This is a master thread with information about everything dealing with mobile entertainment. Please browse through this before asking questions, as they may be answered here. Questions that aren’t answered here can be posted as a new thread. If they are common enough, I will edit this thread to include the answers. Please keep “thank yous” and other comments out of this thread so we can keep it clean with information only. This will be updated regularly, so please check back for new information. If there are any problems or incorrect information, please let me know so I can adjust accordingly. Also, if you have useful information that I missed here, let me know by posting it yourself (I know this thread only contains a bare minimum of information, but it will hopefully be a good starting point). I will probably rewrite your post so I can make sure it stays updated and so I can link it in this first post. Hopefully this will give everyone a head start on upgrading their stereo equipment.

Note: Much of the information here is very basic (I am simply paraphrasing from a number of sources and I did not copy and paste from any of them – if you feel like I’ve plagiarized you in anyway, drop a line and I will edit or list you specifically as a reference). If you wish to learn a lot more, the internet will be your friend. We cannot possibly provide all the information needed on any of these topics, as that would require writing a novel. Also, some of the information presented here is PURELY opinion. Do not take any of this as complete truth, as making this introductory information available has left room open for debate (if you wish to discuss the theory here, start a new thread for debate/discussion – we may all learn a lot from talking to each other). For the most in depth information, please consult a competent audio installer (there are some on these forums) or browse the internet by yourself. Like anything, it is important to do plenty of research before spending large sums of money. Make sure you know what you are getting into before you start!

GlossaryFAQ
Installation
Steering Wheel Interface
Big Three Upgrade
Noise Elimination
Sound Deadening
Gain Setting
Subwoofer Section
Imaging and Sound Stage
Rear Fill
Equalization
Crossovers
Fiberglass Info

Mods, do you think we can make this a sticky?

-Apple

Modified by AppleBonker at 1:49 AM 8/2/2008
Modified by AppleBonker at 1:59 AM 8/2/2008

Glossary of terms

Amplifier – Used to amplify the speaker signal. Almost every headunit has a built in amplifier. These are generally not of the highest quality, so an aftermarket amplifier is generally recommended.

Big Three – Upgrade to electrical system. See this post.

Coaxial Speakers – Speakers that have all of their drivers on the same axis. These will generally include a midrange driver with a tweeter mounted in the middle of it. These speakers are considered “2-way” speakers. There are even “3-way” and “4-way” speakers. These are not necessarily better, but they may be. I believe a lot of this is marketing hype.

Component Speakers – Speakers where the drivers are all separate. Most people will run two-way component setups. This will include a midrange driver and a tweeter that will be mounted in separate locations in the car. Some systems are also designed as three-way. These include a midbass driver, a midrange driver and a tweeter. All of these setups require a crossover to split the signal (by frequency) to the driver intended to handle that frequency range.

Crossover – Divides the signal by frequency to specific drivers. In a two-way setup, this will generally have the tweeter handle the 2,000-20,000+ Hz range, and the midrange will handle from roughly 60-2,000 Hz. A three-way setup will have a midbass handle the 50-250 Hz range, a midrange handling 250-2,000 Hz and a tweeter handling 2,000-20,000+ Hz. These numbers are just generalizations and the crossover frequency can be anything (but it will be close to this). A crossover can be active or passive (see this post).

Crossover Slope – This determines how fast the frequency rolls off from the cutoff. A steeper slope will allow less frequency to pass to the driver than a shallow slope.

Equalizer – This device is used to tune the system. It will selectively increase or decrease the volume of certain frequencies to improve audio quality. Cars are not ideal locations for stereos, so there are certain frequencies that may appear louder than others. The goal is a flat frequency response curve (meaning that a sweep of the entire audio spectrum through the system will not get louder or softer at any given frequency).

Filters (High Pass and Low Pass) – The same as crossovers. A high pass filter (HPF) allows frequencies higher than the set frequency to pass to the driver. A low pass filter (LPF) allows frequencies below the cutoff frequency to pass to the driver.

Gain – The level of amplification from an amplifier. Simply put, this is like the volume control for the amplifier (this is a simplified explanation and this should not be used as the volume control). Gains must be set appropriately to avoid damage to the amplifier and the speakers it powers.

Head Unit – The CD player portion of the stereo. This can be as basic as just a CD player, or as advanced as a touch screen with DVD playback capability and navigation. Many will also offer other options such as XM/Sirius satellite radio or iPod/harddrive/flash drive connections.

Midbass/Midrange – Speakers designed to handle the middle frequencies (between the subwoofer and the tweeter).

Patch Cables – RCA cables (similar to what may be connected in your home theater). These carry the audio signal from the head unit to an external amplifier.

Pre-amp inputs/outputs – The location where the patch cables connect. Higher voltage pre-amp outputs will generally carry a cleaner signal to the external amplifier. A higher voltage output will also decrease the gain level on the amplifier (which is beneficial to avoid damaging components).

Power Cable – Cable from the battery to the amplifiers. This supplies the voltage and current required by the amplifier to power the speakers.

Sound Deadener – Material used to decrease vibrations and mechanical noise of a car. This is not only useful for making the stereo sound clean, but also helps reduce the level of noise that enters the car from the outside world. See this.

