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Old 01-10-2006, 01:04 PM   #1
DJ_Mittens
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So you want to learn about car audio... (Updated 2-17-06)

I've decided to write this post, so I don't have to keep answering the same questions and perhaps contradicting myself therein. Bad news.

So, I'm here to give you an overview about how to best setup your system. I'll point out problems that can occur along the way and how to resolve them.

Theory

This is a disclaimer of sorts. Just to get some things out of the way first.

I like lots of music. Everything but country, but even then there are some tracks that are interesting (Chattahoochie by Alan Jackson is pretty cool). I'm a fan of accurate, warm sound, with careful attention to the lower frequencies. Give me an EQ curve high on the lows, low on the mids (careful, vocals can easily be lost this way), and moderate on the highs. I like listening for parts of the music that are otherwise lost by other listeners, like hearing the full dropoff on a high hat, rather than the initial hit, listening for two distinct drum hits rather than the single hit it's usually muddled as with most audio equipment, and stuff like that. There are definitely times I enjoy loud music, which is why I've spent so much time and money on my car stereo, and why I was once a DJ, but often I prefer a moderate volume that allows your ears to relax, but also be able to hear those small, distinct nuances of a given track.

So, to begin. Audio is subjective. Completely subjective. Some people like clarity (digital audio, metal tweeters), some like warmth (analog audio, like LPs, vacuum tube amplifiers, ribbon tweeters), some like bass (me!), some like treble. It's your system, so NEVER let someone tell you you're wrong if you like a product more than another. NEVER let a salesman try to tell you why your ears are wrong (happens to me all the time). That's why I gave you my background, so you know where I'm coming from when I give a subjective analysis.

Why are your ears not wrong? Ears are not perfect. Actually, they're really crappy microphones. They have pretty high accuracy if they haven't been abused (like mine, other DJs, and construction workers), but have very very bad frequency sensitivity. The sensitivity of your ears starts very high at the high end of the audible frequency spectrum (20KHz), and slopes right down to damn crappy at the low end (20Hz). (FYI, 20Hz isn't QUITE when the audible spectrum starts. With my non-scientific testing, it's about 18-19Hz. Whatever.) I mean, you need bass so powerful you can actually FEEL it before you can hear it down at the bottom end, unless your ears are quite sensitive like mine to lower frequencies. That's a lot of displaced air.

Now you know that your ears suck. Congratulations. You may be asking yourself now why so much time and effort is spent on creating highly accurate equipment when your ears aren't. That accurate equipment is meant to replicate the original recording as closely as possible. Remember, your ears' response may suck, but they are very accurate and can easily pick up the difference between low- and high-fidelity sources. I can tell the difference between 192Kbps MP3 and 256Kbps. At times, I can also tell the difference between different encoders, too. I can't stand 128 at the best of times because the poor fidelity actually hurts my ears. So, spending that extra money can make a difference to what you hear, but the question is, is the difference worth it to you?

Here are a couple tidbits I'll address in this post.

When I say 1000w, I mean 1000wrms, not peak. RMS is generally 1/2 of peak, or the maximum sustainable output of an amplifier / maximum sustainable input for a speaker. RMS = Root Mean Squared, so you square each value, add them together, divide that total by the number of values, and then take the square root of that value. Basically, it makes every value positive and gets the average. It's 1/2 of peak because any power outputs should follow a normal curve (like a bell curve), and the peak will be the highest, and 0 will be the lowest. Most should fall in the middle, which is the (maximum + minimum) / 2. This is in general, because some amps have crappy power regulation and will put out rediculous high power numbers, but their RMS value can be 1/3 or 1/4 of the peak (see Sony, Pyramid, Lanzar, and other Radio Shack brands).

A conventional speaker is about 2% mechanically efficient, give or take. That means 2% of any energy input is converted to a sound wave. The other 98% turns into heat. That means a 1000w driver hooked up to a 1000w amp running at maximum power, 20w will be acoustic power. 980w will be heat. Think of the heat put out by a 100w bulb, and multiply that by 10. That's a pretty good amount of juice. Keep that in mind when you're clipping your speakers and amplifiers.

