Setting up a Worship Band Monitor Mix

Ever have problems with stage volume that’s just too loud? Combating sound issues from performers who can’t hear themselves play—much less think—can be tough.

How many times have you pulled down the master faders to (–)infinity at FOH, and the sound coming off the stage was still so loud you knew you were going to get a visit from the head deacon or usher before the first chorus?

Or how about the worship leader who leads from the piano? His complaint is he can’t hear himself, but he has the high freq section of the monitor aimed at the piano, and the woofer is the only thing aimed at his ears.

The monitor gets turned up and blasts the soundboard of the piano, which is picked up by the piano mic, which gives you a nice 55-gallon drum sound (true story). The piano has a muddy sound in the monitor, no definition, gets turned up (because they can’t hear) and drowns out the worship leader’s voice. Now the vocal needs to be turned up, resulting in a mix that no one is happy with. Not to mention the sound tech must mix over this roar.

The sound mixer has a few options:

1. Raise the overall house volume level to get on top of the stage noise 2. Don’t put any piano in the house mix because there is enough piano volume coming off the stage 3. Touch the knob and smile

Not very good options.

How many times have you pulled the master faders down to (–)infinity and the sound coming off the stage was still so loud you knew you were going to get a visit from the head deacon or usher before the first chorus?

The purpose of this article is not to be condescending, or to start a conflict between stage performers and the sound/media team, but to educate all involved about a few laws of physics that we all have to obey. Many sound problems that are a constant weekly battle can be fixed without spending a ton of money.

Examine your monitor system

The first thing we need to do is take a comprehensive look at your monitor system.

Are you mixing monitors from the Front of House (FOH) mix position, a dedicated monitor console, or onstage personal monitor mixers?

If you are mixing from FOH, make sure your aux sends are “pre-fader”. This means all adjustments happen before the fader and any fader adjustments will not affect your aux mix. A “postfader” aux means that any adjustment that you make, EQ or fader, will affect the aux level. This will give you an inconsistent monitor mix and an unhappy musician because the mix is always changing.

Make sure that your floor wedges are pointing at the musician’s ears. Sometimes wedges are pointing at knees or the ceiling. Be aware of the coverage pattern of the horn. Do you have too many people sharing a monitor?

Have you “rung out” the monitors for feedback?

Start the mix with a clean slate

Many times rehearsals will start with the same mix that ended with last week’s service. The problem is there were three other services and other musicians on stage and you are just compounding problems. Let’s start out with a clean slate by “zeroing” out the mixer.

Now let’s hold that thought for a moment. I would NEVER recommend that you start this new mix 15 minutes before service time. We need a comprehensive sound check before and during rehearsal. Having said that, coordinate this undertaking with your Music Director/Worship Leader. They will appreciate your concern for their mix.

Now let’s get back to our clean slate. “Zero Out” the mixer by turning off all of the aux sends.

The quickest and most efficient way I have found to do a sound check is to run a chorus of the most upbeat song in the set list. Remember to take into account the volume all of the acoustic instruments (piano, drums) will make, not to mention the electric guitar amps, before you turn up any monitor.

I have my band play a chorus with no monitors just to hear what kind of level we are generating before we add monitors.

Then I start with the rhythm section, beginning with the drummer, going through the levels of each of the instruments: bass, electric, keys, lead vocal, until the drummer is happy with his mix.

If I am the worship leader I coordinate with the sound person on my mic. If I am the soundman, I will use a talkback mic and communicate with the musician on every change I am making.

If I have the luxury of a monitor engineer, I am on stage with the musician using hand signals with the monitor engineer.

Listen from the performers’ perspective

I always recommend sound people walk out on stage, especially if they are mixing wedges, to hear exactly what the musician is hearing. Be sure and listen to each monitor. Different brand monitors are going to sound different. Cuing the mix up in a headphone is not an accurate representation, unless you are mixing “in-ear monitors”

This approach has always been successful for me in the worship setting. It lets the musician know the sound tech cares about what their mix sounds like. It is very frustrating for a musician on stage to need something in their mix, or have a problem, and the soundman behind the board never moves from behind it.

I move then to the bass player, then electric, then keys. Usually during the rehearsal musicians will asks for changes and adjustments will be made. Before we stop I always like to run the upbeat opener once again, just so there are no surprises when it is down beat time.

Do away with “fader fighting”

One of the biggest mistakes sound techs make is what I like to call “fader fighting” or additive mixing. If you can’t hear a particular instrument, you push that fader up. If that covers another instrument up, you push its fader up, and so on and so on, until we have a muddy roar.

Try subtractive mixing. Listen for the most offending (loudest) instrument and bring it down in the mix. You will have a much cleaner mix and happier musicians. Remember, “less is more.”

