Brushes Held Like Hammers: Our recording engineer looks at ways to reduce spill without compromising a full–band tracking session.
The audio files available on this page accompany my article in SOS about recording the indie band Brushes Held Like Hammers. The first set of files comprise a section of the complete live multi-track recording which you can import into your own DAW and try mixing for yourself, if you like. The filenames are fairly self–explanatory, but here are some additional notes to describe exactly what you’re hearing in each case:
The kick drum was recorded with two mics in front of the drum, with a makeshift isolation ‘tunnel’ built around them both to reject spill from other instruments. The closer mic was a Blue Kickball phantom–powered dynamic model, set up a few inches outside the hole in the drum’s resonant head and with its low–frequency switch set for minimum emphasis so that it would provide a good solid attack. An ADK S7 large–diaphragm condenser was placed a little further away with its 18dB pad switch in, providing low–frequency extension and tonal warmth. The two mics were mixed to a single recorder track.
The snare drum was also recorded with two mics, this time a Shure SM57 dynamic and a Shure KSM137 small–diaphragm condenser gaffer–taped together about nine inches from the instrument. An offcut of acoustic foam was wrapped around the sides of the mics to take the edge off the hi–hat spill, but as you can hear from 0:40 onwards there’s still plenty of that!
There was so much hi–hat spill on the other drum mics that I concentrated on trying to capture more mid-range body from the instrument with its close mic. There’s still more sizzle than I wanted, but that was easy to remove with a low–pass filter for monitoring and mixing purposes.
This file is the ride–cymbal mic, although the instrument isn’t being played in this particular excerpt. However, the spill on this mic nonetheless contributes to the overall drumkit sound, so I’ve still provided it here so you’re able to experiment with mixing the entire multitrack take for yourself if you wish. (To hear what this mic sounded like with the ride cymbal playing, check out the BucketBaffle02_RideWith audio file.)
These are the Shure KSM141 overheads, which were set up in a spaced configuration about three feet apart over the kit. Given the super–loud hi–hat, I set up the closer overhead mic in the acoustic shadow of one of the cymbals, which helped in terms of the balance, but also made the hi–hat appear to be coming from the opposite side of the kit. (The overheads were panned for an ‘audience perspective’ stereo image, so the hi–hat should have been on the right.)
The room mics were a pair of inexpensive AKG CBL99 boundary microphones laid on the floor behind the drummer about six feet apart. As you can hear at 0:40, the hi–hat is again over-prominent in the balance (as it was in the room). Later in the session I tackled this with some further baffling, as you can hear in the MattressBaffle02_RoomWith example file.
This is the mic over the single rack tom, a super–budget Superlux Pro 228 dynamic mic. The first thing to realise is that the spill is comparatively benign tonally, partly because I’d wrapped an off-cut of acoustic foam around the mic to take the edge off the cymbal spill, especially from the hi–hat. You can hear the instrument itself playing from 0:28.
Here’s what the floor tom close–mic, an AKG C414B–XLS large–diaphragm condenser, sounded like in the raw. I’d switched it to figure–of-eight mode to reject cymbal spill, but what spill remains hasn’t been helped by comb–filtering effects caused by sonic reflections from the ride cymbal mic’s nearby improvised baffle. For a clearer demonstration of this, check out the BucketBaffle example files.
The bass amp was miked with a Groove Tubes GT55 large–diaphragm condenser mic switched to its cardioid polar pattern and placed a couple of inches from the grille cloth over the best–sounding speaker. As you can hear from 0:28 onwards, there was an appreciable room resonance between the floor and ceiling at around 70Hz, and this caused the fundamental frequencies of certain notes to be overplayed in the balance. Besides this, though, I was happy with the fairly warm–sounding amp tone as a complement to the DI signal.
This bass DI signal was taken from the DI output on the player’s amplifier, rather than from a separate direct box. Although the low end is less strong than that of the miked signal, the low frequencies are nonetheless much more consistent, so I ended up using those in the mix, together with some low EQ boost to bring them up in the balance.
This is the combined signal from the first guitar cab’s two close–placed mics: a Groove Tubes GT55 large–diaphragm cardioid condenser and a vintage Sennheiser MD421 dynamic.
The second guitar amp also had two close mics on it: another Groove Tubes GT55 large–diaphragm cardioid condenser and a Shure SM57 dynamic mic.