Steering Wheel Interface – This module will allow you to continue to use the steering wheel mounted buttons to control your aftermarket stereo. For more information on this, check here.

Subwoofer – Speaker that handles the low frequencies. This is generally a larger driver (at least eight inches but it can be as many as fifteen). This speaker generally handles the frequency range from below 20-75 Hz.

Tweeter – High frequency driver. A tweeter is generally used to produce frequencies higher than 2,000 Hz.

Modified by AppleBonker at 1:41 AM 8/2/2008
Modified by AppleBonker at 2:02 AM 8/2/2008

Factory Components and FAQ

Can I upgrade to the factory Bose navigation unit?

If you have the factory Bose non-nav radio, this can be done. I would recommend finding the parts on eBay (you will need the navigation head unit, the front trim panel, the CD changer and the backup camera). Buying these components from a parts retailer will likely cost you roughly $3500, but they can be found on eBay or other sources for much cheaper. With the factory Bose radio, everything is roughly plug and play. You will still need to remove the factory head unit panels (see the installation section for a walk through on this). You will likely be able to achieve better quality with a complete aftermarket setup (which I would recommend in any case).

If you have the basic stereo package (no Bose), this will become a much harder task. The Bose systems have an amplifier mounted in the trunk. You would need to rewire the entire car to have cables running to the trunk to power the amplifier. Then, you would need to run wires to all of the speaker locations. The wiring harness will not be plug and play for this install. At this point, it will be much easier (and more cost effective) to go aftermarket. The wiring for this will be easier and the quality should be noticeably improved.

Can I continue to use my factory Bluetooth microphone with an aftermarket head unit?

I have been looking at this for a while, and I will be attempting this on my own car. Once I get the chance to take my car apart again, I’ll give this a go. There will be more to come at that point. For what it’s worth, the factory microphone is powered, whereas all (as far as I know) aftermarket microphones are not. There are no units on the market that will just have the factory microphone cables plug in and work. If this works, it will require some wire modifications and cutting/splicing. If I get this to work, I will update with plenty of pictures to help you all walk through it.

Can I continue to use my factory XM module?

No. You will need to purchase the XM/Sirius model for your head unit to get satellite radio. Attempting to use the factory component will require serious modification (if it is even possible), driving up the cost. It would be much easier and smarter to use the components recommended by your stereo manufacturer.

Can I use my factory satellite radio/navigation antenna?

Both of these connections reside in the trunk. They are also likely different connectors than on your aftermarket radio. You would need to find a way to extend the cables to your head unit and then change the connectors so they are compatible. This will not be an easy task. You should, instead, just install the aftermarket antenna. You can easily mount these under the dash or on the rear deck.

Will I still be able to use my steering wheel buttons?

See this post for that answer. You will be able to get the stereo buttons to work. However, there is no way to get the cell phone buttons to work at this time. None of the steering wheel control interfaces have this capability. If you have a friend that can crack the operating system on your head unit, this may be possible. It has not been accomplished at this point (as far as I know), so don’t count on it. Unfortunately, you’ll be forced to use your aftermarket radio’s functionality for answering calls and dialing.

Is it possible to add a subwoofer to the stock stereo?

Yes. With the Bose system, you will need to tap into the speaker wires in the trunk (it is best to do this before the amplifier). You should then use a line level converter to take the speaker wire signal and convert it to patch cables. These can then be plugged into the aftermarket amplifier. You will also need to connect a remote turn on lead (the signal that tells the amp to turn on so it is only running when the stereo is on). This can be easily tapped from the turn on lead that already runs to the Bose amp.

If you have the basic stereo (non-Bose), you will need to tap into the speaker wires for the rear speakers. A line level converter can then be used, as mentioned above, to convert the signal to patch cables. If your amp allows it, you may also be able to use the speaker cables for the input (some amplifiers have line-level inputs for this purpose). Please stay tuned for updates as LBC (one of the mods) will be doing this to his car in the near future. Pics should accompany that install.

Modified by AppleBonker at 1:42 AM 8/2/2008
Modified by AppleBonker at 2:02 AM 8/2/2008

Installation

4th GenAlways make sure to disconnect the positive terminal of the battery before doing any installation work. This is imperative to protect your system and, more importantly, yourself from electrical shock. See this article for pictures and step-by-step installation instructions. Thanks to Doc for this one.

If you have manual climate controls (there is no digital LCD readout on these), grab this kit for installing either a single DIN or double DIN radio. It will keep the factory look around the radio.

If you have automatic climate controls (with the digital temperature readout), there is not a factory piece that can be used. You can buy the navigation panel, but it will have a gap. The metra kit mentioned in the install article above should be used to avoid the gap. Or, you can fabricate your own panel (but this is not for the beginner).
Modified by AppleBonker at 1:42 AM 8/2/2008

Steering Wheel Interface

Pac-audio provides interfaces for our car. They are dependent on which head unit you are installing. The SWI-JACK is used for JVC, Alpine, Clarion, Kenwood and Blaupunkt models. The SWI-PS is used for Pioneer, Sony, Advent, Jensen and Dual models. Finally, the SWI-ECL2 is used for Eclipse models. These models require splicing into the wires in the factory wiring harness behind the head unit. They will also require programming before they are operational. The instructions for installation and programming can be found here.

