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    Terminology - Please contribute

    After being confused by a lot of the things said, and hearing a lot of clueless people ask questions (to save this site from redundancy im creating this thread)


    Contribute your information from basic to complex technology regarding car audio, stuff such as (ohm, h/u, mids, and heatsink)

    Keep it short and simple. like...

    SQ - Sound Quality
    or
    Inverted - When sub is placed in the box with the front going in first so it appears reversed

    or elaborate on fairly understood ideas, such as the AMP, we know it powers the sub, but if you know more to it such as"How it powers the sub?", etc.

    Also request terminology you don't know if you want here.







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    Re: Terminology - Please contribute

    http://www.mobileaudio.com/rac-faq/

    copied from the Basic Car audio web site and from FXN


    A power amplifier takes an input signal, usually a preamp level signal, which has both low current and low voltage characteristics, and produces an output which will have higher current and voltage levels. The power supply available to the audio output IC in a head unit is limited to the battery voltage of the vehicle. This means that the head unit can produce an audio signal with a limited (by the battery voltage) voltage swing, and therefore a limited power output to the speaker. Most amplifiers have a special circuit (switching power supply) to boost the available battery/charging system voltage to a higher voltage. The higher voltage developed in the amplifier's internal switching power supply will allow the audio output voltage swing to be greater. This allows the amplifier to produce more power into the speakers connected to the amplifier's output terminals.
    Most amplifiers will have some sort of level or "gain" control. This control is used to match the output of the head unit to an amplifier. The maximum audio output voltage from different head units will vary. If there were no gain controls, some head units would not be able to drive the amplifier to its maximum power level. Other head units may drive the amplifier to full power at a fraction of its volume control's range.
    Virtually all amplifiers have battery, ground and remote connections which must be connected for the amp to operate. The battery connection is the high current +B source that's connected to the battery via a properly fused wire. The size of the power wire is determined by the current the amplifier draws and the length of the wire (from the battery to the amplifier). The ground is another high current connection and is connected to the chassis (body/floor pan) of the vehicle. The ground wire is typically as large as the power wire. The remote connection is a low current control input that tells the power supply of the amplifier to power up.
    The remote input current for amplifiers varies with the amplifier and the model. Some draw minimal current. Others draw a little more. The upper limit of a properly functioning amplifier is approximately 50ma (0.05 amps). If you're using/controlling more than 2 amplifiers, it is (in my opinion) much better to use a relay to control the amplifiers. Actually I really prefer having a relay in the remote circuit (no matter how many amplifiers I'm using) because it protects the head unit's remote output circuit in case of a short circuit.
    The input circuit (sometimes called the 'front end') generally employs a noise cancelling circuit which compares the signal on the center conductor (the audio signal) to the signal on the RCA shield (which generally has little or no signal and is only used as a reference) and amplifies the difference between the two.
    The input impedance is the impedance (that the signal source 'sees') from the center conductor to the shield on an unbalanced input circuit. A typical input impedance would be ~10,000 ohms but some amplifiers may have an input impedance of more than 50,000. If the input circuit uses a mini DIN type connector, the input impedance could be measured from one signal terminal to the other or from the signal terminals to the shield ground. Ideally, the impedance should remain constant throughout the audio band. More than a few amplifiers employ some sort of high frequency noise filter which will cause the input impedance to fall slightly at the upper end of the audio spectrum. These filters are designed to reject high frequency noise from the amplifier's switching power supply. It should also remain constant regardless of the position of the gain control. Some amplifiers (especially budget amplifiers) will have varying input impedance when the position of the gain control is changed. Head units (or equalizers, crossovers...) with low output impedance will handle these variations better than standard head units. Generally, a head unit with high output impedance will have reduced high frequency response if the amplifier's input impedance isn't consistant across the audio spectrum.
    Unbalanced Input Circuit:
    This type of circuit has a shield ground that's not directly connected to the chassis ground but may have only a few hundred ohms of impedance from the shield to ground. This type of circuit would be designed to accept a single ended signal (signal only on the center conductor).
    Balanced Input Circuit:
    Some Amplifiers have balanced inputs. This means that both the center conductor and the shield (if they're using RCA type connectors) can accept an audio signal. If the amplifier uses RCA type connectors and has balanced inputs, it likely uses the chassis ground as a reference (which is a testimony to the noise rejection abilities of a balanced input circuit). If the amp uses a mini DIN or some sort of professional audio connector, the connector will have provisions for two audio signals per channel and a dedicated ground (reference) connection.


    - Steve



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    2006 Kawasaki Ninja ZX14
    Quote Originally Posted by DJGTSR
    I dont mean to be rude, but what is the highest level of education that you finished?