Source

So, to start. Source. Aka head unit. There are a lot (LOT!) of options. Some have fancy dancy shiny things that look really cool but do nothing for performance (see Sony's entire product line), and others that are very simple, not flashy at all, but are incredibly solid performers (Nakamichi, for instance). There tonnes and tonnes of features that head units have that may or may not be wanted/needed. Stuff like:
Time Delay (software delay on certain channels to make the sound from each speaker arrive at your ears at the same time. Works if you're only listening to the stereo from exactly one unchanging spot in your car. Passengers will hear seriously messed up sound the further away they are from the sweet spot).
are generally unnecessary if the speakers were installed properly in the first place. I tried setting this up on my stereo, just for the heck of it. I got a headache because my ears kept trying to follow the sound and given the crazy acoustic properties of a car, it kept changing, depending on the frequency. I turned it off, and it sounded a lot better.

Simple thing to do is to go to a reputable shop, bring some CDs, some MP3 CDs too if you like, maybe some scratched ones, and demo the units. Check out construction and durability (does the faceplate feel like it's going to fall off, does the drive motor make weird noises), performance (time to compile list of MP3 tracks), acoustic quality (does it sound "good" to you?), and the like. If they have an actual listening room setup, make sure you're using the same speakers and amplifier, and only changing the source unit.

The fancy features should be secondary to getting a unit you like the sound of. When you're driving, you're not staring at the slideshow on your head unit. You're listening to the music. Slideshows, mini video displays, blinking lights and shiny things are all well and good, but they are an annnoyance at night, and just something else that can break. Alpine has those touch-glide features that, while kind of neat, are somewhat of an annoyance if you like accurate buttons like I do, and IIRC, were recalled a while back and replaced due to defects.

If you're getting a unit with a display, watch the screen, try to see the maximum viewing angle (look at it from the sides, top, bottom), and try to see the accuracy of the color reproduction. Is it washed looking, too dark, too light, is it something that could be adjusted with a little color correction and the proper contrast or does it just not perform well? Then your decision must factor in acoustic and visual performance.


Amplification

This section is rather important too. This section covers the conversion of a modulating electronic signal into a modulating magnetic field and ultimately into something you hear. This includes both the head unit's amplifier and an external one.

To begin, I dislike head unit amplifiers. They are weak and quite poor fidelity. I seem to recall only seeing one unit that could put out 20wrms per channel. Most are 18, some are 16, and there are some that don't even have one (hooray!). That's a fair amount of power, and no doubt, but at higher volumes, that amp will clip faster than a profession hair sylist. Your speakers will not like it, at all. Clipping speakers = turn down the volume before you break something. Clipping amplifier = speakers and amp on fire.

Why? It involves a myth called "Too Little Power" (see here for the long answer). Some people are under the impression that if you use an amp with far less power than the speaker is rated to handle, you'll blow them up. The short answer is bullcrap, the long answer has a caveat.

An audio signal is just a sine wave of changing frequency (relative distance between peaks) and amplitude (relative height of the peaks). An amp can only put out so much amplitude.



If you're driving an amp at more than it's able to perform, at the intermediate slopes, the amp will put out the power needed to create that part of the curve, but once it maxes out, it will stop increasing the amplitude of the wave and make that plateau. You can keep cranking the system, and get a nearly square wave. That's mega bad news. The speaker will then be moving as far as it can with the amplifier's output, and then will stop, with current still travelling through it's voice coils. Remember what I stated about a speaker's mechanical efficiency. A speaker that's moving back and forth can get enough air over the coil to keep it cooled and keep it from melting. You stop that speaker from moving, even for an instant, and those coils will melt, short out the amp, and burn your car to the ground. If you're clipping the speaker and not the amp, you'll be lucky if you just get mechanical failure, like a torn spider.

Remember that when you are running your system - any system.


Speakers

Speakers are very simple devices. They are nothing but an electromagnet (aka Motor) connected to a diaphragm. You have the magnet, voice coil, and a diaphragm. At rest, the magnet neither attracts nor repels the voice coil in the middle. It doesn't move. However, if you run a current through a wire at a certain voltage, that wire creates a magnetic field. If you have a high voltage, you get a lot of magnetic flux (ie: change in magnetic forces). What happens when you have two magnetic fields in close proximity to each other? Those magnetic forces will act upon each other, either attracting or repelling each other. So, if you put a voltage through the voice coil in one direction, that magnetic field will act on the solid core magnet attached to the basket. Since that magnet is not moving anywhere, the force acts on the voice coil, and the diaphragm it's attached to, moving the diaphragm in or out. If you change the direction of the current, the voice coil will have the opposite force acted upon it and will move in the other direction. Change the amplitude of the voltage and the frequency at which it changes, and you see the speaker pulsate. Change it faster, makes the changes bigger, and eventually you get some significant pressure changes and you get sound.

