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1. Application Notes by
Haw-Renn Chen on Karaoke Scene Magazine
(Page 24, June/July 2001 Issue)
Title: Karaoke Equipment Guide for KJ's
By: Haw-Renn Chen, R&D Engineer, Audio2000'SÒ
KARAOKE EQUIPMENT GUIDE FOR
KJ’S
Why the karaoke equipment failed in the
middle of the shows? Why the sound from the
seemingly perfect system is not as promising as claimed in the product specifications? What factors you need to consider when you are
looking for the karaoke equipment for your next show or your next performance? All of these and a lot of other situations may
have puzzled, scared, and even angered quite a few performers, DJ’s, KJ’s, or
even you!
Then, what should we do to prevent the
above awkward situations from happening?
Well, it all goes with the understanding
and proper matching of the product characteristics and specifications. A typical karaoke
or DJ system generally consists of some microphones, a mixer, a power amplifier, and two
or more speakers.
First needed devices are, of course, corded and/or wireless microphones. For
microphones, we need to consider not only the sound quality of the microphone itself but
also the quality of the microphone cable. A
microphone cable with poor quality will substantially deteriorate the overall vocal sound
results. In general, the length of an
unbalanced microphone cable is better not to exceed 20 feet. A balanced microphone cable needs to be used if
you need to use a microphone cable longer than 20 feet.
A wireless microphone can be a UHF
(Ultra-High-Frequency) system or a VHF (Very-High-Frequency) system. In the United States here, a UHF system may
operate at 600, 700 or 800MHz. A VHF system normally operates at 200MHz range, except that
some systems may operate below 100MHz and be called a VHF system. Some wireless microphones are made to have the
capabilities of adjustable frequencies, which allow the users to adjust the operating
frequencies as needed (for example, if interference signals are encountered.). If feasible, try to get a wireless microphone with
multiple frequencies so that you can avoid interference headache down the road. Before you purchase a wireless system, remember to
check if that system is certified by FCC (Federal Communication Committee). A certified wireless system will have the FCC
certification number on the labels attached to the receiver and the transmitters. A wireless system without the needed FCC
certification not only violates the FCC regulations but also can potentially downgrade the
performances of the entire system by interfering the system setup with an unnecessarily
high radiation power, especially when the connection cables are not properly shielded.
A mixer is the one to mix vocal signals
and music signals from one or more music sources in specific ways as desired by the users. The music sources may be a DVD, VCD, CDG, CD,
cassette tape, phono, VHS or other type of player. It
is recommended to check the output specifications of each player, especially the output
level, and the input specifications of the inputs on the mixer and try to match them. If the output level from the player exceeds the
design specifications of the mixer inputs, you may have a distorted sound output. Be sure to use signal cables with appropriate
quality. A poorly made signal cable may cause
sound distortions and may pick up too much ambient noise. For karaoke applications, the
key-control feature and the microphone echo capability are commonly desired.
In-between the mixer and the speakers, one
or more of power amplifiers are required. The
power amplifiers may be stand-alone power amplifiers or built into a mixer case to form a
mixing amplifier unit. Since the amplifiers
are the ones outputting tons of energy to the speakers, they endure the most rigorous
conditions within all the sound systems. Therefore,
proper cares need to be taken to ensure that the amplifiers are operated properly. Then, what should we look for? First, do not overdrive the amplifier with
speakers having wattage rating way exceeding the power rating of the amplifier. Secondly, do make sure the effective speaker
impedance is above the lowest output load impedance of the amplifier. Thirdly, use appropriate gauges of speaker cables
between the amplifier and the speakers. Fourthly,
make sure the ambient temperature around the amplifier is cool and the hot air can be
vented properly, especially when the power amplifier does not have a built-in cooling fan.
It’s imperative to remember that an
amplifier is designed with a capability to supply a certain amount of power to the
speakers. Be sure to read the specifications
of the amplifier and the speakers to be driven by the amplifier. Normally, the amplifier and the speaker are rated
in both RMS and MAX (or PEAK) terms. The MAX
rating is typically about twice as high as the RMS rating.
Do pay extra attention to the RMS power rating, which indicates the
continuous power supplying capability of the amplifier.
The combined wattage of all the speakers connected to one side of an
amplifier can not be way too high comparing with the amplifier power rating, especially if
you try to use the speakers to its limit with big blasts.
The real wattage loaded to the amplifier is the sum of all the speakers
connected to the amplifier. For example, if
two 100W speakers are driven by an amplifier, the load to the amplifier is 200W , which is
the sum of two 100W: 100W + 100W.
Another important factor is the impedance. The impedance of all the combined speakers can not
be lower than the lowest output load impedance of the driving amplifier. Remember that the effective impedance of multiple
connected speakers is lower than the original single speaker impedance. If we connect two 8 Ohm speakers together, the
effective impedance of the connected speakers becomes 4 Ohms. If we connect three 8 Ohm
speakers together, the effective impedance of the connected speakers becomes 2.7 Ohms. The majority of the karaoke mixing amplifiers are
designed to have the lowest output load impedance at 8 Ohms, while some exceptional good units are designed to
have the lowest output load impedance at 3-4 Ohms. Stand-alone
power amplifiers are typically designed to have the lowest output load impedance at 2-4
Ohms. Some power amplifiers have an impedance
selection switch to allow users to select the output load impedance at 2, 4 or 8 Ohms. In this case, remember to set the switch at the
correct selection. Be always certain to keep
the effective speaker impedance above the amplifier lowest output load impedance!!
