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Ambient Miking: Room For Improvement

Small-room Drum Ambience
By Neil Rogers

Ambient miking can really make your drum sound — even when you’re not blessed with the greatest of spaces.

In an ideal world, we’d always be able to record drums in a great-sounding room — one of a decent size that, with just a little knowledge of mic technique, makes it almost effortless to capture the sound of a live drum kit, enhanced with nice room ambience. The reality for many of us, though, is that we often have to work in a small or less than flattering environment, and although it’s possible to achieve a very respectable tight/dry drum sound in a smallish room, adding depth and interest to your recordings by capturing useful ambience requires more imagination.

The Mid/Sides setup used in option six, with the array facing the centre of the kit about 1.5 back.The Mid/Sides setup used in option six, with the array facing the centre of the kit about 1.5 back.So just how do you make the best of the space you have available? There’s always the option of adding artificial reverb to your close mics, of course — but, while you shouldn’t discount that option, it never seems to me to give quite the result I’m looking for. So instead, through a combination of research and experimentation, I’ve hit upon a few small-room mic techniques that I now use quite often alongside close-miking and, in this article, I’ll explain a few of them to you.

I spent a morning miking up my kit, and recording several different ambient mic setups on the same take, the idea being that you can listen to the audio examples and compare them yourself. You’ll find that each technique on its own won’t work its magic on every track or in every room, but together they form a menu of very usable options to try out.

A Basic Kit Sound

To provide a consistent reference point against which to assess the room options, the kit was miked with a stereo overhead plus close kick and snare mics.To provide a consistent reference point against which to assess the room options, the kit was miked with a stereo overhead plus close kick and snare mics.In order to judge the room mics, you need a basic but respectable kit sound to blend them with. I wanted to keep things simple on the day, so to capture my Mapex Saturn drum kit I used a Royer SF-12 stereo ribbon mic as an overhead to give me a basic balance. This was positioned centrally, about four feet above the snare drum. In all the examples, the stereo-mic recordings are panned hard left and right from the audience perspective of the drum kit. This image was pleasant but needed a little reinforcement: for the 24-inch kick drum, I used a Beyerdynamic M88 placed three inches directly outside the hole in the resonant head; and the snare drum was captured with a Shure SM57, positioned two to three inches above the rim of the snare, pointing towards the centre of the drum. (I didn’t bother to mic the toms, but placed a wallet on one that was resonating unpleasantly.)

These mics combined to provide the foundation for a decent dry drum sound that would be very usable in many mixes, but the overall sound lacked the natural depth or excitement that experience tells me can be achieved with this kit (even with me playing it!). So, next, I started to experiment with a few room-mic techniques, which I’ve separated into different ‘options’ below.

Option 1, ‘Face The Floor’: Option 1: For the first room option a pair of AKG C414’s were positioned 50cm back from the bass drum pointing directly at the floor. The same technique was also tried with the mics set about double that distance from the kit.Option 1: For the first room option a pair of AKG C414’s were positioned 50cm back from the bass drum pointing directly at the floor. The same technique was also tried with the mics set about double that distance from the kit.This technique employs two cardioid mics, which point directly at the floor. I’ve seen a few variations of this technique but they all require you to have some sort of hard reflective floor, so if your room is carpeted, try placing a piece of wood or other reflective material underneath your mics. For this recording I’ve used a pair of AKG 414’s, but it can also be effective with more affordable mics, such as a pair of Shure SM57s.

I tried the same technique in two positions — the first time, placing the two mics about 50cm away from the bass drum’s resonant head, and the second time roughly double that distance. Having the mics close obviously gives you quite a kick-heavy sound, but that can be useful: if you’re careful to check that these mics are in phase with your main kick-drum mic, it can be a good option for adding a sense of low-end power recording, whilst keeping the cymbal and snare elements of the kit relatively under control. As you can hear in the example, placing the mics about one metre back from the kit made the sound less kick heavy, and brought the other elements of the kit more into play.

Option 2, ‘Open Door’: Option 2: A U87 large-diaphragm cardioid condenser mic was set up in an adjoining corridor.Option 2: A U87 large-diaphragm cardioid condenser mic was set up in an adjoining corridor.This option is not so much about using the room itself, but utilising any adjoining space that might be available to add a usable ambience. Outside the room I was using for this session, I had a corridor which opened out into a warehouse-type space, but you might find that a hallway, stairwell or adjoining room works just as well. Leaving the door to the drum room open a crack, I positioned my U87 large-diaphragm condenser mic just outside the door, but not pointing directly into the room (while the U87 works well enough, you could try pretty much any mic in this role). Because there was now some distance from the kit, combined with the fact that the corridor had a larger-room acoustic, it provided a nice amount of natural reverberation with very little direct sound. I’ve found that this technique works particularly well on slower-tempo, kick- and snare-heavy material, but it does provide a slightly uneven frequency response, due in part to the huge wall between the kit and the mic. You can use this to your advantage, as it’s the higher frequencies that tend not to make it, and when heavily compressing room mics, it’s often the cymbal-heavy higher frequencies that you’ll want less of. In the studio I used for these examples, I also found I could adjust the desired amount of top end by varying the degree to which the door was open or closed.