Simple, right? So then why aren't all speakers created equal? For the same reason that not all car engines are created equal. Everything from the weight and strength of the diaphragm to the flexibility of the suspension to the strength of the magnet to the number of wraps and density of the voice coil affect the performance of the driver.

So, what's a good driver? I go back to my original advice - whatever you like. I can't tell you what you like, you have to hear for yourself. But, I will give these bits of advice so you won't get suckered by salespeople.

First, magnet size is meaningless. In theory, a larger magnet will mean you've got a larger VC working against it, and theoretically a driver with higher excursion (Xmax in Thiele-Small (Ts) parameters) and higher power handling, but lower efficiency. But, it's by no means absolute. You can get drivers with relatively smaller magnets but the same or better power handling than drivers with larger magnets. MB Quart, for example has a tendency to have particularely small magnet structures, but quite high power handling and somewhat low efficiency.

If you want more details about TS parameters and what they mean, check out Wikipedia:

http://en.wikipedia.org/wiki/Thiele/Small (overview)
http://en.wikipedia.org/wiki/Electric_charge (definition of Q)
http://editweb.iglou.com/eminence/em...s02/params.htm (Website giving good definitions of major TS parameters)



That is all I'm going to write for now. In future installments, I'll cover wiring, enclosures, and additional hardware you may be interested in getting (dual alternators, dual batteries, capacitors, what have you). Enjoy for now. Got comments, feel free to PM me.
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Last edited by DJ_Mittens; 02-18-2006 at 08:02 AM.
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Old 01-11-2006, 03:34 PM   #2
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Wiring

These sections will be a tad shorter than the other sections, simply because there is less that's important about them.

First, power. Your car's electrical system is physically backwards. Electricity is simply negatively-charged electrons flowing from one point to another. Current is the number of electrons (like the volume of water through a pipe), voltage is the pressure pushing those electrons (the pressure on that pipe). Increase either, and you increase the power output. In real notation, electrons flow from a surplus of negative charge to a deficit of negative charge (positive). So, current in reality flows from -ive to +ive. In your car, however, it's backwards, just as the fathers of electricity had the concept backwards. Power flows from positive (positive balance of "power) to negative (negative balance of "power). So, power is actually flowing out of the +ive on your car to the -ive.

Now, each part of that flow causes resistance against the force pushing it. Whether it's the actual electronic equipment, or just the metal carrying the current, it all has resistance. Some metals have more resistance than others. Silver is the best conductor out there, but it's expensive. Copper is the next best, it's cheap, but it's succeptible to oxidation (increased impurities on the metal's surface negatively affecting it's ability to conduct electricity), aluminum is good and much cheaper than copper but it has more internal resistance, and gold is a poor conductor but is good as a plating on some metals to reduce oxidation, corrosion, and the fact that it's soft and somewhat "sticky" (no, your hand won't get stuck, but it's more malleable) and makes better contact with other surfaces. You can also find nickel, platinum, and lots of other metals, but they are mainly for plating and not the primary conductors. Always go for copper for wiring and connectors, whenever you can. Never get aluminum.

In a normal car, power is carried through dedicated power lines to the various components and grounded to the chassis, which then connects to the battery. For most purposes, this is fine. The aluminum and steel chassis is a decent conductor, and the equipment in the car is so noisy and dirty and inefficient they don't care about unstable power. But, problems occur when you're amplifying minute changes in voltage by factors of a thousand.

I'll assume you're using a pair of RCA cables to connect your head unit to an amplifier.

The way an amplifier works is that it takes a modulating voltage from the RCA cable and compares it to a constant signal (in this case, it's actually the car's ground running through the shielding on the RCA cable). It then amplifies that modulating voltage difference from the car's ground and sends it to the speakers, making lots of sound in the end. There are problems with this. This process operates under the assumption that the ground the head unit (or other source) is seeing is the same as the amplifier. It also assumes that there are no voltage deviations from the head unit to the amplifier. Should either of these not be true, you get problems with noise (you know, alternator whine, feedback, static, whatever you like). This problem can be exacerbated if those RCA cables are running close to another current carrying source (such as those great big lovely power cables you have powering those amplifiers). Remember how a speaker works. It's two magnetic fields interacting with each other. The same goes for all current carrying sources. Those power cables have a lot of current, and put out some serious electromagnetic fields. Not enough for your watch to get stuck to it, but enough to disrupt the voltages in other wires. Since the signal going through those RCA cables measures differences in voltage in the area of millivolts, it doesn't take a lot for it to be affected.

