Johnny Kim

ok, id figure i make a updated one, but mostly for aftermarket stuffs.
pm me info,links,thread,etc and ill add. but heres for now.

The list: Bad, Average, and Good Car Audio
NOT RECOMMENDED:
***Note*** The "NOT RECOMMENDED" catagory's purpose is that these line of brands are poor in quality and can breakdown even under recommended use. Distorted output is constant and the products eventually shut down and fry themselves.

Boss
DHD
Dual
Jensen
Legacy
Optimus (Radio Shack)
Lightning Audio (lower end models)
Pyle
Pyramid
Sony
Soundstorm
Thump
Verge
Volfenhag

AVERAGE
***Note*** "AVERAGE" catagory consists of most mainstream products. These products are somewhat good for the money, but will not satisfy your taste if your going for a true SQ or SPL setup. Ranging from amps to subwoofers, mids and tweets, the AVERAGE catergory is just that, AVERAGE. (decent, but nothing to brag about.)

Bazooka
X-site
MA Audio Visonik Cliff Designs (Anaba Group) (Execpt for high end amps)
Low end Alpine
Kenwood
Lightning Audio (high end)
Pioneer (Minus high end head units and premier series)
Lanzar
Audiobahn
Crunch
MTX (Minus amps)
Panasonic
Rockford Fosgate
Blaupunkt
Kicker (subs)
Alpine (Low end subs and speakers)
Polk
Audiopipe
Concept
Cerwin Vega
Infinity
Alphasonik
Digital Audio
JVC

GOOD
***Note*** The "GOOD" catagory suggests that these products are a better quality than your average setup. More money is put into the performance, but products still lack in overall reliability in some cases. There are many great products in this catergory that we would recommend, but we tend to stick with our "HIGHLY RECOMMENDED" products.

Autotek
Hifonics (for the price.)
MTX (Amps)
Profile (Price is AWESOME.)
Pioneer premier and high end HU’s
MA audio, Visonik, and Cliff Designs high end amps (Especially for SPL applications.)
Phoenix Gold
Directed
Orion
PPI
Viper
Alpine (Higher end subs and speakers, lower end head units)
Kicker amps
Avionixx
Alumapro
Audiomobile
Boston
Clarion
Crystal
Crossfire
Earthquake
JBL
Memphis
Soundstream
MB Quart


HIGHLY RECOMMENDED
***NOTE*** "HIGHLY RECOMMENDED" section are products that have unsurpassed SQ, SPL and SQL capabilities, and are very reliable. These products can range in price based on your budget and specific needs.

Alpine (Higher model head units)
Cadence
Eclipse
JL Audio
Elemental Designs
Helix
a/d/s
Adire Audio
Arc Audio
Brax
CDT
Diamond
DD
Focal
Image Dynamics
Kove (Borderline good/highly recommended.)
McIntosh
MMATS
Morel
OZ Audio
PPI (Old stuff before they were directed)
RE Audio (Resonant Engineering)
US Amps
Zapco
Linear Power
Incriminator Audio
Ascendant Audio
Stereo Integrity
Sound Splinter
Audioque
Xtant
Tru Technology
TC Sounds
Rainbow

The Big 3, what it is, and what it does
Since this question comes up again and again here, I thought this might be a useful post. Performing a "Big 3" upgrade on your vehicle is one way to improve the electrical system performance and its ability to supply power to your audio system. This upgrade will help any vehicle using an after-market amplified stereo system, and most certainly should be performed on any vehicle after a high-output alternator is installed.

Please be sure you read and understand this entire instruction before you begin.

Definition: the "Big Three" upgrade means improving the current capacity of three cables: 1) alternator positive to battery positive, 2) battery negative to chassis, and 3) engine ground to chassis. Some people replace the factory wiring; others add additional cables to the factory wiring. This instruction is to add cables to existing OEM wiring.

