Ambient mic questions--didgeridoo recording project

Discussion in 'Recording' started by didgeridan, Nov 21, 2013.

  1. didgeridan

    didgeridan Active Member

    Jun 11, 2009
    Hi, I'm recording a didgeridoo, tambourine, and clave one-man band (me:) in a nice sounding reverberant building about 115'long x 50'wide x20'tall and I have a few questions for anyone with the time and expertise. In addition to my spot mics, I'm experimenting with a couple (identical cardiod LDC) ambient mics in different places.

    I know every space is different and there are a lot of variables to account for, but on a very general level, can someone suggest a theoretical best spot in such a building for balanced reverb? For didge, it is critical and a challenge to make it bright between 1.5khz to 6khz. I'm liking the results I'm getting, but want to understand what I'm doing more in depth and be aware of any potential issues.

    I've gone around the building clapping and listening for a sweet spot and can identify a spot maybe a third of the way down the length of the building where it seems most saturated, but it's so subtle I'm not even sure. I think when I stand in the middle I hear the shortest delay time as far as reflections from the far walls at each end. So I guess where I place mics depends on how wet I want the reverb or how long the tail? Eg, pointing a mic at the far wall that the didgeridoo is aimed at (maybe 70' away) instead of at the didge will lengthen the tail, because the mic is now capturing reflections with a long delay time, am I right? Also, I'm trying to understand, is the sweet spot for listening the same as the sweet spot for sounding the signal? Shouldn't I have someone else clapping at various places while I stand in various places to get a better idea?

    My two ambient mics are at least ten feet in front of the bell end of the didgeridoo and twenty feet apart from each other, with one mic being very slightly farther from the bell end than the other mic. Each mic is not facing forward but turned in at an angle to face the bell of the didgeridoo. Then each is panned hard left and right. The bass is also rolled off on the two ambient mics. I understand to watch for phasing issues. I am panning the two ambient mics hard left and right for two reasons: one is to broaden the sound of the didgeridoo which is too centered and up close with only my spot mics. With a very slight delay and hard panning it is my understanding that this can broaden a mono source of sound (like a didgeridoo). The other reason for the hard pan is that the ambient mics are also there to capture the sound of the tambourine on my foot and clave in my hand. I want to keep the sound of the tambourine and clave out of the center field, which is reserved for didgeridoo. I don't want to localize the clave and tambourine in a true stereo image (which would place the tambourine at most 10% right and clave 10%left) but I find that I like having them as sparkling accents on the far left and right. I've got my levels such that they are not a distraction that way, but seem like an enhancement. On the other hand, I am playing with ping pong delay, and maybe that combined with tambourine and clave on the far left and right is too much. I'm going to try maybe an 80% pan instead so the sound of the tambourine and clave doesn't mask the sound of the far left and right ping pong coming from my spot mics. Anyway, other than phasing, I am looking for what else to be aware of in this scenario.

    I have read about the different stereo mic techniques and understand the difference in basing a stereo image on differences in signal level (based on coincident pair of directional mics) vs. differences in time(spaced pair). But I'm grasping I correct in understanding that you don't pan with these stereo techniques? And I believe I'm not going for true stereo (because I want to have my claves and tambourine far left and right in the mix instead of where they actually are), but I'm wondering what are the expected consequences to the sound of the didgeridoo when I hard pan left and right with this ambient mic scenario? Do I have the right idea with the slight delay combined with hard pan? Or maybe the purpose of the delay (to broaden the sound of the didge) is already accomplished by the fact that the two ambient mics, being in different positions in this reverberant chamber and picking up possibly more reverb than initial sound source, are not sending the same sonic image anyway--even if each of them is the same distance from the bell of the didgeridoo. With all this in mind, should I have my mics turned at an angle toward the instrument the way I do, or should I have them facing forward as in standard spaced pair technique? Or maybe the mics should be close to each other (but again, I don't think I'm going to for true stereo here).

    I would like a longer tail on the reverb and guess the farther away I place the ambient mics the more I'll get (is this right?), but at the same time, if I place the ambient mics any farther than say fifteen feet away from me, they start to make the tambourine sound distracting because of the delay time, and I lose the brightness of their current position (both the tambourine and bell of the didge are in the mics' cardioid pick-up area).