You'll also see problems if there is a voltage deviation from the source to the destination. This often happens when there is a lot of equipment sharing a similar bloated ground, such as your chassis. Your headlights, heater, fans, distributor cap, everything are on that same ground, and affect the voltage on it. Since there is so much equipment on it, there can be some serious changes. It will show up as feedback, static, and the like. You can remedy this by running dedicated grounds from your battery or other electrical source to the destination (head unit, amp, what have you). This is where second battery setups come in handy (which I'll describe later).

There is other hardware out there like capacitors which help these problems by normalizing the voltage (I mean, 1 farad is a stupidly small amount of power. It's one amp of current at one volt for one second. A normal AA battery puts out about 3,500 farads). But they are no more than a bandaid for weak electrical systems. It's best to take care with the wiring in the first place, and you won't need to worry about capacitors and other effectively useless hardware.


Fuses

This is the most important thing out of everything I'm going to post. Fuses keep your car from starting on fire, plain and simple. They create controlled weak spots in your system that are designed to break the circuit if the current going through them is too great. They are measured in amps, but that number isn't the amperage at which they will break. Rather, they're the point at which a long, sustained current will probably melt them. As you increase the current past that point, you're shortening the life of that fuse and increasing the likelyhood that it will blow. This is a good thing, as it controls large spikes in current, but it also doesn't blow at somewhat moderate levels.

You should have a fuse at any point in your system where you go from a larger gauge (say, 0awg) to a smaller gauge (say, 4awg). This is because that larger gauge can handle larger currents than the smaller one, and given the same current, the smaller will burn before the bigger. It's not a bad idea to be conservative with the fuse ratings or to use them gratuitously, as it keeps your car not on fire (sure, poor grammar, but it's true).

I wholeheartedly encourage you to read this site for more info on fuses and recommended fuse sizes: http://www.bcae1.com/fuses.htm


Power Wire

Simply, the more the better. The bigger the gauge and the shorter the distance, the more power and less damage you'll cause your car's electrical system and all the components associated with it. The first thing to do is to re-do all of the ground wires in the engine bay. The Big Three are the battery-to-chasis, battery-to-engine block, and engine block-to-chasis. It covers all three. This is to ensure that any component that uses your chasis as a ground will experience as little of a power disruption as possible, and puts less strain on your alternator and battery, because of parasitic losses due to the resistance of the current pathways (ie: wiring and/or chassis).

You need relative large gauge wiring because you're moving high amounts of current at low voltages. You can run just about any amount of power through a wire that you want, as long as you keep bumping up the voltage. However, a given wire can only handle so much current before it starts heating up due to the internal resistance, and melts/starts on fire. That's why you'll see huge gauge power wires, and quite small gauge speaker wires coming out. Those speaker wires are carrying a pretty small current but has widely varying voltages going through. I suggest using the maximum power cable your amps can accept, and run the biggest main power line you can. I'm using 0awg from my isolator to my battery to my distribution blocks, and then 4awg to my sub amp and 8awg to my component amps.

The type of cable doesn't matter. More expensive != better. Lots of people have had success using regular welding power wire. The difference, however, will be in the number of strands. The more strands, the more flexible it will be. The fewer the strands, the stiffer it will be. Get copper, not aluminum. Aluminum is cheaper, but it's also a much poorer conductor.

As far as dedicated grounds go, I wholeheartedly endorse them. The power cable is just as important as the ground, so give your hardware the power it needs and give them dedicated grounds for the best, most stable source.


Speaker Wire

Speaker wire doesn't have to be high gauge simply because you're moving a somewhat small current, but higher voltages. For most component speakers, 14-16awg is adequate. Personally, I run larger just because I can. Again, always use copper.