Don’t make adjustments during breaks

Another big no-no is making adjustments while the band is not playing. Musicians tend to make changes to their mix during breaks. Doing so will result in either too much or not enough adjustment. Wait until the band is playing to make the adjustment, and it will be like the baby bear…just right!

What does a band want in their mix?

Every musician is different. But my experience has been that the rhythm section will want various parts of …the rhythm section. For example, drummers will typically want bass, electric, and the lead vocal, and the worship leader’s instrument. Bass will typically want kick, snare (unless they are standing next to the drummer) and the worship leader’s instrument. Electric players will usually want bass, drums, and more electric! Keyboard players will generally want more of the worship leader’s instrument and vocal.

Again, these are not hard and fast rules, just typical generic things that I see. The point is that nobody needs every input in their mix; only what they need to enhance their performance. Many times the acoustic level of a particular instrument is enough.

In conclusion, if you are consistently listening to the wedges that the musicians are listening to, you can help fix the mush in their mix (subtractive mixing), because you know firsthand what you have placed in the mix. Plus you will have built trust with the musician. Have a good mix!

By: Michael Hill, Sennheiser
Courtesy Sennheiser USA

______________________________________
David McLain | Wireless Guy! | CCI SOLUTIONS
Be seen. Be heard.
PO Box 481 / 1247 85th Ave SE
Olympia, WA 98507-0481
Voice: 800/426-8664 x255 / Fax: 800/399-8273
email: dmclain@ccisolutions.com
online: www.ccisolutions.com
blog: www.churchsoundguy.com
facebook: dmclain@ccisolutions.com
linkedin: http://www.linkedin.com/in/davidmclain
podcast: http://www.ccisolutions.com/podcast
Clearance Bin:http://www.ccisolutions.com/clearance

A Tour of the David Crowder*Band's studio.

David Crowder*Band's studio. With David Crowder*Band's screwball sense of humor.

(If you're having difficulty seeing the video, click the title at the top of the page.)

Secrets of EQ

Starting Out

When I first began doing sound, I bought a great set of headphones. I thought to myself - if I'm going to be expected to make something sound good, I should probably know what I'm shooting for.

So I started listening (like crazy) to CDs. Not just bands or styles I liked, but anything and everything I could get my hands on. I listened to the lyrics, chords, melodies and harmonies, but also to how it all fit together. I concentrated on the space that each instrument was taking up.

I noticed that certain instruments seemed always to be sitting in a certain spot — not to where they were panned, but to the frequencies they occupied.

Instrument Frequency Response

How To Get There

When building a mix, we need to think of the song as a line. Each instrument makes up part of that line. If we have too many instruments or frequencies trying to take up the same space our line gets bumpy and the mix gets muddy.

Listen to each instrument and think of a space for it on the line. Keep other instruments away from it (EQ wise) and you will have an easier time hearing that instrument. You wouldn't want to have a really bassy, heavy electric guitar because it would be taking up a lot of the space the bass guitar really needs. Try to keep each instrument in its place.

"Listen to each instrument and think of a space for it on the line."

Think of each instrument as to what the fundamental piece of it is. For instance the fundamental of a kick drum will be low frequencies. That's not to say you don't need highs to make it cut, but there really isn't much midrange going on with it. Try to carve out some of the midrange of the kick to make room for the low midrange of the bass guitar.

Another example is electric guitar. Many engineers mistakenly try to make the electric guitar huge to get a 'larger than life' sound, but if you really listen to a guitar on a CD and focus on what frequencies are really taking up space in the mix, you'll be surprised at how small the range actually is.

"Be attentive to the mix and what's going on inside it. It doesn't mean you have to constantly turn knobs."

I always tell new engineers never to be "done" with the mix. Listen for changes, and more importantly, listen to make sure that everything is in the mix and working together. Be attentive to the mix and what's going on inside it. It doesn't mean you have to constantly turn knobs. Focus less on the actual sound of the individual instrument and more on how it interacts with other instruments in that same range.

There are no "magic" numbers that work every time because all instruments are a little different. The equation gets more complicated when we use different mics or the instrumentalist changes patches on their keyboard, but trust me… none of that is really important. What is important is that you focus on getting a natural sound that blends nicely with the competitors for the same space.

Bridging The Gap
Here are some general guidelines to consider when you are trying to find your space.

General Frequency Tips

20Hz to 80Hz: This is your sense of power in an instrument or mix. It's the stuff you feel more then hear. The kick drum and bass guitar are down here in this range.
80Hz to 250Hz: The area where everything comes together. This is where a lot of things can go wrong and too much in here will make a mix sound sloppy.
250Hz to 2kHz: Most of your fundamental harmonics are in this range. These are some of the most critical frequencies to building a solid mix. Learn what instruments are most dominant in these frequencies and clean up around them.
2kHz to 5kHz: Here you will find the clarity to almost everything. But be careful, too much of a good thing can start to sound harsh. This is an area where subtly is the key.
5kHz to 8kHz: Mostly sibilance and "s" sounds. Much of the vocal consonants are defined in this range.
8kHz to 20kHz: Brilliance is the word here, the top end of cymbals.