Option 3, ‘True Grit’: Option 3: A Beyerdynamic M160 was positioned above the kick drum pointing towards the side of the snare drum. A cymbal guard can help keep cymbal bleed under control and protect your microphone from a stray drumstick.Option 3: A Beyerdynamic M160 was positioned above the kick drum pointing towards the side of the snare drum. A cymbal guard can help keep cymbal bleed under control and protect your microphone from a stray drumstick.This is another technique for which I’ve seen several variations. Many engineers refer to this as their ‘Trash’ or ‘Grit’ mic. It involves positioning a mic above the kick drum, pointing towards the side of the snare drum. I used a Beyerdynamic M160 ribbon mic and experimented with placement until I felt it had a good balance between the kick and the snare. The mic on its own captures quite an unusual sound, as you get a huge amount of attack and ‘click’ from the kick drum.

You have to be very careful with getting the phase right in relation to the other drum mics, but with a little processing (I often have to EQ in some more low end) it can add some serious vibe to your drum recording. When done right, bringing up the level of this mic should almost make you feel like the drummer is laying into the drums more, hitting them with more purpose. I sometimes also like to use a ‘cymbal guard’ of some kind, to help protect the mic and keep some of the cymbal sound out. I have a product which I bought specifically for this purpose (but didn’t use for the examples). However, a carefully positioned piece of foam might do a passable job.

Shure Thing

Option 4: A Shure SM58 was positioned facing into the far corner of the wall, creating a little low-end ‘thump’ and slightly exaggerating the perceived size of the room.Option 4: A Shure SM58 was positioned facing into the far corner of the wall, creating a little low-end ‘thump’ and slightly exaggerating the perceived size of the room.Sometimes, the most useful ambience mics are those you’ve left open by accident — that guitar-cab mic you moved out of the way to the corner of the room, for example! For Option 4, ‘Shure Thing’, I faked this approach, exploring the corners of the room to find a spot that seemed like it might sound interesting. I used a Shure SM58, pointing away from the kit into the far corner of the room. It’s similar to the floor mic, in that it’s placed close to a boundary and the cardioid pattern is picking up mainly reflected sounds, but the reflections in the corner are also more complex, and there’s a natural build-up of bass frequencies there too. I liked the subtle low ‘thump’ that was generated and, this mic being tailored for live vocals, it also offered quite a pronounced mid-range, which can work well at making the snare ‘poke through’ a bit.

Option 5, ‘Easy As SDC’: Option 5: An AKG C451 small-diaphragm condenser mic laying directly on the floor created a boundary-mic-type result — great if you want a brighter drum room sound.Option 5: An AKG C451 small-diaphragm condenser mic laying directly on the floor created a boundary-mic-type result — great if you want a brighter drum room sound.This is something I’ve not tried before, but was inspired by a technique I’ve heard producer Steve Albini describe using on many of his sessions. It involves laying a small-diaphragm condenser mic directly on the floor — which encourages the mic to work a bit like a boundary microphone (though with the capsule probably four or five millimetres further away from the boundary). The close placement to the floor removes the effect of time differences between the direct and reflected sounds, the theory being that this will yield a hefty reduction in comb filtering and coloration, resulting in a clearer sound. For this session, I used an AKG C451 cardioid mic. It’s a naturally bright-sounding mic, but I was still quite surprised with how much of the brighter elements of the drum kit it captured compared with some of the other techniques; it sounded a great deal better than common sense suggests it should! Albini suggests adding a short delay of around 10-20ms, which allows a slight delay for your close drum microphones to ‘speak’ before this room mic is heard. I’ve attempted to create this effect (with limited success!) in the audio examples that accompany this article, in case you’re interested in gauging the potential of this technique. I don’t think I quite achieved perfection on the day, but I would certainly like to explore this technique more in future sessions. One word of warning, though: take great care when leaving expensive microphones laying about on your floor, particularly during a busy session with lots of musicians!

Option 6, Mid/Sides: For the last option (seen in the picture at the top of this article) in this session I explored the mid/sides, or M/S, stereo technique to see if it could provide some useful results in a smaller room. I must admit that I’ve found myself arriving a little late to the M/S recording party, but I’m a real convert — if it’s new to you, I’d encourage you to do a little homework and try it out, as it can be a really powerful and flexible technique. Essentially, you use a figure-of-eight mic with its side null pointing at the kit, and place a cardioid mic pointing directly at the kit, with its capsule as close as possible to that of the other mic. You duplicate the signal from the figure-of-eight mic, panning each instance hard left and right respectively, and polarity-invert one of these channels. Shifting the balance between the Mid mono channel and the two Sides channels enables you to vary the amount of Sides (ambience) and Mid (direct) signals.