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    Re: Terminology - Please contribute

    Highly regulated amplifiers employ PWM switching power supplies. Unregulated amplifiers don't use Pulse Width Modulation to maintain a constant rail voltage. This does not necessarily make one design inherently better than the other. Both designs have their advantages and disadvantages.
    Capacitor:
    A capacitor is an electronic device which consists of two plates (electrically conductive material) separated by an insulator. The capacitor's value (its 'capacitance') is largely determined by the total surface area of the plates and the distance between the plates (determined by the insulator's thickness). A capacitor's value is commonly referred to in microfarads, one millionth of a farad. It is expressed in micro farads because the farad is such a large amount of capacitance that it would be impractical to use in most situations.
    Capacitor and DC voltage:
    When a DC voltage source is applied to a capacitor there is an initial surge of current, when the voltage across the terminals of the capacitor is equal to the applied voltage, the current flow stops. When the current stops flowing from the power supply to the capacitor, the capacitor is 'charged'. If the DC source is removed from the capacitor, the capacitor will retain a voltage across its terminals (it will remain charged). The capacitor can be discharged by touching the capacitor's external leads together. When using very large capacitors (1/2 farad or more) in your car, the capacitor partially discharges into the amplifier's power supply when the voltage from the alternator or battery starts to fall. Keep in mind that the discharge is only for a fraction of a second. The capacitor can not act like a battery. It only serves to fill in what would otherwise be very small dips in the supply voltage.
    Capacitors and AC voltage:
    Generally, if an AC voltage source is connected to a capacitor, the current will flow through the capacitor until the source is removed. There are exceptions to this situation and the A.C. current flow through any capacitor is dependent on the frequency of the applied A.C. signal and the value of the capacitor.
    TECH TIP:
    For a good ground:
    Get a 3/8 inch bolt, nut and lock washer, find a place on the body that can be accessed from the inside of the vehicle and out. You must be able to get to both sides so that you can hold the nut from turning when tightening it up. Drill a 3/8" hole for the bolt, making sure NOT to drill through any fuel lines, brake lines, the gas tank or anything else. Scrape the area under the bolt (inside the vehicle) to remove ALL paint and primer then bolt the ground wire's ring terminal down with the 3/8 inch bolt.

    As a side note:
    For grounding devices that draw only a few amps (like crossovers, head units and equalizers), you can use virtually any type of screw. Many people warn against using the black oxide coated screws but it won't make a big difference because the electrical connection is between the ring terminal and the metal surface that's been sanded clean and not through the screw. The screw simply holds the ring terminal to the metal.
    Amplifier mounting:
    DO NOT mount an amplifier on your subwoofer box. I know that there has been a great deal of discussion over mounting an amplifier to an enclosure and many people do it all of the time with no problems but those people probably build good enclosures from 3/4" (or thicker) MDF with extensive bracing. Most people (especially young impatient people) are too lazy to do that and build unbraced enclosures from 5/8 MDF. These enclosures will flex considerably more than a proper enclosure and will likely cause amplifier failure if the amp is mounted to the enclosure.
    REASON:
    When the woofer(s) moves in or out, the box flexes and therefore causes the sides of the box to vibrate. This vibration is transferred to the amplifier mounted to the box. All of the electrical components in the amplifier have mass. Inertia (an object in motion tends to stay in motion, an object at rest tends to stay at rest) tells them to stay at rest, the box vibration is trying to make them move. The energy from the box's vibration is transferred to the components through the electrical leads which are soldered into the circuit board. All of this will cause the components to break loose and therefore cause the amplifier to fail prematurely. Basically, the amplifier will commit suicide! I'm not telling you this because someone told me it was bad. I've been repairing amplifiers since ~1985. Virtually every amplifier that's come into my shop with parts rattling around inside them have been mounted on the speaker box. It causes the legs of the semiconductors to break (which causes amplifier failure). It causes the capacitors to break off of the board (which can cause catastrophic amplifier failure). It causes solder joints to break on the semiconductors mounted to the heat sink. It causes transformer windings to grind into one another (which causes lots of smoke to pour out of your amplifier). People who repeatedly tell others to mount their amps on the speaker box because they've never had a problem remind me of people who drink and drive and say there's nothing wrong with it because they've never crashed their vehicle. Eventually, in both cases, problems will arise.




    - Steve



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    2006 Kawasaki Ninja ZX14
    Quote Originally Posted by DJGTSR
    I dont mean to be rude, but what is the highest level of education that you finished?

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    Re: Terminology - Please contribute

    AMPLIFIER INSTALLATION NOTES:

    When installing an amplifier:
    ----Disconnect the ground wire from the battery. It doesn't really matter which one is removed because removing either connection from the battery (positive or ground) will break the circuit but if you let the wrench touch to ground (any metal surface) when removing the positive wire, you may do significant damage or seriously injure yourself. If you let the wrench ground out when removing the ground wire, you won't have any problems (except maybe scratching the paint).
    ---- If you don't remove the wire from the battery, at the VERY least remove the fuse (or open the breaker) from the power wire which delivers power to the amplifiers.
    -----When making the power and ground connections on the amplifier, connect the ground wire first. I know it is tempting to connect the RCA cables first because it is instant gratification (having made a connection) but you may damage the head unit or the input section of the amplifier if the amplifier tries to ground through the RCA shield connection.
    -----If the amplifier has screw down terminal blocks which are designed to accept either bare wire or spade terminals, use the spade terminals. If you insert bare wire into the blocks, you may have a strand or two of wire touch to the neighboring terminal which is easily enough to convert the amplifier into a paperweight.
    -----Mount the amplifier down before moving the vehicle. If the amplifier falls or slides against anything, there is a chance that it will be damaged seriously enough to warrant a trip to a repair shop. I know how cool you are (because I know how cool I was at 15 or 16 years old) and nothing could possibly happen but... mount it down anyway.
    -----When making the ground connection for the amplifier, the floor pan of the vehicle is a better choice than some of the braces and other metal structures that you may want to use for ground. Braces and other such structures are sometimes connected to the vehicle's chassis (body) by a few spot welds which will provide a less than optimum ground return path.
    ------If the amplifier's ground is properly connected to the body of the vehicle, it will provide a better return path to the charging system's ground than will a ground wire run back to the battery. This is especially true if the ground strap from the engine block to the chassis is upgraded.