Speaker cables are important also. Try to use as thick the speakers as you can
conveniently connect and use to reduce the power loss in the speaker cables. As a rule of
thumb, use 16G speaker cables for the length up to 25 feet; use 14G speaker cables for the
length up to 50 feet and 12G speaker cables for 50 feet or longer. A better speaker cable can provide less power loss
and sound distortion. How to select good
cables, let’s discuss them next time. Additionally,
keeping the inside and outside of any amplifier cool is always a good practice. If you try to rack-mount an amplifier without a
built-in cooling fan, either place the amplifier on the top slot with a wide top opening
to vent the heat or, if the amplifier is not placed at the top slot, leave at least two
empty rack space over the top of the amplifier and use a fan blow the air above the top of
the amplifier horizontally. You may ask: an
amplifier with cooling fans is better or an amplifier without any cooling fan is better? It is objective to say that each one has its own
advantages in the considerations of conveniences and component reliability. However, the key is “taking good care of your
amplifier and you will get a nice working horse for you!”
Since speakers are the final stage of a
sound system, how to select the right ones are essential to the overall sound system
performances. A two-way loud speaker
consisting a tweeter and a woofer is the popular speaker arrangement. The woofer is generally a cone driven by a coil
and magnets and is used to deliver the sound at a lower frequency band. The tweeter can be
either a piezoelectric type or a compressor type with a replaceable diaphragm. A piezoelectric type tweeter is economical to
manufacture but, in the mean time, has the tendency to generate piercing sound. Also, a speaker with the piezoelectric type
tweeter does not need to have a built-in crossover circuit.
A speaker with a compressor type tweeter or horn needs to have a built-in
crossover circuit and delivers a transparent and smooth sound. Due to the structures as described above, a
speaker with the piezoelectric type tweeter is normally cheaper. The cost and the sound quality is what you need to
decide when you select your speakers next time.
The performance of a sound system is the
accumulated results of all the components involved. To
get the desired sound quality, all the components need to be selected and then connected
carefully. Any not-so-good component can
deteriorate the overall sound performance. Any
not-so-good connection can deteriorate the overall sound performance as well. Do not overlook the importance of the signal
cables and the speaker cables! Get to know
what you have or what you are trying to purchase. The
author welcomes your inputs and welcomes your message if you have something to discuss. Enjoy your sound system!
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2. Application
Notes by Haw-Renn Chen on Karaoke Scene Magazine
(Page 9, April/May 2002 Issue and
Page 9, June/July 2002 Issue)
Title: INTRODUCTION
TO KARAOKE SOUND SYSTEMS – PART I, MICROPHONES
By: Haw-Renn Chen, R&D Engineer, Audio2000'SÒ
Sound systems are normally small local audio systems. In general, there are four
categories of sound systems, including reinforcement sound systems, signal-storage
systems, reproducing sound systems and synthesizing sound systems. Reinforcement sound systems typically supplies
sound amplification in real time while the sound sources and the audiences are in the same
acoustic environment. Signal-storage systems
include cassette tape players, CD players, etc. Reproducing
sound systems direct and amplify sound from a signal-storage system. Synthesizing systems retrieve and amplify sound
from artificial sources.
Depending
on the user’s objectives and preferences, a karaoke sound system may comprise one or
more of the above four categories. Nonetheless,
the reinforcement sound systems are the major concern of the karaoke users due to the fact
that the karaoke singer’s performance and enjoyment on the stage is what the karaoke
is all about. The first link for a enjoyable
karaoke performance is, of course, the microphones being used. As a result, the correct selection of suitable
microphones or wireless microphones are not only the first step, but also the key to have
a successful karaoke show or karaoke joy.
How
can we choose the right microphones? First
thing to consider is how the microphones are to be used? Are they going to be beaten very
harshly by being used as drum sticks hitting
on the edge of a desk? If these microphones
are to be beaten very harshly, probably wireless microphones are not suitable and the
selected wired microphones should not be too costly to replace. Once the uses of the microphones are determined, a
proper budget is next task in the process of acquiring the right microphones. With the budget in mind, you may stand in front of
a salesperson or a microphone display soon. Oops!
What are those words right next to the displayed microphones? What is Impedance? What is Sensitivity? What is
Polar Response? They may not mean anything at
that moment except those dollar signs representing the prices of those microphones.
Before
we proceed to introduce the technical terms, let’s address some points first. Keep in mind: a more expensive microphone may not
be a better one. Compare the specifications
carefully and realistically because some manufacturers may be a little bit more realistic
(or in other words – less tendency to exaggerate their product specifications) in writing their product
specifications. Your ears (not what the
salesperson says or recommends) will be a determining judge also. Don’t hesitate to try the sound of different
microphones first. Decide by yourself which
ones have the sound quality you like. Select
some and purchase those that fit your budget.
The most frequently encountered microphone specifications include: Impedance, Sensitivity,
Max SPL, Frequency Response, and Polar Response.
Impedance is the most often used term in the microphones and sound systems. It is defined
as the total opposition an electric device offers to the passage of an alternating
electric signal. Probably this definition is
not clear enough. Let’s convert the
whole description into the daily understandable words!
The concept is that an electric signal will be generated from the microphone when
any sound is transmitted to the microphone. Depending upon how the electrical components
in the microphone were designed, these components inside the microphone will always have
the characteristics of resisting the generated electric signal to flow through and the
degree of the resistance is determined by the design.
The unit of the impedance is Ohms. The
higher the number of the Ohms, the higher the electric signal resistance. In general, any impedance below 1000 Ohms is
considered low impedance for the sound systems. For
a karaoke sound system, a low impedance microphone will be the right one to use. Normally, the readily available commercial
microphones have the impedance values from about 150 Ohms to 600 Ohms. Microphones with the impedance value of 600 Ohms
seem to be the most popular ones, especially in the economic microphone category.