Parts and Tools:

As a minimum, you will need to purchase the following:

• Sufficient length of high-strand count high capacity power cable.
- The length required differs for every vehicle. You can measure the length of the existing cables and buy the same length, or contact your dealer or a mechanic and ask, or sometimes you can look it up in a manufacturer's wiring book, or guess. If you guess, make sure you over-estimate and buy too much.
- High strand count cable is more flexible and more reliable than low-strand count cable. Never use solid-core wire in a moving vehicle as it will eventually break.
- The gauge of wire you need depends on the total current draw of your audio system, and/or the current generating capacity of your alternator. Never use smaller cable that you used to power your amps; never use smaller cable than what already exists in your vehicle; never use smaller cable than the generating capacity of your alternator; never use smaller than 4 AWG (it's just not worth the time to use anything smaller); if in doubt, always use higher gauge cable than you think you need. If you look at the Power and Ground charts and your amplifier current draw corresponds to 2 AWG cable, use no smaller than 2 AWG cable, and use 1/0 if you can.

• 6 ring terminals or lugs of the appropriate size for the cable chosen. Two of these need to be large enough to fit over your battery posts, or appropriately sized to bolt onto your existing battery terminals.
• 1/2" or 5/8" shrink tubing (or some other form of permanent electrical insulation. Tape is NOT recommended.)
• Cable ties (plastic zip ties.)

• Wire cutters large enough to handle the cable you choose.
• Crimpers large enough to handle the connectors you choose.
• Soldering iron or gun.
• Solder.
• Scotch brite and/or a small wire brush.
• Heat gun.
• Safety razor blade (or other tool for stripping cable).
• Heat gun (if using shrink tubing).
• Wrenches for removing bolts in your vehicle.

Procedure:

1. Make sure your engine is completely cool before beginning. Identify the three cables being replaced. Make sure you can reach both ends of all cables. NOTE: the engine block to chassis cable may be between the engine and the transmission, or connected to the transmission and the fire wall, and is often an un-insulated flat braid cable.

2. Determine the lengths of cable needed to reach between the three locations being upgraded. Be sure you measure with a flexible tape (a tape measure used for sewing works great) and record the total length along the path you intend to install the cable. You do not want your cables to be pulled tight between any two locations as things move and vibrate as you drive. Be sure to include at least 1 inch extra for slack. NOTE: there is no reason to copy the existing wiring layout in your vehicle unless you want to. Also, be sure that the path you choose does not follow or lay across anything that gets hot, like exhaust parts, or anything that must move, like throttle linkage.

3. Cut your new cable to the three proper lengths. NOTE: some people like to use red cable for positive and black cable for negative. Doing this is completely up to you and is nice, but not necessary. You can use cable with any color insulation you like.

4. Strip each end of all cables to the proper length for the terminal lugs being used. NOTE: after full insertion into the lug, a small "band" of bare wire is usually seen between the back of the lug and the beginning of the cable insulation.

5. Begin at any one end and insert the stripped cable into the lug. Make sure it is fully inserted. Crimp the connector to hold the wire in place. NOTE: crimping large cable can be difficult. The intention here is not to make the crimp the sole means of holding the wire, but only to make sure the lug does not slip around during the soldering phase. I do NOT recommend using hammers or pliers or vices to crimp the connector as over-crimping can break the strands of the cable, reducing the current carrying capacity. Do not over-crimp.

6. You may need to use a vise or some other set of "helping hands" to hold the cable while you solder it. Heat your soldering iron and place it on the connector (on the lug side) barrel. Hold a piece of solder against the tip of the iron and melt the solder into the strands of the cable. Use sufficient solder to fill the connector and completely cover all strands of the cable. NOTE: the lug will get hot and will burn you if you try to hold it. Also, if the insulation on the cable starts to melt, you are over-heating the cable and not paying attention to melting the solder into the cable. You do not need to try and melt the cable!

7. Repeat the above steps on each end of all three cables.

8. After the cables have completely cooled, cut a piece of shrink tubing long enough to cover the soldered barrel end of the lugs and reach about 1/2" onto the insulation of each cable end. Slide this over each lug and use a heat gun to recover the tubing in place.

9. Disconnect your battery, starting with the negative cable first then the positive cable. Discharge any caps you may have in the system.

10. Begin adding your new cables along side the existing ones. I usually begin with the alternator positive cable. Locate the output stud on your alternator and remove the nut. Slip the new cable onto the lug and replace the nut. There is no need to disturb the existing cabling. Route the new cable to the battery and position it to connect to the positive battery post (or connect it to the positive terminal on the OEM wiring) but do not connect the battery yet.

