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Session Notes: Faking A Big Ensemble | Media

Audio files to accompany the article. By Mike Senior
Published April 2016

Hannes Keseberg: our engineer helps an artist fake a big-ensemble sound by layering recordings of a string quintet.

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The audio files available on this page accompany my Session Notes article in SOS April 2016 about simulating a big-ensemble string sound by layer recorded takes of a string quintet. The filenames are fairly self-explanatory, but here are some additional notes to describe exactly what you’re hearing in each case. (Incidentally, if you’d like to try mixing the basic string-quintet sound for yourself, just import all the files with the ‘_Raw’ filename suffix into your DAW software at the same starting position and you should be good to go!)


Here’s how the main stereo pair of Shure KSM141 small-diaphragm omni microphones sounded by the time I’d finished shifting it around to my satisfaction. With hindsight, it’s still a touch on the roomy side, but this aspect of the capture wasn’t easy to judge on the session, given that we had to monitor on headphones in the recording room. Fortunately, we’d hedged our bets in this respect by recording a full complement of close microphones, allowing us to introduce more direct sound as required for each individual instrument.


The double-bass spot microphone was a Brauner Valvet large-diaphragm valve microphone operating in its omni mode. I chose this polar pattern primarily for its excellent low-frequency extension, and despite its notionally lack of directionality, it actually picked up a respectable direct/spill balance even at a miking distance of around 60cm from the instrument. Furthermore, the spill it does pick up retains a fairly natural timbre (albeit somewhat dulled by the mic’s off-axis high-frequency insensitivity), which helped retain a representative tone and balance for the ensemble as a whole.


I used ribbon mics for all the other string parts, and selected the highest-quality of these (a Beyerdynamic M130) for the first violin. The mic was about 75cm above and in front of the instrument, pointing downwards towards the soundholes. Once a promising timbre had been found, the figure-eight polar pattern’s null plane was angled towards the neighbouring viola player to improve separation. In this audio example you can hear the raw output from this microphone. Notice how the ribbon mic’s naturally rounded tone prevents the violin from becoming excessively biting at this comparatively close miking location, even when the player moves onto the ‘E’ string at 0:13, and also how spill from the rest of the ensemble is again presented very naturally on account of the well-behaved off-axis response of the figure-eight polar pattern.


All the spot-mic signals other than the double-bass were high-pass filtered at the mix to reduce low-frequency spill and focus their timbre a little towards the mid-frequency definition that was lacking in the main stereo pair’s sound. In the specific case of the first violin, this filter was from FabFilter’s excellent Pro-Q parametric equaliser plug-in, turning over at 150Hz with a slope of 12dB/octave and a moderate Q value of 0.7. This audio demonstration shows what that frequency adjustment sounded like. It’s not an enormous difference, so you might want to compare it with the 03_ViolinSpot_Raw file directly in your DAW to hear it more clearly.


The second violin was miked with a Superlux R102 active ribbon microphone placed about 60cm above and in front of the instrument. The microphone’s rejection null was then directed towards the cellist sitting just past the player’s right elbow. As with the more expensive Beyerdynamic ribbon mic on the first violin, the off-axis tone of the Superlux’s figure-eight polar pattern again renders spill from the rest of the ensemble very naturally.


At the mix, the second-violin spot mic was processed the same way the first-violin’s was: with a 12dB/octave high-pass filter at a Q value of 0.71. Again, this impacted very little on the violin’s own timbre, as you can hear if you compare this example directly against the preceding 05_Violin2Spot_Raw file.


The viola was captured via another Superlux R102 active ribbon microphone, again placed above and in front of the instrument, although in this instance a little closer (more like 40cm away) in order to achieve sufficient separation for the viola’s direct sound — the violin and bass were otherwise overpowering the viola in the close-mic balance, even after careful orientation of the ribbon mic’s rejection plane.


