Setting out onto the Internet's car audio discussion boards can result in a dizzying experience of unfamiliar terms, misinformation and - well, just general confusion - "what should I buy?!" I've put together some general discussion of basic concepts to get you started. By all means, though, feel free to email me with any questions or to talk about other topics not addressed here.
General Considerations -
Rear Speakers
In top-end cars there are no rear speakers because SQ ("sound quality") is setup for optimal performance. In small cars, moreover, rear speakers are even more unnecessary - you only have 2 people in the car and no rear seats! Rear speakers that close to the fronts will collide and cause the audio to sound multiplied. If you listen for a few days, you will get use to it and it will definitely sound better than 4 speakers (or "channels"). Think of it this way, an artist records their music in 2 channel format so the optimum way to listen to it is through 2 channels. It may sound a bit different at first but, as I mentioned, if you give it a few days it should grow on you. Either way save your money and invest it in better front speakers!
Factory Bose "Systems"
Yes, simply put, Bose Systems are by no mean worth the cost they command. Essentially, Bose car audio systems generally consist of a amp and a possessor. When you start turning up the audio, the possessor "looks" at the signal coming form the head unit. It reads it and detects what could cause distortion on the speakers. It than cuts out those frequencies so that no distortion will occur. So, as you turn up your volume, your high and mid frequencies begin to fade out to the point where you can no longer really feel or hear them anymore.
Another poor thing about the Bose System is the pain it can be to upgrade to a better aftermarket system. Truthfully put, it is always best to start from scratch in these instances. If you just upgrade the speakers, the processor will still do the same thing to the signal - cutting out valuable parts of your sound. So, it is necessary to remove the factory amp as well as the head unit. By the time you are done upgrading, you could have saved a bundle of money merely starting from the car's stock audio system rather than the "upgraded" Bose System.
The "JL Myth"
Many of you might have heard that the JL Brand is basically the best you can buy. Respectfully, this is by no means true. There are many better companies out there for around the same or less price than JL's products. A few to start with: Focal, CDT, Image Dynamics, Rainbow, and Dynaaudio. Do not get me wrong, JL is good stuff. There is just a lot more out there that you might consider prior to pulling out your credit card. I'm always happy to talk about your options.
Capacitors
Before I get into this subject, I just want to say - for most of the systems I have seen - and for what the stock alternator is capable of putting out. NO ONE will even need to worry about running one of these. That being said, installing a capacitor into your system CAN reduce or omit headlight dimming while running heavy power loads on your system, but this is more of a band aid than a true fix. What a capacitor does is it stores a charge of power that can be depleted very quickly; this allows some of the strain to be taken off the factory charging system. But the "cap" still has to be "recharged" over and over again. This, in turn, may cause damage to your charging system. If your lights do dim a lot, it might be time to look for a new alternator and/or a second battery for your audio system. The only time you will have to worry about this happening is if you are running over 1000 RMS on a consistent basis.
Stock Wiring
Some of you might be worried about running new speakers on your factory speaker wiring. Well I am here to tell you that, as long as you stay below 50 watts going through the wire, you will be fine. If you are planning on running something like 120 watts to the speakers then you will need to upgrade the factory wires in the doors to a sturdier aftermarket variety. The reason you do this is for safety. If you try to push too much current through too small of a wire, you can cause damage to your equipment or even start a fire in some cases. A good wire to run is 16 or 14 gauge. If in doubt as to the proper gauge to use, please contact me!
Power Wire Size
Power wire is used to send power to your aftermarket amplifier. Usually the rule is the bigger the wire the less resistance the power has going through the wire. The normal size is usually 8 or 4 gauge - the lower the number the bigger the wire (don't ask LOL). 8 gauge wire can carry power up to around 400 watts. If you are going to have more than that or 2 amps I would step up to 4 gauge wire. 4 Gauge is good up to about 1000 watts. After that you will have to step up to 2 gauge or even the big 0 gauge. Now when you run any of these, other than 8 gauge, you can use something called a distribution block. This allows you to hook up multiple amps to the same wire (which is completely fine). Most of them will step down the size, for instance taking a 4 gauge power wire as the input and outputting to multiple 8 gauge wires for the shorter runs to the multiple amps.