WTF, these instructions suck. How do I connect this thing?

Check out this diagram (again provided by Doc) for an illustration of the wires that need to be connected (note: if you are not using a Kenwood head unit, there may actually be a plug that connects to the back of your stereo rather than the blue/yellow remote wire). I would highly recommend using wire tap-ins (available at Radio Shack and other locations) to splice into the factory wires. This will keep you from damaging the factory wiring. When you sell the car you can then remove all of your gear and get the car back to its factory configuration.
Modified by AppleBonker at 1:43 AM 8/2/2008

Big Three Upgrade

Before we get to some details about tuning and component selection, let’s tidy up the installation phase of things. This upgrade is essential to get the most out of your aftermarket audio setup. The upgrade consists of improving the stock cabling for the electrical that is being used by your amplifier.

First, a larger gauge cable is needed to connect the battery negative to the body chassis. You should know that everything in your car can be grounded to the metal chassis of the car. If you are installing an aftermarket amplifier, you will route positive power cables from the battery to the amp. The negative terminal on the amp will then be connected to the body of the car for a ground. Pop the hood and look at the cable running from the chassis to the negative terminal of the battery. It’s pretty small. To allow current to pass through your system with less resistance, this will need to be larger. I would recommend 0/1 AWG cable for this connection.

Next, the cable from the alternator should also be replaced. Again, 0/1 AWG cable will work the best here. In most cases, you can follow the factory cable with your increase size cable. This helps relieve some of the resistance that the alternator will see when charging the battery. Without this, loud thumps of bass can chew up the voltage from the battery at a rate that the alternator cannot replenish. This will result in a decrease in audio performance, as well as potential dimming of the light sources in your car.

Finally, you will need to improve the grounding of the engine. This mechanical device can add noise to a system by altering the voltage felt by the car. Grounding this with 0/1 AWG cable will reduce this likelihood. All you need to do is locate an bolt on the engine that is not used for something mechanical (obviously, a bolt that seals an opening for oil or coolant would not be a good choice, as this may cause these fluids to leak – not a good idea). See if it is possible to use one of the bolts that is used to mount the engine in place.

Some companies sell grounding kits for cars. These are designed to reduce electrical noise, and may contribute to an increase in performance. Generally, they will include at least a new grounding wire for the engine, as well as the wire from the negative terminal of the battery to the chassis of the car. Be sure when you purchase these that they are of the largest wire gauge available. The other grounding wires will help, but the big three are the primary wires you should be concerned about (in terms of audio performance only).
Modified by AppleBonker at 1:43 AM 8/2/2008

Noise Elimination

Since we’ve covered the Big 3, let’s make sure the rest of your system is not introducing electrical noise to the stereo. The key point here is probably ensuring that the power cable you run to the amp from the battery is not near the location of the source (patch) cables. Power cables can and will disrupt the flow of the source signal. The easiest way to do this is to run these wires down opposite sides of the car. For example, my power cable comes in behind the glove box and runs down the passenger side of the car. My signal cables all run along the driver side of the car. This will eliminate interference caused by the two communicating.

Next, be sure all of your connections are secure. Make sure that power and ground cables are properly terminated (it won’t do much good to have excellent cables with crappy connectors, so don’t skimp on this step). The grounding cables should all be connected to a bare spot on the chassis. Cured paint is not particularly good at conducting electricity, so get it out of the way. This can be done by sanding and the use of certain solvents (Acetone and MEK work well – but be careful, these can and will damage the finish of the car, so do not spill them on the exterior of your car unless you want the appearance to be diminished). Also, when determining the size of the wires you are going to use, make sure to use the largest possible. If you are only running one amp for the sub, see what the largest gauge is that the amplifier will accept (it should be at least 8AWG, but many amps allow for 4AWG as well). Run the largest possible, and make sure that the ground cable is of equal size. Smaller size wires will have more resistance (and this can generate heat which will increase the chance of a short by melting the insulation).

Next, invest in a multi-meter if you do not already have one. This will be used during some of the setup stages as well, so it is very useful (not only for car audio applications as well). A good multi-meter can be had at any home improvement store for under $100. Ensure that you have a good ground connection by checking the resistance between your grounding point and the negative terminal of the battery. The resistance should be as low as possible. To do this, check the resistance between the grounding point on the amplifiers with the grounding point on the body of the car. Then check the resistance between the chassis and the negative terminal of the battery. You should hopefully be able to achieve something in the hundredths of an ohm. Doing this should eliminate most of the electrical noise to your audio system. If you still are noticing any noise (generally will be heard as something like a whining sound coming from your stereo), consult the internet for more tests. Also, feel free to ask us here and we’ll try to help. However, if you ask about eliminating noise and you haven’t done these steps, prepared to be told to do these before we can help you any farther.
Modified by AppleBonker at 1:43 AM 8/2/2008

Sound Deadening

Sound deadening is an important step to improving audio quality, as well as driver comfort. This does not apply to car audio alone. If you’ve ever been in a luxury vehicle, you may be surprised by how little you hear of the outside world when the doors/windows are closed (even when the car is moving). While we all might like our Nissans, I seriously doubt anyone would call them a luxury vehicle. Adding sound deadening material works to eliminate noise from entering the cabin, as well as reducing the amount of music leaving the cabin to the outside world (trust me, no one wants to hear your stereo from outside your car – if you’re looking to let people outside your car hear your music, put some speakers in the grille for them).