Sensitivity of a microphone determines how sensitive the microphone is, electronically
(not emotionally!). When sound is transmitted
to a microphone, the level of the electric signal generated by the microphone is the
characteristics of the microphone sensitivity. The
higher the level is, the louder you will hear the output from the sound system. The unit of the microphone sensitivity is dB. On the microphone specifications, you will see
this dB numbers being negative numbers. These
numbers are from the mathematics magic, such as so-called “Logarithm”. Let’s ignore them for now. However, these negative numbers do mean something. The way to look at them is by removing the
negative sign and looking at the number. The
lower the number is, the higher the sensitivity is and the louder the sound you will hear
from your speaker. Sometimes (especially in
the professional applications), you may see the sensitivity is specified with the unit of
“mV/Pascal”. Don’t be panic!
It’s just another way of mentioning the sensitivity without the “Logarithm”
mathematics magic. When you see
“mV/Pascal”, it will be always without a negative sign and it will always mean
that the sound will be louder if the number is higher.
SPL stands for sound pressure level. Max SPL
defines the maximum sound pressure level that can be applied to a microphone without
induce some distortion. The max SPL unit can
be in dB, Pa, N/m2, dyn/cm2, or Bar.
Regardless what unit the max SPL is in, look for a higher number (the higher
the better).
The frequency response of a microphone indicates the range of the acoustic frequency that
the microphone can effectively convert into electric signals. The frequency response is specified with the unit Hz. A
wide frequency response range is what we are looking for.
The frequency response graph chart may be the best tool for you to determine the
sound quality of a microphone, if you know how to interpret the graph. The frequency response specification for a
microphone may be the most important factor for a karaoke system user. Unfortunately, a significant number of the
economic microphones have their specification data written unrealistically or
inaccurately. Don’t just look at the
numbers due to this situation. In reality,
the best way is to measure them by yourself (that’s what some professional sound
engineers do to determine the right microphones for them.).
However, it’s beyond most people’s capability. Your ears may be the best alternative!
The polar pattern of a microphone determines where the sound will be picked up by the
microphone. In general, a microphone can be
categorized as an omni-directional microphone or a directional microphone. An Omni-directional microphone will pick up sound
from all direction, without any preference to any particular direction. A directional microphone will pick up sound better
from sound sources at certain directions. There
are various types of the directional polar patterns.
The most frequently encountered directional polar patterns include cardioid,
super-cardioid, and hyper-cardioid. The
cardioid polar pattern looks like an apple or a tomato on the specification sheet. It’s not edible. This apple or tomato pattern
means that the microphone will pick up sound most effectively at the direction that the
microphone is facing (0 degree). The
effectiveness of the sound pickup by the microphone will be fading as the sound source
goes away from 0 degree. At about 130
degrees, the sound picked up by a cardioid microphone drops by 50%. At the direction opposite from where the
microphone is facing (180 degrees), sound won’t be picked up (totally rejected) by
the cardioid microphone. A microphone with
the super-cardioid pattern has a narrower pickup angle than the cardioid one, but the
super-cardioid microphone can pickup sound at 180 degree.
At about 115 degrees, the sound picked up by a super-cardioid microphone drops by
50%. Sound from sound sources at 126 degrees
will be totally rejected by a super-cardioid microphone.
Then, the sound started to be picked up by the super-cardioid microphone slightly
from 126 degrees up to 180 degrees where the sound can be picked up below 10% level. A microphone with the hyper-cardioid pattern has
an even narrower pickup angle than the hyper-cardioid one, but the hyper-cardioid
microphone will pickup sound more than the super-cardioid at 180 degrees. At about 105 degrees, the sound picked up by a
hyper-cardioid microphone drops by 50%. Sound
from sound sources at 110 degrees will be totally rejected by a hyper-cardioid microphone. Then, the sound started to be picked up by the
hyper-cardioid microphone slightly from 110 degrees up to 180 degrees where the sound can
be picked up at about 20% level.
Since
microphones are the first link of a karaoke sound system, it’s imperative that we
select right microphones that not only match our budget but also match the overall karaoke
sound system. Understanding what each part of
a karaoke sound system can do and will do is the key to set up an enjoyable and
satisfactory karaoke system. We are going to
exploit together the other parts of the karaoke sound systems (including players, mixers, amplifiers, speakers,
sound effectors, accessories, and system integration) in the future issues of this
magazine. See you then.
Haw-Renn Chen is an R&D engineer in
Audio2000’SÒ. He is also one of the
technical Audio2000’SÒ staffs in charge of writing the technical contents for the website www.audio2000s.com.
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3. Application
Notes by Haw-Renn Chen on Karaoke Scene Magazine
(Page 9, Aug./Sept. 2002 Issue)
Title: MIXERS
By: Haw-Renn Chen, R&D Engineer, Audio2000'SÒ
As we discussed previously, a karaoke system may comprise one or more of four
categories of sound systems, including reinforcement sound systems, signal-storage
systems, reproducing sound systems and synthesizing sound systems. The microphones, as the essential part of a
reinforcement sound system, were discussed in detail in the previous article. The sound equipment that the microphones are
normally connected to is called a mixer and this sound equipment, the mixer, is what we
are going to discuss in this article.