The remaining files demonstrate the effects of some of the baffling tactics I mention in the article. For all of these examples I asked the band to play the same song section several times, so that I could move baffling materials around between takes.
In this audio example, you can hear how much cymbal spill was coming down the rack–tom mic without any baffling in place.
With an offcut of acoustic foam wrapped around the rack–tom mic, the cymbal spill was significantly reduced. Compare with the FoamBaffle01_RackTomWithout file.
This is what the ride–cymbal mic sounded like without any baffling. Notice how the ride cymbal itself is more aggressive, as is the spill from the other kit components.
Here’s how the sound was altered by adding in my improvised mic baffle constructed of half a bucket and some acoustic foam. Overall, the spill feels less prominent, but the ride–cymbal sound has also suffered, becoming less open and a little boxy. On balance, I decided during the session that this seemed an acceptably compromise.
What I didn’t notice during the session was that reflections from the back of my DIY ‘bucket baffle’ had impacted on the sound of the nearby floor tom mic. Here’s what that mic sounded like before the baffle was added. Now compare this with BucketBaffle04_FloorTomWith
The DIY ‘bucket baffle’ I used for the ride–cymbal mic negatively affected the sound of the cymbal spill in the nearby floor time mic, as you can hear in this audio example. Check out the section from 0:37, for instance, where a nasty 3.5kHz resonance has developed which wasn’t audible before the baffle wa introduced — check out the BucketBaffle03_FloorTomWithout file for a direct comparison.
This is what the drum overhead microphones sounded like during the recording session. Duvets had been placed on the walls adjacent to each of the electric guitarists to inhibit their sonic reflections from reaching the drum mics.
If you compare this audio example with DuvetBaffles01_OverheadsWith you’ll hear how much difference it made when I hung up the duvets in the recording room, as described in the magazine article.
The duvet baffles weren’t just preventing guitar spill from getting onto the drum mics, but were also trying to reduce the drum spill being picked up this guitar mic. To hear how effective this was, compare this audio example (which uses the baffled recording setup) with the DuvetBaffles03_GtrGT55With demonstration file.
When the duvet baffles are removed from around the guitars, the degree of cymbal spill immediately rises to a much higher level, and with a more audible tone too.
For the first day’s recording the room mics were picking up too much hi–hat on the right–hand mic (when seen from audience perspective). Although I was sure I’d be able to deal with that at mixdown, I still wasn’t that happy about leaving things that way, so I tweaked the setup for the second day to improve matters.
By using a small fold–up mattress to obstruct the sightline between the right–hand room mic and the hi–hat, I was able to achieve a substantial improvement in the room balance. Compare this example with the MattressBaffle01_RoomWithout file and listen for how much less hi–hat you can hear.
For my final set of audio examples, I’d like to demonstrate just how much separation we were able to achieve on this session without splitting up or isolating the performers:
Here’s a rough balance of the live multitracks you’ve already examined in the RawTracks audio examples. Processing is very minimal: high–pass filtering pretty much across the board to avoid a build–up of muddy low–midrange spill; some low–pass filtering on tracks which had picked up too much hi–hat spill, and a bit of gating on the snare close mic from 0:40 for similar reasons; some compression on the snare, drums buss, and master buss; and a half–dozen EQ bands scattered around elsewhere. No send effects have been used at all — any room sound you’re hearing is from the recordings themselves.
Here’s what the mix in the Spill01_RoughBalance file sounds like if you mute the bass and guitar mics. While you can still clearly tell that this is a live take, few people would guess that the guitar cabs were in fact only a couple of feet from the kick drum! In practice, this means that we could have completely rerecorded the electric instruments if we hadn’t liked the performances without any problems.
Here’s the bass part from the Spill01_RoughBalance audio file. Although the cab is only about 6–7 feet from the guitar cabs and kick drum, the level of spill is extremely low, partly on account of the spill–less DI signal that’s mixed with the on–cab mic signal.
Although I used no DI signal for either of the guitars in the Spill01_RoughBalance audio example, you can hear that their two dual–mic recording rigs still don’t pick up any spill from the bass, and only very little from the drumkit — mostly cymbal spill.
And here’s the same section of the final release, as mixed by Algis Juknevicius. Notice how he’s been able to create a very different bass sound for the opening section, even though all the backing instruments were performed together in the single room.