11. Secure the new cable in place by using cable ties every 6 to 8 inches. Secure the cable to cool non-moving parts!

12. Locate where the negative battery cable attaches to the vehicle chassis. Remove this bolt and the OEM battery cable, and clean the mounting area of the chassis using scotch brite and/or a wire brush. Make sure there is no dirt, rust, paint, undercoating, etc in this location. You want bright shiny metal. Connect both your new ground and the OEM ground back to the chassis. NOTE: Some people like to create a new ground location by drilling into the chassis and using a bolt with star lock washers for the new ground cable. Route this new cable back to the battery and position it to be attached, or connect it to the negative terminal. Do not reconnect the battery yet.

13. Secure the negative cable using cable ties every 6-8 inches. Again, don't tie it to anything that moves or that gets hot!

14. Disconnect the engine ground strap at both ends. Using the wire brush or scotch brite, clean both the engine block and the chassis as you did for the first ground strap.

15. Line up the lugs on both the OEM ground strap and your new ground cable, and use cable ties to secure them to each other. This is much easier to accomplish in your lap or on the floor than it is while lying under your car or hanging upside down in the engine compartment. Reinstall both cables at the same time using the factory bolts.

16. Double check to make sure all bolts are tight. Be careful not to over-tighten them as you don't want to strip anything! Also, on some factory alternators it is WAY too easy to twist off the positive output lug. If you break it off, well hell, you really wanted a high-output alternator anyway, right? It is also a good idea at this point to measure resistance of the new cables. Take an ohm reading between the battery end of the new ground cable and the engine block. It should read less than one ohm. Also check between the alternator bolt and the disconnected positive battery terminal, which should also be less than one ohm. If you read too high resistance, double check all connections and make sure you do not have something c**ked sideways or hanging loose.

NOTE: Realize that the "absolute ground" of the electrical system is not the battery negative terminal or the vehicle chassis, but is the case of the alternator itself. This is why perhaps the most important cable among the Big 3 is the engine ground strap, as this is what connects the alternator ground to the vehicle's chassis. Be certain the resistance between the alternator case (the engine block assuming the alternator is properly bolted to the engine) and the battery negative is minimized. (Thanks to the12volt for pointing this out!)

17. When you are sure you are done and anything in your system that you may have disconnected are re-connected, clean your battery posts and reconnect the positive battery terminal first, then the negative one.

18. Start your vehicle. Hopefully the engine starts. Examine the engine compartment and make sure none of your cables are getting hot or are vibrating or shaking around. If they are vibrating too much you may need to relocate them or use more cable ties. If you see smoke, immediately shut off the car and disconnect the battery. Seek help.

19. Assuming all looks good, take a voltage reading at your amplifier and ensure you read 13.8 (or higher) volts. This indicates a properly operating charging system.
-the12volt.com


Questions and Answers
Q. Will other honda/acura radio work with ours?
A. Yes and No. if its a regular radio(cd/am/fm) then it will be an easy install.
If its a navigation unit, things will be complicated.
http://acura-legend.com/vbulletin/sh...ad.php?t=86803

**will add more later**


basic wire gauge recommendation.
The truth about capacitors




This is a real world test that was measured by Richard Clark on a Audio Precision unit to portray what happens with a typical capacitor install.
The main point for those who point out the obvious differences between the Red (cap installed) and yellow (cap not installed)…how much of a dB difference is .1-.4 volts in terms of music? And do you feel you are going to hear this within a car? On with the explaination:

Dark Blue curve---
For our first test we played the system with the engine off and no cap. The result was the purple trace at the bottom. We played the system as loud as we could get it that seemed to produce no audible distortion. This was track 30 of the IASCA disc. It starts off with fairly low level sounds for the first 34 seconds. In order to insure the electrical system was stable we did not start the measurement until we were 20 seconds into the song. This means that our 0 starting point is :20 on the CD counter.
The battery was able to maintain it's voltage just below 12.5 until the loud bass hits at 34 seconds (14 seconds into our chart) At this time it dropped to about 11.5 and had a few large variations due to the music. According to the computer calculations (third chart) the average voltage for this test was 11.7volts. This test was done as a baseline for the following tests.