A mixer that is designed specifically for the karaoke applications is called a
karaoke mixer. The function of the karaoke mixer is to mix the signals from a number of
microphones with the back ground music from one or more music storage sources and to
process these mixed signals to present the uniqueness of a specific karaoke performance. Keep in mind; any karaoke show or performance may
be presented in many different ways depending upon the environment, the audience, the
occasions, and other factors. To achieve this
purpose, the skills of the karaoke hostess or host are important factor. The right selection of the karaoke equipment
sometimes may override the skills and becomes the dominant factor, as poor sound from
wrong equipment may not be converted to a nice sound just by the human skills alone.
Some brain researches have shown that different areas of the human brain are
activated by music and by language. Since all
the karaoke shows rely more on the recorded music and the lyrics on the display screen
than any other live performances, the karaoke audiences tend to process the karaoke
performances with more different brain areas in the music and language fields than the
other live performance audiences do. As a
result, the karaoke mixers, as the brain of a karaoke system, need to be designed and
tuned to fit the unique situations of the karaoke performances.
Then, how do we select the right
karaoke mixer? The level of the karaoke mixer
performance is the first consideration. The flexibility of the karaoke mixer is the second
consideration. The budget is the third consideration.
Then, the other means
associated with the karaoke mixer to be used is the fourth consideration.
The level of the karaoke mixer
means the sound quality and the features of the karaoke mixer. The sound quality, of course, needs to be: the
higher sound quality the better. But, how do
we determine what kind of sound is good? It
may be summarized as: transparency, low noise and adequate amplification.
Transparency is the measure of
how close the sound output from the karaoke mixer is to the original sound. On the specification sheet, we need to look for a
wide frequency response and a low T.H.D. (total harmonic distortion). The wider frequency response is better and the
lower T.H.D. is better.
Noise, as its name implies,
indicates how noisy a karaoke mixer is. As
easily agreed by everybody, the criterion for the karaoke mixer noise is: the lower the
better. On the specification sheet, we need
to look for a high S/N (signal to noise) ratio. That
means: the higher the S/N ratio number is, the better.
The amplification is typically
called gain. It’s normally expressed in
dB. It plays an important role in determining
the overall performance of a system. Since it
is normally not expressed on the data sheet and it is much more technical than the other
terms, let’s rely on the manufacturers for now.
In the future discussions, we may come back to this issue from time to time.
As we mentioned previously, if we
don’t have adequate testing setups to verify how real are those numbers printed on
the data sheet, do not just rely on the specification sheets. The most readily available
test devices are your ears and your feeling. Listen
to various karaoke mixers or other audio mixers and you may surprisingly find out how
different in your own mind are those devices you have tested by your ears and feeling
alone. However, we need to remember that the
environment that a karaoke mixer is tested by our ears may have some bias, and may not be
objective enough. In the system integration
discussions, we may need to discuss some of the environment and setup issues.
The flexibility of a karaoke
mixer indicates the features that are not to be used immediately but have the potential to
be helpful and useful in your future karaoke performance and shows. As it has been for a while, the echo volume, echo
delay, echo repeat and music key control have been the standard features to most of the
karaoke mixer users. Is the feature of
applying key control to the microphone inputs going to be useful? Who knows! Would
it make sense to have it included in your next karaoke mixer just to exploit your future
performance effectiveness? This is what we
mean by flexibility. This flexibility issue applies to other section of sound systems
also, such as amplifiers. We will come back
to this issue from time to time in the future discussions as well.
The term “budget” is so
personal that people normally don’t discuss this in public. Since this article is for everybody, we need to
follow the social tradition and seal our pen for a while…… Nonetheless, we still want to say:” utilize
the budget effectively to get the most with the least expense.”
The other means associated with
the karaoke mixer to be used includes the karaoke hardware and the karaoke software. In the situation that you don’t want to carry
too many equipment around, you may consider a karaoke mixer with a built-in amplifier or
even a karaoke mixer built-into an all-in-one karaoke system. In the situation that the karaoke mixer is going
to be used mainly at home, you may consider to have a karaoke mixer connected to a
receiver at home and have the home stereo system integrated properly into the karaoke
system or vice versa. In the situation that
your song or CD collections tend to be in the soft side, you may want to have a karaoke
mixer being able to provide strong and exciting moments. There are many other various
situations. You need to plan in advance and
choose the right choice for your karaoke show, karaoke
performance, and karaoke joy!
All in all, the karaoke mixer is
the brain and the planner of your entire karaoke system.
Its characteristics and features will determine the overall performance of
your entire karaoke system. You need to know what you need and select the right karaoke
mixer for you. After you have acquired one,
maintain it, the karaoke mixer, properly.
Haw-Renn Chen is an R&D engineer in Audio2000’S Ò. He is also one of the technical Audio2000’SÒ
staffs in charge of writing the technical contents for the website www.audio2000s.com.
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4. Application
Notes by Haw-Renn Chen on Karaoke Scene Magazine
(Page 9, Oct./Nov. 2002 Issue)
Title: AMPLIFIERS & LOUDSPEAKERS
By: Haw-Renn Chen, R&D Engineer, Audio2000'SÒ
Amplifiers
and loudspeakers are normally the last stage of a karaoke system. An amplifier is a device
which converts a line input signal into a greater output signal powerful enough to drive a
set of loudspeakers. A loudspeaker is an
electroacoustic transducer which converts the electrical signal from an amplifier into the
acoustic power to the audience.
One
of the most important features of an amplifier is the average power rating in watts. This average power rating implies how much
acoustic power can be generated from the speakers driven by the amplifier. A peak power rating is twice as high as the
average power rating due to the root mean square calculation. Any other claimed power rating which may imply a
number higher than the peak power rating is unrealistic.