    Amplifier Classes:
    Most mobile amplifiers use complementary transistor pairs to drive the speakers. In this configuration there is a transistor (or group of transistors) which conducts current from the positive power supply voltage for the positive half of the audio waveform and a different transistor (or group of transistors) which conducts current from the negative power supply voltage for the negative half of the waveform. There are some amplifiers which use the same transistor(s) to drive both the positive and the negative halves of the waveform.

    NOTE:Amplifiers in classes A, B, and AB operate their output transistors in a 'linear' mode. Class 'D' amplifiers operate their outputs in 'switch' mode.

    Mode examples:

    Linear mode:
    Imagine that you are the amplifier's output device(s) and you must support a 10 pound iron weight (the speaker load). The most difficult method (linear mode) would be to hold the weight straight out in front of you. This would very roughly simulate the linear mode architecture. Your muscles would start to ache in a short amount of time. Think of this pain as the power dissipation in output transistors.

    Switch mode:
    In this example, you can support the weight in one of two positions. In the first position, you can hold the iron weight directly over your head with your elbows locked so that your're not really using very much effort to support the weight. In the second position, you would let the weight hang down by your side. This would also use very little effort from your muscles. If you held it directly over your head half of the time and by your side for the other half of the time, it's position would 'average' out to be the same as if you held it out straight in front of you like in the previous (linear mode) example. This would roughly simulate the switch mode which we will discuss later in this page. You can see that with this method (switch mode), there would also be little pain (power dissipation) involved in supporting the weight.

    CLASS 'A'
    Many class A amplifiers use the same transistor(s) for both halves of the audio waveform. In this configuration, the output transistor(s) always has current flowing through it, even if it has no audio signal (the output transistors never 'turn off'). The current flowing through it is D.C. A pure class 'A' amplifier is very inefficient and generally runs very hot even when there is no audio output. The current flowing through the output transistor(s) (with no audio signal) may be as much as the current which will be driven through the speaker load at FULL audio output power. Many people believe class 'A' amps to sound better than other configurations (and this may have been true at some point in time) but a well designed amplifier won't have any 'sound' and even the most critical 'ear' would be hard-pressed to tell one design from another.
    NOTE: Some class A amplifiers use complimentary (separate transistors for positive and negative halves of the waveform) transistors for their output stage.

    CLASS 'B'
    A class 'B' amplifier uses complimentary transistors for each half of the waveform. A true class 'B' amplifier is NOT generally used for audio. In a class 'B' amplifier, there is a small part of the waveform which will be distorted. In a pure class 'B' amplifier, the output transistors are not "biased" to an 'on' state of operation. This means that the the part of the waveform which falls within this .6 volt window will not be reproduced accurately. The output transistors for each half of the waveform (positive and negative) will each have a .6 volt area in which they will not be conducting. The distorted part of the waveform is called 'crossover' or 'notch' distortion. Remember that distortion is any unwanted variation in a signal (compared to the original signal).

    CLASS 'AB'
    As we said earlier, a class 'A' amplifier is very inefficient. This is not good for a car audio amplifier. We also said that a class 'B' amplifier will cause a signal to be distorted, which is not good in any audio amplifier. A class 'AB' amplifier is the best compromise. A class 'AB' amplifier is a class 'B' amplifier which has a small amount of "bias" current flowing through the output transistors at all times. This eliminates virtually all of the crossover distortion. The bias current is flowing because the output transistors are always conducting current (even without an audio signal). This differs from a pure class 'A' amplifier in the amount of current flow. A pure class 'A' amplifier has an enormous amount of current flowing through its output transistors with NO audio signal. A pure class 'B' amplifier has NO current flowing through its outputs with no input signal. A class 'AB' amplifier is much more efficient than the class 'A' but without the distortion of the class 'B'. MANY of the car audio amplifiers which claim to be a class 'A' amplifier are just a high bias class 'AB' design. These amplifiers are only class 'A' at very low power output levels. At higher power levels, one of the output transistors will switch off while the other output transistor is conducting. I don't want you to think that I am telling you that there are no class 'A' amplifiers. There are a few high quality mobile amplifiers which are a true class 'A' design.

