Acoustics Issues
The percussive nature of drums is the very root of how and why signal purity
comes into play when we reinforce them. It is the actual hit, followed by the
ring or tone, of a drum that creates its primary value in creating rhythm,
keeping time, establishing feel, developing accents, etc, etc. Without clearly
defined hits, drums are simply lost in the sea of competing sounds emanating
from the platform, and this negatively impacts the musical experience for both
the band and the congregation.
Assuming we have a drummer who plays well and has a good kit, we immediately begin to lose clarity when we corrupt the impact or attack of each drum hit by introducing reflected acoustic energy, multiple pick-up devices (microphones), and/or misaligned reinforcement system speaker components. A poorly designed platform with an errantly positioned drum kit can turn even the best drummer and kit into a sonic mess. Because any issue relating to acoustics is very complicated, my advice here is to direct your efforts towards a subdued (dead) acoustic character in the drum section of the platform. You can accomplish this by putting carpet on the floor and applying thick absorption to the nearest walls. This will greatly reduce reflected energy. But it would be much more productive to employ a qualified acoustician to design this area so that it is able to acoustically reinforce the drums in a controlled and constructive manner.
Another often-encountered problem occurs when positioning the drum set relative to the other sound sources on the platform. We must strike a balance between the need for the drums to be heard by the choir versus the very loud drum hits entering the choir microphones. Likewise, we should not position the grand piano so that its open lid captures the loud drum hits.
Perhaps the only disadvantage to close mic’ing drums with multiple microphones is the resulting quagmire of mixed signals that can result. To supplement what was said in Part One of this article (See Mic’ing Techniques for Acoustic Drums at www.churchproduction.com, click Back Issues, then click May/June 2003) about drum microphone smearing, try the following demonstration: Have the drummer play successive snare hits while you solo the snare microphone and listen through the front-of-house speaker system or headphones. While the drummer continues the snare repetitions, add (also solo) the rack tom microphones, then the hi-hat microphone, now the overhead microphones, and finally the floor tom microphone(s). Then switch back to just the snare microphone. I believe you’ll clearly get the point; even though we have thoughtfully chosen directional microphones, carefully aimed them, and have reduced considerable amounts of leakage, we cannot completely prevent this specific form of bleed from occurring.
One addition to this scenario is that the interaction of the drum microphones, and the degree to which the drums leak into each microphone, is also dependent on the drummer’s playing style.
Electronic Processing and Control
A practical remedy for this condition is to electronically gate the drum microphones
so that each microphone is turned on only when its corresponding drum is hit.
You can easily find a few very good technical descriptions of how gates work
at the web sites of various manufacturers. Unfortunately, cheap gates (2/3
of those out on the market) do not work very well. Even with very well designed
(read: expensive) gates you will need to tweak each channel painstakingly for
it to operate effectively. Further complicating this issue are two more facts
of life: 1) all but the most seasoned drummers play differently during sound
check than they do during the service, and; 2) every drummer gets tired towards
the end of a long service. This simply means that the gate settings that we
set during sound check and at the start of the worship music must be readjusted
throughout the program. Not a big deal. Pay attention.
Compression, when used tastefully, can smooth out the dynamics of selected drums and result in an improved signal. However, beware the pitfalls of over-compressing, which can result in loss of percussive definition and unintended change in timbre. Compressors, as well as gates, should be inserted into individual microphone channels.
Equalization of any audio signal must be carried out thoughtfully and with an awareness of the consequences, as well as the benefits, of the adjustments you choose to make. Boosting the low-frequency control on a given channel without engaging the high-pass filter will result in an increase in low-frequency noise (garbage) as much as the intended boost of musical low-frequency energy, for example. Also, try cutting at various frequencies rather than constantly boosting. You also need to know the lowfrequency limits of your speaker system: don’t boost low frequencies that simply cannot be reproduced as intended.
Like many live sound mixers, I have found that a conservative amount of reverb on snares and toms can add a layer of depth and warmth to the overall sound of the drum kit. But as is the case with any effect, you can over-do it and the result is that you begin to lose the clarity, tone and definition that you have so painstakingly strived for in microphone selection, technique and playing skills. Most seasoned sound mixers learn this skill (and others) by listening to and observing other sound mixers, playing with effects during off hours, and reviewing their own board tapes.
Note that a multi-channel (stereo or LC- R) front-of-house speaker system can be quite effective at reducing timinginduced drum mush. By artistically panning appropriate drum and overhead microphones to the sides of the sound field, we minimize the degree they are combined into a single mix buss, and this reduces the destructive consequences of multiple microphone pick-up. Be sure to choose carefully what and how you pan. For example, the only channels I would ever hard-pan (to the ends of the panoramic field) are stereo effects returns and stereo overhead microphones (in most, but not all, cases).
Triggered drum samples and electronic drums are two other methods we might consider to improve drum sound reinforcement. But due to the extreme and complicated nature of these, those are topics best suited for a separate article.
Once again, a good sound system and appropriate acoustics are important. For every right choice made in these two critical areas you will be able to more effectively (pun intended) employ effects and microphone selection/technique and signal processing. This is simply because you will more clearly hear what you are doing. So will the congregation.
*Author’s note: We are all are of the needless tragedy surrounding the Rhode Island nightclub fire. When applying acoustic treatments (both homegrown and store-bought) and covering them, make absolutely sure that you employ materials that are rated for this application, or are otherwise fire retardent.
Tom Young is a senior consultant in electroacoustics at Jaffe
Holden Acoustics (JHA) based in Norwalk, Connecticut. JHA specializes in both
architectural and electroacoustics for performance and worship spaces. For
more information, visit www.jhacoustics.com.