Instrument Frequency Tips

Kick Drum and Toms: Cut 500Hz to get rid of the cardboard box sound. Add 5kHz to make them cut thru the mix. Add a little 60Hz to 80Hz to make them really thump.
Hi Hat: I generally cut all the lows and a good chunk of low mids. There isn't anything down there anyway.
Snare: Generally I take out a little around 600Hz and add a little around 4kHz, and maybe even boost some 200Hz to make it move a little air, but that really depends on the drum and how it is tuned.
Bass Guitar: So many players and basses are so very different. Usually if it's muddy I cut 160-200Hz and possibly add a little 700Hz to 1kHz if I can't really hear their notes, but be careful because there are a lot of other instruments fighting for that space.
Piano: This is a beast we could probably use a whole article to discuss. It depends mostly on how it's miked. If it's boomy then cut 200Hz to 315Hz. If it's kind of barking then cut more up near 400Hz to 500Hz. Judiciously add a little 2Khz -4kHz to make it cut a little more.
Voice: Boomy? High Pass at 150Hz. Is it too thick? Try cutting 240Hz. Need them to poke out a little more? Add a little 2.5kHz. Having trouble hearing their syllables? Try adding a little between 4kHz and 10kHz.

Trust Your Ears

The most important question is "Does it sound natural?" Does it sound like the CDs you've been l istening to? More specifically, does it sound like you were sitting in front of the real instrument? I keep this in mind throughout the performance.

"The most important question is: 'Does it sound natural?'"

I constantly glance down all the channels and think about each input. Kick, does the kick sound right? Bass, does the bass sound right? Guitar, does the guitar sound right? Piano, does the piano sound right? Vocals, do the vocals sound right? Then I think about it all again and ask if the guitar and vocal are walking over each other. Can I hear the piano? Is it because the guitar has too much midrange near the piano part's midrange? Try taking a little low mids our of the guitar instead of turning up the piano. I think you get the picture.

"Learning to EQ confidently means you know where you are heading."

It's almost impossible to make the initial adjustments to instruments or vocals in the mix with the whole band playing. Instead I try to have a snapshot of what I think the instrument should sound like.

Learning to EQ confidently means you know where you are heading. That's why I recommend listening to CDs with a good set of full range headphones. No cheap earbuds here… you need a p air that will allow you to hear the whole frequency spectrum, and preferably a sealed set, like good earphones or sealed headphones. You'll be able to form a mental soundscape of that you can use when you are back behind the console.

Turn, Turn, Turn!

Here's a bonafide "trick of the trade". Turn some knobs. I mean actually get in there and turn the heck out of the EQ knobs and listen to what they do.

"Becoming a master of EQ is like becoming a master painter. Sometimes you just have to throw some paint on a canvas and see how it works."


Here is a simple technique to use in sound check.

Grab the gain (Figure 1) on the mid EQ of an instrument crank it up a bunch...

now grab the frequency (Figure 2) of the mid and sweep it up and down.

You will hear a spot where it makes that instrument or voice sound horrible. Once you find it, take the gain back to zero, listen for a second again, and then cut out about 6db of it. You will be amazed how much better that instrument sounds when you "get the junk out" as I call it. This is an amazing way to learn what frequencies sound like and the technique will eventually train your ear to hear the junk without boosting it first.

Becoming a master of EQ is like becoming a master painter. Sometimes you just have to throw some paint on a canvas and see how it works.


Courtesy Shure Microphones

About John Mills: A frequent contributor to Shure Notes®, John is an 18-year veteran of the road. He was a frustrated Electrical Engineer who hated college. He left school to pursue a career on the road as a drummer, ended up as a sound engineer and after being blessed to work for many of the top Christian worship leaders, artists and tours, has landed at a job as an audio engineer for a design firm. He says, "I guess Mom was right, she always knew I'd finally got a real job." Check out www.EliteMultimedia.com and www.TechTraining101.com for more about what John is up to.


___________________________________________
David McLain | Tech Talk Translator| CCI SOLUTIONS
Be seen. Be heard.

PO Box 481
/ 1247 85th Ave SE
Olympia, WA 98507-0481

Voice: 800/426-8664 x255 / Fax: 800/399-8273
email: dmclain@ccisolutions.com
online: www.ccisolutions.com
blog: www.churchsoundguy.com
facebook: dmclain@ccisolutions.com
twitter: twitter.com/churchsoundguy
podcast: http://www.ccisolutions.com/podcast
Clearance Bin: http://www.ccisolutions.com/clearance

How Much Amplifier Power Do I Need?