    CLASS 'D'
    We said that class 'A' amplifiers were VERY inefficient. Class 'AB' amplifiers are also inefficient but are more more efficient than class 'A' amplifiers. Class 'AB' mobile amplifiers are generally 60% efficient when driving a 4 ohm load at maximum power (just before clipping). The reason that these amplifier configurations are inefficient is because there is a difference of potential (voltage) across the output transistors and current flowing through the output transistors. When you have voltage across the device and current flow through the device, there will be power dissipation in the form of heat. The power needed to produce this heat is wasted power. When there is (virtually) no voltage drop across a device (such as a large piece of wire or a transistor), there can be a significant amount of CURRENT flow through the device with (virtually) no power dissipation. This means that there is virtually no heat given off (highly efficient). The inverse is also true. If you have a significant amount of VOLTAGE across the device (transistor, wire...) but no current flow through the device, again, there will be no wasted power.
    OK, now to the point. A class 'D' amplifier, which may also be known as a switching amplifier or a digital amplifier, utilizes output transistors which are either completely turned on or completely turned off (they're operating in switch mode). This means that when the transistors are conducting (switched on) there is virtually no voltage across the transistor and when there is a significant voltage across the transistor (switched off), there is no current flowing through the transistor. This is very similar to the operation of a switching power supply which is very efficient.

    - Steve



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    2006 Kawasaki Ninja ZX14
    Quote Originally Posted by DJGTSR
    I dont mean to be rude, but what is the highest level of education that you finished?

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    Re: Terminology - Please contribute

    Amplifier bridging is simply using 2 driven output channels to drive a common load. For 2 channel amplifiers, one left signal and one right signal is used to drive a mono speaker load. Keep in mind that mono and bridging are not necessarily the same. Mono means that there's only one output signal. There could be more than one speaker but each speaker will have the same output. Bridging means that you are using more than one source of power to drive a load (speaker). The sources of power are one each output from either channel of the amplifier. A long time ago, amplifiers had signal on the positive output speaker terminals only. To bridge one of those amplifiers, you'd have to use some means to invert the signal on one channel (remember the old 'bridging modules' for Orion amplifiers?). Today's bridgeable amplifiers have an inverted channel as part of their design. For many amplifiers, the left positive and right negative are are the signal outputs. A few use the left negative and the right positive. Others still (mostly mono amplifiers that are to be used in bridged pairs) require that you choose 0° or 180° via a switch to invert the signal.
    Note:
    Before we go any farther let me say this... It it NOT necessary to bridge an amplifier to make it produce maximum power. Bridging is simply one option. If an amplifier is 2 ohm stereo stable (and therefore 4 ohm mono stable), it will produce the same power into a 2 ohm stereo load as it will into a 4 ohm mono load.
    Many people feel that they have to connect every amplifier they own in a 2 ohm mono configuration. These are generally the same people who have owned (and destroyed) many amplifiers. This is because very few amplifiers (especially Class A/B amplifier) are capable of safely driving a 2 ohm mono load.
    Refresher:
    Remember that the AC voltage across a speaker's voice coil is what determines the amount of power dissipated by the voice coil (and ultimately how much sound pressure the speaker will produce). In other words, when more voltage is applied to a speaker, the speaker will play louder. If one speaker terminal is connected to a reference point which has no signal (commonly referred to as ground-indicated by the red line) and the other speaker terminal is connected to the signal (speaker output) lead of the amplifier, you will only be able to get half of the power supply's total voltage across the speaker at any point in time.

    Realize that a speaker must move equally in both directions from its point of rest. If the amplifier's power supply output is 40 volts total or ±20 volts with "ground" as the reference, the maximum instantaneous voltage that can be applied across the non-bridged speaker's terminals is 20 volts. Well this would be true if the amplifier components were 100% efficient. In the real world the output voltage would be somewhat lower due to inefficiencies but we won't worry about inefficiency right now. For now assume that the full power supply voltage (positive or negative) can be driven into the speaker.
    Now, what if you have only a single 4 ohm speaker and a 2 channel NON-bridgeable amplifier with sufficient current output capability to drive a 2 ohm load on each of its output channels? You know that the amplifier could produce MUCH more (and also maximum) power into four 4 ohm speakers (which would be equal to a 2 ohm load per channel), but maximum power would not be produced into the single 4 ohm speaker on a single output channel (i.e. left OR right). To produce maximum power into a single 4 ohm speaker (without increasing the rail voltage) you could simply invert the signal of one channel and bridge the speaker on the amplifier. This is why some of the older amplifiers used a 'bridging module' (it inverted the signal going to one channel). It is very easy to invert one channel when designing an amplifier and it makes the amp much more versatile. When one channel is inverted, it's output voltage is of the same magnitude as the "normal" channel but is of opposite polarity.
    At any point in time, if the normal channel's output voltage is positive, the inverted channel's output voltage is negative and vice-versa. The inverted channel is basically a mirror image of the normal channel. Now remember that 4 ohm speaker and the fact that the power dissipated in it's voice coil is determined by the voltage across its terminals. With the bridgeable amp, one of the speaker's terminals would be connected to the normal output channel (violet waveform) and the other speaker terminal would be connected to the inverted channel (yellow waveform) of the amplifier. This allows you to get the total power supply voltage across the speaker. Remember, we are not concerning ourselves with inefficiencies within the amplifier. You can see by the following formula, that the power getting to the speaker is much greater.