Yellow curve—no cap
For this test the volume was left as it was for the baseline test. The engine was started. Notice that at low volume the alternator was able to maintain about 14 volts. When the loud music hit the voltage dropped to about 12.5 where it remained
except for a few short moments where it actually climbed back to over 13.5 volts. The computer averaged calculations for the average voltage during the 100 seconds of this test was 12.973 volts.

Red curve—cap added
This test was identical to the previous test except the cap (15 farad type) was added 6 inches from the amp with 4 gauge wire—no relays or fuses. The red curve seems to overlay the yellow except that the actual peaks don’t rise as fast or as high during the brief quiet moments. I feel this would be due to the alternator having to recharge the cap. The voltage on loud passages hovered around 12.5 volts. The computer averaged calculations for this test show the average voltage to be 12.878 volts. I see no meaningful differences with or without the cap. I certainly don’t see the voltage sitting solid at 14 volts. One note I might add is that this was a two thousand watt system driven right to clipping and the average voltage stayed above 12.8 with a stock 80 amp alternator. Under these conditions the battery would never discharge! The green and light blue curves were done just for kicks while we had the system set up. In both these tests we turned the volume up until the system was very distorted. This placed a severe load on the alternator and caused the voltage to dip as low as 12 volts. The curves seem to follow each other so closely that unless you have a good monitor it is doubtful you can tell there are two curves. The average voltage for these two curves were both 12.277 and 12.295 volts. If this volume were sustained for very long periods of time this battery would discharge

Breaking in subs

Here's a procedure I learned that is fairly simple to use to break in a woofer. If you are installing your own woofers, be it for car or home use, and have found this thread because you're the type who wants to go about the installation systematically, covering all bases, then this procedure is for you:

You need a test tone CD (here is a download) with a 10 minute track of the tone that corresponds with the Fs of the woofer. You need to be able to hang the woofer up in mid air, through one of the mounting holes in the frame, letting it hang freely. There should be no walls close to the woofer, and the woofer certainly shouldn't be laying on the table on its magnet (as you often see in videos). The nearby table or wall acts to compress the air behind the cone so avoid those types of disturbances.

The idea is to play the sine wave tone through the woofer at resonant frequency in free air. A very slight amount of power will enable the woofer to move at full excursion. You have to first find out what the Xmax is so that you can look at the excursion and gauge (by eye) the approximate excursion you're putting the woofer through. A subwoofer with a one-way excursion of 12 mm would look like its moving about an inch as the voice coil moves back and forth. You'll note that you are allowing only a few watts of power to reach full Xmax, so be careful with the volume control.

If you're working with a car subwoofer, you can prop the trunk lid and hang it from that. If you're working with a home sub, you can hang it from the ceiling of the room near the amplifier. Play the tone at Fs, watch the cone movement while adjusting volume, and let it flap and whirrr for the 10 minute period. It will sound more like a fan than a subwoofer. Allow 10 minutes cooling time, then run it again a few sets. Your woofer is now broken in.

There is only a small percentage of DIYers who will go through this procedure. They are the ones who make sure they have a test tone CD for setting gains, who make sure they damped all the sheet metal while the car is torn apart, who made sure they grinded all the paint off the metal before securing the ground wire. This is just another of the steps to ensuring that when you are ready to debut the system, it will sound the way you had hoped it would.
http://www.the12volt.com/installbay/...N=1&TPN=2#post

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acc-unit

damn johhny, nice write up bro, this should be a sticky

ps- your sig is too big

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1990 Legend sedan - RIP
1995 6 spd coupe

Johnny Kim

ye, i got info from other post by other members.

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slick

Thanks for making some of the stuff I posted into a sticky!

BTW, I noticed that the one image isn't working. Do you need me to host the image, so it will always work?

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Chris-
Visit the For Sale section for my G2 LS Sedan partout.

Johnny Kim

my server is down temp. crapp lol. can you host it for time being till my comes back online?

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slick

Yeah, I'll see if I can save the image. If so, I can just permanately host it on my photobucket account.

