12 ft apart with the wall being around 8ft away from the kit. The mics are around 7 ft up from the floor. Not ideal, not measured (I've a feeling I've answered my own question here) but the rest of the kit sits well against the room mics except the kick.

The sound isn't phasey, more flammy, like the distance to the mics is too great and there is an audible delay. Except I'm not hearing it on any of the other kit components.

I'm planning on re-sitting the PZMs with a drummer in situ next time I'm using them, but right now I have a mix waiting to go with this flam problem. I'm thinking moving the tracks around to fix it up from a phase coherence point of view, but the phrase 'can of worms' keeps popping into my head- if I am to do this, are there any pitfalls I should watch out for? What part of the kit would I ideally be aligning everything to?

Along with the room mics, the kit was multi mic-ed with both a mono overhead (4038) and stereo overheads (414) to give a little choice, everything else close mic-ed.

Any past experience would be gratefully heard as always.

Much love

Gav
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Post by HeavyHand » Tue Oct 02, 2012 8:24 am

is it any better if you use just one of them. it would only be mono but maybe only one of them is causing a problem. either way, i would be listening in mono when i nudge those tracks to make it easier to identify phase issues.
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Post by T-rex » Tue Oct 02, 2012 8:45 am

If the phase is ok but they are too far away, you can play with delaying or un-delaying the track a bit. You could nudge the room mics up or back like 20 ms and keep nudging from there and see how it sounds. Its better to get the mic in a great place to start with, but if you have a good track already recorded, try that and see what you think. May make things worse may be awesome, just listen and see.
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Post by T-rex » Tue Oct 02, 2012 8:48 am

Don't align anything, I mean you can; but I generally think that makes things worse. If everything sounds good but the room mics, just nudge them. And if you can't make them work ditch them.
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Gregg Juke
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Post by Gregg Juke » Tue Oct 02, 2012 9:01 am

Or go mono on the room mikes instead of stereo. I always used stereo rooms; I am now a mono room mike convert. No more phasey-phase.

I assume you tried bringing-out some lower end with EQ?

GJ

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Post by Gregg Juke » Tue Oct 02, 2012 9:02 am

PS-- This is why I think it's best to individually multi-mike a kit, even if you're a "lean heavy on the room mikes" kind of guy...

GJ

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Nick Sevilla
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Post by Nick Sevilla » Tue Oct 02, 2012 10:16 am

8 ft away from the kick, but also 7 ft high.

Algebra, to the rescue!!!

Avg speed of sound at 20 ℃ = 1,126 ft/s

True distance of one pzm mic from kick (avg, since no exact measurement is given)

Using the Right triangle formula to find c, the missing true distance.

a sq. + b sq. = c sq.
if
a=8 ft b= 7 ft c = 10.63ft

From the kick to the first pzm there is 10.63 ft. Which gives a sound delay of 9.44 mS.

For the second pzm mic, we infer that since it is 12 ft away from the first mic, the triangulation will be to measure the delay between the first mic and the second one, and keeping in mind there will also be a very small delay variation between the kick and this second microphone :

12 ft gives a sound delay of 10.65 mS between the first and second pzm mics. Which will be very close to the delay between this second mic and the kick, but is probably a little more. Which means you have three delays: the first one at about 9mS, a second delay close to that, and a THIRD delay between the pzm mics of about 10.6mS. Three flammy sounds far enough from the kick to make caca.

This will make the kick transient sound weird, since most kick transients are only a couple of uS (picoseconds) in duration, so these delays are definitely distinct from the original sound.

The reason the kick sounds strange is that the human ear cannot truly distinguish the three the delays of the mics. The human ear can really start differenciating identical sounds when they are 10 mS or further apart, and your mics are right at the boundary of this borderline.

Knowing this fact, I would recommend either making that true distance between the mics and the kick Larger, mainly by elevating the pzms to the celiing and further away from the kick as possible, or to use them on the floor Closer to the kick and in front of it, trying to get about the same distance of both mics to the kick, while giving enough "stereo" left and right spread for the whole kit.

And lastly, you would probably do better by using only one pzm mic, as this will only introduce one small delay on the kick, and not two close together ones.

Cheers
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Post by MoreSpaceEcho » Tue Oct 02, 2012 10:59 am

fwiw, my stock drum micing setup is a couple close mics, mono overhead and two omni room mics. the omnis are on the floor about 6 ft in front of the kick. spaced close, they're maybe two feet apart, i have them pointing at the kick drum spurs.

this is an old pic, and the camera angle makes them look way further from the kit than they are, but:

Image

i almost always have a ton of compression on the room mics, and they're usually at least 50% of the final drum sound, if not more. never had a problem with flammyness, and i find i actually get a lot of high end definition and snap on the kick from the room mics, that the close mic doesn't get.

so i would say try the pzm's on the floor and see what you think.

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Post by dfuruta » Tue Oct 02, 2012 11:27 am

Nick Sevilla wrote:8 ft away from the kick, but also 7 ft high.

