Questions, Suggestions & Tips: from friends and readers

Q: When I turn on our sound system, I get some loud "pops." Can this damage our equipment, and how can I prevent them?

Suggestion: Voltage and signal transients (peaks) are sent through any circuit when equipment is powered on or off. These signal surges can be potentially damaging in the long run to components like power amps and especially speakers. An effective prevention is to think of the flow of "sound material" or program from its source to its destination. Always turn the components on in the direction from source through destination (i.e., first plug in mic, then turn on mixer, signal processor, last power amp/speakers). Conversely, turn them off in the opposite direction - from destination backwards toward the source. This way, the "feeder" transients from the mixer and signal processor will never be amplified by the power amp and broadcast at high volume through your speakers.

Q: "Chaining" or "piggybacking" multiple monitor speakers in parallel is a common and convenient practice. What does that do to the power amp that drives them? How many such speakers can we chain together?

Suggestion: This is an important issue that, understood properly, can keep you from burning out an amp. Speakers - monitor type as well as mains - are rated according to their wattage output power into an impedance or electrical resistance measured in "ohms". The most common speaker cabinet impedance is probably eight, while one also encounters four-ohm and sixteen-ohm speakers. A fact of electrical/acoustical physics is that when each additional speaker is "chained" in parallel, the net impedance in that channel or circuit is reduced. The formula for that reduction is: RT = 1/(1/R1 + 1/R2 + ... + 1/RN) where "R" represents each speaker box’s impedance, and RT = the total combined impedance. Accordingly, two piggybacked eight-ohm monitors present a four-ohm load to the power amp channel to which they’re connected. (If #you work these examples through the formula, you are guaranteed to learn the principle.) When this impedance is cut in half, the power load on that amp channel increases by approximately one-half (i.e., a 300-watt amp would run at about 450 watts. The addition of a third chained eight-ohm monitor cuts the combined impedance to 2.7 ohms. A four-speaker chain of eight-ohm speakers presents a two ohm combined impedance. Into a resistance of two ohms, the same power amp would crank at about 700 watts (~450 x 1.5). If the amp isn’t rate#d as capable of enough power to operate at these wattage output levels, it is likely to overheat, and will probably fail prematurely.

Tip: Understanding the inverse relationship between load impedance and power levels will ensure that the number of speakers you chain into an amp channel is properly matched with the amp that drives them. A safe habit is to deploy your monitors in equal numbers on either right or left channel of your power amp, so that the

output load is matched, or at least approximately so.

Q: I attend a "blended" worship service where the senior pastor -

who has a pretty decent voice - also

is miked, and leads hymns. Unfortunately, the amplification system makes his voice so loud that hardly anybody in the congregation can hear thei##r own singing. What do you suggest?

Suggestion: An ounce of discretion can go a long way. Perhaps a polite observation to your music director or sound person can make them aware of the situation. You have a good point, congregational singing is just that. It’s a joy to hear the raising of voices around you - including your own - and it is possible and desirable to lead singing without drowning everybody else out. It may well be that neither the music director nor the sound person knows how it sounds where you the parishioner stand. They are probably physically in different places most of the time during the service. Try the discreet approach. Even a great voice should not be amplified as a song leader to the point where the congregation can’t hear itself.

Q: We have a music team with a gifted singer who means and sings well, but can be overbearing insisting that everything be done their way. What does one do with a "pouting diva"?

Suggestion: Little idiosyncrasies are to be expected - we all have them. But when someone needs to have the group revolving around them, it can become dysfunctional for all. Prayer before rehearsal and worship performance can remind all of their servanthood in the privilege of ministry. Private one-on-one counsel may help. In the long run, you can’t let the tail wag the dog.

Got a question or a gem to share? Send it to Feedback, Christian Sound & Song, 3112 Lexington Park Drive, Elkhart, IN 46514, or fax to 219.522.5150.