MoAv said:
I have to say this has been very interesting reading - and it really brought home to me how a person uneducated in audio equipment can really be taken in. When I have gone to stereo shops, the salesman quickly realizes I don't know squat about audio, the whole tone of the conversation changes. It's kind of like "here, just put this stuff in to the tune of 2500 bucks, and you'll be fine."...sort of the pat on the head type thing. Know what I mean?
You all seem to be very knowledgeable on this subject. Could I challenge you to take this a step further for us audio idiots? Maybe explain watts/amps and what they mean to each other? What's a crossover? You know, just basic info. Why do I need a certain size amp? Tune a sub? What does "push" mean? "In" phase "out of" phase
?? Have absolutely no clue on that parametric EQ thing...
I've researched on the web for info, but each store has their own info geared toward their own equipment. Is there a way to cut through all the crap and maybe start a thread with audio 101 for idjits? Or is there site somewhere that I haven't found that will explain all this simply?
I hope this makes sense..
You post could elicit literally volumes of text. However, I will give you a brief rundown of car audio basics.
Head unit: This is commonly known as your radio or your CD player. Most have a built-in amplifier for running full-range speakers such as those installed from the factory. However, in a high-end system, the radio power will never be used. A good head unit will have several sets of low level outputs?commonly known as RCA outputs. These pass the same signal as does the powered outputs, however they are not amplified and operate at relatively low voltage. The voltage of the low-level outputs, however, is very important. The more output voltage you have means the more power your amplifiers will make before clipping. Clipping is when your amplified output attempts to exceed the product of the input voltage and the operating power. It is called clipping because, instead of producing a pretty round parabolic wave form, the tops and bottoms of the waves are square, or ?clipped.? This is also known as distortion, and this also means death to speakers.
Crossover/processor: A crossover is the unit that divides up the audio spectrum into units manageable for your individual speakers. For instance, a woofer cannot produce the same portion of the spectrum as can the tweeter?so why try? A crossover will allow you to send only, for instance, 80hz and down to your subs, discarding the remaining portion of the spectrum. Likewise, will will only want to send high frequencies to your tweeters?say, 35khz and up. If you try to make the tweeters do the work of the subs, they should last all of about three seconds before you release the speakers magic smoke. The more channels a crossover has, the more segments you can divide the sonic spectrum into.
A processor is usually combined with a crossover, however, sometimes it is a standalone unit. Not everyone needs a processor, as this is to fine-tune your system to a more audiophile level. A processor can delay signal to any of your channels to allow the sound to reach your ears at the same time. It can align the phase of the speakers to adjust for sonic reflections, it can adjust independently small portions of the spectrum?also know as an equalizer?and it can add cool effects like echo to simulate different listening environments.
Amplifiers: An amp is the testicular grunt of your system. Amps are measured in watts. Be sure to pay attention to watts RMS, or route mean squared. This is the amount of power your amp can comfortably sustain. The max wattage is usually produced in a lab under unrealistic, unsustainable conditions. Wattage=voltage*amperage. So, a safe means of figuring what an amp is capable of doing is this: Take your input voltage?12 volts?and look at the fuse ratings?lets say, 40 amps. 12*40=480 watts. This is the higher limit of what the amp is capable of producing for a sustained period. However, all of the wattage is not being produced as music wattage. A percentage of this is being used up in the amplification process. The amount of wattage produced as music power is called the amp's efficiency. For instance, if the amp has 50% efficiency, then that 480 watts is reduced to 240 watts of music. The other 240 watts is being outputted as heat. Most amps nowadays have an efficiency of at least 65%, with many digital amps having an efficiency of around 85-90%. Obviously, these amps will produce more music power, while using less amperage. The down side to digital, or ?class D?, amps is that the amplification process produces high frequency switching noise. Therefore, these amps can only be used for low frequency production. The up-side to this is the fact that higher frequencies can be produced by amplifiers with lower efficiency, because not as much power is needed to produce a proportional level of this portion of the spectrum. There are also variable such as impedance curves and so on that we really don't need to get into during a remedial survey of this subject.
Speakers: Most everyone is familiar with coaxial speakers. These are the inexpensive speakers that you can find at Wal-Mart. These are identified with a larger speaker with smaller speaker suspending in the center. If you are trying to assemble a system of any degree of quality, then treat these like the plague. A higher-end option is that of component speakers. This is a set that consists of a set of mids/woofers, a set of tweeters, and sometimes a separate set of mids. These will also come with a passive crossover, though sometimes, you can buy individual component speakers without purchasing the set. The word ?passive? refers to a crossover that is on the amplified section of the music stream. This is to say that it is located between the amp and the speaker, rather than between the head unit and the amp. A crossover that falls between the head unit and the amp is called an ?active? crossover, or sometimes an electronic crossover. An easy way to think about this is: If a crossover required a power input, then it has to turn on to work. When it turns on, it becomes ?active. If a crossover's only inputs are speaker wires, then it just sits there waiting to filter music?therefore it is ?passive.? Usually, Active crossovers are superior to passive crossovers. The reason for this is that it is easier to filter a low-powered signal without introducing a large amount of distortion than it is to accomplish the same with a high-powered (amplified) signal.
The term ?phase? refers to the portion of the wave form that is being heard. For instance, imagine a parabolic (up and down) wave form. If the wave from one speaker reaches your ear and the wave form is at the top and when the wave from the other side reaches your ear, it is at the bottom, you are hearing output that is ?out of phase.? Your brain will interpret these two conflicting wave forms as a cancellation. That is to say that, it will sound somewhat as if the canceled frequencies are not even being produced. Cancellation can be interpreted by your brain as it interprets signals from your left and right ears, or it can occur mechanically between two speakers in proximity of each other. A good example of this is swapping the + and ? on one of two subs. You will hear that they are playing, but you will not hear very much output, and no bass at all. That is because these lower frequencies are being canceled out. The reason that it is sometimes beneficial to invert the phase on one tweeter or mid is because, at certain distances, the inverted phase of the speaker will allow two speakers with different path-lengths (the distance of the speaker to your ear) to actually be in phase when processed by your brain. This is because higher frequencies have a much shorter wave form, and therefore they can be aligned with minimal differences in distance. This is also known as phase alignment, and can be accomplished by many higher-end processors.