I apologize for the length of this week's post; we're addressing a complicated subject. I am including two answers to this question: the first is from an amplifier manufacturer (Crown), the second from a speaker manufacturer (EAW) to cover both viewpoints.

See also Danger! Low Power!

I'm playing folk music in a coffee shop. How much amplifier power do I need?
Our rock group will be playing in a 2000-seat concert hall. How many watts will we need?
I just bought some PA speakers. I want to play them as loud as they can get without blowing them up. Which amplifier should I get?

At Crown, we often are asked similar questions, and this article will provide some answers.

First, define your goal. Do you want to power some loudspeakers so they play as loud as possible without burning out? If so, all you need to read is the section below. Do you want to achieve a certain loudness in a certain venue? If so, skip to the section called Power vs. Application.

How much power can my speakers handle?

You can determine this by looking at the speaker's data sheet. Look for the Nominal Impedance spec. Typically it will be 2, 4, 8 or 16 ohms. Next, look for the loudspeaker specification called Continuous Power Handling or Continuous Power Rating. It might be called IEC rating or Power capacity.

If you can prevent the power amp from clipping (by using a limiter), use a power amp that supplies 2 to 4 times the speakers continuous power rating per channel. This allows 3 to 6 dB of headroom for peaks in the audio signal. Speakers are built to handle those short-term peaks. If you cant keep the power amp from clipping (say, you have no limiter and the system is overdriven or goes into feedback) the amplifier power should equal the speakers continuous power rating. That way the speaker wont be damaged if the amp clips by overdriving its input. In this case there is no headroom for peaks, so you'll have to drive the speaker at less than its full rated power if you want to avoid distortion.

If you are mainly doing light dance music or voice, we recommend that the amplifier power be 1.6 times the Continuous Power rating per channel. If you are doing heavy metal/grunge, try 2.5 times the Continuous Power rating per channel. The amplifier power must be rated for the impedance of the loudspeaker (2, 4, 8 or 16 ohms).

Here's an example. Suppose the impedance of your speaker is 4 ohms, and its Continuous Power Handling is 100 W. If you are playing light dance music, the amplifier's 4-ohm power should be 1.6 x 100 W or 160 W continuous per channel. To handle heavy metal/grunge, the amplifier's 4-ohm power should be 2.5 x 100 W or 250 W continuous per channel.

If you use much more power, you are likely to damage the speaker by forcing the speaker cone to its limits. If you use much less power, you'll probably turn up the amp until it clips, trying to make the speaker loud enough. Clipping can damage speakers due to overheating. So stay with 1.6 to 2.5 times the speaker's continuous power rating.

Power vs. Application

This section will suggest how big a power amplifier you need to fill a venue with loud, clear sound. Basically, the louder the sound system and the bigger the room, the more power is required. Loudspeakers with high sensitivity need less power than loudspeakers with low sensitivity.

The list below recommends the total amplifier power needed for several applications. Each application has a range of power based on the desired loudness and the typical loudspeaker sensitivity.

In compiling this list, we made the following assumptions:

  • Typical loudspeaker sensitivity is 85 dB SPL/W/m for home stereos, 95 dB SPL/W/m for small PA speakers, 100-105 dB for medium PA speakers, and 110 dB for large PA speakers.
  • The recommended power allows for signal peaks of 10 dB for folk, jazz and pop music. Actually the peaks might be as high as 25 dB, but we're allowing for some inaudible short-term clipping.
  • The recommended power allows for signal peaks of 6 dB for rock music that is highly limited or compressed.
  • According to Crown's chief amplifier engineer, Gerald Stanley, amplifier continuous power and amplifier peak power are nearly the same. Typically, peak power is only 1 dB higher than continuous power, and depends on peak duration.

Total amplifier power required in various applications

  • Nearfield monitoring: 25 W for 85 dB SPL average (with 15 dB peaks), 250 W for 95 dB SPL average (with 15 dB peaks)
  • Home stereo: 150 W for 85 dB SPL average (with 15 dB peaks), 1,500 W for 95 dB SPL average (with 15 dB peaks)
  • Folk music in a coffee shop with 50 seats: 25 to 250 W
  • Folk music in a medium-size auditorium, club or house of worship with 150 to 250 seats: 95 to 250 W
  • Folk music at a small outdoor festival (50 feet from speaker to audience): 250 W
  • Pop or jazz music in a medium-size auditorium. club or house of worship with 150 to 250 seats: 250 to 750 W
  • Pop or jazz music in a 2000-seat concert hall: 400 to 1,200 W
  • Rock music in a medium-size auditorium, club or house of worship with 150 to 250 seats: At least 1,500 W
  • Rock music at a small outdoor festival (50 feet from speaker to audience): At least 1,000 to 3,000 W
  • Rock or heavy metal music in a stadium, arena or amphitheater (100 to 300 feet from speaker to audience): At least 4,000 to 15,000 W

Although a rock concert in an arena could be powered by 15,000 watts (allowing only 6 dB of headroom for peaks,) you'll often see large touring sound companies using 80,000 to 400,000 watts total. That much power is needed to handle 20-to-24 dB peaks without any clipping, and to power extra speakers for even coverage of a large area.