RCA cables

RCA cables send the signal from your head unit to the amp. They operate as I described earlier, by amplifying a modulating voltage against a reference signal (in this case, the ground). There are many different ones, many different qualities and prices. It's not necessary. As long as the cable is well shielded and using a good clean conductor and interconnects, it will be as good as the RCA next to it. Twisted cabling is a good way to help reduce interference, especially if you're using a third non-conductive cable to get close to 90-degree crosses in the braids, for the best noise cancellation. Directional shielding is not important if you've run the cables properly, and neither are any of the other fancy pantsy things these cables are purported to do. Monster interconnects are only minutely better than the $9.99 interconnects at Radio Shack. Save your money and put it elsewhere. Get midrange RCAs and you'll be set.


Remote Wire

The remote wire is what tells your amplifiers and other peripheral hardware to turn on. It's nothing but a 12v signal that, when present, tells the device to turn on. There's a remote wire from your ignition to the head unit, and another from the head unit to everything else. Each device only requires about 0.125A of power on the remote line. Your head unit is capable of about 0.5A on the remote line. If you're going to have a lot of accessories on that line, use a SPDT (single pole, double-throw) relay. I'll describe them later, too. But, you only need a relay if you're using more than two or three accessories off the remote line. I'm using 7.




That's it for part 2. Part 3 will cover a little more.
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Anytime anyone gets in your face, just take everything they've got to give. If the urge to fight back rises, just remember: What Would Jesus Do If He Were A Peeping Tom?
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Old 02-01-2006, 05:17 AM   #3
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great info, very intresting read. should i be expecting part 3 anytime soon?
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Old 02-01-2006, 08:11 AM   #4
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Possibly this afternoon, though not likely. Lots of school work to take care of until spring break, so I'll definitely have it done around then.
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Anytime anyone gets in your face, just take everything they've got to give. If the urge to fight back rises, just remember: What Would Jesus Do If He Were A Peeping Tom?
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Old 02-14-2006, 12:46 AM   #5
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Stickied. Good write-up.

I can't believe I still have the power to sticky threads ! LOL
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Old 02-17-2006, 11:00 AM   #6
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It has been a while, sorry for the delay. School and junk, and next week I have four exams, so I won't be able to make an update for another month; that would really be unfortunate.

So, since I'm bored at work, I thought today we will learn about enclosures.


Speaker Enclosure Differences

There are two main designs. I'll be brief about each, and for more information you can consult these websites:

http://www.x-bb.org/%7Eefmax/123_amg.htm (My favorite site. Read it, memorize it, worship it)
http://www.caraudiohelp.com/custom_c...udio_boxes.htm


Sealed

Sealed is the best design to start with. It's smaller, easy to design, flexible construction tolerances, and a smoother, shallower response curve. In general, the bigger the box, the less the power required for a certain volume, the lower the power handling, and the lower the response curve. The reverse is also true. You can simply scale up sealed drivers by doubling the interior volume. You should get the same response curve, but twice the power handling, and twice the SPL (roughly a 3dB gain) by doubling the number of drivers. Enclosure sizes are roughly 0.5-1.0cF for 10", 0.8-1.5cF for 12", and 1.5-2.5cF for 15" drivers, for a single driver, but consult your driver manufacturer for the ideal enclosure sizes.

Sealed enclosures generally have a little bit smoother bass hit. You'll still feel the kick drums, they'll still be sharp, but for a simple sine wave you won't get a significant throbbing effect, and you won't get a compression effect. Resonance will be dictated by your car more than the enclosure itself.

Construction is easy, just a box with a hole for the driver, and connectors for the wiring. If you're using a few drivers, you may want extra bracing in the middle, but it's not totally necessary. If you exceed 1500wrms, you will probably want the bracing.


Ported

Ported is a little harder to work with. They're just like a sealed enclosure, except there's a hole and pathway leading into the interior of the enclosure. The size (area) of the port opening and length of the port will affect the response of the enclosure. In general, larger port in area and length will lead to a lower response curve, as will enclosure size as described in sealed. They are also physically larger than sealed enclosures, ranging from about 0.8-1.2cF for 10", 1.0-2.0cF for 12", and 1.5-3.0cF for 15".