Ground Wire
This is an incredibly important aspect of any system. Believe it or not, DC ("Direct Current") flows from negative to positive. SO your ground wire is as - if not more - important than your power wire. Now, your ground should be on a solid piece of metal - preferably on a main beam or brace of the car. Not to say that you cannot use another piece of metal, just these are the better points to utilize if possible. Many people, like me, prefer not to drill additional holes so we look for bolts that we can place the ground wire under it. Before just drilling a hole, make sure to check under were you are drilling - you do not want to drill into a fuel line!!! After you drill your hole, sand or grind the paint off so that your ground is a solid connection. Finally, before I physically install my ground wires I put some dielectric grease on the wire/connection.
Fuse Rating
These little babies help from you starting a fire in your nice car! Fuses are simply there to protect the wire and the electronics from shorts - whether it be from accidentally touching a wire to the ground, or some other wire slipping off an amp's connection point. The easiest way to find out what kind of fuse you need for your amps is look at the fuses on your amp, then add them up and that will yield the wattage of your correct fuse. Most people just run what fuse comes with the wiring kit. This may or may not be your best option. Feel free to ask if in doubt.
Speaker Types
Let's start by discussing "component" speakers. A component setup usually consists of crossovers, a tweeter, and a woofer. This makes for the best you can get. The reason for this is because of the first component - the crossover. Before power even gets to your speakers, the crossover filters the frequencies of the music and makes sure that only those frequencies that the speaker can reproduce (essentially, that it can "handle"), gets to them. The next part, the tweeter - this takes all your high frequencies and is dedicated to those pitches. Tweeters that can be mounted at the location of your choice are ideal, as you can put them as if you were at a concert - e.g., around ear level; giving you a more true experience with your music.
Coaxial speakers - these are cheaper and, admittedly, easier to install. Typically, these are designed for rear fill, or for someone who wants to do a quick and easy install. The tweeters are built right into them as one unit. This causes loss of power from the woofer as it can not move as far as one without the tweeter built in. Also it can not sound as faithful to your audio source because there is resistance to the movement of the woofer by virtue of the tweeter's location. In such a setup there is usually no crossover to divert the low/higher frequencies to the appropriate speakers.
Ohms
This is a very commonly misunderstood subject. Ohms or Ohm's Law is the degree of resistance that a material or item demonstrates. In car audio, we describe speakers using ohms to signify a given speaker's resistance. For example, if you have a subwoofer with a 4 ohm single voice coil, that sub can be connected to an amp which similarly has a resistance of 4 ohms.
After resistance, the next consideration relative to ohms is power. If you look at any amp's specs, you will see that is has something like "100 watts RMS x 4 at 4 ohms (150 watts RMS x 4 at 2 ohms)," "300 watts RMS x 2 bridged output at 4 ohms (4-ohm stable in bridged mode)." So, let's look at the first one. What they are saying is that the amp can run 100 watts per channel (or "per-speaker") as long as each speaker has a resistance of 4 ohms (it's measure of resistance). The second example states that as long as the speakers are rated at 2 ohms, the amp can put out 150 per channel. Finally, the last example states that the amp can output to 2 channels at 300 watts per channel if the speakers are rated at 4 ohms.
Remember that the higher the ohms rating, the greater the resistance. So, when you opt for a lower ohms rating it may supply much more power to your speakers. You may be asking, well can I wire different ohm rated speakers to two different sets output on an amp? You can do this ONLY if your amp is setup for it. If you want to speak in much more detail about Ohms, just fire up trusty Google, or simply shoot me an email.
RMS
Now you may have noticed in the previous section when watts were being explained it said "RMS." For instance, a statement like "100 X 4 at 4 ohms RMS." This is a very important consideration when choosing an amp. RMS stands for Root Mean Square. In ordinary terms, this describes the power level that an amp can continue to provide for extended periods of time (rather than, say, it's "peak" rating for short spurts). In your browsing, you will surely see some companies advertise things like "1200 watts MAX." Basically, this is a gimmick in that the amps will never produce such power; no matter how hard you try, it will just not reliably or consistently happen.
Amp Settings and Gains
So great... you've got your new amp and are wondering what in the world are all these knobs and switches on it for? Well here is your answer: gain or volume. Think of them as a "second" volume for your system. When you are all done installing your system it is time to put a quality test CD or a source with a test tone of 80 HZ. Next, go to your amp and turn the gain all the way down then go back to the head unit and turn the volume all the way up to the maximum. Next, you go back to your amp and slowly start turning up your gain until you hear distortion. At that point, turn it back just a hair. This will safeguard your speakers against distortion (or damage).