First, there are many different brands of sound deadening materials. The most commonly known is Dynamat. That name has become synonymous with sound deadening (like Kleenex with facial tissue). However, that does not mean they are the best. In fact, Dynamat is frequently one of the more expensive materials, and other brands can match the performance (if not exceed it) for less cost. I’m not here to plug any brands (I wish they would pay me to do so, but they don’t), so investigate yourself. I have used or heard good things about the following: Second Skin Audio, B-Quiet and eDead. For information and a comparative test on these materials, check this out. There is a bunch of information there on choosing sound deadening materials, as well as performance results.

Applying sound deadener is a time consuming task. It will require you to remove all of the interior of the car. I know it seems like a daunting proposition at first, but once you get going you will realize how simple it is. The first thing I would recommend (and I cannot stress this enough) is pick up the service manual for your car. This will generally tell you how to remove the entire interior of the car to get to the sheet metal. I am not going to give you a link to the service manuals (as they cost money and I’m sure that would have legal ramifications), but you should be able to purchase them somewhere. Also, make sure you do your work in a covered area (you probably don’t want pieces of your car sitting outside in the rain). Additionally, you may want to do this in a heated area, or when it is warm outside. I have personally cracked plastic interior trim pieces, and the string of profanity that follows is inevitable. Then, you have to go and purchase new pieces to replace them. When warm, the paneling is much less likely to crack as it is more flexible.

Sound deadening works by reducing the ability of your body panels to vibrate. Large pieces of sheet metal can bow and flex easily. This will negatively impact the audio performance of your vehicle. Applying these materials adds weight to the body panels, making them more rigid. Most of these products are a rubber adhesive with a foil-like backing. They will easily stick to the metal of the car. Be prepared to cut yourself on the aluminum backing (kind of like a paper cut but thicker). This will definitely happen (likely on multiple occasions), but the finished product is well worth the time and slight discomfort (oh yeah, you’ll probably have to contort your body in ways you never imagined to get to those tough to reach spots). I would not recommend having a shop do this step, as it is relatively simple but time consuming. They will charge an arm and a leg for this, and it can easily be done on your own during free time (I did my car on weekends only over the course of about a month). When installing, the goal is to get as much contact as possible between the deadener and the metal of the car. I’ve found it is easiest to cut the sheets into small pieces when applying. Some people may try to use large sheets, but this can entrap air that will hinder the ability of the material to work. This may not make an audible difference (theoretically, there is definitely going to be a difference in performance, but you might not hear it), but if you’re going to do it you might as well take your time and do it right. Start slow, and once you’ve figured out what you’re doing you will be able to pick up the pace.

After deadening the sheet metal, it is a good idea to add closed cell foam (closed cell means that water cannot enter the foam and be entrapped, later resulting in mold which will make the car smell awful). The brands listed above all sell this material as well. This will help block noise and some vibration between body panels and the frame/sheet metal of the car. It will also dampen the vibrations the sound waves make when hitting the body of the car (resulting in less echo-effect so there is less cancellation of frequencies that you hear).

If all of these things are added, you will be amazed at how quiet the car sounds without the radio on. Road noise will be severely diminished, and obtrusive sounds from the outside world will as well. This can be an expensive step if done correctly as these materials are not cheap. However, why would you want to run an expensive setup and not get the best performance possible? Ask anyone who as deadened their car, and they will tell you it is well worth it.

The area of primary importance will most likely be the trunk. If you are installing a subwoofer, there will be a great deal of pressure build up in the trunk that will make it noisy. I’m sure most of you have heard a car with a sub or subs in the trunk that sounds like rattling cans from the outside. This car is almost certainly not sound deadened. Also, if you can hear those noises outside the car, you’ll be able to hear them inside as well. The stereo may seem to cover a lot of it up, but listen closely and you’ll hear that it is still there. Since the goal here is accurate sound reproduction, this bit of noise is costly in terms of the whole system performance.

By now, you are probably wondering how much material this will take. The closed cell foam, when applied liberally throughout the interior cabin of the car will maybe take 50-75 square feet. The rubber adhesive-type deadener will be applied over much more of the car, so the requirement will be higher (for the coupe I would recommend 200 square feet and about 250 square feet for the sedan). Again, these estimates are for a liberal application. The doors of the car have an outer skin (this is the metal that is painted on the exterior of the car) and an inner skin (the metal that the door panels are mounted to). Both of these sections should be deadened for optimum performance. I have always found it is better to order more material and have some left over; you never know what rattles you might pick up on after your complete installation. If you have extra material, you can then easily go back and re-apply deadener to those problem spots.
Modified by AppleBonker at 1:44 AM 8/2/2008