If one loudspeaker won't handle the total power required, you need to divide the total power among multiple loudspeakers and multiple amplifier channels. For example, suppose you need 1000 watts to achieve the desired average loudness, but your speakers power handling is 250 watts continuous. You could use a power amplifier of 500 watts per channel. Connect two loudspeakers in parallel on each channel. That way, each speaker will receive 250 watts (not considering the change in amplifier power at different impedances, and not considering cable losses).

Note that if you parallel two speakers, their total impedance is halved. For example, two 8-ohm speakers in parallel have an impedance of 4 ohms. In that case, each speaker would receive half of the amplifier's 4-ohm power.

Power Calculator

On the Crown website is a calculator that determines the amplifier power required to achieve the desired SPL at a certain distance. It also accounts for the number of dB of amplifier headroom needed for audio peaks. Text accompanying the calculator gives the equations used. Click on the following link to go to Crown's power calculator: Calculator

To use that calculator, you need to know the loudspeaker sensitivity, peak headroom, listener distance, and the desired SPL. Let's examine each factor.

Sensitivity
The sensitivity spec can be found in the loudspeaker's data sheet. Typical sensitivity for a PA loudspeaker is 95 to 110 dB-SPL/watt/meter. Bigger speakers generally have higher sensitivity than smaller speakers, and high-frequency drivers have higher sensitivity than low-frequency drivers.
Peak headroom
Because music has transient peaks that are 6 to 25 dB above the average level, the power amplifier needs to produce enough power to handle those peaks without distortion.

For example, if you need 100 watts continuous power to achieve the desired average SPL, you need 1,000 watts continuous to handle 10 dB peaks, 3,162 watts to handle 15 dB peaks, and 10,000 watts to handle 20 dB peaks. Clearly, the peaks require far more power than the average levels. In the calculator's Peak Headroom field, enter 6 dB for rock music that is compressed or limited, or enter 20 to 25 dB for uncompressed live music. If you can live with some short-term clipping which may be inaudible, enter 10 to 15 dB.

Listener distance from source
This is the distance from the loudspeaker to the farthest listener. If you are using several loudspeakers that extend into the audience, this distance is from the nearest loudspeaker. For example, if the audience is 100 feet deep, and you have speakers at 0 feet and 50 feet, the listener distance is 50 feet.

If you don't know this distance, you can make a rough estimate from the typical values below. Be sure to enter the distance in meters (m).

Coffee house: 16 to 32 feet (4.8 to 9.8 m)
Small club or auditorium: 32 feet (9.8 m)
Medium club, auditorium or house of worship: 45 feet (13.7 m)
2000-seat concert hall: 110 feet (33.5 m)
Small outdoor festival: 50 feet (15.2 m)
Stadium or arena: 100 to 300 feet (30.5 to 91.4 m)

Desired SPL
Listed below are typical sound pressure levels (SPLs) for various types of music. The SPL meter was set to C-weighting, slow response. You might want your system to be at least 10 dB above the background noise level to achieve a good signal-to-noise ratio.

New age: 60-70 dB
Folk: 75-90 dB
Jazz: 80-95 dB
Classical: 100 dB
Pop: 90-95 dB
Rock: 95-110 dB
Heavy metal: 110 dB.

Other Considerations

The calculations discussed here apply to anechoic or outdoor conditions. If the sound system is inside a venue, the room reverberation will increase the SPL typically by 6 dB. You can use this room gain as extra headroom.

Suppose you need to supply 1000 watts for peaks, and your speaker's continuous power handling is 250 watts. A speaker's peak power handling is typically 4 times its continuous power handling. So the speaker can probably handle 1000 watts peak. That means you can use a 1000 watt amplifier to drive that speaker -- as long as you use that power for peaks, and do not drive the speaker continuously with 1000 watts. In other words, don't turn up the amp so high that it clips.

What if your sound system uses an active crossover and a separate power-amp channel for each driver? Apply the calculator to each driver type. Say you have a 3-way system. Determine the power separately for the subs, midrange drivers and high-frequency drivers. All three types of driver should produce the same SPL at the same distance. Note that horn-loaded drivers tend to have much higher sensitivity than subwoofers, so the horns need less power to produce the same SPL as the subs.