    P=E*E/R
    Power=(40*40)/4 ohms
    Power=400 watts

    You can see that this is considerably more power! (100 watts unbridged and 400 watts bridged)

    VERY IMPORTANT...
    If an amplifier is only rated to drive a 4 ohm minimum load on each of its channels, it WILL fail if you try to drive a 4 ohm bridged mono load. If you have an amplifier rated to drive a 2 ohm stereo load (2 ohms on each channel), it's only going to be able to drive a 4 ohm bridged mono load. A 2 ohm bridged mono load will more than likely destroy the amplifier.

    There seems to be some confusion as to why a 4 ohm mono and a 2 ohm stereo load are the same, as far as the amplifier is concerned. When two 4 ohm speakers are connected to each channel of a 2 channel amplifier, the amplifier is capable of driving the speakers with half of the total power supply voltage. If the amplifier has a power supply which produces plus or minus 20 volts, it will not be able to drive the speakers on a single channel with any more than 20 volts at any point in time. If we have a 2 ohm load on each channel, at the highest point on the waveform the amplifier will apply 20 volts to the speaker load. Remember that we are only considering a single point in time for this example. If we go back to ohms law...

    I=V/R
    I=20/2
    I=10 amperes

    If we take a single 4 ohm speaker and bridge it on that same amplifier, the amplifier will be able to apply twice the voltage across the speaker. This is because while one speaker terminal is being driven positive (towards the positive rail), the other terminal is being driven towards the negative rail. This will allow the entire power supply voltage to be applied to the speaker's voice coil. It will now be able to drive the 4 ohm speaker with 40 volts instead of 20 volts in the previous example. Back to Ohm's law...

    I=V/R
    I=40/4
    I=10 amperes

    The same amount of current flows through the output transistors whether the amplifier is driving a 4 ohm mono load or 2 ohm stereo load. As far as the amplifier is concerned, they are the same load.

    NOTE:
    Some people say that when an amplifier is bridged onto a 4 ohm load, it 'sees' a 2 ohm load. While it is true that the same current flows whether the amp is bridged on a 4 ohm load or a 2 ohm stereo load, the amplifier is driving a 4 ohm load across its outputs. A single 4 ohm speaker can never be a 2 ohm load.

    a 4 ohm mono load is the same as a 2 ohm stereo load as far as the amplifier is concerned.


    Stereo vs Mono:
    The terms stereo and mono are often used when referring to amplifier connections. A stereo amplifier has two independent channels, one left and one right. The left and right signals of the stereo signal are similar but not exactly the same. The two channels are used to give the audio a sense of depth. If one instrument or voice is only produced in the left channel, it will seem to originate from the left side of the listening area. If a particular sound is only slightly louder in one of the channels, that sound will seem to originate off center slightly toward the channel in which the sound is louder. If you have two speakers but supply mono signal to both of them, there will be no sense of separation or depth. If a mono signal fed to both channels of a stereo amplifier, with a speaker on each channel, the output will mono. If a stereo signal is fed to the same amp/speaker set up, the output will be stereo. If a speaker is bridged onto a stereo amplifier, the output of the speaker will be a mono output, even if the signal fed into the amplifier is a stereo signal. Even if 2 speakers are bridged onto the amplifier, the output will still be mono because the output from each speaker has the same content.
    It is always afer to run the amplifer to get the most out of it in the highest ohm load that gives you the most power for your application.

    Prior to 1970, there were no easy or affordable methods accepted as standard in the industry for obtaining comparative data about loudspeaker performance. Recognized laboratory tests were expensive and unrealistic for the thousands of individuals needing performance information. Standard measurement criteria were required to enable manufacturers to publish consistent data for customers to make comparisons between various loudspeakers.

    - Steve



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    2006 Kawasaki Ninja ZX14
    Quote Originally Posted by DJGTSR
    I dont mean to be rude, but what is the highest level of education that you finished?

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    Re: Terminology - Please contribute

    Thiele-Small Parameters

    In the early seventies, several technical papers were presented to the AES (Audio Engineering Society) that resulted in the development of what we know today as 'Thiele-Small Parameters'. These papers were authored by A.N.Thiele and Richard H. Small. Thiele was the senior engineer of design and development for the Australian Broadcasting Commission and was responsible at the time for the Federal Engineering Laboratory, as well as for analyzing the design of equipment and systems for sound and vision broadcasting. Small was, at the time, a Commonwealth Post-graduate Research Student in the School of Electrical Engineering at the University of Sydney.
    Thiele and Small devoted considerable effort to show how the following parameters define the relationship between a speaker and a particular enclosure. However, they can be invaluable in making choices because they tell you far more about the transducer's real performance than the basic benchmarks of size, maximum power rating or average sensitivity.