Gain Setting Tutorial

Ok, before we get into more of the tuning and audio theory stuff, we need to finish up the installation work. Personally, I set the gains on my amplifiers before I begin any tuning whatsoever. Here comes a simple physics law… Ohm’s law states that voltage is equal to current times resistance (V=I*R : where V is volts, I is amps and R is ohms). The power law equation states that power is equal to current times voltage (P=I*V : where P is watts). Now, with your speakers you know the power handling, as well as the power capabilities of your amplifier. You also know the resistance provided by the speakers (so we know P and R). This means we must solve for either voltage or current. Voltage is easier to solve, so let’s go:

P=I*VSo P/V=I

V=I*RSo V/R=I

Set these equations equal, since I=IGiving P/V=V/R

Now we can show that R*P=V*V

Therefore V=square root(R*P)

Great, now the math is done. Now, if we plug in the values for resistance and power, we can determine the voltage needed to meet these requirements. Let’s use a real-world example for this one. Let’s say you have a subwoofer that can handle 1,000 watts RMS (do not use the peak power here) at two ohms of resistance. We also have an amplifier that will supply 1,500 watts RMS at 2 ohms. We will use the lesser value for power, because supplying 1,500 watts RMS to the sub will be able to damage it. So now we know that P=1,000. We’ve already stated that the resistance of the sub is two ohms, so R=2. Great, plug this into the equation and you will see that V=square root (1,000*2). This means that V = 44.72. Now we know what we need to set the gain to.

To do this, it is best to find an audio track of just pink noise that we can play (search for these on the internet, they can be found or purchased on setup CDs). Make sure the car is on (if not, the battery will drain and the voltage supplied to the amplifier from the battery will not be at operating levels, so when the car is running your gain levels will be too high and might damage the sub or amp). Now, unplug the subwoofer from the amp. Use a multi-meter and press the positive and negative leads of the meter to the positive and negative terminals on the amplifier (where you would connect your subwoofer). Now, make sure that the head unit has any equalizations set to flat, and that the bass boost or anything like that is set to zero. Turn the radio on to the loudest level that you will listen (probably about 75% of maximum level). Have the pink noise playing on the radio, and measure the voltage that the amplifier is supplying to the speaker terminals. Adjust the gain up or down so that the reading reaches 44.72 volts. You’re done! Now repeat this step for your speakers if you are connecting them to an aftermarket amp as well.

Now that the gains are set, you are done with this step in the trunk. Keep in mind that this is the loudest that you can play your stereo safely. It will be unsafe on your speakers or amps to adjust the volume louder or turn the gain up any from this default level. Now reconnect the speakers and have a listen. Most likely, this will not sound right. Well what did we just do this for? So we can see what the maximum level is. Be prepared to turn either the sub or interior speakers down now so that the bass isn’t blasting out the music, or conversely so that the bass can be heard over the interior speakers. In my car, the gain for the sub is set at almost the maximum level, while the interior speakers are set significantly below maximum level. Now that this is done, we can move on to tuning and the fun begins!
Modified by AppleBonker at 1:44 AM 8/2/2008

Subwoofer and Enclosure Selection

Which enclosure type is right for me?

There are four basic types of subwoofer enclosures. Type I (small sealed box), Type II (medium sized enclosure that can either be sealed or ported), Type III (large sealed or ported enclosure) and Type IV (bandpass enclosure). Some of this selection will be based on the subwoofer purchased. Please consult the manual for your particular speaker to determine the requirements. The manufacturer will generally recommend the size of the enclosure needed (usually measured in cubic feet of volume) with two sizes: one for a sealed enclosure and one for ported. Some subs will not perform well in ported enclosures, and the manufacturer will likely tell you this. Remember, the size of the enclosure required by the speaker specs will NOT include the volume taken up by the magnet portion of the sub. For example, if the sub requires a one cubic foot enclosure, an enclosure with one cubic foot of volume will be too small. It would be a good idea to aim for more like 1.2-1.3 cubic feet (to compensate for the space that the driver occupies).

SealedA sealed enclosure will give the best audio quality. There will be no frequency peaks provided by the enclosure (meaning that the output will be very accurate and should result in a “tight” sounding bass hit). Any users interested primarily in sound quality should stick with this type of box. This is also the easiest box by far to manufacture yourself.

PortedA ported enclosure has a port (or vent) that allows air to pass from inside the box out to the world (probably into your trunk if this is where it is mounted). Enclosures will have a frequency that the port is tuned to. Around this frequency, the sub will play much louder (and will have a much “boomier” feel to it). Searching the internet can provide designs for constructing these boxes at a given volume and port frequency. With these boxes, it is HIGHLY recommended to set a cutoff frequency (or HPF) so that frequencies much below the port frequency will not be seen by the speaker. Subwoofers require pressure to function. When the subwoofer fires out into the vehicle, the pressure in the box is greatly reduced. This pressure pulls the subwoofer back into the enclosure. The sub is designed to work against this pull (or push when the sub retreats back into the enclosure). If the sub is working at a frequency much below the port frequency, these pressures do not build up and the sub will not function correctly. Doing this can easily result in a damaged speaker.

BandpassThis type of enclosure may be considered the most “showy” as lighting can be added to the box. These will generally be seen with plexi-glass showing off the subs inside the box. These enclosures are generally louder than any other enclosure type. In my opinion, they are also the least accurate. Personally, I would never use one of these do to the lack of accuracy provided. Some users, however, want the loudest sound possible out of a budget setup, which may make this ideal.