Ported enclosures have a specific feature called "tuning". The tuning frequency is the particular frequency at which the enclosure will resonate; that is, at which frequency the peaks and troughs of the sound wave within the enclosure that are bouncing off the sides are actually matching up, and instead of cancelling out a bit, are actually reinforcing each other, doubling the realized sound wave for the same power input, and the driver cone itself will physically move less at the resonant frequency than non-resonant. The impedance the subwoofer generates will also be quite quite high. This frequency can be higher or lower, depending on what bass you like, an operates on powers of two, so if you've enclosure is tuned to 30Hz, you'll get resonant frequencies at 30, 60, and 90hz. Higher is better for rock, as kick drums and bass guitars are higher (relatively) in the frequency spectrum, while rap has bass that can go quite low. The problem with this effect is that below the tuning frequency, the driver will encounter considerably less resistance and can be over-driven and physically damaged with very little power (comparatively).


Infinite Baffle

Wait? I though I said there were only two designs. Well, there are. An Infinite Baffle (IB) enclosure is exactly like a sealed enclosure, except that it is of infinite volume. It involves isolating the sound waves generated by the front of the cone from the back, but by letting the interior volume be of infinite size, it lets the driver act as though there was no back pressure. It's also sometimes called free air. IB is a good design, when used in the proper location. If you're doing it in your car, say in the back seat, you need to make sure the trunk is completely sealed from the interior of the car, or it won't work properly.

IB setups have very little back pressure, so that while they are quite efficient, you can easily rip apart your subwoofer if the suspension can't handle the power you're feeding it. You need to have durable hardware and low power levels to keep your subs in one piece. Most subwoofers won't work in IB setups because of the strength of the suspension needed. It's usually preserved for component speakers in car doors. In fact, most components are designed for IB only, and will have negatively impacted performance in any other enclosure; MB Quart, for example.


Bandpass

Okay, I lied again. There is another kind of enclosure. Or is there? This is a somewhat popular way of making cheap enclosures, mainly because they look fancy. Simply, a bandpass enclosure is a series of connected chambers that are supposed to be the best of both sealed and ported enclosures - efficiency and output like ported, with a response curve of a sealed.

The problem with bandpass enclosures is that they have very, VERY strict fault tolerances, in the range of less than 1/8". Even small deviations in construction will greatly affect their performance. They are also designed for the exact driver they're being built for, dictated by the T/S parameters of the driver. Their size and complexity are dictated by what you want the enclosure to do. You can go somewhat simple with a 4th Order enclosure (sealed/ported combination), or go nuts with a compound 8th Order transmission line enclosure.

See this page for some more details on bandpass creativity and advantage/disadvantage breakdowns:

http://www.danmarx.org/audioinnovation/theories.html

Personally, I don't touch them due to the complexity of such enclosure designs. Pre-fab bandpass are simply the worst, because they are generic construction with no concern for the driver actually being thrown in. But, people buy them because they look cool. I suppose they also buy Bose (sorry, sorry, I'll stop the badmouthing now.....)


Construction

This is just some comments on construction of enclosures.

The two primary materials in enclosure construction are Medium Density Fiberboard (MDF) and fiberglass.


MDF

MDF is nothing but sawdust glued together. It's somewhat dense, low-resonant, very strong, and very uniform in material composition. It's these features which make it particularely good for enclosure design. Most are made of MDF, because it's easy to work with, cheap, and readily available. 1/2" is a popular thickness for smaller enclosures, but for larger ones, 3/4" with extra bracing is best. Unless you're running 100wrms, 3/4" is the best bet in most circumstances. It does need a good saw to cut through though, as it will burn through conventional bits pretty quickly (like those Dremel cutting bits - trust me on that one).

Corners can be easily braced at 90-degree angles for most needs, though a 45-degree or bevelled edge would make it much stronger and give it a better seal. You can also use biscuit joiners which can further help strengthen the joint, but their main feature is holding the joint together while the glue sets.

Speaking of glue, most wood glue will work fine. They're usually able to withstand several thousand pounds of pressure - it's in fact stronger than the wood it's attached to. You don't need to use screws except, like biscuits, hold the joint together while the glue sets. The glue is the strong part, and also important because it hermetically seals the joints, keeping air from leaking.

For more info, just search on Google. There are thousands of pages out there.


Fiberglass

Fiberglass is a little bit more fun to work with. Having never used it, but having read a lot of other people's experiences, I can give some details. Again, for more info, just search on Google or here on PP.com, looking for jesseunovas' install. Also check here: http://www.bcae1.com/fibrglas.htm for a lot more detail. I mean, definitely check there, and don't do anything until you have. Don't take my brief description as the word of god (even though I am, I know, I'm conceded).

