I started out wanting to write about the design task of coming up with hybrid microphone and pickup rigs for Punch Brothers (a progressive acoustic band that I work with) and building a completely self-contained stage and mix system. But that initial focus has changed, where I now feel the need to share some of what I’ve learned by plugging it in to many different sound systems, as well as offer some observations on stuff that works and stuff that does not.
Punch Brothers had been touring for several years with a carefully conceived “microphone only” system that worked very well in controlled concert situations, but we found ourselves seriously limited in many louder venues and made the decision to add pickups to it. The goal was to put together a “bulletproof” package that would work in every venue, everywhere.
After much research and discussion, we booked time in a rehearsal room with a sound system and a pile of gear to build our pickup systems (despite our serious dislike of pickups) with a highly developed sense of what we thought the instruments should sound like. We tried various combinations of pickup, preamp, and effects with all of us sitting as jury, until everyone was satisfied with all sounds and our house mix output sounded as much like the record as possible.
This self-contained stage system included all stage wiring, monitor mixer with passive split, in-ear monitoring, pedal boards, front-of-house preamps, processing, and mixer all packaged to be checkable and able to fly. It was carefully designed to make setup and strike easy. and so that the only things that would change technically from show to show were the snake to FOH, the amps, the processing, and the loudspeakers.
Amplifying acoustic instruments is always difficult at best, and having an entirely repeatable input scheme gave me an efficient way to judge the performance of sound systems and to avoid making corrections at the console that should be made on the system. It tended to make any kind of system problem readily apparent, and I became more aware of issues related to acoustic amplification that tend to be problematic.
First in line is a very general comment on amplifiers, loudspeakers and their associated processing. Most of the systems I encountered were technically adequate, but there were all too many that were optimized for loudness and then locked in the system processor beyond all discussion.
In terms of amplifying acoustic instruments I would argue that any equalization that is done in setting up a sound system, whether by ear or even by technical measurement, is completely subjective and does not relate to how my inputs will react on “this stage with this system.” I would go so far as to say that good amplified acoustic sound does not require fidelity in a sound system as much as it demands absolute
control of it.
All acoustic instruments are completely subject to their sonic environment. They require the application of energy to make mechanically produced sound. When the sound of the instrument is amplified with a mic or a pickup, the sound from the loudspeakers becomes additional energy applied to the instrument and microphone, creating a passive feedback loop between the main loudspeakers and the instrument, with a resonant peak consistent with that of the instrument itself.
The fact that this resonant peak occurs in the same frequency range where most sound systems have been beefed up to get loud makes for a double handful of energy to keep under control. This makes the term “flat” have little or no meaning in live sound and may be the main difference between recording to a reference loudspeaker and amplifying sound in a room.
Correcting these resonant peaks and feedback loops with input channel EQ is always the right place to start, but the cut made should be done equally in the main loudspeaker system as well, in order to avoid thinning (or reducing gain on) what is coming through the console too much. Keep in mind that finding that balance point between console and system EQ can be difficult with multiple loudspeaker systems and
multiple inputs, but if you know that input sounds right at the console, you can lean more and more on system EQ – and even reduction of gain to the amps.
Sound systems that are optimized for loudness (which is most of them) are basically the opposite of what is needed for acoustic instruments. The fact that systems do have a lot of power in low mid and low end, and are often placed too close to the stage always makes it difficult to get a musical balance with an acoustic instrument.
By musical balance, I mean when the amplified instrument can play all notes in its range with the same perceived loudness in as many places as possible in the room. It’s always the interaction of the instrument with the system that dictates the degree of control needed. This contrasts sharply to a rock band that has very loud sound sources and directly synthesized sounds with little or no interaction with the main loudspeakers.