Applications Tip: Compressor vs. Loudspeaker

Applications Tip: Compressor vs. Loudspeaker
Here is a common complaint made by the owner of a
damaged loudspeaker: "How could I have blown a
loudspeaker? I have a compressor!" Unfortunately, while
compressors and limiters help prevent audio transients
from causing clipping or possibly damaging a loudspeaker,
high-level transients are not the only cause of damaged
loudspeakers. In fact, over-compression of the audio signal
can contribute to premature loudspeaker failure.
It is standard practice to use an amplifier with a power
rating at least twice the loudspeaker’s continuous power
rating (e.g. use a 200 watt amplifier for a 100 watt
loudspeaker). The extra headroom afforded by the larger
amplifier allows for peaks in the program material to be
delivered to the loudspeaker without clipping. The majority
of the amplifier power goes largely unused since the
average level of an uncompressed audio signal is
considerably lower than the peaks. Highly compressed
signals have an average level much closer to the peak
level. If the level of the compressed signal is raised to take
advantage of the additional amplifier power (thereby
making it louder for the audience), the average power
delivered to the loudspeaker may be more than the
continuous power rating of the loudspeaker, overheating
the loudspeaker’s voice coil and causing failure.
As with all audio processors, using a compressor
does not eliminate the need for proper system operation.
Though a compressor or limiter is essential for reducing
transient peaks, excessive compression is the enemy of
the loudspeaker.

Limiters

A limiter functions in much the same way as a
compressor, differentiated more by its application than its
operation. Similar to a compressor, a limiter also reduces
signals that pass a threshold by a certain ratio. The ratios used
by limiters, though, tend to be much greater than those used
by compressors. Typical limiter ratios can range anywhere
from 10:1 to ∞:1 (infinity:1, where the threshold setting dictates
the maximum signal level). The goal of
a limiter is usually system protection, by preventing transient
audio peaks from causing distortion further up the audio chain
or, worst case, damaging loudspeaker components. Typically,
limiter threshold settings are also much higher than on
compressors; low threshold settings on a limiter lead to excess
compression. Limiters also share other parameters with
compressors, including attack and release.

Graphic Equalizers

 The most common equalization tool for sound
reinforcement is the graphic equalizer. A typical graphic
equalizer consists of a bank of sliders (or faders),
corresponding to specific frequencies, which can cut or
boost the chosen frequency. The center
frequencies of these filters are identical for all graphic

Poor Speech Intelligibility

Bad acoustics and/or an inadequate sound system can
make speech difficult to understand. Everyone can hear
the preacher, but most can't understand, or at best have
to strain to understand. The result is wandering attention
to the message and poor communication between
the praise and worship team and the congregation.
Worshippers feel isolated from the mass; their understanding
of the message, lessons, and announcements
is hampered and their participation is more distant.
This can directly impact attendance and contributions
to every phase of parish life

Acoustics

The Acoustics Are Bad And Expensive To Fix
Bad acoustics can make music sound bad and require
a more expensive sound system. When this is the case,
music will never sound good until the acoustics are
fixed, often at great cost and with a big mess during
construction.

The Acoustics

• Fine sound systems can often be made invisible if the
consultant and the architect work together.
• It is always cheaper and better to do it right the first
time.
• If budgets are limited, it is far better to have the design
work done correctly and defer the purchase of
options such as an organ or a sound system.
• Acoustic and sound system consultants are good
insurance against serious problems later on.
• Acoustics and sound system design are applied
physics, not “black magic.” Poor acoustics and sound
system performance means either that the design
team made mistakes or their recommendations were
not properly implemented.
• Good acoustics rarely happen by accident. Poor
acoustics are a far more likely result when there is no
consultant on a project.
• No sound system can remove reverberation from a
space. If contemporary music will be part of the worship,
reverberation must be carefully controlled.
• Contemporary music and traditional European music
make very different and conflicting demands on
room acoustics. It is quite costly (and often impractical)
to provide a workable acoustic environment for
both forms in the same space.
• Any architect who knows anything about acoustics
will hire a good acoustic consultant for any church
or other large space. The opposite is also true — any
architect who doesn't hire a good acoustic consultant
for these spaces thereby demonstrates his
incompetence.
• Some of the worst acoustic environments I've ever
experienced were designed on the advice of an organ
builder. Not only were they nearly impossible for the
spoken word, they were awful for for the choir, congregational
singing, and other musical components
of worship.

Acoustic consultants

Acoustic consultants work with churches and their
architects to provide an acoustic environment that fits
their form of worship. When a church is being built
from the ground up, this means helping determine
the size and shape of the worship space, as well as the
choice and placement of finishes and furnishing within.
It also means looking over the design of mechanical
systems and room layouts to insure that the church is
quiet and free of interfering noise. If the church building
already exists, it may mean major rebuilding and/or
refinishing of the worship space.

