Sound - What is it?
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| Sound Waves |
| Sound Waves |
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| Octaves and Harmonics |
| Octaves and Harmonics |
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| SPL |
| SPL |
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| Imaging |
| Imaging |
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A Sound wave can be described by two basic characteristics, the speed of the vibration (Frequency), and the extent of the vibration (Amplitude).
An octave is a doubling or halving of frequency. One octave up from 100 Hz is 200 Hz, where one octave down from 100 Hz is 50 Hz. A harmonic is a doubling (2nd harmonic), tripling (3rd harmonic), quadrupling (4th Harmonic... etc) of a fundamental frequency. Musical instruments (with the exception of synthesizers) do not create pure tones. The fundamental (main frequency) is combined with its harmonics at various levels to create the sonic signature of that instrument.
Our ears have a tremendous ability to evaluate sounds that range from very soft to very loud. The decibel (dB), named after Alexander Graham Bell, is a method of describing acoustic pressure, without having to deal with the billion-fold range of sound pressures to which our ears are sensitive. A Bel is the difference in loudness produced by a ten fold increase in power.
By comparing arrival times at both ears, our brain can determine the direction from which a sound came from. A sound arriving at both ears simultaneously tells our brain that the sound is centered either in front, above, below, or behind us. The brain then looks at the frequencies received, and compares these frequencies with sounds that we have heard before. When the brain remembers a sound like the sound it just heard, it looks at the late soundwaves that arrived at the eardrum that were reflected off the outer ear. This process allows us to perceive height. When a soundwave comes from behind, the soundwave must pass through the pinna. This causes a filtering of high frequencies in comparison with reflections off of walls, ceilings, and floors. This is what allows us to localize sound sources behind us.
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Electronics
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| Electrons |
| Electrons |
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| Current |
| Current |
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| Potential |
| Potential |
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| Resistance |
| Resistance |
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| Power |
| Power |
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| AC/DC |
| AC/DC |
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| Resistors |
| Resistors |
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| Capacitors |
| Capacitors |
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| Inductors |
| Inductors |
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| Semiconductors |
| Semiconductors |
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Atoms are made up of three smaller particles; protons, electrons, and neutrons. Electrons have a unit negative charge, protons have a unit positive charge, and neutrons have no charge. Usually there are an equal number of protons and electrons in an atom yielding a net zero charge. When some kind of energy (electromagnetic, chemical, etc.) is applied, some of the electrons may be broken free, thus leaving an imbalance of protons and electrons in the atom. This will result in the atom having a net positive charge
The movement of free electrons from one atom to another is called current flow. Current always flows from negative to positive. A good analogy can be made with a water hose. The hose may be considered a conductor, and the water moving electrons. The current, measured in amperes, would be the volume of water passing by a point along the hose in a given amount of time. The higher the volume, the more current.
For current to flow, there must be a potential difference between two objects. This potential difference is created from an excess of electrons at the source, and a lack of electrons, or positive charge, at the destination. Using our hose analogy, the potential difference, measured in volts, would be the pressure of the water within the hose. The higher the pressure, the more potential difference, and the higher the voltage.
Most all conductors exhibit a property called resistance. Resistance impedes the flow of current. It is measured in units called Ohms. With the water hose, resistance could be regarded as friction between the water and the hose. A larger hose would create less friction and have a lower resistance than a smaller hose.
Power is the amount of work done in a specified amount of time. The electrical unit of power is the Watt.
Referring back to our water hose, the flow of water can be considered to be Direct Current (DC), meaning that current always flows in the same direction. If the valve that controls the volume of water flow could also change the direction of the flow, it would be called Alternating Current (AC). In general, audio signals are AC, and Battery Voltage is DC.
The resistor is a device that resists, or limits current flow. Their value is specified in ohms. A resistance to current flow creates heat, and as such, these devices have a maximum power dissipation, rated in watts. Placed in series with a voltage source, they limit current to a device. In parallel with a voltage source they make up a voltage divider. A potentiometer is a special type of resistor which, when the shaft is rotated, changes resistance via a sliding contact arm. They are used as volume controls, gain matching controls, etc.
A capacitor is a device that resists change in voltage. It stores a charge. For our uses it will pass AC but not DC (while it is charging it will pass DC). Their value is expressed in Farads (or more commonly in microfarads). They have a working voltage (called DCWV) that must never be exceeded. They can be found in both polarized and nonpolarized versions. The most commonly used types are the electrolytic, mylar and poly (polypropylene, polystyrene, polyester). They are used primarily for filtration (in power supplies), noise suppression, and speaker crossovers.
