Theory and Practice

Like it or not, monitor mixing tends to get a "water-boy" image compared to the FOH position. But a bad monitor mix situation can really create a bad performance as performers suffer through less than ideal conditions. And, interestingly enough, a bad FOH mix may not even be noticed by the performers as they enjoy a good vibe onstage thanks to a great monitor mix.

I want to share my mindset when monitor mixing, because one can achieve great pride doing this task and not worry much about the prima donna working out at the FOH console. After all, you are working for the band, and the job is to deliver maximum satisfaction to them within the limits of the equipment. However, I also look at monitor mixing as how I would want things done for me if I were performing on the stage. And if you are a current or former musician, monitor mixing should be a position you desire.

In Part 1 of the Wireless Microphones piece, I described wireless mic limitations, preferred locations of mic and receiver, RF link budgets and antenna polarization. In Part 2, we'll cover radio frequency names, antenna patterns and compression/expansion circuits.

Superlatives

Us techno-geeks are quick to toss out acronyms like VHF and UHF without a care, hoping that no one will bother to ask why a user might choose VHF or UHF as the frequency band for transmission. Starting with HF (high frequency), we move up to VHF (very high frequency), then on to UHF (ultra high frequency), then to SHF (super high frequency) and, believe it or not, EHF (extremely high frequency). Each of these high-frequency superlatives stand for a range of frequencies, or bandwidth. HF has 3 megahertz to 30 megahertz, VHF has 30 megahertz to 300 megahertz, UHF has 300 megahertz to 3 gigahertz, SHF has 3 gigahertz to 30 gigahertz, and EHF has 30 gigahertz to 300 gigahertz. And these are all waves per second of radiated electromagnetic energy, better known as radio frequencies (RF).

Of all the mail that I receive, the subject of power distribution seems to bring the most pleas for more info. I have plenty of stories of arcs and sparks, but thankfully, few have emanated from my handiwork. I will tell you a secret: I have been deathly afraid of medium voltage (120, 240 volts) ever since I was a kid; and I think that my healthy perspective has helped me from being overconfident. But my parents do remind me that I, as a toddler, did stick my hands into a few uncovered outlet boxes; received a shock, ran crying back to my parents and repeated my curiosity a few more times that day. And you wonder why I am an electrical engineer today?

While this month's column is not theory, it is a whole lot of "practice" –the contractual technical description of your provided rig is an important part of winning bids. Yes, you can call contract terms part of the "biz," as most of the smaller gigs you take do not include riders and just want you to deliver the sound (and sometimes, stage lights) in a professional manner. But by describing your services in quantitative and generic ways, you connotatively express to your customer that you are all business and not over-promising a touring rig for an amateur event.

When putting together a mix, it is handy to have knowledge of your sound sources and the frequencies generated by each. This article is intended to be a quick reference (with a table) to frequency bandwidths of various music sources.

Drums

Starting with the traditional left side of the console, drums are usually tuned to resonance from about 160Hz to 800Hz. But the total bandwidth of each drum can range from two octaves below to batter head sounds (click) into the presence bands (2 to 8KHz). For example, a 22-inch kick drum batter head is typically tuned to E3 or 164Hz. But sub-harmonics are given off at 82Hz and 41Hz, with these becoming the chest "thump" that should felt more than heard. And with the second harmonic suppressed (328Hz) to make room for other instruments, all that is left is the "click" around 3KHz Other drums are typically tuned a bit higher, like a 16-inch floor tom resonance at C4 (261Hz), 14-inch floor tom at F4 (349Hz), 12-inch rack tom at A4 (440Hz), 10-inch rack tom at D5 (587Hz) and a snare at G5 (783Hz). If you set drum gates, then the first suboctave below the batter head resonance is usually where the frequency band is set. From the above example for drum tunings, the kick is at 82Hz, 16-inch floor tom at 130Hz, 14-inch floor tom at 175Hz, 12-inch rack tom at 220Hz, 10-inch rack tom at 293Hz and snare at 366Hz.

One of the things that still aggravates me are questions about loudness that are formatted like; "How many ampli- fier watts per person are needed for a rock 'n' roll show?" And the oft-repeated, "How many speakers do I need for a room of this size?" While the innocent are allowed to ask such questions, I find it disconcerting to hear experienced sound people asking the very same questions. This Theory & Practice column shall attempt to cover the basics on estimating the Sound Pressure Levels provided and–the reverse–to estimate the amount of gear need to achieve a desired SPL.

I addressed this topic more than two years ago, but took a historical and Q&A approach to justify things like 0dBu levels, gain/level settings and +22dBu brick walls. While nice and informative, a lot of readers said that they needed to delve into the real knobs-and-faders portion of setting up their consoles. This article will revisit gain structure in a straightforward way.

All Those Controls

When you contract for a new gig at a venue you've never been in before, checking out or "advancing" the venue well before the gig is a good idea–and doing it a few weeks before is a very good idea. By knowing ahead of time what you are facing in terms of logistics, your truck/trailer pack can be optimized so you are not bringing in the "kitchen sink" to cover the unknowns.

Come Prepared

My favorite saying is, "Everything is an antenna, some things just work better than others." When it comes to wireless microphones for live sound, the rules of the game are stacked against wireless mic manufacturers. The best we can do as users–and operators–of wireless mics is to understand the situation and play it to our best advantage. This article takes a practical look at how to best operate wireless mics and introduces some rationale into how things are done.

I believe the role of road cases is critically important to the profitability of a sound company. But not every case made out there is really road-worthy. A lot of my anklebiter friends think I am insane to pay $600 or more on semi-custom rack cases to haul power amplifiers and signal processing gear. I look at it as cheap insurance to keep the gear performing throughout its scheduled life, and to put more gear on wheels instead of having my back do the lifting. So this month's installment is about rack road cases, and a guide to getting them built and maintained.