    Fs------This parameter is the free-air resonant frequency of a speaker. Simply stated, it is the point at which the weight of the moving parts of the speaker becomes balanced with the force of the speaker suspension when in motion. If you've ever seen a piece of string start humming uncontrollably in the wind, you have seen the effect of reaching a resonant frequency. It is important to know this information so that you can prevent your enclosure from 'ringing'. With a loudspeaker, the mass of the moving parts, and the stiffness of the suspension (surround and spider) are the key elements that affect the resonant frequency. As a general rule of thumb, a lower Fs indicates a woofer that would be better for low-frequency reproduction than a woofer with a higher Fs. This is not always the case though, because other parameters affect the ultimate performance as well.



    Re--------This is the DC resistance of the driver measured with an ohm meter and it is often referred to as the 'DCR'. This measurement will almost always be less than the driver's nominal impedance. Consumers sometimes get concerned the Re is less than the published impedance and fear that amplifiers will be overloaded. Due to the fact that the inductance of a speaker rises with a rise in frequency, it is unlikely that the amplifier will often see the DC resistance as its load.


    Le--------This is the voice coil inductance measured in millihenries (mH). The industry standard is to measure inductance at 1,000 Hz. As frequencies get higher there will be a rise in impedance above Re. This is because the voice coil is acting as an inductor. Consequently, the impedance of a speaker is not a fixed resistance, but can be represented as a curve that changes as the input frequency changes. Maximum impedance (Zmax) occurs at Fs.

    Q Parameters---------Qms, Qes, and Qts are measurements related to the control of a transducer's suspension when it reaches the resonant frequency (Fs). The suspension must prevent any lateral motion that might allow the voice coil and pole to touch (this would destroy the loudspeaker). The suspension must also act like a shock absorber. Qms is a measurement of the control coming from the speaker's mechanical suspension system (the surround and spider). View these components like springs. Qes is a measurement of the control coming from the speaker's electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock. Qts is called the 'Total Q' of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same.
    As a general guideline, Qts of 0.4 or below indicates a transducer well suited to a vented enclosure. Qts between 0.4 and 0.7 indicates suitability for a sealed enclosure. Qts of 0.7 or above indicates suitability for free-air or infinite baffle applications. However, there are exceptions! The Eminence Kilomax 18 has a Qts of 0.56. This suggests a sealed enclosure, but in reality it works extremely well in a ported enclosure. Please consider all the parameters when selecting loudspeakers. If you are in any doubt, contact your Eminence representative for technical assistance

    Vas/Cms--------Vas represents the volume of air that when compressed to one cubic meter exerts the same force as the compliance (Cms) of the suspension in a particular speaker. Vas is one of the trickiest parameters to measure because air pressure changes relative to humidity and temperature — a precisely controlled lab environment is essential. Cms is measured in meters per Newton. Cms is the force exerted by the mechanical suspension of the speaker. It is simply a measurement of its stiffness. Considering stiffness (Cms), in conjunction with the Q parameters gives rise to the kind of subjective decisions made by car manufacturers when tuning cars between comfort to carry the president and precision to go racing. Think of the peaks and valleys of audio signals like a road surface then consider that the ideal speaker suspension is like car suspension that can traverse the rockiest terrain with race-car precision and sensitivity at the speed of a fighter plane. It’s quite a challenge because focusing on any one discipline tends to have a detrimental effect on the others

    Vd------This parameter is the Peak Diaphragm Displacement Volume — in other words the volume of air the cone will move. It is calculated by doubling Xmax (Voice Coil Overhang of the driver) then multiplying the result by Sd (Surface area of the cone). Vd is noted in cc. The highest Vd figure is desirable for a sub-bass transducer

    BL------Expressed in Tesla meters, this is a measurement of the motor strength of a speaker. Think of this as how good a weightlifter the transducer is. A measured mass is applied to the cone forcing it back while the current required for the motor to force the mass back is measured. The formula is mass in grams divided by the current in amperes. A high BL figure indicates a very strong transducer that moves the cone with authority!

    Mms------This parameter is the combination of the weight of the cone assembly plus the ‘driver radiation mass load’. The weight of the cone assembly is easy: it’s just the sum of the weight of the cone assembly components. The driver radiation mass load is the confusing part. In simple terminology, it is the weight of the air (the amount calculated in Vd) that the cone will have to push


    Rms------This parameter represents the mechanical resistance of a driver’s suspension losses. It is a measurement of the absorption qualities of the speaker suspension and is stated in N*sec/m.


    EBP-----This measurement is calculated by dividing Fs by Qes. The EBP figure is used in many enclosure design formulas to determine if a speaker is more suitable for a closed or vented design. An EBP close to 100 usually indicates a speaker that is best suited for a vented enclosure. On the contrary, an EBP closer to 50 usually indicates a speaker best suited for a closed box design. This is merely a starting point. Many well-designed systems have violated this rule of thumb! Qts should also be considered.