An inductor is a device which resists change in current flow. Usually it has a low DC resistance but a high AC impedance. This means that it passes DC well, but does not pass AC easily. It is electrically opposite to the capacitor. Its value is expressed in Henries (more commonly milliHenries). There are two major types of inductors, air core and iron core. The other important factor is the gauge of wire that is used to make the inductor. The heavier the gauge, the less signal loss and the higher the current capability. For a given value and wire gauge, air core inductors are more expensive, but they do offer some benefits. The greater the current flowing through an inductor, the larger the magnetic field produced. With iron core inductors, there is a point where the core saturates and no greater field may be produced. At this point, severe distortion sets in. Air core inductors for the most part do not exhibit saturation.
A diode (or rectifier) is a semiconductor which allows current to flow in only one direction. It can be used to change (rectify) AC into DC. The two leads of a diode are labeled anode and cathode. A diode is said to be forward biased when its cathode is at least .7 volt more negative than its anode. A diode is reverse biased when its cathode is not at least .7 volt more negative than its anode. Forward biasing a diode causes current to flow, and reverse biasing causes no current to flow. Although there are numerous types of diodes, the ones of interest to the mobile electronics installer are power diodes, or rectifiers. A rectifier’s value is expressed in amps, and is the maximum forward current which the device can safely handle.
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Speakers
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| Excursion |
| Excursion |
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| Power Handling |
| Power Handling |
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| Thiele/Small |
| Thiele/Small |
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How loud a speaker can play depends on how much air it can move without overheating. How much air can be moved is determined by the surface area of the cone and the excursion capability of the motor system.
Loudspeaker power handling ratings are one of the most commonly quoted, but most poorly understood of specifications given by loudspeaker manufacturers. It seems that every company has its own way of measuring and specifying power handling. That’s because Marketing departments are always looking for ways to be able to list higher numbers for power handling in order to impress their customers with the apparent ruggedness of their products. It is sometimes difficult for product users to understand how these specifications relate to real world amplifiers or how they relate to the way they listen to their favorite kinds of music on loudspeaker systems. Loudspeakers fail in one of two ways - mechanically or thermally. Mechanical failures occur when one of the moving parts of the speaker such as the surround, spider, or cone become fatigued, tear, or break from the effects of continued long excursions. Thermal failures occur when the electrical power dissipated in the voice coil as heat causes the adhesives holding the turns of voice coil wire together to break down, or the insulation on the wire to fail, resulting in shorted turns. Also, the wire itself can melt, which means an open voice coil, or the coil support can melt or burn, again meaning failure of the loudspeaker.
Research done in the study of loudspeakers has been conducted by a number of individuals. The works of Neville Thiele and Richard Small are considered to have the most impact on the loudspeaker design field.
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Glossary
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| Decibel |
| Decibel |
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| Damping Factor |
| Damping Factor |
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| Driver Volume |
| Driver Volume |
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| Enclosure Volume |
| Enclosure Volume |
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| Hertz (Hz) |
| Hertz (Hz) |
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| Impedance |
| Impedance |
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| Net Volume |
| Net Volume |
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| Power Handling |
| Power Handling |
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| Sealed Volume |
| Sealed Volume |
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| Vented Volume |
| Vented Volume |
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| Volume |
| Volume |
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| Xmax |
| Xmax |
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| Wiring |
| Wiring |
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The basic unit of measurement in electronic and acoustic work. It is a logarithmic scale to express the difference between two values. For simplicity, it can be regarded as a measure of relative loudness; for example, in frequency response measurements.
The ability of an amplifier to control the load without overhang. This applies to how tight the bass is. Usually the higher the number, the better, although it is debatable if anything over 50 is audible. Damping factor is calculated by dividing the load (speaker) impedance by the output impedance of the amplifier. Thus, a given amplifier’s damping factor will decrease as the speaker’s impedance decreases. This means an amp running at 4 ohms will provide tighter bass than at 2 ohms.
The amount of enclosure airspace that is displaced by the speaker itself.
The total amount of internal airspace of an enclosure. This includes the net, driver and vent volumes.
The unit of measurement for frequency. 1 Hz is equal to one cycle per second, or the complete cycle of an alternating wave form per second.