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Chris-
Visit the For Sale section for my G2 LS Sedan partout.

Johnny Kim

ill shoot you an IM tonite.

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bl420

you should put some subwoofer enclosure information also...

some common terms would be good too.

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**Anti Alpine Type-R Thread**

Johnny Kim

will get to it, thanks.

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slick

I sent you a PM with the photo uploaded. Now just update the FAQ post.

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Chris-
Visit the For Sale section for my G2 LS Sedan partout.

Johnny Kim

updated. thanks man.

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pwnt by pat

Here's something I wrote up for my home forum. Some is covered above. This is a very basic faq that I have been adding to on my home forum in my spare time:

The golden rules:
1) 90% install 10% product
2) ALWAYs, ALWAYS unplug your battery whenever you do any kind of electrical work

Also, don't forget, a system isn't a subwoofer and amp, it's a well rounded stereo system including head unit, speakers, sub, and amps.

Asking questions
If you have a what to get question, feel free to include a few helpers:
1) match oem colors
2) price range
3) what functions do you need from it? ipod, processor control, navigation, etc
4) any experience you've had in the past (had x head unit and y subwoofer / first timer and have no experience)
5) sacrafices you're willing to make (cost, size, sound, functionality)

What should I buy? threads
It depends on a lot of factors. How much are you willing to spend? How good of an install can you perform? Most will recommend head units first, then speakers, then amps, then subs.

If you're happy with the sound of the stock system but want a little more, personally, I advocate using sound deadening on the doors. It's the cheapest and probably most cost effective if you're happy with stock. Brands include elementaldesigns.com secondskinaudio.com raamaudio.com dynamat, and peel and seal (roofing tape)

Audio basics: head units
There are many great brands. The most recommended will always be Pioneer and Alpine. Other great brands include Eclipse, Nakamichi, and the Excelon line of Kenwoods.

Some headunits have more functionaliy than others. Some let you do everything from your seat. Others, you have to have post-headunit equipment to do all the sound manipulation work for you. Some, like some Alpines and the Pioneer P9, let you attach processors directly to the unit and have all the control from your seat.

What kind of controls can you get? Well, crossovers, equalizers, and time alignment are the most common. What are they?

-Crossovers block frequencies from reaching the speakers. There are two types of filters. One is a Low Pass which lets all of the low speakers "pass through" the filter. You use this for subwoofers and depending on your install, midwoofers. High pass lets all of the high music go through and blocks low frequencies. This is for some midwoofers and tweeters. You use a crossover to block sounds that the speaker can't produce properly or may damage the speaker. Most head units don't have equalizers, but the good ones do. Crossovers aren't brick walls, however. They have what's called slopes. These slopes change the rate that sound drops off, the higher the slope, the faster the drop-off rate. Here's how to set your crossovers.

-Equalizers allow you to increase or decrease certain frequencies. The human ear can hear 20-20,000 hz (lower the hz the deeper the note). Say you're lacking output in the 500hz region, you can bump it up. Most headunits typically have bass, treb, and high equalizers. 100hz, 1000hz and 10,000-15,000hz typically. The more levels of equalization you have, the better you can adjust the sound. Equalization is NOT a means for producing more bass. It can't fix unproperly set up equipment. This can be often done by a well trained ear, however[url=http://www.diymobileaudio.com/forum/showthread.php?t=17] here's how to do that, right.[/b]

- Time alignment lets you tell the head unit to pretend a speaker is closer or farther away from you. This adjusts the pathlengh of the speaker (distance away from you) to make it seem like all of the speakers are equal distances from you. Most head units don't have this, although the good ones do.

- Other features: most head units give you rca out and few give you optical out. These are connections that run to either amplifiers or external processing and are VERY helpful when setting up a stereo system. The difference is RCAs use an analog signal while toslink/optical use a digital signle that's completely immune to noise. Voltage of the RCAs don't make much of a difference and should only be your deciding factor if everything else is dead even (and you're using amplifiers). RCA's can be substituted by using a line out converter, which converts speaker wires into RCAs. Line out converters can also be used for using the stock headunit with an aftermarket system.