Now, the "low pass" and "high pass" knobs, etc. In a typical system with components in the front (e.g. with crossovers as discussed above), the crossover will take care of the filtering so your front should stay on "Full" at your amp (so as not to filter signal away BEFORE it gets to the crossover). If your system has rear speakers, I recommend turning on the High Pass Filter and dial it in to about "80" or maybe a bit higher. What these filters do are to basically insure that the speaker will not get frequencies that it cannot reproduce. The Low Pass Filter is designed for when running a subwoofer - and your cut off point should be about 60 Hz for your sub input.
Subwoofer Wiring
This is one of the trickiest points to master in car audio. There are many ways to wire a subwoofer (or "sub"). There are generally four types of subwoofers: the SVC ("single voice coil") in 4 and 8 ohm variants; then the DVC ("dual voice coil") in 2 and 4 ohm variations. The SVC are pretty easy. You can hook up a 4 ohm coil as a 4 ohm or if you have 2 you can wire them as 4 or 2 ohms. If you have a SVC 8 ohm sub than you can hook it up as 8 ohms. If you have 2 of them as a 2 ohm or a 8 ohm load. You can not wire different ohm rated subs or speakers together this will damage the sub and or the amp. Again, please, if you need help, just ask!
Head Unit Selection
Finally, because many of you are likely shopping for a new receiver or "head unit," I'll provide a quick run down through some of the more prominent and visible brands out in the marketplace:
Alpine- Very nice head units. Great sound quality from the factory - or even if you are using an aftermarket amp. Great Interface for the ipod as well; almost as if it was made for the ipod, which some of the units in fact are.
Boss- A very cheap brand usually sold at Walmart or at flea markets. Not by any means great or even "good." These units have a crappy interface and the music that they transmit can actually make your system sound worse!
Cadence- This company is more known for their amplifiers than their head units. I have known no one that has used them or has tried them. IMO, I would keep away.
Clarion- Still offers one of the top of the line SINGLE DIN head units for a SQ (sound quality) focused setup. Only thing is that they are quite pricey - and...honestly...a bit ugly with regard to appearance and interface.
Dual- Yet another brand sold by flea markets and bargain stores. These units are basically the lowest end that I would allow in a car.
Eclipse- A fantastic head unit for a nice setup. It is right up there with the Alpines. These are very nice head units for the money and have a nice interface as well. The only one I may stay away from is a model that is no longer manufactured - namely, the one with the integrated Tom Tom GPS. In that model, you had to share your main screen with your audio functions along with the GPS which was a bit cumbersome.
Fahrenheit- Another low class brand not even sold at flea markets. Some will try to trick you into these as if they are great units. They are not. Buyer beware.
Jensen- While not the top (or even middle class), these do have a lot to offer - but it comes at a price. The screen is by no means good for GPS, let alone a movie. Furthermore, the signals it sends out can have engine nice as well.
If you are looking for a low-end one to put in your wife's car to make her mad (now, why would you do this?!) this is the one.
JVC- Middle class head units. While I have not had much to do with them, I have still played with a few and such. The "flashy" screens attract those teens that want that boom boom boom in the trunk. They are nice units, and can be fairly easy to use, only - for the money - you can always get something much better.
Kenwood- Fantastic interface with the best NAV and bluetooth I have seen. You can not beat these DD (double din, or full size) units. If you are looking for a nice Nav interface and a nice unit for music, look no further.
Panasonic- If you can get past the flashy blue screen you may like these single-din units. The double dins are nice as well, but as soon as you want to add Nav you are slammed with an extra 500 bucks.
Pioneer- If you do not know me by now, I have sort of a beef with Pioneer. When I started installing car stereos years ago I used Pioneer units and have nothing but problems. In my own cars, or for clients, problems ranged from faceplates "dying," internal amps frying, CDs not ejecting, engine whining noises and so on. But I will say this, their Premier units are pretty nice - and the sound quality out of them can be decedent as well. However, the ipod interface is junk and slow. Other than that, not bad units.
Sony- This company used to be the milestone in sound quality. Now, pretty much just commercialized junk. I have seen these units literally short themselves out. The power signal you get from these head units and amps are garbage, and so on. Stay away!
Valor- Yes they look like a great package don't they? Do not be fooled. Another bargain basement brand where looks are, I promise, quite deceiving!