What type of material should I use to build my enclosure?

Fiberboard is generally the material of choice for subwoofers. It is rigid and durable, so it will hold up to the pressures produced by the subwoofer. It is generally recommended to go with no less than ¾” MDF (medium density fiberboard) for an enclosure. A perfect cube is about the worst possible design for a sub (mostly due to the cancellations that occur within the enclosure, but we do not need to get into the physics of this). MDF is rigid over flat surfaces. One of the downfalls to fiberboard is that it cannot be easily molded into curved shapes. If there are a lot of curves where you are trying to squeeze in your enclosure, see the next paragraph for a suggestion.

Fiberglass enclosures are highly versatile for housing subwoofers. They can be made to fit nearly any shape and size. Fiberglass is also significantly lighter than fiberboard, so if weight is a concern, this may be the box for you. However, fiberglass is a much harder component to work with, so building your own will be significantly harder than using MDF. Fiberglass is not as durable over flat surfaces as MDF. If your enclosure location will have a large flat area, you will probably want to use MDF for this portion of the build. It is certainly possible to make a hybrid enclosure using both materials. For example, the base of my fiberglass enclosure is ¾” MDF while the top is all fiberglass. This provides me with the durability and space saving that I wanted to employ in my Altima coupe. There are many specialty mobile entertainment shops that will custom fabricate a fiberglass enclosure for you. These will generally be quite expensive (at least $500 for the enclosure is not unheard of) due to the amount of time that is needed to make the box. The materials are not the expensive portion of this build. If you are determined to try to make a fiberglass enclosure yourself, please read this.

How do I wire my sub?

If your sub only has a single voice coil, this is simple. Whether or not the sub has dual voice coils should be well documented in the provided manuals and may be contained in the name of the sub. With one voice coil, the positive terminal on the sub is connected to the positive terminal on the amp. Do the same with the negative terminals. Done!

If your sub happens to be dual voice coil, this gets a bit more complicated. Dual voice coil subs will likely come in dual 2, 4 or 8 ohm configurations (although others may be possible, just not common). From physics we know that the total resistance (RT) is equal to the sum of the individual resistances of the components (we’ll call these R1 and R2 for voice coils 1 and 2). So a dual 2 ohm VC sub wired in series will be a 4 ohm load. In parallel, the inverse of RT (1/RT) is equal to the sum of the inverse of the resistances in parallel (1/R1 + 1/R2). A dual 2 ohm VC sub wired in parallel will be (1/RT = ½+1/2 = 1, so 1/1 = 1) 1 ohm.

What if I have two or more subs?

Do the same calculations. There are numerous possibilities here, so if you need help with this, ask. Run through all of your options and pick the lowest resistance that your amplifier can support. Make sure when you wire your sub or subs that you are not below the resistance the amplifier can support. If you were to run a 2 ohm load through an amplifier that is only 4 ohm stable, the amp will heat up rapidly and go into protect mode to save itself from your mistake. Doing this will turn the amplifier off until it cools down, so you music will turn on and off (which is not what you want out of your stereo). Check the manual for your amplifier to see what resistance it can support. Higher end amplifiers can support as low as 1 ohm (maybe even lower), so use this to determine your subwoofer wiring configuration.

Modified by AppleBonker at 1:45 AM 8/2/2008
Modified by AppleBonker at 2:03 AM 8/2/2008

Imaging and Sound Stage Info (Tuning)

One of the primary focuses for the audio enthusiast is accurately producing the origins of the audio in a spatial sense. With a high quality audio setup, you should be able to differentiate the location of the origin of the sound being reproduced. If you go to a concert, you will hear the sound coming at you from the front. If you go to a concert that is not using microphones and amplification (say the orchestra), to can sit in the middle of the theater and hear where sounds are coming from (your left, right or directly in front). For example, imagine the brass section is to your left, the wind instruments are center stage and the strings are to your right. Imagine how confused you would be if you were watching this performance and you were hearing sound coming from behind you, or the brass coming from your right. That is why most orchestra halls are designed to reduce reflections (etc.) so that what you see matches directly to what you hear. Now, imagine this performance is being recorded in a stereo (two channel) sense for you to listen to whenever. In a perfect world, you would be able to replay this recording and again hear the brass to your left, the wind instruments in front of you and the strings to your right.

In your car, this should be your goal. Unfortunately, the car is not the best place to be designing a listening room (placing the speakers where the windows are would probably reduce your ability to operate the vehicle). However, when tuned properly, you can achieve this image with the speakers where they are currently placed (although audio from the rear will make this difficult, more on that later). To do this, you will need to make use of time correction. We know from physics that sound travels at a fixed speed through a medium (in this case, air). Notice that the passenger-side speakers are further from you than the driver-side speakers. It should be obvious that a tone emitted from both speakers at the same time will then reach your ears at different times. High quality head units will allow you to delay the audio from the driver-side speakers so that it reaches you in unison with the passenger-side speakers. Some head units will even come with a microphone that you can setup in your listening position and they will detect this for you (like most automated processes, this will get you close but YOU will need to listen and tune to get this perfect).