How to hook up a head unit:
Headunits don't require anything fancy to turn on and opperate. At the bare minimum they need power, ground, accessory, and wires to the speakers. Power is just a +12v signal from the battery. Ground is a wire going to the chassie. Accessory is a +12v signal wire that turns on whenever the key is in the accessory (or on) position.

Unless you're doing a custom install, the easiest thing to do is get a wiring harness adapter. These typically run 10-20 dollars and can be found any any Walmart, Best Buy, Pep boys, Circuit city, etc. They attach the special propreitary (only for this specific unit) head unit harness to the stock harness without cutting or splicing any wires. On MOST harness adapters, the colors are coordinated with the headunit's wire colors (these are standard, so just match the colors and the stripes). Most also have the description of the wire's function printed on the wire itself.

Wires on the harness adapter are as follows:
red: accessory - VW harness does have an accessory wire, except the new metra harnesses don't correctly tap into it. You MUST run a new wire if you use the metra harnesses. If you use an older harness, you can use the in-harness accessory line. For running a new line, the easiest places are a black wire with a gold stripe behind the fuse box under the dash, or a brown wire with a red stripe in the ignition column. The black with gold stripe is just a switched 12v line. The brown/red wire is the key-in wire. Once the car has been turned off, as long as the key is in the ignition, the radio will still operate (similar to the power windows).
black: ground - This wire needs to go directly to the chassie. See below for good grounding procedures.
yellow: power (or mem or vmem) - this wire always gets 12v from the battery. It's how your radio keeps it's time and settings.
orange: illumination and/or brightness - usually useless. I personally haven't ever seen them work. Illumination slightly dims the headunit when the head lights are turned on and brightness adjusts the brightness of the head unit in conjunction with the brightness of the interior lights. brightness rarely if ever owrks
Blue: Accessory out - this is for turning on external amplifiers and units. When the radio is on, this wire gets a 12v signal. You should string no more than 3 devices to this wire unless you use a relay (see below)
blue-white stripe: power antenna - some vehicles have an antenna that extends whenever the radio is turned on - that's what this is for
green/white/purple/gray and stripe - these are for the interior speakers. white spkr wires: driver-side front
gray: pass side front
green: driver side rear
purple: pass side rear

Audio Basics: Speakers
There are millions of these for every application imagineable - more than you would realize and more than I care to remember. They fit every application and price range. These are best left to specific thread details, however, here's a few points

Resistance?
- Each speaker is an electronic device called an inductor. At rest, the speaker has a fixed resistance. This resistance is a good tool in measuring the power applied to the speaker. The most common resistance is 4-ohms. As the number of ohms increases, the resistance increases. 0-ohms is a direct short. The resistance of the speaker changes with several factors, including the design of the enclosure, heat of the speaker, frequency played, amount of power applied, and natural resistance (impedeance) curve of the speaker.

Amp or head unit power?
- head unit power typically works but amped will ALWAYS sound better

Midbass vs Midrange vs Tweeter
- midbass are woofers specifically designed to play almost subwoofer frequences to the top of most male vocals. Midrange are for most of your vocals and most of the music you hear. Tweeters are for high sounds, cymbals, beeps, boops, etc. Most midrange also function as midbass.

Component vs coaxal vs braxial
- component have a crossver between the tweeter and woofer (inbetween amp and speakers) and the tweeter is a seperate unit from the midwoofer. Coaxial have the tweeter mounted directly on the midwoofer and crossover built into the speaker. Braxial are a mix of both, sometimes having a crossover, sometimes not, but the tweeter can be mounted anywhere or on the midwoofer like a coaxial.

2-way coaxial vs 3-way and 4-way and etc
- Anything past 2-way coaxials just add supertweeters to play really high frequencies. They're typically really harsh sounding and a pure marketing gimmic to lure in the gullable.

Oval vs round (vs square and whatever shape)
- Oval (6x9's) have more surface area than round speakers, however, distort much easier making them sound worse. The best theoretical shape for speakers is round as it provides the best ridgitiy.

How much power can the speaker take?
- Each speaker is different in the amount of power it can handle. Some can handle more than advertised power, and some can't ever handle advertised power. This comes from how the speaker is tested - which there is no industry standard for. How much power the woofer can take relies on the cooling abilities, design of the enclosure, and quality of materials the speaker can handle. Usually rated power is close to what should be applied, however, in extreme cases, some speakers can handle over 10kw of power.