Suppose your sound system has multiple loudspeakers that extend into the audience area. For example: an outdoor festival with speaker clusters on delays every 100 feet, or a set of ceiling-mounted speakers. Apply the calculator to each nearby speaker cluster or speaker.

Crown Amplifier Selection Guide (rated by total power)

Once you know how much power you need, you can select a Crown amplifier from this list. There is some overlap in this list because each power amplifier produces different amounts of power depending on the load impedance.

You might want to choose an amplifier that has more power than you need in case you expand your applications. Also, it's wise to specify a little more power than you need. You can always turn down a power amp if the system is too loud, but you can't turn up a power amp past maximum if the system is too quiet!

Total power (both channels combined)
25-50 W: D-45
50-100 W: 180A, 180MA, D-75A
100-200 W: 280A, 280MA, CP660
200-400 W: 1160A, 1160MA, CP660, CTs 600, XLS 202
400-800 W: CE 1000, CE 2000, CH1, CL1, CTs 600, CTs 1200, K1, MA-602, MA-1202, SR II, XLS 202, XLS 402, XLS 602
800-1,000 W: CE 1000, CE 2000, CH1, CH2, CL2, CTs 4200, K1, MA-1202, SR II, XLS 402, XLS 602, Xs500, Xs700
1,000-1,500 W: CE 1000, CE 2000TX, CE 4000, CH2, CH4, CL1, CL2, CL4, CTs 1200, CTs 2000, CTs 3000, CTs 4200, CTs 8200, K1, K2, MA-1202, MA-2402, SR II, XLS 402, XLS 602, Xs500, Xs700, Xs900, Xs1200
1,500-5,000 W: CE 4000, CH4, CL2, CL4, CTs 2000, CTs 3000, CTs 8200, I-T4000, I-T6000, K2, MA-3600VZ, MA-5002VZ, SR I, XLS 602, Xs700, Xs900, Xs1200
4,000-8,000 W: I-T6000, I-T8000, MA-5002VZ

With the tools and advice in this article, you should be able to purchase or recommend a power amplifier with the right amount of wattage for the style of music and venue.

Courtesy Crown Audio

How Much Power Amplifier Do I Need?

There is no exact answer to the question of how much amplifier power you should use for a particular loudspeaker. Actually, there are three separate and very distinct issues regarding selecting amplifier power for loudspeakers.

LOUDSPEAKER POWER HANDLING RATING

The power handling rating in EAW's specifications means that the loudspeaker has passed our standard power handling test. In this test the loudspeaker is “exercised” to a point of damage or failure. The power rating resulting from this test is intended to be used as a point of comparison with the power ratings of other loudspeakers. This rating does not necessarily correspond to the best amplifier size to use nor is it a measure of the "safe" amplifier size to use under actual operating conditions.

Discussion: EAW’s power handling test primarily determines the limit of a loudspeaker’s thermal power handling. This limit is the point where a sustained input signal (measured as an RMS voltage) causes permanent damage to or failure of the loudspeaker due to heating. During this test, the loudspeaker is also subjected to peak input levels of up to 6 dB above the RMS level of the input signal. To a certain point, these peak levels test the loudspeaker’s peak handling capability. The pink noise signal used for full-range loudspeaker testing is shaped to a standard EIA (Electronics Industry Association) frequency response. This response shape emulates the average frequency response of typical musical programs.

Nonetheless, this shaped pink noise signal cannot be considered representative of all real audio signals nor how a loudspeaker will react to those signals. Generally, it is a more stressful signal for a loudspeaker to reproduce than typical music or speech signals in terms of thermal limits. However, some audio signals, such as rock and dance music and even some classical music, can have content that is more stressful than the shaped pink noise signal.

Because there are no universally accepted standards, most professional loudspeaker manufacturers use different test methods to arrive at a power handling specification. In spite of this, these different tests can yield surprisingly close numbers. The ratings are known variously as the thermal, continuous, RMS, average, AES, EIA, or sustained power handling. Differences in power ratings are often simply a result of differences in testing methods or test equipment, rather than actual differences in the loudspeaker capabilities. Thus, loudspeakers within a factor of about +1.5 of each other in power handling can usually be considered of equal capability. A factor of +1.5 is equal to about a +1.5 dB difference in output. For example, a loudspeaker rated for 600 watts and a similar one rated for 900 watts are likely to be equally capable in terms of power handling for real audio signals.

Note that “music”, “program”, “peak”, or similar power ratings are usually two or more times the thermal (or RMS, continuous, etc.) power rating. However, these ratings are rarely the result of actual measurements. Usually, these ratings can only be considered as an indication that the loudspeaker can handle peak inputs that are higher than the maximum rated thermal power limit.

SELECTING AN APPROPRIATE AMPLIFIER SIZE

The amplifier for your loudspeaker should be sized according to both the sound levels required and the type of audio signals that will be reproduced. If you are unsure of how to determine these things, consult a qualified professional or contact EAW's Application Support Group.