    Xmax/Xmech--------Short for Maximum Linear Excursion. Speaker output becomes non-linear when the voice coil begins to leave the magnetic gap. Although suspensions can create non-linearity in output, the point at which the number of turns in the gap (see BL) begins to decrease is when distortion starts to increase. Eminence has historically been very conservative with this measurement and indicated only the voice coil overhang (Xmax: Voice coil height minus top plate thickness, divided by 2). Xmech is expressed by Eminence as the lowest of four potential failure condition measurements times 2: Spider crashing on top plate; Voice coil bottoming on back plate; Voice coil coming out of gap above core; Physical limitation of cone. Take the lowest of these measurements then multiply it by two. This gives a distance that describes the maximum mechanical movement of the cone.


    Sd------This is the actual surface area of the cone, normally given in square cm.


    Zmax-----This parameter represents the speaker’s impedance at resonance.

    Usable frequency range---------This is the frequency range for which Eminence feels the transducer will prove useful. Manufacturers use different techniques for determining ‘Usable Frequency Range’. Most methods are recognized as acceptable in the industry, but can arrive at different results. Technically, many loudspeakers are used to produce frequencies in ranges where they would theoretically be of little use. As frequencies increase, the off-axis coverage of a transducer decreases relative to its diameter. At a certain point, the coverage becomes ‘beamy’ or narrow like the beam of a flashlight. Following is a chart that demonstrates at what frequency this phenomenon occurs relative to the size of the transducer. If you’ve ever stood in front of a guitar amplifier or speaker cabinet, then moved slightly to one side or the other and noticed a different sound, you have experienced this phenomenon and are now aware of why it occurs. Clearly, most two-way enclosures ignore the theory and still perform quite well. The same is true for many guitar amplifiers, but it is useful to know at what point you can expect a compromise in coverage.

    - Steve



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    2006 Kawasaki Ninja ZX14
    Quote Originally Posted by DJGTSR
    I dont mean to be rude, but what is the highest level of education that you finished?

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    Professor ss3079 takes no prisoners.........




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    Power handling-------------This specification is very important to transducer selection. Obviously, you need to choose a loudspeaker that is capable of handling the input power you are going to provide. By the same token, you can destroy a loudspeaker by using too little power. The ideal situation is to choose a loudspeaker that has the capability of handling more power than you can provide lending some headroom and insurance against thermal failure. To use an automobile as an analogy; you would not buy a car that could only go 55mph if that were the speed you always intended to drive. Generally speaking, the number one contributor to a transducer’s power rating is its ability to release thermal energy. This is affected by several design choices, but most notably voice coil size, magnet size, venting, and the adhesives used in voice coil construction. Larger coil and magnet sizes provide more area for heat to dissipate, while venting allows thermal energy to escape and cooler air to enter the motor structure. Equally important is the ability of the voice coil to handle thermal energy. Eminence is renowned for its use of proprietary adhesives and components that maximize the voice coil’s ability to handle extreme temperatures. Mechanical factors must also be considered when determining power handling. A transducer might be able to handle 1,000W from a thermal perspective, but would fail long before that level was reached from a mechanical issue such as the coil hitting the back plate, the coil coming out of the gap, the cone buckling from too much outward movement, or the spider bottoming on the top plate. The most common cause of such a failure would be asking the speaker to produce more low frequencies than it could mechanically produce at the rated power. Be sure to consider the suggested usable frequency range and the Xmech parameter in conjunction with the power rating to avoid such failures.

    Car Batteries

    What you need to know about your vehicle's battery.

    Most of us don't think much about the battery in our vehicle; we simply turn the key and expect the engine to start. We expect the battery to be reliable, long-lasting and maintenance-free. Once it fails, however, odds are you'll have to replace it, and knowing which type and size battery you need is important. Will it be conventional, maintenance-free or recombination?
    Conventional Batteries
    A 12-volt automotive battery has six compartments or cells. Each cell has a series of alternating positive and negative plates separated by isolators. All negative plates in the battery are connected, as are all positive plates.

    Each plate has lead sheeting bonded to it and every cell is filled with a solution of sulfuric acid and distilled water (electrolyte). As the battery supplies electricity, or discharges, the electrolyte reacts with the lead, forming lead sulfate and weakening the electrolyte.

    Conversely, as it charges, the acid is returned to the electrolyte and the lead sulfate is converted back into active material in the plates. During this cycle, hydrogen, and oxygen molecules evaporate out of the electrolyte, which is why batteries often need topping up with distilled water. Over time, continual charge/discharge cycles slough lead off the plates that build up in the bottom of the battery. Eventually, the plates short out and the battery dies.

    Maintenance-free Batteries
    A maintenance-free battery is essentially the same as a conventional battery, except for thicker plates and more electrolyte. Most new vehicles come equipped with this type of battery since it is more reliable and lasts longer. However, these batteries cannot be topped up and once the electrolyte evaporates and the plates are exposed, the battery is no good.

    Another type of maintenance-free battery is the gel-type. It has the electrolyte in gelatin form and does not lose electrolyte through evaporation. However, because the use of electrolyte gel requires the use of thinner plates for proper distribution of the acid it means that a gel battery in marginal condition can literally shake the plates apart as the vehicle rides over rough roads.