So, that's a starting point covering some basic ground. If you have questions about of the topics above - or anything else for that matter - please feel free to send me an email. It is my pleasure to help people make informed decisions so that they will be satisfied with their installs and sound systems.
-Matt
General Considerations -
Rear Speakers
In top-end cars there are no rear speakers because SQ ("sound quality") is setup for optimal performance. In small cars, moreover, rear speakers are even more unnecessary - you only have 2 people in the car and no rear seats! Rear speakers that close to the fronts will collide and cause the audio to sound multiplied. If you listen for a few days, you will get use to it and it will definitely sound better than 4 speakers (or "channels"). Think of it this way, an artist records their music in 2 channel format so the optimum way to listen to it is through 2 channels. It may sound a bit different at first but, as I mentioned, if you give it a few days it should grow on you. Either way save your money and invest it in better front speakers!
Factory Bose "Systems"
Yes, simply put, Bose Systems are by no mean worth the cost they command. Essentially, Bose car audio systems generally consist of a amp and a possessor. When you start turning up the audio, the possessor "looks" at the signal coming form the head unit. It reads it and detects what could cause distortion on the speakers. It than cuts out those frequencies so that no distortion will occur. So, as you turn up your volume, your high and mid frequencies begin to fade out to the point where you can no longer really feel or hear them anymore.
Another poor thing about the Bose System is the pain it can be to upgrade to a better aftermarket system. Truthfully put, it is always best to start from scratch in these instances. If you just upgrade the speakers, the processor will still do the same thing to the signal - cutting out valuable parts of your sound. So, it is necessary to remove the factory amp as well as the head unit. By the time you are done upgrading, you could have saved a bundle of money merely starting from the car's stock audio system rather than the "upgraded" Bose System.
The "JL Myth"
Many of you might have heard that the JL Brand is basically the best you can buy. Respectfully, this is by no means true. There are many better companies out there for around the same or less price than JL's products. A few to start with: Focal, CDT, Image Dynamics, Rainbow, and Dynaaudio. Do not get me wrong, JL is good stuff. There is just a lot more out there that you might consider prior to pulling out your credit card. I'm always happy to talk about your options.
Capacitors
Before I get into this subject, I just want to say - for most of the systems I have seen - and for what the stock alternator is capable of putting out. NO ONE will even need to worry about running one of these. That being said, installing a capacitor into your system CAN reduce or omit headlight dimming while running heavy power loads on your system, but this is more of a band aid than a true fix. What a capacitor does is it stores a charge of power that can be depleted very quickly; this allows some of the strain to be taken off the factory charging system. But the "cap" still has to be "recharged" over and over again. This, in turn, may cause damage to your charging system. If your lights do dim a lot, it might be time to look for a new alternator and/or a second battery for your audio system. The only time you will have to worry about this happening is if you are running over 1000 RMS on a consistent basis.
Stock Wiring
Some of you might be worried about running new speakers on your factory speaker wiring. Well I am here to tell you that, as long as you stay below 50 watts going through the wire, you will be fine. If you are planning on running something like 120 watts to the speakers then you will need to upgrade the factory wires in the doors to a sturdier aftermarket variety. The reason you do this is for safety. If you try to push too much current through too small of a wire, you can cause damage to your equipment or even start a fire in some cases. A good wire to run is 16 or 14 gauge. If in doubt as to the proper gauge to use, please contact me!
Power Wire Size
Power wire is used to send power to your aftermarket amplifier. Usually the rule is the bigger the wire the less resistance the power has going through the wire. The normal size is usually 8 or 4 gauge - the lower the number the bigger the wire (don't ask LOL). 8 gauge wire can carry power up to around 400 watts. If you are going to have more than that or 2 amps I would step up to 4 gauge wire. 4 Gauge is good up to about 1000 watts. After that you will have to step up to 2 gauge or even the big 0 gauge. Now when you run any of these, other than 8 gauge, you can use something called a distribution block. This allows you to hook up multiple amps to the same wire (which is completely fine). Most of them will step down the size, for instance taking a 4 gauge power wire as the input and outputting to multiple 8 gauge wires for the shorter runs to the multiple amps.
Ground Wire
This is an incredibly important aspect of any system. Believe it or not, DC ("Direct Current") flows from negative to positive. SO your ground wire is as - if not more - important than your power wire. Now, your ground should be on a solid piece of metal - preferably on a main beam or brace of the car. Not to say that you cannot use another piece of metal, just these are the better points to utilize if possible. Many people, like me, prefer not to drill additional holes so we look for bolts that we can place the ground wire under it. Before just drilling a hole, make sure to check under were you are drilling - you do not want to drill into a fuel line!!! After you drill your hole, sand or grind the paint off so that your ground is a solid connection. Finally, before I physically install my ground wires I put some dielectric grease on the wire/connection.