There are many tools that can be used to perfect this setup (these should be used after allowing your head unit to automatically setup the time correction, but they can be used as the only tool if your head unit does not offer this option). Search online for car audio test track CD’s. There are some available from the organizations that sponsor car audio shows/competitions (find a list here). They will provide CD’s with the tracks that can be used to perfect the time correction on your car. On these, you will likely find simple audio tracks that can be used to adjust the time correction until the source of the audio appears right in front of you (you might be able to do this with your favorite music, but your music is definitely more complex than some of these tracks so that might become quite difficult). Once you’ve got the imaging correct, you can move on to the equalization.

Modified by AppleBonker at 1:45 AM 8/2/2008
Modified by AppleBonker at 2:04 AM 8/2/2008

Rear Fill Information

Now that we’ve briefly discussed imaging, let’s hit this topic (since the use of rear fill may diminish your chances of getting a realistic sounding image). Rear fill, or the speakers in the back of the car, is an often debated subject. Generally speaking, rear fill is not needed (those looking for excellent sound quality will want to avoid rear fill). Now, you might be thinking “hey, my car has locations for speakers in the back, so why shouldn’t I use them (or why would the manufacturer put them there if they aren’t needed)? “. Well, the answer goes back to older cars. Most older cars did not have much space in the front for larger speakers (and larger speakers are designed for reproducing deep frequencies – bass – exactly why you don’t see 4” subwoofers). Because the speakers up front cannot reproduce lower frequencies, manufacturers placed speakers in the rear that were larger (it is a lot easier to fit larger speakers on the rear deck). The theory is good here, and some car audio enthusiasts will mount subwoofers in the rear deck. However, the manufacturers decided to supply ALL frequencies to the rear speakers. Why they chose to do this is beyond me, but it is what transpired. Doing this will disrupt the imaging of the speakers as the soundstage will not be centered on the driver (and let’s face it, it is your car and your stereo, so shouldn’t everything be setup in the best possible way for YOU to listen to?).

Examine high end stereo (2-channel) home theater setups. These will not utilize surround sound speakers. If the source is only two channels, reproducing the sound with more than two channels worth of speakers is less than ideal (think, why aren’t there speakers near the back at live performances?). Nearly all sources you will listen to in your car are only 2-channel: CD’s, radio, digital music (mp3, WMA, etc). Eliminating rear fill can allow you to save up money and invest in a much better front soundstage. This will greatly improve the quality of the audio in your car. Don’t worry, the passengers in the back seat will still be able to easily hear the music from the front (think of how many times you’ve been in the back of a car with the stereo turned up and couldn’t even hear the discussion in the front seats over the speakers behind your head). Blasting the passengers out of the discussion is not a necessity.

Now, you may be asking why I still have rear fill in my car if I spent all of this time “bashing” it. I’ll tell you. Some will not agree with me, but I do enjoy listening to multichannel audio in my car from time to time (audio purists would argue that the car is no place for surround sound). Therefore, I use the rear fill ONLY when I am watching DVDs (which I won’t recommend while driving), or listening to multichannel audio (such as DVD-Audio). Honestly, the rear speakers in my car are probably only used about 2% of the time. Additionally, my head unit allows me to easily turn off or on the rear fill through the head unit. For most users, DVD playback capability is not a necessity, so neither is rear fill.

One final reason to include rear fill is for the kids. While this obviously doesn’t help the imaging of your soundstage, I can respect the need to keep the kids occupied during long drives. If you have children and have a head unit with DVD capabilities, it may be a good idea to have rear seat monitors. In this case, a good mobile entertainment setup will allow for multiple “zones”. This way, you can listen to your music up front, and the kids can watch a movie in the back and have the audio come from the rear speakers. This is the only other reason I (remember, personal opinion) can see to have rear fill.
Modified by AppleBonker at 1:46 AM 8/2/2008

Equalization (More Tuning)

Ok, we hopefully have setup the stereo imaging now. If so, it is time to move on to the last major step in tuning the stereo. Equalizers are used so that the speakers create a neutral reproduction of the source material. Nearly all speakers will have certain frequencies that they favor and will produce at higher amplitude. This is clearly not a good thing, as it colors the audio output. When something is recorded, great care is taken to make sure it is recorded accurately. Then this audio is processed to create the most realistic sounding recording possible. All of this is pointless for the end user if their speakers are introducing their own flavor to the mix.

Now, how to go about eliminating frequency spikes or dips. First, some manufactures will publish frequency response curves for their drivers. Most of their measurements will be made in an anechoic chamber (meaning that the speaker’s environment is not affecting the output). This may help as a starting point, but your car is definitely not an anechoic chamber. Certain frequencies will, inevitably, be amplified by acoustic reflections from the materials used in the car. To tune to a flat frequency response curve, you can do this by ear. Play music that you are familiar with and adjust the EQ until the music sounds right. If the subwoofer is too quite, turn the level up on the lower frequencies. If the treble is too harsh (very loud in the high pitched range), turn the level down on the higher frequencies. This step is not easy, and performing this by ear can take a long time to perfect. A good audio setup will be tuned by the user for great periods of time. I spent a couple of hundred hours physically installing my equipment in my car. Since then, I’ve spent easily double this amount of time tweaking my setup. Some head units will have presets that can be saved for the EQ. I use multiple EQ settings depending on what kind of music I’m listening to.