    Recombination Batteries
    Recombination batteries recombine the gases formed during charging, keeping electrolyte concentrations optimum. They are completely sealed, never need topping up, and come with either liquid or gel-type electrolyte that is bound into the separators. There is no sloughing of lead and the plates in these batteries are tightly packed. The result is a powerful, compact battery with quicker charging time and a longer lifespan. The down side is often a higher price tag.

    How Batteries are Rated
    To help you determine what battery your car needs, batteries are rated by ampere hours (Ah), cold cranking amperes (CCA) and reserve capacity. These ratings tell you how much power a battery can produce under marginal conditions.

    Ampere hours rate how much current can be drawn from a battery over a 20-hour period without voltage dropping below 1.75 volts per cell. A healthy battery should keep the parking lights lit for 20 hours. For powering accessories without the engine running, this is an important measurement.

    Cold cranking amperes rate a battery's ability to start an engine under marginal conditions. CCA measures how much current can be delivered in amperes for 30 seconds at minus-18 degrees Centigrade (zero degrees Fahrenheit) with a final voltage of 7.2 volts per cell or higher. If you live in a cold-weather climate, you want this number as high as possible.

    Reserve capacity, measured in minutes, tells how long a battery can keep the engine going if the alternator fails. During this test, 25 amperes are drawn from the battery for as long as voltage does not drop below 10.5 volts. Any battery you purchase should have a reserve capacity of at least 120 minutes, so you can always make it home.

    Finally, always buy a battery rated for the vehicle and all the accessories it uses. Generally, this means a high Ah, high CCA, and high reserve capacity. Buy a quality, name-brand battery. Those sold in no-name battery discount stores are often poorly assembled and use inferior materials in the plates and separators.

    The Big 3 Are:
    1. negative battery wire to ground - just replace the negative batt. terminal and wire and ground it to the factory location
    2. engine block to ground - replace the ground wire from the engine block to the chasie with a bigger wire (maybe 4 guage)
    3. alternator to batt - add a fused wire from the postive post on you alternator (the one comming from the battery) to the postive terminal on your battery. DO NOT exchange wires just add a extra one. make sure it fused the same size as your factory fuse.

    hope thats helps

    Note on #2- Some cars have a batt-engine block connection stead of chassis to engine block...

    - Steve



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    2006 Kawasaki Ninja ZX14
    Quote Originally Posted by DJGTSR
    I dont mean to be rude, but what is the highest level of education that you finished?

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    Moderator

    2007 Chrysler 300C

    2005 Chevrolet Silverado 2500HD Crew Cab
    Optima, Volant, Bully Dog, Corsa, Gibson, Powermaster, California Super Trucks, Fox Racing, Airaid
    Alpine 7998, Alpine HDA-5460, Arc Audio MEQ-30, (2) Adire Audio Shiva, Image Dynamics CD-2COMP, Image Dynamics CX64, (2) Image Dynamics ID8V.2, Arc Audio 2100CXL, Arc Audio 4150CXL, Arc Audio 1500D-R

    2006 Kawasaki Ninja ZX14
    Quote Originally Posted by DJGTSR
    I dont mean to be rude, but what is the highest level of education that you finished?

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    Re: Terminology - Please contribute

    thanks, im gonna read all that ****...once i get a day off, or two...


    thanks again




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    Re: Terminology - Please contribute

    what about speaker ****???? I hear that a lot but can't seem to "relate" to what it might be. I only have 56k so I can't download those videos people post.




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    Re: Terminology - Please contribute

    Quote Originally Posted by ss3079
    I could go on, but no one wants to read all of that stuff anyway.


    - Steve
    got that right



    ---
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    Re: Terminology - Please contribute

    speaker **** or amplifier **** are just terms used to desribe the break down of equipment. Im not good at being direct, but here are some examples.

    Amplifier **** would be something like, the inside guts of an amplifier. Showing all the circuits or what not

    Speaker **** would be something like a video showing a subwoofer moving and u can see how much it moves

    Just like some people are **** junkies, well car audio has its own type of ****



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    Re: Terminology - Please contribute

    Quote Originally Posted by KARLEON
    speaker **** or amplifier **** are just terms used to desribe the break down of equipment. Im not good at being direct, but here are some examples.

    Amplifier **** would be something like, the inside guts of an amplifier. Showing all the circuits or what not

    Speaker **** would be something like a video showing a subwoofer moving and u can see how much it moves

    Just like some people are **** junkies, well car audio has its own type of ****
    If anyone knows a better way in saying what i just said, please post. As i said, im not good in exact definintions, but i can give examples to get my point across



    ULTIMATE SOUNDS & PERFORMANCE Presents TWO DUDES SPL SHOOTOUT - 1st Place Champion


    REFERENCES: Bigbassman, Rangerman, Deserheat, Bavarian, Req, Vosschs, George, Mountaineer Man, NGSM13, Kingpin_jeffie, Harrison, Dustin19, Iceteebone, Electrodynamic, Memphis4L, RaiN, Mikemareen, Omietrice, Suleman36, Jmanpc, Kickerlivinloud, ibanender, massiveaudiocw, phoenix88, polecat, j3bus2k3

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    Re: Terminology - Please contribute

    yah that definition hit the spot, we understand. thanks.




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