    If you have read this far, thanks much and thanks for any suggestions or explanations. If interested, I'll post a sample.
  2. Boswell

    Boswell Moderator Distinguished Member

    Apr 19, 2006
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    Well, you've got a real mixture of techniques here. The two cardioid hall mics placed at a distance L and R do not fit into any recognized microphone configuration, but that's not to say they won't give you results you could use. Additionally, LDCs in cardioid are not ideal for this application.

    The fact that you are panning these mics hard L and R in the recording (effectively treating them as two mono channels) does not mean that you can consider them independently in terms of distance from the source. The business of phase cancellation etc does not happen just at the electronic level, but also produces effects where the channels are eventually combined, that is, inside the listener's head.

    If you are going to use ambient mics in this way, I would at least try them configured as A-B pattern outriggers, i.e. switched to omni and at placed at the same distance from the principal sound source (the didgeridoo). With them in omni, you can bring them in towards the sound source somewhat, as the omni pickup pattern will capture a lot of the reverb that you felt needed the distance to get when in cardioid.

    Tell us a little bit more about what you are using for your close miking.
  3. didgeridan

    didgeridan Active Member

    Jun 11, 2009
    Thanks for the reply. The cardioid mics are all I have for now. I have them at the same distance from the didgeridoo. After experimenting more tonight I realized I like what they do for the sound of the tambourine more when they are far off in front of me, at least 30 feet.
    The reason I had the mics so far apart from each other is I understood that the more the separation, the more extreme the stereo spread. My two ambient mics are the same distance from the bell of the didgeridoo, which makes them not the same distance from the tambourine, which is a couple feet to the side of the didge and seven feet behind it (on my foot). BAsically, I want to exaggerate how far off center the tambourine is and have it far left and right, not in the center. It seemed like placing the mics wide and hard panning would exaggerate the off-center tambourine. And it did, but the problem is (and I realized in experimenting tonight that I had misunderstood this) I don't want to just hear it exaggerated over to the left side, but on both sides. So, now that I'm hearing my tambourine in the far left because of my ambient mic placement, then I take my spot mic for the tambourine (it's less than 6 inches from the tambourine) and pan it hard right. Then I adjust the volume on the tambourine spot mic until it feels balanced. I like this effect, but now am wishing the ambient mics were farther away because of how it changes the tambourine sound. So I guess, from what you said, if I were using omni mics for this, I might still get the tambourine to sound how I like it. If I do end up placing my two ambient mics farther from the didgeridoo (like 30 feet in front of it), with the two mics staying the same distance from each other as before, should I expect it to reduce the stereo spread, the farther out the mics go from the sound sources?
    I understand what you mean about phase cancellation. I didn't pan the mics hard L and R thinking this would avoid such a problem, but for the other reasons I stated. As far as I can tell, phasing doesn't seem to be an issue, maybe because the volume I like my ambient mics at is well below my didgeridoo spot mics and so it wouldn't really be perceivable. Plus the bass is rolled off on the ambient mics, so there's no conflict there. It sounds right as far as that goes. I would like to develop a better ear, though, to really be able to detect it when it is occurring.

    I have three close mics: One is a mic I made from a subwoofer (I play notes on the didge as low as 37hz), the second mic is a Sennheiser e906 right up close to the bell, and the third mic is a Shure SM137 a little farther back, with a bump in the 2-6khz range, and the bass rolled off. I've spent a lot of time checking and re-checking for phase problems and it sounds nice. If you're wondering why all this, you have to realize I"m not playing traditional didgeridoo style but a lot of beat-boxing-ish kind of stuff, it is very percussive, and compression really comes in handy for conveying some very technical soft-stuff in between. To get an idea of the sounds I'm talking about: I just posted a sound sample last week, but it was before I started experimenting with two ambient mics. If you listen though to the most recent sound I posted, you can hear the results of my three spot mics and one ambient mic about 30 feet in front, in the same auditorium I'm recording in now. Oh, also, you'll hear enhanced vocals because I have a piezo on my throat:) THe piezo also adds nicely to other notes on the didge; I have it gated though because it is super noisy. To open the gate, I press on the piezo (which is taped to my throat) only when I need it during a part of a song. The kick drum sound is what I call a "stomp wedge" (because it is wedge shaped); it is simply a three inch subwoofer mounted in a little wedge I tap on with my foot.

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