The
loudspeakers that are driven by a power amplifier must have total rated average power
consumption equal to or lower than the average power rating of the driving power
amplifier. The total rated average power
consumption of the loudspeakers is determined by adding the rated average power
consumption of each loudspeaker. The same
rule applies to the rated peak power.
Based
upon the calculation of the average power rating and the amplifier output signal
amplitude, the lowest value of the amplifier output load impedance is determined. The effective impedance of a loudspeaker must be
higher than the lowest value of the amplifier output load impedance to prevent damage to
the amplifier or sound distortion. The
typical lowest values of the amplifier output load impedances are 8 Ohms, 4 Ohms or 2
Ohms. For a professional power amplifier,
the capability to drive a 2-Ohm load is a basic requirement.
As
we discussed in the previous article, the
effective impedance of connected speakers is lower than the original single speaker
impedance. For instance, if we connect two
8-Ohm speakers together, the effective impedance of the connected speakers becomes 4 Ohms.
If we connect three 8-Ohm speakers together, the effective impedance of the connected
speakers becomes 2.7 Ohms. Keep in mind that
it is always a good practice to maintain the above impedance-matching guideline regardless
which types of amplifiers and speakers are to be used.
The
interconnection cable between the amplifier and the speaker needs to be adequate to reduce
the degree of power loss from the amplifier to the speaker.
For the general speaker cable selection guidelines, please refer to the
previous articles for details.
Once
the electrical power is transferred from the amplifier to the speaker through the speaker
cable, the type of the speaker really plays an essential role in converting the electrical
power into the acoustic power. The
loudspeakers used the most in the karaoke performances contain the following component
devices: cones, compressor drivers and horns. The
cones are widely used to produce low-frequency power. The compressor drivers are used to
generate the high-frequency acoustic power. The
horns act as acoustic transformers and are coupled with the compressor drivers to
significantly increase the acoustic conversion efficiencies. The improvement in the acoustic conversion
efficiencies results in higher loudspeaker efficiencies such that the acoustic power can
be delivered to a wider area.
The
cones and the coupling of the horns to the compressor drivers produce different band of
acoustic frequencies and hence crossover networks are normally needed in loudspeakers for
optimal acoustic performances. Although
there are various loudspeaker designs, the loudspeakers with a compressor driver horn and
a cone may be the best selection for the karaoke performances. The technical considerations on how to determine
good crossover networks, compressor drivers and horns, and cones are the keys to have
excellent loudspeakers, however, they involve too many technical/mathematical jargons and
are beyond the scope of our discussions.
If
a karaoke show is to be held in a very grand fashion, a biamplification arrangement can be
achieved by placing an active crossover between the karaoke mixer and two power amplifiers
in a way that one power amplifier drives the low-frequency loudspeaker and another power
amplifier drives the high-frequency loudspeaker. This
arrangement can have much cleaner acoustic results than the above loudspeaker and
crossover network arrangement. However, this
biamplification arrangement is more costly and difficult to set up than the loudspeaker
and crossover network arrangement.
In
a karaoke system or any sound system, the power amplifiers and the loudspeakers are
responsible for the overall power conversion tasks and, hence, are enduring the harshest
conditions in the karaoke system or the sound system.
Great deal of care needs to be taken to prevent the conditions of overload,
overheat and other adversary situations that may render the power amplifiers and the
loudspeakers at risk of being damaged. Do
treat a power amplifier as a heat generator. Use
common sense to have the heat removed from the location of the power amplifier
effectively. Try not to place any power
amplifier in an area with stagnant airflow conditions.
Once the power amplifier you use in a karaoke show encounters overheat
conditions, it’s the end of your show. If
this happens, it is not the power amplifier’s fault.
You need to blame whoever causes the power amplifier to be overheated.
The
power amplifiers and the loudspeakers are pieces of acoustic art. We may not realize we encounter these pieces of
acoustic art daily in the cars, in the nightclub and bars, in the malls, at home, and
everywhere. Think about it – they do
become part of our life. Let’s take a
moment to appreciate the results of such acoustic pieces.
It’s the author’s hope that the above content may be just a
beginning for us to look at the power amplifiers and the loudspeakers at various angles. The more we exploit the power amplifiers and the
loudspeakers, the more we can utilize them effectively in the environment we want and the
more we can enjoy the entertainment results from these pieces.
Haw-Renn Chen is an R&D engineer in Audio2000'SÒ. He is also one of the technical Audio2000'SÒ staff in charge of writing the technical contents for the website
www.audio2000s.com.
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5. Application
Notes by Haw-Renn Chen on Karaoke Scene Magazine
(Page 9, Dec. 2002 / Jan. 2003
Issue and Page 9, Feb. / Mar. 2003 Issue)
TITLE: KARAOKE SOUND SYSTEMS AND ACOUSTIC
ENVIRONMENT
By:
Haw-Renn Chen
When a sound system is to be installed or to be
used, the acoustic environment that the sound
system is to be used therein plays a significant role in determining the results to be
generated by the sound system.
A carefully selected sound system can
deliver the expected results ONLY when the sound system users understand the acoustic
environment they are encountering and arrange the sound system in the environment
correctly and accurately.
Since a lot of the DJ’s and/or the
karaoke jockeys have their mobile shows move from one location to another all the time, it
won’t be a surprise to hear that a great percentage of the DJ’s and the karaoke
jockeys complain about some of their poor show results.