(measured in Ohms) The total opposition to the flow of alternating current in an electrical circuit. The measure of the magnitude of an electrical load when using alternating currents, such as in audio. It describes the combined effect of resistance, capacitance and inductance.
The amount of airspace that is enclosed within the enclosure. This does not include the airspace taken up by bracing, vents, or the speaker itself.
(Measured in watts RMS) It is the continuous sine wave power that can be dissipated by the voice coil/magnet assembly without failure. Most speakers fail because the amplifier is driven into hard clipping. Hard clipping produces square wave distortion which can be considered DC. Voice coils are not designed for DC because music is AC. Hard clipping is difficult to identify in subwoofer systems because it is very hard to hear the results of square wave distortion at lower frequencies.
The amount of enclosure airspace on one side of a woofer in a bandpass system that acts as a sealed enclosure.
The amount of enclosure airspace on one side of a woofer in a bandpass system that acts as a vented enclosure.
(Enclosure, Internal - measured in Cubic Inches, Feet or Meters) The result of the product of three linear measurements. Length times width times depth or height, (LXWXH). Volume describes a loudspeaker enclosure size.
(Measured in inches or millimeters) It is the measure of a speaker cone’s maximum excursion in one direction while maintaining a linear behavior.
(Series or Parallel) How two or more speakers are wired together to form a mono system. The wiring of two or more drivers can affect impedance for the whole system. Care must be taken to assure that the resulting impedance does not exceed the amplifier’s requirements.
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Subwoofers
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Amplifiers
| TM1805 |
| TM452 |
| TM601D |
| TM904 |
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Speakers
| TM6001 |
| TM6502 |
| TM6502WB |
| TM652WB |
| TM7702 |
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What is ASTM B117 testing?ASTM B117 is a standarized method for testing the corrosion resistance of different materials to gauge their effectiveness in wet/humid environments. MTX ThunderMarine products have undergone this testing method for a full 500 hours. You can be confident in knowing that our ThunderMarine products will survive almost everything that mother nature can throw at them. What type of enclosure do I need to use with my ThunderMarine subwoofer?ThunderMarine subwoofers are designed to function in a variety of installation scenarios. They have an infinite baffle design which means they can be installed and used without having to have a specific enclosure made for them. This means that you can install the subwoofer anywhere and the subwoofer will sound great. Under a captain's chair, in a footwell, or anyother place that you can fit it, the subwoofer will work. You can also use the subwoofer in an enclosure if you so choose. Consult the specifications to determine the appropriate size enclosure needed for the subwoofer. Why are the plastic covers over the controls on my amplifier?Those covers are made out of Plexiglass and they are designed to create a water tight barrier that prevents moisture from getting into the internal section of the amplifier. Although the circuit board and pre-amp have been conformal coated which makes them water resistant, the plexiglass covers act as an addtional barrier to ensure your amplifier runs like brand new everytime you take your boat out. What is a mono block amplifier?A monoblock amplifier is a 1 channel amp (mono literally means 1). Since bass is omnidirectional, meaning you can tell where it's coming from, it isn't necessary to run subwoofers in stereo. you may see 2 sets of speaker teminals on monoblock amps and they will be labeled as either speaker 1 and speaker 2 terminals, or simply + + and - -. that is because the two + terminals are connected to each other inside the amp, as are the two - terminals. The second set is there simply to make it easier to connect multiple speakers to the amplifier. Do not confuse the two sets of terminals as separate channels. if you're not sure whether an amp is a mono or two channel amp, you can look at the labels above the speaker terminals. a multichannel amplifier will have the separate channels labeled as Left and Right, or L and R. What does Class D mean?An amplifier's Class refers to the amplifier's output stage. Although a Class D amplifier can also be a digital amp, the "D" does not stand for digital. What "Class D" does signify is that certain parts of this amplifier turn On/Off to create a signal instead of constantly varing the voltage or current. Changing how long these parts are On or Off changes what you hear. Class A and Class A/B amplifiers are always "On" to some extent, being more or less On as the audio being amplified calls for. The benefit of Class D topology is that current only flows when the parts are On, meaning they run cooler and are more efficient. The problem is that the switching creates distortion, so a low pass filter must be used to counter the distortion produced, because of certain characteristics of the parts used in this circuit, it is much easier to adapt Class D technology for low frequency (subwoofers) applications than for full range speakers. See the Technology section to learn more about MTX