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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'S

 

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'S

         

            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’S.  He is also one of the technical Audio2000’S 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'S

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.  He is also one of the technical Audio2000’S 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'S

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'S.  He is also one of the technical Audio2000'S 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’S.  He is also one of the technical Audio2000’S 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’S.  He is also one of the technical Audio2000’S 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.  He is also one of the technical Audio2000’S staffs in charge of writing the technical contents for the website www.audio2000s.com.

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