Getting the Acoustics and Sound System Right

The factors that make for good sound in a church need
to be built into the design from the beginning. Since
the acoustics of a space are so highly dependent on its
shape and finishes, improving the acoustics after the
building is completed is often a very expensive proposition.
Having the proper loudspeaker and microphone
systems installed in the right place is fundamental to
good sound system performance. If the architect has not
provided for the right loudspeaker system in the original
building design, the congregation has to make a
choice between looking at ugly loudspeakers that work
well, not seeing loudspeakers that don't, or spending a
lot of money to hide them after the fact.
Not all churches need the same kind of acoustic
environment. Good acoustics for one congregation
may be unsatisfactory for another. A Gothic structure
is a wonderful environment for a congregation whose
normal liturgy is rooted in European music and Gregorian
chants, if it has a good sound system to make
speech intelligible. The same church would be unusable
for contemporary Christian music, and wouldn't work
very well for a jazz mass or a choir in the contemporary
gospel tradition.

Sound Systems as Problem Solvers

Well-designed sound systems can help overcome
acoustic problems and enhance the worship experience.
To work well, they must work hand-in-hand with
room acoustics. They are used in churches in three
basic ways.
1. Sound systems make sound louder, so that a weak
voice or musical instrument can fill the church without
great effort. They can reach into distance seating
areas such as those in and under balconies where
worshippers would otherwise feel isolated or have
difficulty hearing.
2. Sound systems can provide speech intelligibility in
spaces that would otherwise be too reverberant. The
right kind of sound systems can eliminate the acoustic
conflict between music and speech by bringing
amplified speech more directly to the listener
without allowing it to bounce around the walls of the
worship space in an uncontrolled way. The church is
still reverberant; its acoustics can support traditional
church music that demand reverberation. The sound
system provides an additional means of controlling
the sound. Music which needs reverberation does
not utilize the sound system, taking advantage of the
acoustics of the room.
3. Sound systems can sometimes allow contemporary
music to be effective in an environment than would
otherwise be too reverberant. They do this in the
same way that they control speech — by controlling
the amplified sound, carefully focusing it on listeners
rather than allowing it to be turned into reverberation
by the acoustics of the space. Sound systems
that will be used for contemporary music need to
be capable of providing the naturalness, impact and
dynamics the form requires.

LCR Panning – an introduction to three-channel live systems

There is stereo panning and there is LCR panning. So what’s the difference and why would you want to
choose LCR panning? After all, it adds quite a cost to a console and stereo is stereo right?
Well, not really. Let’s just remind ourselves that Stereo panning simply adjusts the amount of signal
sent to the left and right outputs. The actual mix output may not be totally stereo, and probably
includes a high degree of spoken words as well as singing which is mono. This is particularly true in
Dramatic performances and Houses of Worship, and being able to pan voices to their true stage
position can be difficult in straight stereo. This is because we are always balancing the voices between
the left and right speaker positions. Some voice will always come out of both speakers unless panned
hard one way or the other.

Although monitor engineering is often thought of as subordinate to handling the FOH sound, in reality it's at least as important.

To create a musical performance, two things have to happen: your audience needs to hear you, and you need to hear yourself. If you can't hear yourself clearly, how will you know that you're playing or singing well? In purely acoustic music, being able to hear oneself is often taken for granted. But there are situations where this doesn't happen as it should. For example, in an orchestra performing on stage, each musician needs to hear his or her own instrument clearly and distinctly from the other instruments around them. But sometimes the acoustics on stage make this difficult. Suddenly, one's ability to perform well has been diminished severely by the inability to hear one's own playing.

The same applies to amplified music. In the early days of pop and rock bands it was common to provide only front-of-house (FOH) amplification, commonly mixed from the stage by a member of the band (who, of course, couldn't hear the FOH PA properly). Although many exciting performances (and undoubtedly many distinctly unexciting ones) have been given in this way, the fact is that no-one is properly in control of what the audience hears. The one advantage is that the band can angle the speakers and set their levels so that they can hear themselves and each other reasonably well, most of the time.

Fortunately, progress has been made and we now recognise that it is essential to have the mix position at front-of-house, placed centrally amidst the audience area. The FOH engineer is now ideally placed to control the sound the audience hears. The problem now is that the band are no longer in any kind of control whatsoever of what they hear. Clearly, in an ideal scenario, there should be a completely independent system to provide the band with crystal clear sound so they can hear their own individual performances and the overall sound of the ensemble. This is what stage monitoring should provide.