Simply, fiberglass is nothing but glass strands and hardened resin to keep the strands together. The more layers' the stronger it is. It end up with a thinner enclosure, lighter than MDF, and the main advantage is that it is "painted" on, so that it can be custom-shaped to anything you want. Two popular ones are midbass pods in the footwells in the front and spare tire wells in the trunk (in fact, that's going to be my install location this summer).

To build the enclosure, get a bucket of short-strand fiberglass (anywhere from Part Source to Wal-Mart), some hardener, fiber matting, old clothes, face mask, lots of latex gloves, garbage bags or tinfoil, masking tape, Pam cooking spray, paint brushes, mixing container, and a warm well-ventilated room.

Decide on the location for the enclosure. Seal off wherever you're doing the install with garbage bags, like the rear deck and speaker pods, to help control odors. Put the garbage bags and tinfoil where you're installing the speaker and hold it together with tape. Tin foil would be better because it holds the shape of what you press it against better, which means your enclosure will be a better fit, plus fiberglass doesn't stick to it like it does to plastic and especially masking tape. Over-tape, too, all around where you're going to work, because if you get resin where you don't want it, you're SOL. Spray the surface with Pam, then lay down the matting, cutting it close to the shape of the location.

Mix up the fiberglass and hardener, and using the paint brush, "stab" it into the matting, to get the resing to full impregnate the matting. Don't add so much that it's dripping, just enough that it's soaked through. Then, let it dry for an hour or two. Repeat 3 or 4 times, depending on how strong you want it to be. Then pull it out, sand it down, cut the sharp edges, and get rid of the tape. Build a front baffle out of MDF, seal up the corners with more fiberglass or glue, and away you go.

You can also create shells out of pieces of MDF and matting, then build up the matting and resin around the outside of the shape you've made.

When you're done, sand it down, fill in the low spots with some putty, like Bondo, and then sand again. Paint a couple times with primer, gloss, and the an enamel finish for a real slick install.

Some tips:
- You're going to get fiberglass in your clothes. Throw them out afterwards, not only will washing not get the itchy fibers out, but it'll get in all your other clothes too.
- It takes a long time to sand fiberglass. Do it before it dries fully, like after an hour or so. And take your time, and take breaks. Use low-grit at first, then wet sand a couple times with higher grits to get it smooth as glass - fiberglass, that is
- Don't smoke while glassing - the coal can ignite the resin fumes and make a bit of a mess, to say the least.
- IF YOU GET DIZZY OR A HEADACHE, STOP!!!!
- Let the enclosure air out for 24-48 hours before mounting the driver. The fumes can eat rubber surrounds, making them brittle and eventually destroying them. It may not happen right away, but after a year's exposure in a sealed environment, you'd better believe it will.

Enjoy!
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Old 06-19-2008, 03:14 AM   #7
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very informative however my fav subject of ice hasnt been covered. THD or total harmonic distortion although im sure the op knows what im talking about. THD is an amp or sources ability to create a sound without adding static or hiss to it. the lower the percent the cleaner the sound. it should be noted most fancy decks have a high percent of thd as there are alot of electronics crammed into a small space while the simplest of decks ie nakamichi (named before) and mcintosh (my fav but too pricey for me atm) are extreamly baisic looking yet produce the cleanest sound. also signal to noise should be touched on. THD as taken from wikipedia:

The total harmonic distortion, or THD, of a signal is a measurement of the harmonic distortion present and is defined as the ratio of the sum of the powers of all harmonic components to the power of the Fundamental frequency. Lesser THD, for example, allows the components in a loudspeaker, amplifier or microphone or other equipment to make a violin sound like a violin when played back, and not a cello or simply a distorted noise

and signal to noise ratio:
Signal-to-noise ratio (often abbreviated SNR or S/N) is an electrical engineering concept, also used in other fields (such as scientific measurements, biological cell signaling), defined as the ratio of a signal power to the noise power corrupting the signal.
In less technical terms, signal-to-noise ratio compares the level of a desired signal (such as music) to the level of background noise. The higher the ratio, the less obtrusive the background noise is.


thats my .02 albeit probably useless info. feel free to add or edit info as you see fit to make it more useful to the luder = )
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Old 08-09-2011, 02:30 PM   #8
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good info!
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