M/S is thus a great way of imparting an exaggerated sense of width to a recording. In the case of a drum kit, which doesn’t have a huge amount of natural width (yes, kit parts can be panned left to right, but in the context of a larger room, everything’s coming from a similar place), it can create a really interesting effect. Remembering that you already have some sort of drum sound from your other mics, you can even try blending in only the Sides signal from this mic configuration. The other big plus of M/S recording and balancing is that it is inherently mono-compatible — something that can’t be said of all width-enhancement techniques.

I used a pair of AKG C414 B-ULS condenser mics for my session, with the Mid microphone set with a cardioid polar pattern and positioned looking centrally in front of the kit, about 1.5m back. The Side mic was positioned below, in figure-of-eight configuration, with care taken to ensure the Sides of my recording would be capturing a balanced spread of the kit.

I really like what an M/S room-mic setup can contribute to my drum recording, and I can think of several ways this could be used creatively in a mix, such as bringing up the ‘wider’ effect for a chorus or middle-eight section, for example. I think the idea of being able to have a solid and adjustable mono option for your room elements is really useful as well. It also seemed to produce a very nice balanced sound for the whole kit, which was perhaps also due to the more conventional placement compared to some of the other techniques. It would be perfectly plausible to use mics correctly positioned like this instead of your overhead mics — although much of that seductive width might get lost or become problematic as you start to add other elements into a busy track.

Changing Rooms

Most ambient mics in less-than-ideal rooms will require some sort of EQ and processing. Here, the M/S signals are decoded in Ableton Live, and a touch of EQ and compression is applied to the result.Most ambient mics in less-than-ideal rooms will require some sort of EQ and processing. Here, the M/S signals are decoded in Ableton Live, and a touch of EQ and compression is applied to the result.It’s very often the case that, when working in a space that doesn’t really enhance an instrument, much of the job involves finding an ambient option that can be transformed with EQ, compression or other processing into something that has a sense of life about it. I’ve provided a full set of audio examples to accompany this article and, as well as the raw recordings, I’ve provided some examples of how all of these techniques might be enhanced with a little processing.

When it comes to EQ, I typically find myself cutting frequencies from this sort of material, rather than boosting, usually to remove some muddiness in the 200 to 350 Hz region, and often some boxiness around 600 to 800 Hz. Obviously, the exact frequencies will depend on the technique you use and the nature of your room. If you want the bass drum to have more clarity in the mix, using a high-pass filter on the ambience tracks — to allow room for the close kick-drum mic — can work well, and using a low-pass filter can help tame out-of-control cymbals. Heavily compressing your room mics and then blending them in with the rest of the kit — almost like parallel compression — is a very common technique, and heavy compression with fast attack and release times can create nice pumping effects that enhance the groove of a drum take, or just bring some extra attitude to proceedings. And, of course, you can bring such effects in only for specific sections of the song.

Phase is extremely important with multi-mic drum recordings. It’s well worth taking the time to explore how the room-mic signals interact with the different elements of your conventional kit recording when the polarity is reversed. It can often involve small trade-offs between a fuller kick or snare, and it’s important to make sure you check these issues in the context of whatever track or production you’re working on. For room mics that are positioned further away from the kit, it’s also worth experimenting with phase-aligning the audio files, either manually or with one of the number of plug-ins that are now available to experiment with (I often use the freeware Betabugs Phasebug for this). Hopefully, the audio files I’ve provided will help you get a feel for these options and encourage you to experiment. Just don’t judge my playing too harshly though as I spend most of my time the other side of the glass these days!

Having Your Fill

I commonly use variations of all the techniques described when recording live drums and find that it’s often the part of the process that I find most enjoyable. It’s hugely important to remember that this is all about enhancement, and that you really do need to get your more conventional drum mics set up and working as desired first. Then, rather than throw everything at one session, as I’ve done here, when you find yourself on a session, just pick a couple of room options to try. Which ones work best will depend on the room itself, the time you have available, what equipment is available and what experience tells you is lacking in the main sound.

While I will usually choose to record room mics, I’ll often find that I don’t actually end up using any of them in the mix. Sometimes, though, a mic will sound so amazing alongside the rest of a particular track that it ends up providing the majority of the drum sound. You’ll then sometimes find that, when you move on to mix the next track from the same session, this ‘wonder mic’ no longer works at all, and find it hard to understand why. Variables such as tempo, the amount of cymbals and fills used in the drum part, general musical aesthetic and structure all contribute to determining what works and what doesn’t. So, if a technique doesn’t work for one particular track, don’t discard the idea forever — it might just be perfect for your next track!

Audio Examples

I’ve prepared a number of audio examples to accompany this article. These include both the raw files captured using the techniques described, and versions that have been processed using EQ and/or compression.

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Published February 2015