Stage monitoring is taken very seriously by top professionals, and should be by anyone working in live performance, right down to pub gig or theatre foyer level. Good monitoring consists of having the right equipment, suitable for the nature of the venue and performance, setting it up well and, of course, operating it effectively.

Above all, musicians need to feel that they are making great sounds. If they feel that the performance is good, the performance will be good and the audience will go away whistling the tunes. Also, performers need to feel secure. Security comes from knowing what the other band members are doing, knowing where they are in the song, and being certain that the notes and rhythms they are playing fit in with the rest of the band.

So let's imagine you're the lead singer of a band. The lead singer needs to feel that his or her voice is strong, in tune, and communicating emotion to the audience. Clarity and good tone of voice are paramount. Also, the lead singer needs to hear the band, so that they know they are in tune and are fully comfortable that the band are following them precisely. If the band are playing to a click track or a recorded backing, strict tempo will be an issue and the lead singer may need the band to be more emphasised in the foldback, since now everyone has to follow the click (even though only the drummer would normally hear it) or recording; the band cannot follow the singer.

The other band members have their own individual requirements, but in general they also need to feel that they sound great. They need to hear the vocal, too, otherwise they might have a blank moment and forget whether they're in verse two or verse three (that's scary when it happens). They will also have a preference about which other instruments they need to hear most clearly, to feel as though they're 'gelling' with the rest of the band.

20 Tips On Mixing

20. Listen to your finished mix again the day after you've finished it, as your perception is likely to change after
resting your ears overnight. Also check the master recording on as many different sound systems as you can,
to ensure it sounds fine on all of them. Even then, save all your mix information and track sheets, including
effects settings, as you never know when you might want to try to improve on the 'final mix'!

20 Tips On Mixing

19. If a closemiked
sound seems unnaturally lifeless, but you don't want to add any obvious reverb, try an
ambience or early reflection setting to induce a sense of space. The shorter the reverb time, the easier it is to
move the treated sound to the front of your mix.

20 Tips On Mixing

18. If you are recording a primarily MIDIbased
track, try not to look at your sequencer display while mixing; the
visual stimulus interferes with your ability to make subjective judgements based only on the sound. If
necessary, close your eyes. Watching your sequencer progress through the arrange page can also give you a
false impression of how well the arrangement is working, which is why some composers prefer hardware
sequencers.

20 Tips On Mixing

17. In a busy mix, try 'ducking' midrange
instruments such as overdrive guitars and synth pads under the control
of the vocals, so that whenever the vocals are present, the conflicting sounds fall in level by two or three dBs.
Just a little ducking can significantly improve the clarity of a mix. Use a fairly fast attack time for the ducker
(which may be either a compressor or a noise gate that has ducking facilities), and set the release time by ear.
Shorter release times will cause more obvious gainpumping,
but in rock mixes, this can add welcome energy
and excitement

20 Tips On Mixing

16. Don't vary the level of the drums and bass unnecessarily during a mix, as the rhythm section is traditionally
the constant backdrop against which other sounds move. Natural dynamics within rhythm instrument parts is
OK, but don't keep moving the faders on these sounds.

20 Tips On Mixing

15. Check your mixes on headphones as well as speakers. Headphones show up small distortions and clicks that
you may never hear over loudspeakers. However, don't rely solely on headphones for mixing, for they
represent the stereo image differently to loudspeakers and are notoriously unpredictable at low frequencies.

20 Tips On Mixing

14. Don't monitor too loudly. It may make the music seem more exciting (initially), but the end user is unlikely to
listen at the same high level. High monitoring levels also tend temporarily to shift your hearing perspective and
can lead to permanent hearing damage. It's fine to check the mix loudly for short periods, but most of the time,
it's useful to try and mix at the level you think the music will eventually be played. (Forget I said this if you're
mixing dance music for nightclubs!)

20 Tips On Mixing

13. From time to time, check your mix balance by listening from outside the studio/bedroom door. This tends to
show up level imbalances more clearly than when listening from directly in front of the monitors. Nobody is
quite sure why, but it works.

20 Tips On Mixing

12. Compress the vocals to make them sit nicely in the mix. Few vocalists can sing at a sufficiently even level to
be mixed successfully without compression. Softknee
compressors tend to be the least obtrusive, but if you
want the compression to add warmth and excitement to your sound, try an optocompressor
or a hardknee
model with a higher ratio setting than you'd normally use. Be aware that compression raises the background
noise (for every 1dB of gain reduction, the background noise in quiet passages will come up by 1dB), and
heavy compression can also exaggerate vocal sibilance.

20 Tips On Mixing

11. If possible, fix problems by using EQ cut rather than boost. The human hearing system is less sensitive to EQ
cut than it is to boost. This is especially true if you are using a lowcost
equaliser or the EQ in your desk.