Fuse Rating
These little babies help from you starting a fire in your nice car! Fuses are simply there to protect the wire and the electronics from shorts - whether it be from accidentally touching a wire to the ground, or some other wire slipping off an amp's connection point. The easiest way to find out what kind of fuse you need for your amps is look at the fuses on your amp, then add them up and that will yield the wattage of your correct fuse. Most people just run what fuse comes with the wiring kit. This may or may not be your best option. Feel free to ask if in doubt.
Speaker Types
Let's start by discussing "component" speakers. A component setup usually consists of crossovers, a tweeter, and a woofer. This makes for the best you can get. The reason for this is because of the first component - the crossover. Before power even gets to your speakers, the crossover filters the frequencies of the music and makes sure that only those frequencies that the speaker can reproduce (essentially, that it can "handle"), gets to them. The next part, the tweeter - this takes all your high frequencies and is dedicated to those pitches. Tweeters that can be mounted at the location of your choice are ideal, as you can put them as if you were at a concert - e.g., around ear level; giving you a more true experience with your music.
Coaxial speakers - these are cheaper and, admittedly, easier to install. Typically, these are designed for rear fill, or for someone who wants to do a quick and easy install. The tweeters are built right into them as one unit. This causes loss of power from the woofer as it can not move as far as one without the tweeter built in. Also it can not sound as faithful to your audio source because there is resistance to the movement of the woofer by virtue of the tweeter's location. In such a setup there is usually no crossover to divert the low/higher frequencies to the appropriate speakers.
Ohms
This is a very commonly misunderstood subject. Ohms or Ohm's Law is the degree of resistance that a material or item demonstrates. In car audio, we describe speakers using ohms to signify a given speaker's resistance. For example, if you have a subwoofer with a 4 ohm single voice coil, that sub can be connected to an amp which similarly has a resistance of 4 ohms.
After resistance, the next consideration relative to ohms is power. If you look at any amp's specs, you will see that is has something like "100 watts RMS x 4 at 4 ohms (150 watts RMS x 4 at 2 ohms)," "300 watts RMS x 2 bridged output at 4 ohms (4-ohm stable in bridged mode)." So, let's look at the first one. What they are saying is that the amp can run 100 watts per channel (or "per-speaker") as long as each speaker has a resistance of 4 ohms (it's measure of resistance). The second example states that as long as the speakers are rated at 2 ohms, the amp can put out 150 per channel. Finally, the last example states that the amp can output to 2 channels at 300 watts per channel if the speakers are rated at 4 ohms.
Remember that the higher the ohms rating, the greater the resistance. So, when you opt for a lower ohms rating it may supply much more power to your speakers. You may be asking, well can I wire different ohm rated speakers to two different sets output on an amp? You can do this ONLY if your amp is setup for it. If you want to speak in much more detail about Ohms, just fire up trusty Google, or simply shoot me an email.
RMS
Now you may have noticed in the previous section when watts were being explained it said "RMS." For instance, a statement like "100 X 4 at 4 ohms RMS." This is a very important consideration when choosing an amp. RMS stands for Root Mean Square. In ordinary terms, this describes the power level that an amp can continue to provide for extended periods of time (rather than, say, it's "peak" rating for short spurts). In your browsing, you will surely see some companies advertise things like "1200 watts MAX." Basically, this is a gimmick in that the amps will never produce such power; no matter how hard you try, it will just not reliably or consistently happen.
Amp Settings and Gains
So great... you've got your new amp and are wondering what in the world are all these knobs and switches on it for? Well here is your answer: gain or volume. Think of them as a "second" volume for your system. When you are all done installing your system it is time to put a quality test CD or a source with a test tone of 80 HZ. Next, go to your amp and turn the gain all the way down then go back to the head unit and turn the volume all the way up to the maximum. Next, you go back to your amp and slowly start turning up your gain until you hear distortion. At that point, turn it back just a hair. This will safeguard your speakers against distortion (or damage).