If you happen to have occasional poor
karaoke show results, do not blame the sound system right away. Some adjustment of your sound system arrangement
to fit the acoustic environment may be the answer. But
how?……
First, we need to know what the karaoke
sound system is for. A karaoke sound system
is an electrical unit for amplifying the voice from one or more persons and the music
stored in a media and delivering the amplified sound to a desired area where the audience
groups are gathered. The locations of the
loudspeakers are the sources of the amplified sound.
The amplified sound will be transmitted from these sources. As the amplified sound transmits farther, the
sound pressure or the sound loudness will be reduced further. How much loudness and clearness of the amplified
sound at certain location is entirely depending upon the sound pressure/quality delivered
by the speakers and the surrounding environment.
Secondly, we need to define the acoustic
environment. An acoustic environment is the
general acoustic characteristic factors of a designated area. The general acoustic characteristic factors
include the ambient temperature, time of a day, humidity, air composition, wind velocity (speed and direction), wind velocity
variation, ground configuration, ground
material, and the material and configuration of all the objects above the ground.
In order to analyze the acoustic
environment, we can do the quantitative analysis or the qualitative one. As the quantitative analysis takes very much
discussion time and space, we just need to know that a group of physicists have developed
various theories and applications of acoustics with the three-dimensional partial
differential equations, called wave equations, since the late nineteenth century. In the early twentieth century, a group of
physicists and sound engineers developed further application know-hows with the empirical
equations and calculations, which further enhance the acoustic application capabilities we
have today. As a result, we will depend
solely upon the qualitative analysis.
Sound travels at the speed of about 1,100
feet per second. The sound speed will be
increased if the ambient temperature is raised. When
the ambient temperature is lowered, the sound speed will be reduced. Therefore, sound emitted from a sound source
located on an area with the ground temperature warmer than the air temperature will be
bent upwards as the sound speed at the lower air layer is higher than the sound speed at
the higher air layer. When the ground
temperature is cooler than the air temperature, sound
emitted from a sound source in the area will be bent downwards.
Based upon the above observation, the
loudspeakers are better to be placed higher than the audiences in the karaoke shows to be
held in the early morning, late at night or whenever the ground temperature is lower than
the air temperature. If the ground
temperature is higher than the air temperature, such as at noon with clear sky and burning
sunbeam, the loudspeakers are better to be placed at the lowest ground of the show area
and let the audiences be seated at the higher ground area.
Since the audiences may block the sound transmitted from the loudspeakers,
it may be a good practice to have the loudspeakers be higher than the height of the
audiences sitting on the first few rows.
Sound will be attenuated by the air and
the degree of attenuation depends upon the relative humidity of the air. The higher the sound frequency is, the higher the
sound will be attenuated. Also, the higher
the relative humidity is, the lower the sound will be attenuated. For instance, a highly directional sound beam with
frequency of 1,000 Hz will travel about 1,200 feet before the sound pressure drops to one
half level at 20 percent relative humidity and
70 degree Fahrenheit. The same 1,000 Hz
highly directional sound beams will travel about 2,500 feet before the sound pressure
drops to one half level at 80 percent relative humidity and 70 degree Fahrenheit. If the sound frequency is increased to 5,000 Hz, a
highly directional sound beam will travel about 70 feet before the sound pressure drops to
one half level at 20 percent relative humidity and 70 degree Fahrenheit. The same 5,000 Hz
highly directional sound beams will travel about 230 feet before the sound pressure drops
to one half level at 80 percent relative humidity and 70 degree Fahrenheit. At 10,000 Hz, a highly directional sound beam can
travel only 30 feet and 60 feet at 20 percent relative humidity and 80 percent relative
humidity respectively before the sound pressure drops to one half level.
Consequently, the high attenuation rate of
the sound in dry air (low relative humidity) at the high frequency sound band is a
consideration for projecting the karaoke show results, especially in the California desert
climate. Be preparing for the audiences
sitting at the farther locations to hear less of the high frequency sound.
The air composition does affect the sound
attenuation also. Generally, the oxygen
component contributes a great deal in attenuating the sound level. The sound level attenuation by the air is higher
for higher sound frequency. A highly
directional sound beam at 1,000 Hz can travel about 2,000 feet before the sound pressure
drops to one half level. A highly directional
sound beam at 10,000 Hz can travel only about 120 feet before the sound pressure drops to
one half level. The end results are the same as the effects of the humidity as discussed
above.
Based on the calculation in the
thermodynamic theories, the wind blowing toward the sound source can cause the imaginary
vertical temperature gradients such that the sound beam from the sound source will be
refracted upwards. In the same token, the wind blowing away from the sound source can have
the sound beam from the sound source be refracted downwards. The higher the wind speed is, the greater degree
of the sound beam upward or downward refraction will be.
As a result, it is advisable that the sound system used in a karaoke show is
placed at a location so that the audiences will be sitting at the down-wind locations in
order to have the sound beam from the loudspeakers refracted downwards toward the ears of
the audiences.
Wind speed and direction variations with
elevation can also cause the sound beams to bent. This
may not be a great concern to a regular karaoke show.
For a grand size outdoor show or performance, these wind velocity variations
with elevation will be another factor to consider.
Ground configuration is a measure of the
elevation and contours of the ground. If the
ground level is flat, it simplifies the situation slightly.
If the ground is not flat, you need to be very careful in selecting the
location of the sound system for your show and the locations where the audiences are to be
seated. Try to select a location for your
sound system such that the loudspeakers are able to project their full sound power to
every corner where your audiences may sit or stand. In
general, it may be to your advantages to select the lowest location for the sound system
and to arrange the audiences at the locations over the upward slope. Then you can place the loudspeakers at appropriate
heights and directions to cover all the audiences in both the situations of a cooler
ground or a warmer ground. Try to avoid
having the audiences be located in a downward slope away from the loudspeakers.
