Divide and Conquer

Mixing drum kits can be fun. Banging on something to produce a rhythm may have been our first musical experience as a species. Modern recording tools finally gave musicians the ability to share that emotion with a much wider audience of fans and other musicians than live shows alone could reach. Rock and roll can be traced back to early blues and folk music that was popularized in the late 1800’s and early 1900’s. The excitement of listening to W.C. Handy play his Boogie Woogie piano was intoxicating. Right hand playing melody, left hand pounding bass counterpoint, foot stomping in rhythm with the bass line the whole time. A very plausible precursor to the modern concept of drums and bass. Kick drums grew in popularity after mid-1909, when the Ludwig brothers secured the patent for a successful kick drum pedal. The bass guitar has been completing the rock rhythm section since the beginning of the genre. The 1953 Chess Records recording of “Hoochie Coochie Man” by Muddy Waters, featuring Willie Dixon on upright bass and Elgin Evans on a 4 piece drum kit, was probably the first rock and roll rhythm section in audio recording history. The rhythmic beat of the kick drum and the upright bass were synced up. The blues beat of the kick drum lay on the same beats as the notes on the bass. The bass and kick drum melded into a single groove, forming a rhythmic backbone supporting the sinuous flowing flesh of melodic instruments and vocals. I find the kick drum/bass guitar relationship crucial to the level of emotion or excitement a mix can convey. The way I approach that combination is by separating and optimizing different aspects of each instrument.

To sculpt my kick drum sound, I use two transducers with vastly different techniques and results. I want to be able to control the ratio level between the midrange beater attack and the low frequency thump and decay. Divide and conquer. Inside I have a Shure Beta91A on a Shu mount which does a great job of capturing the impact of the beater head and the decaying resonances of the shell. In the console, I apply both a high pass and low pass filter to tailor the bandwidth of the Beta91A to fit my mix. The high pass filter rolls off at 80Hz and the low pass filter varies around 4kHz. In some rooms I raise or lower that frequency to give me more or less high frequency detail from the beater impact. If the room is boomy and reverberant, the low pass can be as high as 6kHz, but if it’s a sterile room with a short reverb decay time (RT60), the filter may be as low as 3kHz. For the low end of the kick drum, I use a subkick style speaker, the Tang Band W6-1139, which has a free air resonant frequency of 38Hz. The speaker is mounted on a stand, in front of the kick drum, close to the head. In the console, I don’t need any filters since the speaker naturally rolls off very rapidly above 80Hz. I do delay the Beta91A signal to align with the subkick. Neither kick drum signal has inline compression applied, although I do use parallel subgroup compression to reduce the overall dynamic range of the kick drum. This makes it much easier to mix with the dynamic range of the bass guitar. I also sometimes use a gate on the speaker using the Beta91A as a key input, depending on room acoustics.

The sound I want to get from the bass guitar is a bit more complicated and nuanced. Ryan Stasik of Umphrey’s McGee is a great bass player and loves using effect pedals to create unique tonal textures. I should talk about his rig first. When I began mixing Umphrey’s McGee, Ryan was playing through an Ampeg SVT Classic amp driving one Ampeg 4×10 cabinet and one Ampeg single 15” cabinet. That rig had a hard time playing at his preferred volume, in addition to sounding muddy and indistinct. Ryan asked me to help improve his tone and power. I played around with a few things and arrived at my ultimate bass guitar rig. After his pedal board, his signal goes to a Gallien-Krueger 2001RB amp which feeds the same 4×10 cabinet, but with B&C 10CL51 PA drivers replacing the old 10” Ampeg woofers. This greatly improved the midrange tone. Measured distortion on the 10” speaker was reduced from 15% to less than 2%. Octave dividers and sub-harmonic generators are among Ryan’s favorite pedals. To help reproduce those, we chose a pair of Bag End SE18E-I single 18” subwoofers powered by a QSC CX702 amp, processed with the Bag End ELF-M2 processor. They do a phenomenal job of reproducing his thunder tones. The 18’s cover from 8Hz to 80Hz and the 10’s takeover at 80Hz continuing out to about 5kHz. The Bag End ELF is fed from the XLR direct out on the GK amp.

To capture the full range of his tone, I also take a divide and conquer approach. I divide the audio spectrum into two frequency ranges, treat each differently and mix them back together for the final result. From about 250Hz down, I prefer the accuracy and low distortion of the direct signal from his Direct Box, a custom tube DI based on a Telefunken ECC83. In the console, I use a low pass filter to roll off those higher frequencies. For the midrange portion of his tone, I prefer the sound from his 10” B&C woofers. The amp and speaker impart a pleasant hairiness and texture to the midrange of the bass guitar. We use a Beyerdynamic M88 microphone on the upper right 10”woofer, with high pass and low pass filters set to trim the bandwidth, passing signal from 250Hz to 5kHz only. Both signals are compressed with on board Midas compressors, The ratio and threshold are set to act more as mild limiter to keep the level in check when he turns on all of his pedals. Most of the time he is only tickling the compressor, with 0-3db of gain reduction. I add 0.33ms of delay to the DI so that it aligns to the microphone signal.

The big advantage to this approach is that I can use my faders to quickly change the tone of the kick and bass by varying the ratio of the midrange and low frequency parts of each. If the song will benefit from more kick drum attack but less bass guitar midrange, it’s an easy change in fader level without upsetting any EQ or compressor settings. Umphrey’s McGee is known for their prodigious use of improvisation and a wide song selection. I don’t use scenes but need to be ready for any song style at the drop of a hat. I personally prefer to have lots of beater attack from the kick drum, without being clicky, and speaker midrange from the bass guitar in almost equal amount, high in the mix. The subkick and DI should combine effortlessly. The subkick signal has a peak at 38Hz, well below most of the range of the bass guitar. When Ryan does use his sub octave pedals, the parallel compression of the kick drum signal allows them to be heard equally in the mix without resorting to reductive EQ to allow them to coexist. Some engineers will sculpt the low EQ of the kick drum and bass guitar, applying complementary cuts aimed at preventing a muddy result. I don’t do that, but my kick drum and bass guitar are well defined with power and nuance. The kick drum drives the downbeat, perfectly timed with the strumming of a bass guitar string. The thunderous low frequency decay of the subkick melds perfectly into each sustained bass note, dropping in level just enough to usher in the next kick drum downbeat. I get excited just thinking about it.