Now, the "low pass" and "high pass" knobs, etc. In a typical system with components in the front (e.g. with crossovers as discussed above), the crossover will take care of the filtering so your front should stay on "Full" at your amp (so as not to filter signal away BEFORE it gets to the crossover). If your system has rear speakers, I recommend turning on the High Pass Filter and dial it in to about "80" or maybe a bit higher. What these filters do are to basically insure that the speaker will not get frequencies that it cannot reproduce. The Low Pass Filter is designed for when running a subwoofer - and your cut off point should be about 60 Hz for your sub input.
Subwoofer Wiring
This is one of the trickiest points to master in car audio. There are many ways to wire a subwoofer (or "sub"). There are generally four types of subwoofers: the SVC ("single voice coil") in 4 and 8 ohm variants; then the DVC ("dual voice coil") in 2 and 4 ohm variations. The SVC are pretty easy. You can hook up a 4 ohm coil as a 4 ohm or if you have 2 you can wire them as 4 or 2 ohms. If you have a SVC 8 ohm sub than you can hook it up as 8 ohms. If you have 2 of them as a 2 ohm or a 8 ohm load. You can not wire different ohm rated subs or speakers together this will damage the sub and or the amp. Again, please, if you need help, just ask!
Head Unit Selection
Finally, because many of you are likely shopping for a new receiver or "head unit," I'll provide a quick run down through some of the more prominent and visible brands out in the marketplace:
Alpine- Very nice head units. Great sound quality from the factory - or even if you are using an aftermarket amp. Great Interface for the ipod as well; almost as if it was made for the ipod, which some of the units in fact are.
Boss- A very cheap brand usually sold at Walmart or at flea markets. Not by any means great or even "good." These units have a crappy interface and the music that they transmit can actually make your system sound worse!
Cadence- This company is more known for their amplifiers than their head units. I have known no one that has used them or has tried them. IMO, I would keep away.
Clarion- Still offers one of the top of the line SINGLE DIN head units for a SQ (sound quality) focused setup. Only thing is that they are quite pricey - and...honestly...a bit ugly with regard to appearance and interface.
Dual- Yet another brand sold by flea markets and bargain stores. These units are basically the lowest end that I would allow in a car.
Eclipse- A fantastic head unit for a nice setup. It is right up there with the Alpines. These are very nice head units for the money and have a nice interface as well. The only one I may stay away from is a model that is no longer manufactured - namely, the one with the integrated Tom Tom GPS. In that model, you had to share your main screen with your audio functions along with the GPS which was a bit cumbersome.
Fahrenheit- Another low class brand not even sold at flea markets. Some will try to trick you into these as if they are great units. They are not. Buyer beware.
Jensen- While not the top (or even middle class), these do have a lot to offer - but it comes at a price. The screen is by no means good for GPS, let alone a movie. Furthermore, the signals it sends out can have engine nice as well.
If you are looking for a low-end one to put in your wife's car to make her mad (now, why would you do this?!) this is the one.
JVC- Middle class head units. While I have not had much to do with them, I have still played with a few and such. The "flashy" screens attract those teens that want that boom boom boom in the trunk. They are nice units, and can be fairly easy to use, only - for the money - you can always get something much better.
Kenwood- Fantastic interface with the best NAV and bluetooth I have seen. You can not beat these DD (double din, or full size) units. If you are looking for a nice Nav interface and a nice unit for music, look no further.
Panasonic- If you can get past the flashy blue screen you may like these single-din units. The double dins are nice as well, but as soon as you want to add Nav you are slammed with an extra 500 bucks.
Pioneer- If you do not know me by now, I have sort of a beef with Pioneer. When I started installing car stereos years ago I used Pioneer units and have nothing but problems. In my own cars, or for clients, problems ranged from faceplates "dying," internal amps frying, CDs not ejecting, engine whining noises and so on. But I will say this, their Premier units are pretty nice - and the sound quality out of them can be decedent as well. However, the ipod interface is junk and slow. Other than that, not bad units.
Sony- This company used to be the milestone in sound quality. Now, pretty much just commercialized junk. I have seen these units literally short themselves out. The power signal you get from these head units and amps are garbage, and so on. Stay away!
Valor- Yes they look like a great package don't they? Do not be fooled. Another bargain basement brand where looks are, I promise, quite deceiving!
So, that's a starting point covering some basic ground. If you have questions about of the topics above - or anything else for that matter - please feel free to send me an email. It is my pleasure to help people make informed decisions so that they will be satisfied with their installs and sound systems.
-Matt