The ground material does affect your
ability to deliver the full sound power from the loudspeakers to the audiences. The ground plays the role of the sound absorbent. Some ground material, such as carpet or grass,
tends to be better sound absorbent than the
others, such as concrete. If your karaoke
show is to be held on a ground with good sound absorbent material, the advantage of
reflecting sound from the ground will be greatly reduced. Do pay extra attention to the seats at the farther
sides away from the sound system. Rearranging
the locations of the loudspeakers may be a solution to any problem you may encounter
thereon.
Objects above ground include the
audiences, plants, furniture, personal belongings, food
stands, supporting equipment and building structures.
Sound can be reflected or diffracted by any of these objects. An object larger than ten feet in diameter will
reflect all the audible sound. An object
with the size between one inch and ten feet will partially reflect the audible sound. A higher frequency sound tends to be reflected
more often than the lower frequency sound. The
portion of the audible sound that is not reflected is either absorbed or diffracted around
the objects.
The reflected, diffracted and absorbed
sound, cooperating with the direct sound from your loudspeakers, shape the overall sound
characteristics of that particular show. This
type of sound characteristics will be different from one location to another. One of the most important characteristics is the
forming of a reverberant sound field, which may muffle or reinforce your overall sound
results depending upon the objects on the ground and your sound system setup. Although there are guidelines, theories and
equations, which can lead us to estimate the overall effects of these objects over sound
and the manipulation of the reverberant sound field, they are out of the scope of our
discussions.
In summary, the sound system and the
acoustic environment are two subjects that need to be combined together in order to
achieve controllable and satisfactory sound results.
While the sound system involves mainly the electrical engineering field, the
acoustic environment involves quite a few differential equations, mathematical
calculations, thermodynamics, and some degree of architecture. The combination of both of the sound systems
and the acoustic environment is not only a science but also a delicate art. A karaoke show and any other music performances,
therefore, are not only the expressions of the spirit of the vocal music and instrumental
music but also the art of science dated as far back as the first music note appeared on
earth.
Haw-Renn Chen is
an R&D engineer in Audio2000’SÒ. He is also one of the technical Audio2000’SÒ
staffs in charge of writing the technical contents for the website www.audio2000s.com.
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6. Application
Notes by Haw-Renn Chen on Karaoke Scene Magazine
(Page 9, Apr./May 2003 Issue)
Title: KARAOKE, MUSIC AND SOUND
By:
Haw-Renn Chen
Sound, as it surrounds us all the time, is a familiar term to us. Sound is such a close company to us that we very
often ignore its existence. When it is quiet,
we may assume there is no sound at all, although it’s there, with us! Is it possible to have absolutely quiet time? Of course, if we stay in an absolute vacuum space!
In everyday language, the concept of sound
is actually the sensation of hearing. In
reality, sound is a group of elastic waves involving the displacement of atoms and
molecules of the air through which sound propagates.
Whenever these elastic waves propagate through the air (or liquid or solid)
to reach our ears, they produce vibrations in our ears’ membranes. These vibrations provoke a nervous response
constituting the process known as hearing. Due
to the limitation of our nervous system, we can hear sound in the frequencies between 50
to 20,000 Hz. Outside these limits, sounds
are not audible, but the elastic waves are still called sound. However, these elastic
waves with frequencies above 20,000 Hz are called ultrasonics.
Sound, as described above, is the result
of the displacement of molecules in the air, which is a type of mechanical agitation. Intuitively, we should have expected sound to be
mechanical, rigid and noisy!
Then, why certain type of sound is
pleasant to us and is called music? Why?
……
Before we discuss the sound and music
further, let’s ask: why we like sweet food? I
believe everybody can provide tons of reasonable and correct answers. However, the fundamental reason for the sweet food
to be attractive to us is that sugar is the source of heat and our energy. Reasonable amount of sugar in various parts of our
body is essential not only to provide the energy for our daily activity but also to
maintain good health.
In the same token, there are a number of
fundamental reasons for us to be pleasant with music.
To exploit these fundamental reasons, let’s start with the definition
of music in the dictionary. Music is defined
to be an art of sound in time which expresses ideas and emotions in significant forms
through the elements of rhythm, melody, harmony, and color.
It is indicated that music is related to ideas and emotions. If we look into the nature of ideas and emotions,
we may find that the assertion of security
and the expressions of feeling and love are our basic needs
to maintain a good mental health.
Since feeling and love is such a delicate
subject, the expressions of feeling and love tend to be lengthy and progressively
harmonic. We can find this tendency in the
animal world. The animal that gets the
desired company normally can depict its capability by providing lengthy, persistent and
attractive sound.
The assertion of security is primarily related to the maintenance of safety. Since safety is such a strong necessity, the
expressions of the assertion of security tend to be short, repetitive and strong. We also can find this tendency in the animal
kingdom. The animals use short and strong
sound to claim their territory that is the basic element for their survivorship.
Since music is the fundamental tool for us to express our needs and capability in
our community and society, we are born with the gift being able to appreciate it. As a result, music can penetrate deeply into our
core mental processes. We are all influenced by music.
Different type of music may affect our feeling and, in the long run, can
affect our brain activities and shape our personality and intelligence. How can different type of music affect the personality and intelligence (and
eventually the order in the society) and the degree of the effect are subjects to be
exploited further.