Mods, I know the rules about linking to other forums, but I would like to link to a home theater forum for EQ configuration with electronic equipment. Please let me know if I can do this.
Modified by AppleBonker at 1:46 AM 8/2/2008

Active vs. Passive Crossovers

What is a passive crossover?

For simplicities sake, we will only consider a 2-way setup in this section (a 3-way setup works the same way, but will utilize one more crossover per speaker location). Ok, a passive crossover is a hardware device that splits frequencies between a midrange driver and a tweeter. If you purchase a component setup, it will generally come with a passive crossover. This will be a box that the speaker wires connect to from the amp. The box will then have two sets of outputs (one will run to the tweeter and one to the midrange). The manufacturer of the speaker system will establish which frequency they want to cross the speakers at (this is done based on the performance of the speakers). The crossover frequency here cannot be adjusted. These are relatively simple setups to install (although just a touch more difficult than coaxial speakers).

What is an active crossover?

An active crossover is a software crossover. This will be controlled by an audio processor of some sort. I do not personally know of any head unit that has this control built in (although one may exist). My setup consists of an Alpine head unit (IVA-W205) and an Alpine audio processor (PXA-H701). With these two linked, I can control the active crossovers from the head unit. There are other audio processors that will not connect directly to a head unit that perform the same function, but there are dials on the processor that must be adjusted to change the crossover frequency.

The active crossover is not at a set frequency. The user has control to change the frequency to whatever he or she wishes. The benefit to this is that you can set the frequency to what will fit your speakers. This will allow you to mix and match brands (my tweeters are a completely different brand from my midranges). This is a good thing when there is a specific tweeter or midrange speaker you want to use. This means you can pick the best tweeter you can afford along with the best midrange, regardless of brand.

The major disadvantage to this setup is the difficulty in tuning. It will take much longer to tune as this opens up a large amount of options. You must also be careful not to send the wrong frequencies to the wrong driver (sending a low frequency signal to a tweeter can potentially damage it). The main advantage is being able to control more facets of your audio setup. Nearly all of the highest end mobile audio setups will use active crossovers. This will also make them more expensive. If you are a complete novice in the mobile audio area, this may not be the route to go. However, at some point you may want to make this jump. The only way to learn is to try and work with it. If you are lucky enough to have a friend who has an active setup, ask them to demo what the controls do for you (on that note, anyone ever around Chicago can hit me up and I’ll gladly show them my system and how it works). Since this is usually fairly in depth process, I will not go into any more of the details here. If you are interested in going this way, ask questions away and we’ll all try to help you.
Modified by AppleBonker at 1:46 AM 8/2/2008

Fiberglass Info

Ok, so you’re thinking about building a fiberglass enclosure? This could be to house your subwoofer/s or to make some custom kick panels for your car. This is not an easy step, but will make for a truly custom car stereo installation. I will write up a full blown procedure if people are interested, but for now, I’ll just stick with the basic information.

What do I need to make a fiberglass enclosure?

First, you need materials. Fiberglass work is done using a resin and fiberglass mat. You can find resin all over the place. I have read many reviews of people that have loved the B-440 from US Composites. This is what I used for my build. You will also need fiberglass mat. For this, I would recommend the 1.5 oz. chopped strand mat from US Composites above. The resin will come with hardener (which is used to cure the resin). In addition to these things, you will need:

Plastic mixing cups (I found these in quart size at Home Depot)Paint brushes (get some cheap wood ones in various sizes)Blue painters tapePlastic drop clothA respirator (I cannot stress this enough, these are your lungs and you do NOT want to destroy them – get a respirator with organic vapor cartridges from a home improvement store)Body filler (such as Bondo which can be found at all car parts stores)SandpaperCarpet or paint (up to you how you want to decorate your enclosure)

All of these items can add up in cost. Building a fiberglass enclosure will certainly be more expensive than building an MDF enclosure, but it will be lighter weight and much more custom in your car. If you are planning on attempting this, be prepared to learn from your mistakes. Your first enclosure will almost certainly not be perfect, so it is best to attempt a small project at first. My subwoofer enclosure was the first time I ever worked with fiberglass. After doing this, I can honestly say I wouldn’t recommend doing this. While my enclosure is functional, if I were to make another one I’d be able to make it much better. If you want to try your hand at this, start up a thread and I will help you through this as much as possible (although I must say that I am obviously no expert). This section is short because I’ve only done one fiberglass project. As I attempt more, I’ll try to elaborate on this process to help you all out.
Modified by AppleBonker at 1:47 AM 8/2/2008

Adam,

What an incredible writeup! This will remain a sticky so everyone can see it, and will remain locked so no one will post in it. If you have more to add, hit me up via email, and we will get it in here. Talk to Tyler, Shift_Coupe, about getting a custom user title. You've earned it

I love being able to post on locked threads..

Not only is this info on par (apple and doc know their stuff)... but the format, detail and completeness are Dyno-MIIIIITE!

Apple, im glad your here!

Custom title? Email me!