As with the other ribbon spot mics, high-pass filtering was used to avoid a build-up of low-frequency spill. For this track the cutoff frequency was set slightly lower than for the violins, at 120Hz, but with the same 12dB/octave slope and Q value of 0.7. Given that the lowest fundamental frequency a viola puts out is around 131 Hz, it’s hardly surprising that the processing doesn’t dramatically affect the instrument’s sound character.


Here’s the raw cello recording, captured by my third Superlux R102 active ribbon microphone. The mic was about 60cm from the instrument roughly at the player’s head height and pointing downwards towards the middle of the fingerboard. The microphone’s null plane did a very good job in this instance of rejecting the other members of the ensemble, although some significant bass spill is still apparent.


I set the cutoff point for the cello’s high-pass filter to 100Hz, which not only removed a good deal of bass spill from the signal, but also significantly recessed the cello’s lower fundamentals, simply because there already felt to me to be plenty of low-end weight coming from the main stereo pair (as you heard in the previous 01_MainPair_Raw audio file). The filter’s slope was again set to 12dB/octave with a Q value of 0.7.


This audio example demonstrates the combined sound of all the spot mics, each panned to roughly to match its instrument’s position onstage. While experimenting with polarity settings for each track, I preferred the overall sound with the second violin and cello mics polarity-inverted. Beyond this, however, no further processing has been applied beyond the individual high-pass filters on each of the four ribbon mics.


The only further EQ processing I applied to the spot microphones for mixdown purposes was a global high-frequency boost. Ribbon mics are by nature rather restrained at the high end, and I felt that they needed to be a little more forward-sounding on the whole within a modern production context. It wasn’t a big deal though — just a simple 4dB boost using a gentle Q=0.15 high shelf set at 9kHz. Directly compare this demonstration with the 11_Quintet_AllSpots file in your DAW to hear the difference most clearly.


Combining the processed spot mics with the main stereo pair of omni microphones now gives us the sound you can hear in this audio example. Comparing this mix with the 01_MainPair_Raw file, you can hear how much the spot mics help focus the individual instrument sounds. Comparing against the 12_Quintet_AllSpotsHFLift file, on the other hand, demonstrates how much life and space is provided by the main stereo pair’s more holistic pickup. Although I was pretty happy with this sound already, I thought I’d experiment to see whether the room mics might add anything further of merit.


Here is the raw room mics recording. As you’d expect of a spaced-pair stereo rig with an eight-foot spacing, the sound is super wide. I quite like recording room mics this way, because it allows me to use them to create width without having to stretch the ensemble itself too much across the stereo image. However, if I’d tried to add this signal to the mix you hear in the 13_QuintetMainsPlusSpots audio file, I’d have quickly started blurring the low end.


Tightening up the low end of the raw room mics signal you heard in the 14_RoomMics_Raw audio file was a simple matter of gently rolling off the low-frequencies from about 200Hz with a gentle (Q=0.25) 12dB/octave high-pass filter — this time using the ReaEQ parametric equaliser plug-in bundled with Cockos’s Reaper DAW software. To hear how this signal functions in context, check out the following 16_Quintet_FullMix audio file.


Here’s my full mix of the string quintet, comprising signals from the main stereo pair, the five spot mics, and the pair of room mics. I’ve also put a little level automation onto the spot-mic signals to clarify the instrument balance at a few points.


Combining three takes of the music heard in the 16_Quintet_FullMix audio file results in the following ‘fake’ ensemble sound.


In addition to the normal takes, we also recorded some passes with the players sitting further away from our mic rig. Here’s a mix of a couple of those takes, so you can hear how the position change affected the sound. I’ve also muted the bass spot mic for these takes, the idea being that when they’re later added to the close-position takes heard in the 17_Orchestra_FullMixCloseLayers audio file, you’ll get more of the high-strings bias you get in a real-world string orchestra, where the violins, violas, and cellos typically outnumber the double-basses.


And finally, here’s the complete simulated large-ensemble string sound, combining three close-position takes and two distant-position takes. In total, this mix uses very minimal processing — a total of five high-pass filters, one high shelving EQ boost, and two polarity-inversion switches — so you’re mostly hearing just what came out of the mics themselves.