Discussion:

Do not confuse the specified power rating with the maximum sound level that can be achieved. This is a function of BOTH the amplifier actually used and the sensitivity of the loudspeaker. Thus, a loudspeaker used with a 100 watt amplifier with a sensitivity of 97 dB (1 watt @ 1 meter) will achieve the same maximum output as loudspeaker used with a 200 watt amplifier with a sensitivity of 94 dB (1 watt @ 1 meter).

Loudspeaker drivers, particularly compression drivers, can usually withstand momentary power peaks well in excess of those they are subjected to in EAW’s power handling testing. Some very dynamic audio signals have high momentary peak levels such as from percussion instruments. Some audio signals, such as speech, have large moment-to-moment variations in levels. To fully exploit the peak capabilities of the loudspeaker and to avoid amplifier clipping, an amplifier larger than the power rating may be needed to reproduce the peak levels in the audio signal.

For audio signals with low dynamics, such as heavy metal rock or highly compressed music, an amplifier with a rating at or below the power handling specification might be needed to avoid overstressing the loudspeaker’s thermal capabilities.

On the other hand, a loudspeaker rated at 500W continuous (or RMS, continuous, etc.) might be used to reproduce background music at low levels. In this case, perhaps only a 25 watt amplifier would be needed to reach the desired acoustic level.

Thus, the power amplifier size actually required for a given application may be considerably more or considerably less than the amplifier wattage specified as the power handling.

As a rule of thumb, where the full capability of the loudspeaker is needed to achieve appropriate acoustic output levels, EAW recommends an amplifier that is twice the loudspeaker’s power handling specification. This assumes that its operation can be properly controlled (See Section 3). This allows the amplifier to reproduce peaks 6 dB above the specified power handling. This is consistent with both the test signal and the amplifier output capabilities used for EAW’s power handling test. However, this recommendation does NOT guarantee trouble-free operation. That is the next issue discussed.

PREVENTING LOUDSPEAKER DAMAGE

Preventing damage to or failure of a loudspeaker is not a function of amplifier size nor the loudspeaker’s power rating. Preventing damage is a function of operating an audio system so that a loudspeaker is not stressed beyond its limits. If an audio system is operated improperly, damage to or failure of a loudspeaker can occur even with an amplifier sized well below the loudspeaker’s power rating. Contrarily, if an audio system is operated properly, damage to or failure of a loudspeaker can be avoided even with an amplifier sized well in excess of the loudspeaker’s continuous (or RMS, average, etc.) power rating.

Discussion:

Proper audio system operation includes being aware of the types of audio signals being reproduced, controlling output levels accordingly, and operating all electronic equipment so that no electronic clipping occurs within the signal chain. Examples of improper operation include:

1. Sustained microphone feedback

2. Applying equalizer boosts at frequencies beyond the operational range of the loudspeaker.

3. Applying excessive equalizer boosts within the operational range of the loudspeaker.

4. Allowing electronic clipping anywhere in the electronic chain including the mixing console, signal processing equipment, or the power amplifiers.

5. Allowing loudspeakers to be “pushed” to a point of obvious distortion.

6. Reproducing sustained tones, like synthesizer notes, at full amplifier output. Each of the foregoing examples can easily result in damage to or failure of a loudspeaker regardless of the loudspeaker’s power rating or the size of the amplifier used. It is the responsibility of the audio system operator to ensure that all equipment in the system is operated within its capabilities. That is the only way to ensure that loudspeakers do not get stressed beyond their limits to the point of damage or failure.

APPENDIX: ABOUT LOUDSPEAKER “POWER”

Power tests done by EAW and, for that matter, most professional loudspeaker manufacturers, are not really power tests but voltage tests. The quantity invariably measured for such tests is the RMS or average voltage of the input signal. Power is calculated from this number using the traditional formula:

Power = voltage squared / nominal impedance

However, the result calculated from this rarely has a basis in reality because of the following reasons:

1. The nominal impedance is rarely equal to the actual impedance of the loudspeaker. In fact, a typical loudspeaker’s impedance usually varies considerably over its frequency range.

2. The loudspeaker is usually a reactive load. This means it behaves, depending on the frequency, as both an inductor and capacitor. Voltage and current are not in “sync” in reactive loads, so the actual power cannot be calculated without knowing what the phase angle is between the voltage and current. This must be included this in the power equation so it becomes:

power = (voltage squared x cosine phase angle) / impedance

Unless this formula is used to calculate the power for each frequency within the operating range, the total power calculated will not be correct. Usually only one out of the four terms in the above equation is measured, and that is the voltage. If only one term is known, you cannot solve this equation.