Patented Adaptive Class D Technology and its added benefits. What does the input sensitivity adjustment on my amplifier do?The input sensitiviy adjustment, or Gain, on an amplifier is designed to match the input voltage of the amplifier with the output voltage of the head unit (source). Different head units have different pre-out voltages, 2v, 4v...8v. Unfortunately, no one tells you what that means or why they're offered. the speaker level output of your head unit has been amplified internally, the pre-outs have not. everything that an audio signal has to pass through will lower the "quality" of the signal by adding it's own distortion to it. in most cases, it's so little we can't hear it, but it adds up. since the pre-out signal has not been amplified in the head unit, which is why it's considered to be a "cleaner" signal to send to an amplifier. the higher the signal voltage, the better the signal to noise ratio, which is why you see higher pre-out voltages with more expensive head units. How do I bridge my amplifier?Bridging an amplifier is often most useful when you have a 2-channel amplifier that you want to use to run as a mono channel or a 4-channel amplifier that you want to run as a 2-channel amplifier. Bridging is the combination of the left and right channels of an amplifier, using one terminal from each side, to make 1 (mono) channel with a higher output than either channel running separately. A mono block amplifier has only 1 channel and cannot be bridged. The 2 outputs of a mono block amplifier are there to easily connect multiple subwoofers. If you are not sure whether your amp is a mono block or a multi-channel model, look at the speaker terminals. Multi-channel amplifiers are labeled Left and Right while mono block amplifiers are labeled Speaker 1 and Speaker 2. Every amplifier has different requirements for bridging, so consult your manual or installation instructions before making any connections. What size power wire do I need to connect my amplifier to my battery?As a general rule you should use the largest gauge power wire that your amplifier's input terminal is designed to accept. For example, if your amplifier has a 4 AWG power and ground wire input you should use a 4 AWG power wire. Consult your owners manual or installation instructions if you are unsure what size input terminal your amplifier has. My amplifier is going into thermal protection, what can I do?Thermal protection is not a defect in your amplifier. Every amplifier has thermal protection built into it as a safety precaution against damaging critical electronic components within the amplifier due to excess heat. The amplifier once cooled down will resume playback. If your amplifier is going into thermal protection often, check the setting of your input sensitivity to ensure that it is properly set to match the output voltage of your source unit. You can also lower the volume on your source unit to increase the intervals between thermal events. What is volume displacement?Volume displacement is the amount of air that a subwoofer or speaker can move during use. Volume displacement relates to the speakers ability to generate higher levels of SPL. Volume Displacement is calculated by multiplying the Surface Diameter (Sd) of a subwoofer, most often measured in square inches in the U.S., times the Xmax of that subwoofer, most often measured in inches in the U.S., with the resulting volume displacement number being measured in cubic inches. The final equation then looks like this: Vd = Sd*xmax. The values for Vd, Sd, and Xmax can most often be found in the Thiele/Small parameters of the subwoofer. My subwoofers are distorted, what is wrong?If your subwoofers are distorted you may have the input sensitivity (gain) on your amplifier incorrectly set. Distortion is caused when a soundwave has its amplitude adjusted from a traditional sine wave (round peaks) to a square soundwave (square peaks). Square waves are caused when the input sensitivity (gain) is set in excess of the output voltage of the source unit (ie. radio) and the volume is turned up louder than when the amplifier was set. This "amplified" signal results in the square soundwaves that you hear as distortion. You can use an ossiloscope to check the output wave if you have one available or you can use a multimeter and measure the output voltage of the amplifier at the speaker terminal and then use this calculation to determine if your gain is set correctly. Voltage equals the square root of RMS Power times Resistance. For example if you have a 1000W RMS amplifier connected to a 2O subwoofer the optimum voltage should be 44.72V. You can adjust the gain up or down while measuring the voltage until the multimeter measures that voltage and your amplifier would be properly set and the distortion should be eliminated.
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MTX Audio is a proud part of the Mitek Electronics & Communications Group which is a privately held, American owned corporation that manufactures high quality mobile, residential, and commercial audio products. We are always looking for hard working people to join our team and help us to continue the MTX and Mitek tradition of delivering American engineered and manufactured high quality audio products. Click the link below to visit our corporate Human Resources page at www.mitekusa.com to see listings for open positions and to upload your resume.
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