Subwoofers: These are also known as woofers, though this is a misnomer. A woofer is a speaker capable of producing somewhere between 40 and 1000 or so hz. A sub-woofer, is a speaker capable of producing sound to the lower limits of the audible spectrum?around 20hz. These are the large speakers capable of inducing bowel movements and female happy times. You really need to know more about subs than you do other speakers?that is, if you are a audio novice. This is because certain specs will cause greater variances than with higher frequency speakers. This is true also because, most novices want bass before anything else.
The first spec is size, or displacement. When it comes to being loud, there is no substitution for size?sorry, this is the truth. There is a saying in the world of racing: There is no replacement for displacement. This is also true when it comes to bass. However, larger speakers can have a difficult time being articulate. Articulation of a speaker is known as the ?attack? and ?decay? times, however, this is better left for Audio 102. For now, lets just say that smaller subs are better for ?tighter? bass.
The next spec is power handling. Again, you need to be sure that you are looking at the RMS or continuous power rating. However, please note, if you say to a person that knows anything about audio; ?my speakers make 500 watts? and you base this assertion on the wattage rating of the subs, they will look at you funny and laugh at you behind your back. Speakers do not make wattage. They consume wattage. They take this wattage and convert it to sonic energy through the energizing of a resistive coil which causes the piston (cone) to move up and down, being propelled and contracted by counteracting magnetic forces. The wattage rating is how much power your speakers can safely consume without releasing aforementioned ?magic smoke.?
The next spec, and the hardest to understand, is the resistance, or ?ohm? rating. The term ?ohm? is derived from ohm's law, which is a set of calculations used to measure the different facets of electricity. For instance, when we used the formula of V*A=W, this is an ohm's law equation. However, here the word ?ohm? refers to the speakers resistance. Most people do not realize this, but the + and ? connectors on a speaker are connected. Between these connections is a tightly wound copper coil. Many people have seen a demonstration where a copper coil can be energized to create an electromagnet. This is what is happening inside your speakers. The more wire in the coil means the higher the resistance. However, the higher the number means the speaker will consume less power. 0 ohms is tantamount to a dead short. For instance, it you take your speaker wires and touch them together, this is a 0 ohm load?this will also make your amplifier very unhappy. Most subs are either 4 or 8 ohms. This must coincide with an amp's ohm load stability. If an amp is 4 ohm stable, then you can use it to run a single 4 ohm speaker. However, you can also run two 8 ohm speakers wired in parallel?parallel meaning the speakers are connected positive to positive and negative to negative. The other method of wiring is know as ?series? wiring. Here, when using two speakers, the ohm load is doubled. So, instead of 4 ohms, two 8 ohm speakers wired in series would yield a 16 ohm load. I won't get into this any further as this may again be a topic for another day. To figure your parallel ohm rating for more than two speakers, use this shorthand method. Lets say you have four 4 ohm speakers and you wire them in parallel. Take the ohm rating, 4, and divide it by the number of speakers, 4. 4/4=1. This would yield a 1 ohm load. This is the ohm rating for higher-end subwoofer amps. However, groupings of three speakers has become popular. For this, use the same equation. 4 ohms /3 speakers= 1.33 ohms. This trend is the reason why JL Audio began producing dual voice coil 6 ohm woofers years ago. If you wired one of the two voice coils from each speaker in parallel, you get 2 ohms. Then, you wire the other three voice coils in parallel. Finally, you wire these two ohm connections in series and you get a 4 ohm final load, making this a perfect fit for 4 ohm stable amps. For those who know about this, I know there is another way of wiring this configuration, but I am trying to keep it simple.
If you see that an amp's rated power is 500 watts at 4 ohms, this means that it will produce 250 watts at 8 ohms and about 1000 watts at 2 ohm if it is 2 ohm stable. I say ?about? because when you get closer to a dead short, the doubling factor is compromised a bit due to increased strain on the electrical components.
Now, I honestly just barely scratched the surface of what is out there on the topic of audio. This is why this is such a difficult subject to master. The good thing about of many of the more affordable products is that, seeing that the products are aimed at an audio novice, much of the guess work has been engineered out of the product. For instance, you can buy 4 6.5? coaxials capable of handling 100 Watts, and buy an amp capable of producing 100 wattsX4, hook it all up, set the gains and built-in crossovers, and then your rocking. Given it won't sound as good as an advanced setup, but you also don't need the equivalent of a PhD in electrical engineering to figure it out.
In closing, I would like to say this: If you find a really good installer that you can work with, count your blessings and treat him well. Being a really good installer is far more difficult than anyone can imagine. This requires that you be masterful in electrical knowledge, acoustic engineering, carpentry, upholstery, fabrication, fiberglass working, and many other fields that are recognized as professions in and of themselves. On top of all of this, that person must have a wondrous imagination and the ability to translate mental imaging into tangible, real-world manifestation. I labor for 12 years to become a good professional installer. I managed to secure installer and management positions in the top shops in the state, and even became MECP certified. Despite this, I never made more than 35K a year, and ended up with a quirky back from too much time laying upside down with my head buried under a dash. I went back to school at 27, and right now I am working on realizing my second preference profession?being an attorney.
Speaking of hair moving