The bottom line is that for a given power specification at a given “nominal” impedance, the voltage is the same whether you are looking at a loudspeaker or amplifier specification. For example: for 200 watts at 8 ohms, the test voltage would be 40 volts RMS whether this refers to an amplifier or loudspeaker.

In effect the power ratings we use in audio are merely surrogate numbers for what is actually measured – voltage. However, power ratings are perfectly fine to use as a matter of accepted convention and convenience for purposes of comparing different amplifiers and different loudspeakers. Just keep in mind that, scientifically, they do not represent the actual power into a loudspeaker.

courtesy EAW

___________________________________________
David McLain Remote Tech Director CCI SOLUTIONS
Be seen. Be heard.

PO Box 481
/ 1247 85th Ave SE
Olympia, WA 98507-0481

Voice: 800/426-8664 x255 / Fax: 800/399-8273
email: dmclain@ccisolutions.com
online: www.ccisolutions.com
blog: www.churchsoundguy.com
facebook: dmclain@ccisolutions.com
twitter: twitter.com/churchsoundguy
podcast: http://www.ccisolutions.com/podcast
Clearance Bin: http://www.ccisolutions.com/clearance


New Digital Console (and some announcements)

if you email me directly (dmclain@ccisolutions.com), I can send you the PDF's of the announcements, including preliminary pricing. - David


Meet the newest member of the VENUE live sound family — the VENUE SC48 console.

SC48 is the definitive, all-in-one live sound solution, combining all I/O, digital signal processing, and tactile control into one compact console, making it the most affordable and portable VENUE system yet. SC48 features the hallmarks for which VENUE is known, including amazing sound quality, performance, and reliability, offers a built-in Pro Tools LE® interface, and introduces several new workflow innovations, making it the perfect console for small to medium-size clubs, houses of worship, theatres, and corporate events.

Please note: new price books, sales materials and user guides on the new VENUE SC48 will be available to you after the official product launch, which is scheduled for May 6, 2009. We will contact you about these shortly. You will also be able to find new materials on the customer facing website http://www.digidesign.com/ starting May 6, 2009.

PLUS:

New VENUE D-Show 2.8.1 Software Upgrade

VENUE customers can now gain even more flexibility and ease of use with the new VENUE D-Show® 2.8.1 software. This latest version introduces several new workflow innovations, adds popular user-requested features, and offers many enhancements to increase workflow and mixing efficiency for all VENUE system users—especially for monitor mix and theater engineers. Please review attached channel announcement for details. D-Show 2.8.1 will be available June 1, 2009.

PLUS:

VENUE Live Sound Line Gets Rebranded

In an effort to streamline the VENUE live sound offerings and make it easier for our customers to understand how all of the components relate, Avid has rebranded the names of all VENUE components and systems as listed in the chart below.

Please be sure to refer to VENUE systems and individual components by these new names when speaking with your customers. “VENUE” is the brand name for the entire live sound product line — all part numbers, configurations, and prices remain the same.

Old Name

New Name

Description

VENUE Components

D-Show®

VENUE D-Show®

New name refers to the expandable console component as a whole; individual components include:

· VENUE D-Show Main unit

· VENUE D-Show Sidecar

D-Show Profile™

VENUE Profile™

Compact console component

FOH Rack

VENUE FOH Rack

DSP and local I/O component

Stage Rack

VENUE Stage Rack

Remote I/O component

Mix Rack

VENUE Mix Rack

Integrated remote/local I/O and DSP component

D-Show® software

VENUE D-Show® software

Common software platform across all VENUE systems

VENUE Systems

D-Show® Main and Sidecar System

VENUE D-Show® System

Includes the following components:

· VENUE D-Show Main unit

· VENUE D-Show Sidecar

· VENUE FOH Rack

· VENUE Stage Rack

· VENUE D-Show software

D-Show Profile™ System

VENUE Profile™ System

Includes the following components:

· VENUE Profile

· VENUE FOH Rack

· VENUE Stage Rack

· VENUE D-Show software

D-Show Profile™ Mix Rack System

VENUE Mix Rack System

Includes the following components:

· VENUE Profile

· VENUE Mix Rack

· VENUE D-Show software

n/a

VENUE SC48

New all-in-one system combines all I/O, DSP, and tactile control into one compact console. Includes D-Show software.




_______________________________________
David McLain | Professional Nerd | CCI SOLUTIONS
Be seen. Be heard.

PO Box 481
/ 1247 85th Ave SE
Olympia, WA 98507-0481

Voice: 800/426-8664 x255 / Fax: 800/399-8273
email: dmclain@ccisolutions.com
online: www.ccisolutions.com
blog: www.churchsoundguy.com
facebook: dmclain@ccisolutions.com
twitter: twitter.com/churchsoundguy
podcast: http://www.ccisolutions.com/podcast
Clearance Bin: http://www.ccisolutions.com/clearance