Heat and Cooling
- Each speaker naturally cools itself. If it didn't it would burn up right away. The movement of the speaker is what forces air over the internal components. When a speaker is driven too hard and the cooling can't keep up, then parts begin to break down and the speaker will die.

Matching speakers and amplifiers
- My amp does 50wrms and my speakers are advertised to take 50wrms. Is this safe? Most likely. Advertised numbers are usually conservative to begin with. What you have to realize is there are several factors at play. Typically advertised power for the speaker is thermal, meaning a value for heat, whereas the power for amplifiers is just that, the power it produces. Next, amplifiers RMS power is the maximum unclipped power the amplifier produces times .707. As a personal rule, I always use an amplifier that's capible of producing more power than the speaker is capible of. I do this because I like the headroom and ability not to go into clipping (see below).

Audio Basics: Amplifiers
The only thing really you can say about amps is they go between the headunit and speakers to provide more power to the speakers. That and you get what you pay for. Some amps are really high quality, some are better used as door stops or target practice. Amps to avoid are Sony, Boss, Pyle, Pyramid, Audiobahn (avoid everything from them) and anything else really cheap.

Amplifiers power is displayed as RMS power. This is the maximum unclipped power times .707. Clipping is when the sound wave producted (normally a nice smooth curved sin wave) starts to square off. When this squaring occours, the amplifier produces twice the total power. You would think this is a good thing, more power, however, due to the nature of the wave, it will actually damage your speakers. The best way to control clipping is properly setting your gains, as seen here. Clipping not only damages your speakers, but will also damage your amp.

Some amps have crossovers in them, some have other features. Mostly these extra (non-crossover) features are a marketing gimmic.

Some amps make rated power (what you're told) and most don't. Most amps are tested at 14.4v, which in a car you will never get. You'll get approximately 13-13.5v. The good amps are rated at 12v and will actually make more power than advertized. The better companies send sheets that show the actual power produced by the amp, called a birthsheet.

Amps put out certain power at certain "loads". A load is how much resistance a speaker has. Typically, the lower the load (smaller the number), the more power an amp will make. Most amps are stable to two ohms, some only 4, and some as low as .24ohms. In contrast, most speakers are four ohms. When the load is too low, the amplifier can go into protect mode, which is a "safe mode" for the amplifier that it may or may not come out of.

Some amps are bridgeable. What this means is that you can turn a two channel amp (left and right) into a single channel and get more power out of it.

Placement of amplifiers depend greatly on the amplifier. Some amplifiers get hotter than others, though, so their placement options are limited. Most amplifiers can be mounted anywhere or in any position. The heatsink of most amplifiers are designed for the amp to be most effective when the amp is mounted vertically. As long as there is airflow over the amplifier, it can be mounted in any position. This is how in show cars the amplifier can be mounted under plexy or in ampracks.

Audio Basics: Subwoofers
Sub x vs Sub y - search for the name of a sub, then post. Like woofers, this is better handled in a case-specific thread.

Things to look for:
SPL vs SQ
- this is how loud a woofer gets vs how good it sounds. Some can do both. What a sub can do is 100% dependant on the enclosure type

Sealed vs Ported vs Freeair vs Bandpassed.
- Sealed is just a sealed box, no holes. They're sonically accurate but inefficient and require more power to get louder
- Ported is a box with a hole in it, but the length and size of the hole are tuned to get extra output at a specific frequency. The box is more efficient, but requires lower power and the ability to properly design the enclosure.
- Freeair is no box, the woofer just sits there. It's not good for your speakers because you won't get any noticeable output and will damage the woofer.
- Infinate baffle is similar to free air except better =). It's technically 10x VAS (which just means a really really big sealed box. They are not very efficient (don't get as loud) and require lower power, but with the right woofer, can be sonic bliss
- Bandpass is simlar to a sealed box except the woofer fires into another box, which has a port tuned for a certain frequency. These are very efficient, the loudest of the boxes, at the cost of sound quality. They can achieve a flat response, but can have all kinds of delay and/or phasing problems.

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