Algebra, to the rescue!!!

Avg speed of sound at 20 ℃ = 1,126 ft/s

True distance of one pzm mic from kick (avg, since no exact measurement is given)

Using the Right triangle formula to find c, the missing true distance.

a sq. + b sq. = c sq.
if
a=8 ft b= 7 ft c = 10.63ft

From the kick to the first pzm there is 10.63 ft. Which gives a sound delay of 9.44 mS.

For the second pzm mic, we infer that since it is 12 ft away from the first mic, the triangulation will be to measure the delay between the first mic and the second one, and keeping in mind there will also be a very small delay variation between the kick and this second microphone :

12 ft gives a sound delay of 10.65 mS between the first and second pzm mics. Which will be very close to the delay between this second mic and the kick, but is probably a little more. Which means you have three delays: the first one at about 9mS, a second delay close to that, and a THIRD delay between the pzm mics of about 10.6mS. Three flammy sounds far enough from the kick to make caca.

This will make the kick transient sound weird, since most kick transients are only a couple of uS (picoseconds) in duration, so these delays are definitely distinct from the original sound.

The reason the kick sounds strange is that the human ear cannot truly distinguish the three the delays of the mics. The human ear can really start differenciating identical sounds when they are 10 mS or further apart, and your mics are right at the boundary of this borderline.

Knowing this fact, I would recommend either making that true distance between the mics and the kick Larger, mainly by elevating the pzms to the celiing and further away from the kick as possible, or to use them on the floor Closer to the kick and in front of it, trying to get about the same distance of both mics to the kick, while giving enough "stereo" left and right spread for the whole kit.

And lastly, you would probably do better by using only one pzm mic, as this will only introduce one small delay on the kick, and not two close together ones.

Cheers
The math is wrong here; the kick is 8 feet from the wall, not the mic (right?). There's no delay between the two pzms, assuming they're oriented symmetrically around the kit. The kick is the sound source, not the microphone.

us is microsecond (10^-6), not picosecond, and kick transients are _way_ longer than that?think about the pitches. If we're looking at a 120Hz overtone on the kick, just as an example, one cycle is 8ms.

The ear normally doesn't perceive echoes within 20ms as distinct (Haas effect). Are you sure that the PZMs aren't picking up some weird flutter echo or something? Maybe the specific placement is just catching something gnarly.

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Post by dfuruta » Tue Oct 02, 2012 11:37 am

MoreSpaceEcho wrote:so i would say try the pzm's on the floor and see what you think.
Not totally on topic and I'm sure you know this already, but if you take an omni mic and point it directly at the floor or some other surface, with the capsule almost touching (as close as is safe), that's a PZM. The Crown or Radio Shack ones just build the barrier into the mic. The frequency response is probably a little different than if the capsule is pointing perpendicular to the floor; might be interesting to play with!

This situation will do better at high frequencies if the capsule is as close to the barrier as possible. The farther away it gets, the more cancellation happens.

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Post by MoreSpaceEcho » Tue Oct 02, 2012 11:44 am

that's why i have them on the floor, no comb filtering from the bounce off the floor. also i find that with the mics on the floor you get more drums/less cymbals.

one other thing i just started doing is putting a couple cardioids up, facing at the far walls...one of them is actually in the bathroom off the live room...anyway a little of those mics in the mix is nice to just extend the reverb tail a bit...

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Post by mindsound » Tue Oct 02, 2012 12:05 pm

I agree also with the suggestion of using just one room mic.
you can also try cutting around 4-10 k (or a hi shelf) a bit in the room mic. You'll have less of the kick beater sound and a more warm room sound anyway. It may help.
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Post by mindsound » Tue Oct 02, 2012 12:08 pm

oh....and I'm forgetting....try to apply a fast attack comp. with generous amount of compression to your room mics. It may sound really cool, pushed underneath of your other mics kit.
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Post by Nick Sevilla » Tue Oct 02, 2012 2:19 pm

dfuruta wrote: The math is wrong here; the kick is 8 feet from the wall, not the mic (right?). There's no delay between the two pzms, assuming they're oriented symmetrically around the kit. The kick is the sound source, not the microphone.

us is microsecond (10^-6), not picosecond, and kick transients are _way_ longer than that?think about the pitches. If we're looking at a 120Hz overtone on the kick, just as an example, one cycle is 8ms.

The ear normally doesn't perceive echoes within 20ms as distinct (Haas effect). Are you sure that the PZMs aren't picking up some weird flutter echo or something? Maybe the specific placement is just catching something gnarly.
I guess I worded it "wrong"...
Howling at the neighbors. Hoping they have more mic cables.

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Post by cgarges » Tue Oct 02, 2012 3:10 pm

dfuruta wrote:The ear normally doesn't perceive echoes within 20ms as distinct (Haas effect). Are you sure that the PZMs aren't picking up some weird flutter echo or something? Maybe the specific placement is just catching something gnarly.
This.

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