Karaoke is one of the ways to express the appreciation of music. Live performance is another way of expressing the
appreciation of music. The live performance
presents music by exchanging and communicating the spirit and interpretation of each music
piece among the performing artists,
therefore, the live performance is dynamic and unique for each show. The karaoke singer or
singers present music by communicating with a karaoke system, therefore, the karaoke show
is affordable, is open to the public and is enjoyable to every participant.
Due to the fact that the background music from a karaoke system is repeatable and
predictable, it becomes imperative for a karaoke show to arrange the music delicately. Just like selecting the right karaoke system for
the show is essential, the right arrangement of the music in the karaoke show is equally
important. In the karaoke music arrangement, try not to consider solely on the style of
the music, such as rock’n roll or country.
The various music characteristics pertaining to the fundamental
expressions of our feelings and security needs must be taken into account and utilized
effectively. To achieve this goal, we need to
study the music as diligently as we study the sound equipment electronic and acoustic
terminologies. The aforementioned discussion
may be a starting point for us to think and understand further.
Karaoke is a part of music and music is a part of sound. Sound is the result of the natural phenomenon. Music is the result of embedding our spirit needs
and feeling into the natural phenomenon: sound. Karaoke
gives us the freedom to exploit music conveniently. While there is a cause, there is a
result! We need to appreciate our given gift:
music and karaoke. We need to exploit the
potential of music and karaoke even more hoping for a better life and a more harmonic
society!
Haw-Renn
Chen is an R&D engineer in Audio2000’SÒ. He is also one of the technical Audio2000’SÒ
staffs in charge of writing the technical contents for the website www.audio2000s.com.
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7. Application
Notes by Haw-Renn Chen on Karaoke Scene Magazine
(June/July 2003 Issue)
Title: KARAOKE FEST
By:
Haw-Renn Chen
May 19, 2002
seemed to be just not long ago. It was a
Sunday and the Karaoke Fest was going to be held in the Queen Mary.
As a gold sponsor of the Karaoke Fest, our company was assigned with a nice size
exhibition space. As a result, in the early
morning two-truck loads of the exhibition display and products were on the Great Los
Angeles freeways. Vehicles seemed to be far apart and the asphalt patterns were flying
backwards fast!
It felt slightly chilly and a stratus cloud lies on the surface of the upslope
hillsides. The rising sun seemed to be
hiding, behind the stratus cloud and the far-away cloud named altocumulus.
Behind the steering wheel, I looked forward and felt some kinds of puzzle. Any trade show always gives me some unknowns as
the time waves fly toward the upcoming future. Time
waves are always ruthless while we just live in a point of the time reference!
Here came the destination: the Queen Mary! After
unloading, the display setting-up process brought me to the reality: the Karaoke Fest- a
combination of a trade show and a performance entertainment.
On the show floor, entertainers, merchants and visitors were walking around the
show booths. The sound of music, talking and
laughing fulfilled the space just like a grand opera being played on a stage with great
excitement.
I opened the carton boxes and placed all the gadgets on the tables. The Singer’s Power all-in-one system was the
main sample. The AC cord was connected and
the DVD tray got opened. A selected CD was
dropped into the CD tray. A series of sound
waves were delivered. Gradually, a crowd of
visitors came and started the real work.
The questions were around a few “how to use”’s.
Microphones, mixers, amplifiers, speakers and sound effectors were all interesting
subjects. We didn’t rule out the
philosophy and jokes either!
Technical questions gave me the opportunities to refresh my engineering memory,
from the textbooks to the practicality.
To sum up all the technical questions, they could simply be put in three subject
matter parts: particles, interactions & fields, and waves.
Particles in our subject primarily include the electrons and the air elements. The electrons live in such a tiny world that their
behaviors are highly guarded by the physics of the quantum mechanics. Electrons in the
quantum mechanics make the modern electronic and computing gadgets become true. The air
elements are so elastical that they bounce around to have sound waves get delivered.
Fields include the electromagnetic fields which, working with the interactions, are
utilized to control the transistor gates, to convert the mechanical sound energy to the
electrical energy, or to convert the electrical energy to the sound energy.
Waves are such a romantic term. They
remind us the pretty waves raised by the breezes. However,
in this subject, waves include the mechanical sound waves, the waves on the sound
instrument, the electrical signal waves, and the electromagnetic waves.
The technical discussions, the philosophy and the jokes were all so real and
exciting. The seconds were just ticking away. Soon it was twelve at noon. The crowds simply shifted from the show booths to
the ballroom. The melody from the karaoke contest rippled through the air and pumped our
heart. Enjoyment and satisfaction got fulfilled!
There is never an
eternal banquet. Noon became afternoon. Afternoon became evening. Evening became night. The karaoke contest went to an end. The crowds disappeared. We rushed to disassemble
the display. We rushed to pack all the products. At
this moment, it seemed to be eternal- a work seemingly no end!
The
temperature was mildly low and I wandered where the sweat came from?
Finally,
we became the last group on the floor! We worked harder! But why our arms were out
of control??
Slightly
tired, the loading was done. Under some mist, two vehicles left the parking lot of
the Queen Mary.
Although
the eyelids were forced to open, the beautiful night sight still made me amazed.
The
vehicles were running with the opera-like show booths and the karaoke contest still
lingering in my mind.
The vehicles were
running, running,…. The night sight of the Queen Mary and then the City of Long Beach
gradually faded away from the rear mirror. Gradually
fading away…. one day’s energy was. This
ended the story of the May 19, 2002 Karaoke Fest!
Haw-Renn Chen is an R&D engineer in Audio2000’S Ò. He is also one of the technical Audio2000’SÒ
staffs in charge of writing the technical contents for the website www.audio2000s.com.
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