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most DAWs, most or all sends are usually switchable between pre and post. When tracking, most sends might be set to pre for routing to headphones, and when mixing, the same sends are often switched to post for driving effects processors. Headphone mixes: Conflicts and solutions Anyone who has ever engineered a multi-musician recording session will tell you that it can be frustrating to manage headphone mixes. It is not natural to make music wearing headphones, and many players can be grumpy and demanding when faced with trying to be creative in an isolated and artificial environment. To make matters worse, many musicians have no clue as to what they actually need to hear in their phones to perform successfully. Other players might know what they want, but are unable to communicate their needs effectively to the engineer. For example, a musician might ask for more drums, bass, and guitar, when what they really require is simply less vocal. If the engineer complies with the request, and turns the individual instruments up to match the vocal level, the next demand from the musician will inevitably be to turn the entire mix down because it is now too loud. Thus successful engineers must learn to read between the lines and anticipate musicians’ needs. I have found this to be true: The better the headphone mix I start with, the fewer musician requests I have to face. To make a decent mix, of course, requires that I actually put on headphones and take a listen to what the talent is truly hearing. As an audio educator, I often see students blindly creating headphone mixes. If you want the musicians to be happy and successful, you have to listen too and correct their mixes! Don’t just turn up aux sends and think the performers will be satisfied. Listen! Personal monitor mixers To mitigate engineer and musician frustrations, many recording studios invest in personal monitor-mix solutions. Whether it is commercial products from Aviom, Movek MyMix, Furman, or others, or homemade configurations built from small mixers, personal monitoring puts the actual headphone mix in the musicians’
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hands: Individual tracks are routed from the recorder or console directly into the personal monitor-mixer network. Next, each musician makes their own mix on their own personal mixer, with little or no tweaking of aux sends required by the engineer. It’s a great solution, when it works... While personal mixing may seem like the Holy Grail of headphone monitoring, in reality a new set of frustrations are created. On the technical level, personal mixers are expensive, require fragile cabling, and always seem to fail in the midst of important tracking dates. On the human level, personal mixers require musicians to double as their own personal engineers. This is problematic, as musicians inevitably are distracted, or simply lack the technical chops necessary to create a decent mix. Thus even with personal mixers, headphone-mix drama is inevitable. To avoid problems, always create a decent headphone mix on every personal mixer before the musician sits down and begins messing with things. Also, label each mixer with console tape and Sharpie so musicians know what instrument is on which knob. Lastly, take a listen to the cans before the musician does! You can solve a lot of problems in advance be simply hearing what the musicians will hear! Latency and monitoring Musicians and engineers recording in a modern DAW environment face an additional monitoring challenge: latency. As discussed in detail in last month’s column and reiterated at the beginning of this article, monitoring should always be on the monitor path, that is, sourced from the output of the recorder. With traditional analog tape recorders, the electrical signal travels through the machine nearly at the speed of light and musicians hear their “sound” simultaneously in the instant they create it. Digital recording, however, is computer based, and time is required for analog audio from microphones to be converted to digital, processed, and then converted back to analog before being sent to analog headphone amplifiers. This lag time is called latency, and in some situations it can be very bothersome. Computer-based DAWs see the greatest latency issues, as a variety of tasks (redrawing the screen, accessing the hard drive, buffering the RAM, etc.) inevitably interrupt audio processing, delaying audio output by a fraction of a second. Not surprisingly, latency can be very distracting to musicians. In the extreme, musicians simply cannot perform because the sound in their headphones echoes what they hear from their instruments. When shorter latency exists, annoying comb filtering occurs between the headphones and live in-the-room sound, often giving the impression to musicians that the audio being recorded is hollow or nasal sounding. I’ll discuss comb filtering in the future when exploring phase issues. You get what you pay for Digital Audio Workstations tackle latency challenges in a variety of ways. Many bypass excess processing while in record mode to minimize issues. Pro Tools HD, for example, disables latency-heavy RTAS processing whenever an audio track is in record. In most DAWs, the amount of latency present is adjusted with a buffer-size setting. Longer buffers permit greater processing power and thus more plug-ins and audio tracks. Shorter buffers translate to less power but shorter latency. Experienced DAW users know the latency dance: set the buffer high when mixing but low (with fewer plug-ins) when recording. As with all forms of technology, greater investment affords more options. Expensive DAWs (such as Pro Tools HD or Apogee Symphony) offload critical processing to dedicated hardware, greatly reducing latency while simultaneously increasing track count and plug-in ability. Users of inexpensive systems are not so fortunate and tend to see latency improvement only when upgrading to faster computers. Some inexpensive systems do offer unique workarounds, though. Older Avid Mboxes, for example, include a mix control on their front panels to give the user the ability to monitor a mix of the record path entering the interface from the microphone and the monitor path exiting from computer. This funky solution allows musicians to hear themselves without delay, but introduces other problems such as comb filtering and/or punch-in/out limitations. Luckily, these sorts of latency workarounds seem to be disappearing as computer processing speeds increase. Eventually, latency issues will be forgotten. Well, we have made it to the end of this column’s cursory investigation into Signal Flow. A huge topic indeed, it will certainly be re-examined in these pages at a later date. As long as you monitor off the record path and never take a listen to musicians’ headphone mixes, you’ll do great on your next session (NOT!). Just kidding! Eric Ferguson (ferguson@recordingmag.com) spent a dozen years as a freelance audio engineer in Los Angeles, and is now on the faculty of the New England School of Communications (NESCOM) in Bangor, ME.

Recording - November 2012

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